STRUT AND JOINT FOR SPACEFRAME STRUCTURE ASSEMBLIES

Abstract

A node and a strut connect to one another to form a spaceframe structure, in which the strut has a strut bending stiffness and defines a strut axis. The node has a main body and an arm connecting to and extending from the main body along the strut axis and toward the strut. The arm has a node end attaching to the main body, a strut end connecting to the strut and a midsection extending there between. The midsection includes a neck portion having a neck bending stiffness being less than 20% of the strut bending stiffness. The strut includes primary and secondary sections that axially slidably connect to one another to position them between adjacent respective end-fittings of adjacent nodes, and partially axially overlap and secure to one another and to the end-fittings respectively. At least one of the end-fittings connects to the strut end of the arm.

Claims

1. A node device for connecting to at least one strut having a strut bending stiffness and defining a generally rectilinear strut axis, said node device comprising: a main body; and at least one arm connecting to and extending from the main body along the strut axis and toward the at least one strut, the at least one arm having a node end attaching to the main body, a strut end for connecting to the at least one strut and a midsection extending between the node end and the strut end, the midsection including a neck portion having a neck bending stiffness being less than about 20% of the strut bending stiffness.

2. The node device of claim 1, wherein the at least one strut has a strut length to define a strut bending stiffness per unit length and the neck portion has a neck portion length to define a neck bending stiffness per unit length, the neck bending stiffness per unit length being less than about 600% of the strut bending stiffness per unit length.

3. The node device of claim 1, wherein the at least one arm includes a plurality of arms for connecting to a plurality of struts, each one of the plurality of arms connecting to a respective one of the plurality of struts, and the neck portion of each one of the plurality of arms having a neck bending stiffness being less than about 20% of the strut bending stiffness of the respective one of the plurality of struts.

4. The node device of claim 3, wherein all strut axes of the plurality of struts intersect with each other at an axis intersecting point located adjacent the main body, each one of the plurality of arms extending from the main body along the respective strut axis and away from the axis intersecting point.

5. The node device of claim 1, wherein the main body and the plurality of arms integrally form a single piece.

6. The node device of claim 1, wherein each strut end, preferably releasably, connects to the respective strut via a strut end-fitting.

7. A spaceframe structure, comprising: at least one strut having a strut bending stiffness and defining a generally rectilinear strut axis; at least one node connecting to of the at least one strut, said at least one node including: a main body; and at least one arm connecting to and extending from the main body along the strut axis and toward the at least one strut, the at least one arm having a node end attaching to the main body, a strut end connecting to the at least one strut and a midsection extending between the node end and the strut end, the midsection including a neck portion having a neck bending stiffness being less than about 20% of the strut bending stiffness.

8. The spaceframe structure of claim 7, wherein the at least one strut has a strut length to define a strut bending stiffness per unit length and the neck portion has a neck portion length to define a neck bending stiffness per unit length, the neck bending stiffness per unit length being less than about 600% of the strut bending stiffness per unit length.

9. The spaceframe structure of claim 7, wherein the at least one arm includes a plurality of arms for connecting to a plurality of struts, each one of the plurality of arms connecting to a respective one of the plurality of struts, and the neck portion of each one of the plurality of arms having a neck bending stiffness being less than about 20% of the bending stiffness of the respective one of the plurality of struts.

10. The spaceframe structure of claim 9, wherein all strut axes of the plurality of struts intersect with each other at an axis intersecting point located adjacent the main body, each one of the plurality of arms extending from the main body along the respective strut axis and away from the axis intersecting point.

11. The spaceframe structure of claim 9, wherein at least one of said plurality of struts is located between two adjacent ones of said plurality of nodes.

12. The spaceframe structure of claim 11, wherein the at least one of said plurality of struts being located between two adjacent ones of said plurality of nodes has a predetermined combined axial strut coefficient of thermal expansion.

