NASA CASE NO.

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The invention disclosed in this document resulted from research in aeronautical and

space activities performed under programs of the National Aeronautics and Space

Administration. The invention is owned by NASA and is, therefore, available for

licensing in accordance with the NASA Patent Licensing Regulation (14 Code of

Federal Regulations 1245.2).

To encourage commercial utilization of NASA-owned inventions, it is NASA policy to

grant licenses to commercial concerns. Although NASA encourages nonexclusive

licensing to promote competition and achieve the widest possible utilization, NASA

will provide the necessary incentive to the licensee to achieve early practical

application of the invention.

Address inquiries and all applications for license for this invention to NASA Patent

Counsel, Langley Research Center, Code 212, Hampton, Virginia 23681-0001.

Serial No.: 08/325,723

10/14/94 LaRC

(NASA-Case-LAR-15136-1) JOINT FOR

A VARIABLE GEOMETRY TRUSS AND

METHOD OF CONSTRUCTING SAME Patent

Application (NASA. Langley

Research Center) 18 p

N95-14138

Unclas

G3/39 0029849

LAR 15136-1 - 1- PATENT APPLICATION

JOINT FOR A VARIABLE GEOMETRY TRUSS

AND METHOD OF CONSTRUCTING SAME

Origin of the Invention

5

The invention described herein was made by a U.S. Government

employee and may be manufactured and used by or for the government for

governmental purposes without the payment of any royalties thereon or

therefore.

Background of the Invention

Field of the Invention

10 This invention relates in general to deployable truss beam structures,

and specifically, to a joint suitable for a variable geometry truss able to

statically or dynamically move, in a controlled way, one end with respect to the

other end.

Description of the Related Art

15 Deployable truss beam structures that can maneuver in a serpentine

manner, i.e., are adaptive, are particularly useful in space-borne applications,

such as a robot manipulator, a berthing device between spacecraft, joints in a

crane or boom, and as a support structure for other moveable structures.

Space-based deployable structures, however, must be transported into space by

20 rocket driven vehicles, such as the U.S. space shuttle, where storage space is
LAR 15136-1 -2- PATENT APPLICATION

limited. In order for a deployable truss beam structure to be useful on such

missions, it must be possible to collapse it into a compact pacl;age for

transportation, and to extend it to its fully extendedlength during usein space.

Examples of prior deployable trussesinclude the two-axis gimbal and

5 geodesictrusses. However, two-axis gimbal trussesare limited in terms of the

load they cansustain and deployablegeodesictrussesare not capable of lateral

motion. A deployable truss beam structure that is maneuverable in a

serpentine manner is disclosed in a June 1985 paper entitled "Deployable

Controllable Geometry Truss Beam" by Marvin D. Rhodes and Martin M.

10 Mikulas. The Rhodes/Mikulas truss consists of cross-longeronsand battens.

The cross-longeronsareof fixed length and attach one comer of a three batten

triangle to the next plane defined by another three batten triangle. The length

of every other batten triangle can independently vary in length creating a

variable geometry truss. When the variable length battens are telescoped from

15 the fully extended position to the fully dosed position, the truss goesfrom a

completely collapsed to a fully deployed position. By changing the length of

the variable length battens, the truss can be maneuvered in a serpentine

manner. Based on the rotational requirement of the joints in the

Rhodes/Mikulas truss, two different types of joints are required which limits

20 the useability of the truss.

Summary of the Invention

25

Accordingly, it is an object of the present invention to provide a joint

for a variable geometry truss which allows the truss to statically or dynamically

move, in a controlled way, one body with respect to another body.

It is another object of the present invention to provide a single joint
LAR 15136-1 -3- PATENT APPLICATION

suitable for use at every joint location in a variable geometry truss.

It is another object of the present invention to provide a truss joint

having significant load capability.

It is a further object of the present invention to provide a simple type

5 of joint structure for avariable geometry truss.

It is still a further object of the present invention to provide a method

for constructing a joint for a variable geometry truss.

These and other objects are accomplished by a joint for a truss having

battens and longexonscomprising a first joint for pivotally connecting at least

l0 two battens forming a pivotal axis, and a secondjoint connected to said first

joint for connecting at least two longerons such that each longeron has at least

two axes of rotational freedom.

These and other objects are further accomplished by a method for

constructing a joint of a truss comprising the steps of pivotally connecting a

15 first and second batten to form a joint having a pivotal axis, and connecting

a first and second longeron to one side of the joint such that the first and

second longeron has three axes of rotational freedom, the intersection of each

axis of rotation of the first and second longeron lying on the pivotal axis of the

joint.

20 Brief Description of the Drawings

25

The present invention and the objects achieved by it will be understood

from the description herein, with reference to the accompanying drawings, in

which:

FIG. 1 is an isometric view of a simplified first embodiment of the

invention in a fully deployed variable geometry truss.
LAR 15136-1 -4- PATENT APPLICATION

FIG. 2 is an isometric view of a simplified first embodiment of the

invention as used in a variable geometry truss deployed in a serpentine

manner.

