US20040128940A1

US20040128940A1 - Lightweight truss joint connection

Info

Publication number: US20040128940A1
Application number: US10/325,412
Authority: US
Inventors: Mark LaForge
Original assignee: Individual
Current assignee: Maxar Space LLC
Priority date: 2002-12-19
Filing date: 2002-12-19
Publication date: 2004-07-08

Abstract

A unique structural system particularly suitable for space based satellite manufacturing is provided which comprises a lightweight truss system, for example, having at least a primary structural tube carrying a uniquely shaped bracket conforming to the periphery of the tube and bearing a flange and secondary strut elements which are connected to the bracket.

Description

I. FIELD OF INVENTION

This invention is directed generally to a novel construction system and, more specifically, to a lightweight truss system.

II. PRIOR ART

Various tubular truss systems are known in the prior art as, for example, U.S. Pat. No. 4,624,599 issued Nov. 25, 1986 to Piasecki entitled Multi-Tubular Truss Joint and Method of Joining Tube Ends wherein a structural joint and method of making the joint employing an end portion of each of a plurality of tubes is partially flattened into an elongated, oval annular shape of a cross sectional contour so that the flattened ends of the tubes can be telescopically nested within one another, and the tubes are arranged to have their axes coplanar to intersect at the joint node with the tube flattened ends in a telescopically, mutually nesting relationship to each other. A splice plate extends into the interior of the nested array of flattened tube ends and has upper and lower surfaces in an underlying, closely adjoining relation to interior surfaces of each of the tube flattened end portions, and fastening means are provided which tightly clamp together the nesting, flattened tube ends and splice plate contained therewithin.

In U.S. Pat. No. 6,170,560B1 issued Jan. 9, 2001 to Daily et al entitled Truss Structure Design there is disclosed “A method for producing a mold for making an integrally formed three-dimensional truss structure, containing outer top and bottom plane surfaces thereof comprising interconnected rod segments integrally formed at their points of intersection on the outer top and bottom surfaces, the top and bottom surfaces also integrally joined together through additional interconnected rod segments passing through an integrally formed intersection, wherein the additional interconnected rod segments passing through the integrally formed intersection form a three-dimensional continuous array of triangles.”

A truss bracket is described in U.S. Pat. No. 5,653,079 issued Aug. 5, 1997 to Loeffler et al entitled Truss Bracket which is described as “A unitary truss clip for interconnecting adjacent truss members comprising a base, first and second top flanges extending from the base in opposite directions, first and second bottom flanges extending from the base in opposite directions and nail receiving openings in each of the top and bottom flanges.”

In U.S. Pat. No. 5,575,129 issued Nov. 19, 1996 to Goto entitled Connector for Truss Structure there is described a connector for a truss having a high shearing resistance and a superior safety in which the connector can be inserted into and fixed in advance to the abutted surfaces of the structural members to be connected, wherein adjustment of orientation of the connector is not needed, workability and installing workability can be remarkably improved and further the inserted and fixed connector can be prevented from being pulled when the connector is connected to the structural member. “The connector of the present invention includes the flat-plate like connecting

plate

2, a hollow tubular member 3 having one end fixed to each of both surfaces of the connecting plate 2 and opened at the other end, a branch pipe engage part 7 communicated from a side of the tubular member 3 facing to the connecting plate up to the hollow part, a hollow branch pipe 8 having the engage part 9 removably engaged with the branch pipe engage part 7 formed at at least one end thereof, and a fixing hole 12 formed at a predetermined part of the connecting plate 2.”

None of the aforementioned truss structure systems provide connection through a shaped bracket which conforms to the periphery of the tube mechanism described, nor bears a flange to provide further connection. There is, thus, seen to be a continuing need for a lightweight truss system which is devoid of the above noted deficiencies.

III. OBJECTS OF THE INVENTION

It is therefore an object of this invention to provide a simple standard connection between tube elements that allows complex, three dimensional truss structures without custom designated connections.

It is a further object of this invention to provide a uniquely shaped bracket which is applied to and conforms to the periphery of a tubular structure so that tube elements can be assembled in a very wide range of angles and orientations.

Yet again another object of this invention is to provide a unique lightweight truss system employing a uniquely shaped bracket carrying a flange.

IV. SUMMARY OF THE INVENTION

These and other objects of the instant invention are accomplished generally speaking by providing a lightweight truss system, for example, comprising at least a primary structural tube to which is applied a uniquely shaped bracket conforming to the periphery of the tube and bearing a flange and secondary strut elements which are connected to said bracket.

This unique structural system finds particular application to the space-based satellite manufacturing sector. Applications may include antenna support assemblies requiring lightweight, stiff and dimensionally stable structures and other applications include a variety of types of terrestrial truss structures including roof trusses, towers, etc.