13. The spaceframe structure of claim 12, wherein the predetermined combined axial strut coefficient of thermal expansion takes into consideration the respective one of said plurality of arms from each said two adjacent ones of said plurality of nodes connecting to the at least one of said plurality of struts.

14. The spaceframe structure of claim 7, wherein the at least one strut includes: a primary section having first and second primary ends with the strut axis extending therebetween; and a secondary section having first and second secondary ends, the second primary end axially slidably connecting onto the first secondary end between a first configuration in which the first primary end and the second secondary end are positionable adjacent first and second end-fittings respectively for axial positioning of the at least one strut therebetween, and a second configuration in which the first primary end and the second secondary end are axially overlapping the first and second end-fittings respectively for securing thereto with the primary and secondary sections securing to one another, at least one of the first and second end-fittings connecting to the strut end of the at least one arm.

15. The spaceframe structure of claim 14, wherein the primary section has a first length and is made out of a first material having a first axial coefficient of thermal expansion, and the secondary section has a second length and is made out of a second material having a second axial coefficient of thermal expansion, the first and second lengths being defined to provide the at least one strut with a predetermined combined axial strut coefficient of thermal expansion.

16. The spaceframe structure of claim 15, wherein the predetermined combined axial strut coefficient of thermal expansion takes into consideration the respective one of said at least one arm of said at least one node connecting to the at least one strut.

17. The spaceframe structure of claim 16, wherein the predetermined combined axial strut coefficient of thermal expansion of all of the at least one strut is essentially identical.

18. A strut device for use in a frame structure and for mounting between first and second fixed nodes having first and second strut end-fittings, respectively, the strut device comprising: a primary section having first and second primary ends and defining a strut axis therebetween; and a secondary section having first and second secondary ends, the second primary end axially slidably connecting onto the first secondary end between a first configuration in which the first primary end and the second secondary end are positionable adjacent the first and second end-fittings respectively for axial positioning of the strut device therebetween, and a second configuration in which the first primary end and the second secondary end are axially overlapping the first and second end-fittings respectively for securing thereto with the primary and secondary sections securing to one another.

19. The strut device of claim 18, wherein the primary section has a first length and is made out of a first material having a first axial coefficient of thermal expansion, and the secondary section has a second length and is made out of a second material having a second axial coefficient of thermal expansion, the first and second lengths being defined to provide the strut device with a predetermined combined axial strut coefficient of thermal expansion.

20. The strut device of claim 18, wherein the primary and secondary sections are cylindrical in shape.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Further aspects and advantages of the present invention will become better understood with reference to the description in association with the following Figures, in which similar references used in different Figures denote similar components, wherein:

[0046] FIG. 1 is a perspective view of a spaceframe structure in accordance with an embodiment of the present invention;

[0047] FIG. 2 is a broken enlarged perspective view of a 6-arm node with connecting struts of the embodiment of FIG. 1;

[0048] FIG. 3 is a top side perspective view of a 2-arm base node with connecting struts of the embodiment of FIG. 1;

[0049] FIG. 4 is a perspective view of the node of FIG. 2 with the connecting end-fittings of the connecting struts;

[0050] FIG. 5 is an exploded perspective view of the node of FIG. 4, showing the end-fitting connected thereto;

[0051] FIG. 6 is a perspective section view taken along line 6-6 of FIG. 4;

[0052] FIG. 7 is an exploded elevation view of a strut of the embodiment of FIG. 1, shown between the two nodes in a first insertion configuration with the two strut sections (or tubes) inserted between the two end-fittings secured to the nodes;

[0053] FIG. 8 is a view similar to FIG. 7 but not exploded, showing the strut in the first insertion configuration with one of the two tubes slidably telescopically connected to one another and inserted between the two end-fittings;

[0054] FIG. 9 is a view similar to FIG. 8, showing the strut in a second fully installed configuration with the two tubes connected to the two end-fittings and telescopically connected to one another; and

[0055] FIG. 10 is a schematic bottom perspective view of another embodiment of a spaceframe structure in accordance with the present invention that is used to support an antenna reflector.