FIG. 3 is a lateral cross-sectional view of a joint for a variable length

5 batten in accordance with the first embodiment of the invention.

FIG. 4 is an isometric view of a second embodiment of the invention in

a fully deployed variable geometry truss.

FIG. 5 is an isometric view of an alternate joint according to the first or

second embodiment of the invention.

10 FIG. 6 is a lateral cross-sectional view of a joint according Fig. 5.

Detailed Description of the Preferred Embodiments

FIG. 1 is an isometric view of a variable geometry truss 10 having a joint

16 according to a first preferred embodiment of the invention. FIG. 1 is

simplified to show only those elements necessary for an understanding of the

I5 invention. A variable geometry truss is comprised of three components: a

plurality of fixed length longerons 14, a plurality variable length battens 12,

and a plurality of joints 16. Three variable length battens 12 are connected

together by the joints 16 to form a triangle. Depending on the application and

the length requirement, one or more such triangles are formed and connected

20 together by the fixed length longerons 14. In the example, as shown in FIG.

I, and as discussed herein, three such triangles are formed by two end triangles

and a center triangle. Each end triangle of variable length battens 12 is

connected to the center triangle by six fixed length longerons 14 arranged in

a so-called "Steward platform" configuration by the joints 16. In other words,

25 each point of the variable length batten I2 in each end triangle is connected
LAR 15136-1 -5- PATENT APPLICATION

by fixed length longerons 14 to two points of the adjacent variable length

battens triangle. Each point in the center triangle is connected to two other

triangles by four fixed length longerons 14.

Each variable length batten 12 can be independently lengthened and

5 shortened through the use of a hand-cranl_ 22. The hand-crank 22 is attached

to an inner rod 30 (see FIG. 3) of the variable length batten I2 through a cage

25 which forms a main pivot joint, having a main pivotal axis, with bracket 26

of another variable length batten 12. A yoke 18 is pivotally connected to the

outside of cage 25. The center triangle has two yokes 18, one on each side of

10 the joints 16. The yoke 18 rotates about the same pivotal axis as the bracket

26 in the cage 25. Each yoke 18 is provided with a rotatable rod 20 which

rotates perpendicularly to the rotation of yoke 18 forming a universal joint

having two degrees of rotational freedom. Two fixed length longerons 14 are

pivotally connected to each rotatable rod 20 by an end bracket 28. In the first

15 preferred embodiment of the invention, the end bracket 28 is free to rotate in

a direction perpendicular to the rotation of both the rotatable rod 20 and the

yoke 18 thereby providing each fixed length longeron 14 with three

intersecting degrees of rotational freedom. At one end of each fixed length

longeron 14 is a revolute joint 19 which allows rotation about the longitudinal

20 axis of the longeron 14.

FIG. 2 is an isometric view of the variable geometry truss 10 deployed

in a serpentine manner. The variable length battens 12 allow the orientation

of one end triangle with respect to the other end triangle to be changed in a

controlled manner. The length of each variable length battens 12 is controlled

25 by rotating the hand crank 22. By rotating the hand crank 22, an inner

threaded rod 30 is made to rotate against a threaded joint 24 connected to an

outer rod 29. Thus, the length of each variable length batten 12 can be
LAR 15136-1 - 6- PATENT APPLICATION

precisely controlled to displace the end triangles of the variable geometry truss

10 in both a vertical and lateral manner.

FIG. 3 is a lateral cross-section view of a variable length batten 12 with

joint 16. The hand crank 22 is connected to the inner rod 30 via a bolt 22b.

5 The inner rod 30 extends through the cage 25 and inside the outer rod 29.

The outer rod 29 is capped with the threaded joint 24. Threads 23 on the

inner rod 30 engage the threads on the threaded joint 24. A bracket 26 is

connected to the opposite end of the outer rod 23. The bracket 26 has two

end arms 27. Each end arm 27 is provided with a hole 27a to allow

10 attachment to the cage 25 of an adjacent variable length batten 12. The cage

25 of the variable length batten 12 is provided with holes 25a for pivotally

connecting, about the same axis, the yoke 18 and the end arms 27 of another

variable length batten 12 via bolt 25b. The yoke 18 is provided with opposing

holes 18a for attachment of the rotatable rod 20 via bolts 20b. The rotatable

15 rod 20 is provided with a throughhole 20a, intersecting the pivotal axis of the

yoke 18, for pivotally attaching the end brackets 28 of the fixed length

longerons 14. The cage 25, the bracket 26, the yoke 18, and the rotatable rod

20 form the joint 16.

The joint 16 pivotally connects two variable length battens 12 about a

20 main pivotal axis. The joint 16 further connects at least two fixed length

longerons 14 such that each fixed length longeron 14 has three intersecting

axes of rotation. At one end of each fixed length longeron 14 is a revolute

joint 19 which allows rotation about the longitudinal axis of the longeron 14.