This unique combination of a uniquely shaped bracket with primary tube and secondary strut elements may be used to create very complex truss structures. The ends of the struts can employ conventional, for example, “Clevis” type fittings and may be attached to a bracket by, for example, a “shear pin.” The brackets may be attached to primary tubes in the truss with a structural adhesive, by welding for metallic tubes, or by other mechanical means. These brackets may be easily arranged in the truss to provide a wide variety of angles and orientations for the smaller elements.

The system of the instant invention resides in the combination of three elements, i.e., the primary tube, strut to tube brackets, secondary strut elements, and a uniquely shaped bracket carrying a flange. The construction of this basic shape lends itself to ease of manufacturability, with holes drilled as desired for various connections. The material, wall thickness, and size of the bracket can be customized to fit a wide range of the tube sizes and strengths. Different sizes of the bracket can be combined to create large, complex, or simple and small truss structures depending on the specific application.

This system is particularly applicable to provide a stable support for components with mass in a particular, fixed position. In operation, these structures are generally fixed and static, although they may be employed as a rigid part of a dynamic system or mechanism.

In a typical application, for example, in a commercial satellite program: 1) a basic arrangement is determined including position and orientation of the components that need to be supported; 2) a primary structural tube element(s) is placed to meet stiffness objectives of overall structure(s); 3) intermediate struts are added including orientation and position of strut to tube brackets; 4) strut angles are determined as to azimuth and elevation at each node; and 5) each node is designed by selecting and placing the strut to tube brackets.

V. BRIEF DESCRIPTION OF THE DRAWINGS

While the present invention has been described in terms of the specification and accompanying preferred embodiments, it may be more specifically understood with regard to the accompanying drawings in which: [0016]
FIG. 1 depicts the basic truss structure employing lightweight truss structure of the instant invention. [0017]
FIG. 2 depicts a tube to strut bracket embodiment of the truss structure system of the instant invention. [0018]
FIG. 3 depicts the various embodiments relating to connection of the lightweight truss system of the instant invention. [0019]
FIG. 4 depicts a cross section of a multi-strut connection of the lightweight truss system of the instant invention. [0020]
FIG. 5 depicts an embodiment wherein a clevis type fitting is depicted.[0021]