DETAILED DESCRIPTION OF THE INVENTION

[0056] With reference to the annexed drawings the preferred embodiment of the present invention will be herein described for indicative purpose and by no means as of limitation.

[0057] Referring to FIGS. 1 to 5, there is shown a spaceframe structure or assembly in accordance with an embodiment 10 of the present invention, typically for use onboard of spacecraft or the like.

[0058] Referring more specifically to FIG. 1, the structure 10 typically includes a plurality of struts 20 interconnected to a plurality of nodes (or joints or hubs) 40. Each strut 20 defines a generally rectilinear strut axis 22 and has a strut bending stiffness E.sub.SI.sub.S (or the lowest thereofsee hereinafter for details) about that strut axis 22. The bending stiffness essentially refers to the Young Modulus (E.sub.S) of the material of the strut times the inertia (I.sub.S) of the geometry of the strut cross-section. Each node 40 connects to plurality of struts 20, with each strut 20 being located between two adjacent nodes 40. All struts 20 that connect to a same node 40 have the respective strut axes 22 intersecting with each other at an axis intersecting common point 24, as seen in FIGS. 2 and 3.

[0059] Each node 40 includes a main body 42 located adjacent (or circumscribing in the case of inter-strut nodes (see FIGS. 2 and 4-6), as opposed to base nodes 40 (see FIG. 3) used to secure the structure to a panel 12, other equipment or the like) the axis intersecting point 24, and, for each strut 20 connecting thereto, an arm 44 connecting to and extending from the main body 42 along the respective strut axis 22 and away from the axis intersecting point 24. Each arm 44 has a node (proximal) end 46 attaching to the main body 42, a strut (distal) end 48 connecting to the respective strut 20 and a midsection 50 extending between the node end 46 and the strut end 48. The midsection 50 includes a neck portion (or striction) 52 having a (lowest) neck cross-sectional bending stiffness (E.sub.NI.sub.N) (Young's or elastic modulus E.sub.N? area moment of inertia I.sub.N of the neck portion 52) about the strut axis 22 being less than about 20%, typically less than about 10%, and preferably less than about 5% of the corresponding strut cross-sectional bending stiffness (E.sub.SI.sub.S) about the strut axis 22. Essentially, the neck portion 52 has a bending stiffness (E.sub.NI.sub.N) sufficiently low to significantly release structural moments at the hub end 46.

[0060] Alternatively, since the length (L.sub.S) of each strut 20 (as shown in FIG. 9) may considerably vary, as opposed to the length (L.sub.N) of the neck portion 52 (as shown in FIGS. 5 and 7), the ratio of the area bending stiffness per unit length (E.sub.NI.sub.N/L.sub.N) of the neck portion 52 is alternatively less than about 600%, typically less than about 300%, and preferably less than about 150% of the corresponding tube bending stiffness per unit length (E.sub.SI.sub.S/L.sub.S).

[0061] Preferably, the main body 42 and the plurality of arms 44 integrally form a single node piece 40. As better seen in FIGS. 4 and 5, the strut end 48 of each arm 44 typically releasably connects to a strut end-fitting 26, preferably using an axial threaded connection or the like.

[0062] Typically, in order to be able to connect each strut 20 between the corresponding two nodes 40 that are already positioned relative to one another, the strut 20 includes a first (or primary) section 28 having first 30 and second 32 primary ends and a second (or secondary) section 34 having first 36 and second 38 secondary ends. The second primary end 32 axially slidably connects onto the first secondary end 36 (in a telescopic manner) between a first (insertion) configuration 60 in which the first primary end 30 and the second secondary end 38 are positionable adjacent the corresponding strut end-fittings 26 respectively for axial positioning of the strut 20 there between (as shown in FIGS. 7 and 8), and a second (installed) configuration 62 in which the first primary end 30 and the second secondary end 38 axially overlap (via axial slidable insertion of one over the other, preferably of the strut end 30, 38 over the end-fittings 26) the corresponding strut end-fittings 26 respectively for securing thereto with the first 28 and second 34 sections securing to one another with a remaining overlap there between (as shown fully installed in FIG. 9). Once in the second configuration 62, all parts are typically bonded together. Typically, at least one, and preferably all of the struts 20 are telescopic within a spaceframe structure 10.

[0063] In order to ease the analysis and the assembly of the spaceframe structure 10, all cross-sections of the arms 44, end-fittings 26 and strut sections (or tubes) 28, 34 are preferably axisymmetric or circular, with the end-fittings 26 and tubes 28, 34 being typically cylindrical and preferably hollowed or tubular in shape.

[0064] In order to control the overall coefficient of thermal expansion (CTE) of each strut 20, the first 28 and second 34 section are typically made of different first and second materials having first and second axial CTEs, respectively, and have predetermined first L1 and second L2 lengths. The first and second lengths, along with the first and second CTEs are determined to provide the predetermined combined axial coefficient of thermal expansion of the strut 20, typically taking all materials into consideration between the two intersection points 24 positioned onto the axis 22 of the strut 20, i.e. including the portions of the main bodies 42, the two arms 44 and the two end-fittings 26 connecting to the same strut 20 and all bonding adhesives (with the respective lengths along the strut axis 22). This tuning of each strut CTE, preferably with all strut CTEs of a same assembly being essentially identical and preferably around zero, enables to easily control the Thermo-Elastic Distortion (TED) behavior of the spaceframe structure 10 over temperature. Typical materials used for the different strut sections 28, 34 and end-fittings 26 could be different composite materials, different steels, titanium and other alloys and the like. Depending on the selected materials for each strut 20, the lowest area bending stiffness of the two sections 28, 34 and end-fittings 26 will be considered as being the strut bending stiffness (E.sub.SI.sub.S). In other words, the bending stiffness of a strut 20 is essentially the lowest bending stiffness over the entire length of the strut.

[0065] During the manufacturing/assembly sequence of the spaceframe structure 10, when a strut 20 is being assembled and connected at its ends 30, 38 to the two nodes 40 via the end-fittings 26, each node 40 that is not a base node 40 typically includes a tooling interface/grappling feature 64, extending from the main body 42 (similarly to an arm 44), that is typically used to interface with a robot or the like (not shown) which acts as a positioning device, as better shown in FIGS. 4-6. The tooling feature 64 is also typically used as an alignment reference feature, attachment point for thermal blankets (not shown), or the like.

[0066] In FIG. 10, there is shown another embodiment 10 of a spaceframe structure in accordance with the present invention, in which the structure 10 including a plurality of nodes 40 (partially illustrated) and struts 20 supports an antenna reflector 14.

[0067] Although not illustrated, one skilled in the art would readily realize that, without departing from the scope of the present invention, the struts 20 could be made out of only one or more than two sections 28, 34 of different materials if required, and that spaceframe described within is not limited to spacecrafts and/or antennas as described as the preferred embodiments. Furthermore, in the embodiments 10, 10 illustrated and described hereinabove, the arms 44 are preferably integrally made out of the same piece of material (via machining, 3D-printing and the like) of the main body 42 and attached to (bonding, screwing and the like) the end-fittings 26, but could be, without departing from the scope of the present invention, either different pieces than the main body 42 and the strut end-fittings 26 and connected thereto, or be integral with the end-fittings 26 only (not the main body 42).

[0068] Although the present invention has been described with a certain degree of particularity, it is to be understood that the disclosure has been made by way of example only and that the present invention is not limited to the features of the embodiments described and illustrated herein, but includes all variations and modifications within the scope of the invention as hereinabove described and hereinafter claimed.