VI. DETAILED DESCRIPTION

In FIG. 1 there is depicted an embodiment employing a clevis type fitting ([0022] 3) which connects to the primary tube (2) which carries the tube to strut bracket (1).
Referring to FIG. 2, there is seen a flange for attachment to struts ([0023] 4), optional flanges placed at desired angles depending on strut angles (5), mating surface to primary tube (6) having an inside radius slightly larger than outside radius of primary tube. The bracket (7) inside radius can range largely to accommodate a wide variety of primary tube sizes. The α1 and α2 angles depicted of flange to edge (8) angle can range from ˜10 degrees to 180 degrees. The bracket may also be fabricated to encircle the complete circumference of the tube. The thickness of flange (9) can range accordingly to accommodate size and strength requirements of application. The height (10), designated as “h”, of flanges can range accordingly to accommodate size and strength requirements of a particular application. The length (11), designated as “l”, of the bracket can range accordingly to accommodate size and strength requirements of a particular application. The profile of the flange (12) can vary accordingly to accommodate multiple struts at various angles as well as the shape of the bracket (13) and the thickness of the bracket (14).
In FIG. 3, there is seen the strut to tube bracket ([0024] 1), the primary tube (2) and the strut with clevis type fitting (3) as previously depicted in FIG. 1. The strut to tube bracket mating surface to primary tube (6) is also depicted as previously seen in FIG. 2. The thru-hole (15) in the bracket is seen to connect to a clevis fitting of the strut with Pin (16). The bracket to the strut is connected to the primary tube at the mating surface (17) of the primary tube with, for example, mechanical fasteners, welding or with structural adhesive.
In FIG. 4 there is seen the strut to tube bracket ([0025] 1), primary tube (2), strut with clevis type fitting (3) as previously seen in the recited drawings above with multi-flange bracket (18) attached to the outer surface of brackets mounted directly to the primary tube. Numerous azimuth and elevation angles for struts may thus be obtained and connection (19) between the bracket and primary tube can be accomplished by mechanical fasteners or with structural adhesive or other suitable conventional methods as previously recited.
In FIG. 5 there is seen the primary tube ([0026] 2) and strut with clevis type fitting (3) as previously set out in the above recited drawings with node (20) providing multiple connections.
Thus it is seen that complex three-dimensional truss structures may be built with the lightweight truss system of the instant invention evidencing a minimum of design and fabrication effort. Truss structures with regular and repeated geometry are particularly suited for this system. Truss structures with repeated geometry and uniform angles and other dimensions will result in nodes with identical strut angles, and consequently standard strut to tube brackets. FIGS. 1 and 5 are examples that depict the use of the truss system of the instant invention in conventional applications. [0027]
Although the inventive system may be applied to uniform structures resulting in higher numbers of standardized and lower costs, non-uniform and irregular truss structures may also be enhanced employing this system. [0028]
The unique shape of the strut to tube bracket ([0029] 1) has a circularly curved base (6) and one or more flanges (4,5), that are oriented radially with respect to the primary tube centerline. Additionally, the mid-plane of each flange is coincident with the center line of the primary tube (2). Shape and size variations of the strut to tube bracket dimensions are tailored depending on the particular application. These would include the base radius (7), base profile (13), base thickness (14), base length (11), flange angles (8), flange profile (12), flange height (10), flange thickness (9), hole number and location (15). The base profile of the bracket (13) may be a rectangular, rounded or a facetted polygon or other suitable shape. The cross-sectional shape of the bracket is particularly suitable to mass production using the extrusion manufacturing process.
The material choices for the strut to tube bracket ([0030] 1), primary tube (2) and secondary strut element (3) may be any suitable material depending on application and manufacturing factors. Typical materials for use in the primary tube, secondary strut element and strut to tube bracket include steel, aluminum, graphite reinforced plastics among others. Any suitable method of attachment may be employed in the system of the instant invention. Typical methods include welding and mechanical fastening. It should be noted that plastic tubes and bonded attachment methods may also be employed for low load, low cost applications. Where higher performance requirements are present, graphite fiber reinforced plastics are employed for the tubes and struts, and titanium may be employed for the brackets. Graphite materials and titanium are materials best suited for space applications where dimensional stability is often a requirement.
Thus it is seen that when the truss system of the instant invention is employed in either uniform or non-uniform structures, the basic shape of the strut to tube bracket ([0031] 1) may be varied to accommodate a large range of applications, primary tube (2) sizes, and applied loads. The thickness and profile of the bracket flange (4) may be standard for regular truss structures, or modified for non-regular trusses. The number of flanges (4) of the bracket may be increased (5) to accommodate high numbers of struts at node.
The preferred strut arrangement will provide strut centerlines, or “lines of action”, coincide at a common point at the centroid ([0032] 21) of the bracket mating surface (6), for a given bracket (1) as seen in FIG. 2. This minimizes load path eccentricities that reduce stiffness and strength. Additionally, all brackets (1) at a given node should be located such that their centroids (21) are all at the same elevation on the primary tube (2).
While the present invention has been particularly described with respect to a preferred arrangement of elements, it will be understood that the invention is not limited to these particular elements and/or arrangement described in the preferred embodiments or in the final structures depicted in the drawings. On the contrary, it is intended to cover all alternatives, modifications and equivalents as may be included within the spirit and scope of the invention defined by the appended claims. [0033]
In particular, the scope of the invention is intended to include, for example, those structures wherein refinement of the local attachment including internal reinforcement of the tube locally at the nodes will enable lighter weight, higher performance structures. This truss system may be employed in power transmission, radio towers, roof trusses, cranes, and amusement park rides among others. [0034]

Claims

What is claimed is:

1) A lightweight truss system which comprises:

a) A primary structural tube,

b) a shaped bracket which conforms to the periphery of the primary tube bearing a flange and

c) secondary strut elements which are connected to said shaped bracket.

2) The system as defined in claim 1 wherein the material of construction for said primary structural tube is selected from a group consisting of: steel, titanium, aluminum and plastic including graphite reinforced plastics.

3) The truss system as defined in claim 1 wherein said shaped bracket may be constructed from materials selected from the group consisting of: steel, titanium, aluminum and plastic including graphite reinforced plastics.

4) The system as defined in claim 1 wherein said secondary strut elements which are connected to said shaped bracket are comprised of materials selected from the group consisting of: steel, titanium, aluminum and plastic including graphite reinforced plastics.

5) A system for providing lightweight truss systems having dimensional stability for space applications comprising:

a) a primary structural tube

b) a shaped bracket which conforms to the periphery of the primary tube bearing a flange

c) and secondary strut elements which are connected to said shaped bracket to provide said lightweight truss system.

6) The system as defined in claim 5 wherein said structural tube is comprised of graphite reinforced plastic.

7) The system as defined in claim 5 wherein the shaped bracket is comprised of titanium.

8) The system as defined in claim 5 wherein the secondary strut elements are comprised of graphite reinforced plastic.