FIG. 4 is an isometric view of a variable geometry truss with a joint 16

25 according to a second embodiment of the invention. FIG. 4 is simplified to

show only those dements necessary for an understanding of the invention. In

the second embodiment of the invention, the variable length battens 12 are
LAR 15136-1 -7- PATENT APPLICATION

provided with motors 32 to allow for automatic lengthening and shortening of

the variable length battens 12. The variable length battens 12 are lengthened

and shortened by the motor 32 via a standard ball screw mechanism (not

shown). It will be recognized by one sldlled in the art that other mechanisms

5 may be used, such as pneumatic or hydraulic actuators. It will also be

recognized that the invention according to the first embodiment can be

automated by replacing the hand crank 22 by an automatic drill-like

mechanism. One advantage of using the ball screw mechanism in the variable

length batten 12 is that the inner rod 30 is not required to extend through the

10 joint 26, and thus allows the use of a much more compact joint structure.

In the second embodiment, as shown in FIG. 4, the variable geometry

truss 10 is only provided with one triangle of variable length battens 12. A

pair of fixed end plates 34, upon which various structures can be attached, is

provided to form end planes for the variable geometry truss 10. The fixed

15 length longerons 14 are connected to the end plates via joints 38 which

provide two degrees of rotational freedom. In this configuration, the fixed

length longerons 14 can be attached to the rotatable rod 20 via a fixed-angle

bracket 36 which restricts the movement of the fixed length longerons 14 by

maintaining a constant angle between them. Due to the limited range of

20 available motion in this configuration, the joint 16 is provided with restriction

plates 42 to prevent over-extension of the variable geometry truss.

FIG. 5 is an isometric view of an alternate joint 16, constructed in

accordance with the first or second preferred embodiment of the invention.

As shown in FIG. 5, the joint 16 is configured to allow for multiple planes of

25 variable length batten triangles by allowing rotation as between the fixed

length longerons 14, similar to the first embodiment as shown in FIG. 1. In

this configuration, a bracket 45, forming the main pivot joint of joint 16, is
LAR 15136-I -8- PATENT APPLICATION

provided to rotatably connect the end brackets 26 of two variable length

battens 12 with two yokes 18 via a common center pin 44. Each yoke holds

a rotatable rod 20, via bolt 48, whose axis of rotation is perpendicular to and

intersects with the centerline of center pin 44. The fixed length longerons 14

5 are rotatably connected to the rotatable rod 20 via a bolt 50 whose axis of

rotation intersects the axis of rotation of center pin 44. For use in the second

embodiment, a restriction plate 42 is attached to adjacent yokes 18 to cause

the variable length battens 12 to rotate simultaneously about the center pin

44. This in turn causes the battens 12 in the adjacent batten planes to become

10 fixed length battens of equal length.

As can be seen in FIG. 5, the variable length battens 12 are driven by

a motor 32 via a belt 52. The motor 32 is held in place via a bracket 54. The

variable length battens 12 are provided with an expansion joint 46 which

protects the gap between the inner rod 30 (not shown) and the outer rod 29,

15 allowing for deployment in environmentally hostile situations.

FIG. 6 is a lateral partial cross-sectional side view of the joint 16 in

accordance with Fig. 5. An axis of rotation 56 of the common centerpin 44

lies perpendicular to and intersects with an axis of rotation 58 of the rotatable

rod 20 (not shown). Because the variable length battens 12 are activated via

20 motors 32, the joint 16 is compactly designed using easily machined parts.

The use of motors 32 to automatically adjust the length of the variable

length battens 12 enables the use of remote controllers for deployment in

environmentally hostile situations. The remote controllers can be embodied

in computerized controls that automatically adjust the relationship between

25 the end planes of the variable geometry truss 10.

In all of the embodiments of the joint 16 for the variable geometry truss

10, according to the preferred embodiments of the invention described above,
LAR 15136-1. -9- PATENT APPLICATION

the variable length battens 12 and the fixed length longerons 14 share a

common axisof rotation 56. Further, the axisof any other degreeof rotational

freedom provided to the fixed length longerons 14 preferably intersects at the

samepoint on the common axisof rotation 56. This common axis of rotation

5 56 is provided by the structure of joint 16. While two specific embodiments

have been described, it will be recognized by one sldlled in the art that other

configurations can be used. Specifically, any joint that provides rotations

about two axes, just as if there were an actual two-axis gimbal operating at the

joint, can be used. The embodiments of the invention provide a single joint

I 0 for variable geometry truss that can be retracted compactly for storage and

transportation, and has excellent structural stability during and after

deployment, while displaying great dexterity.

Numerous modifications and adaptations of the present invention will

be apparent to those sldlled in the art. Thus, the following claims and their

15 equivalents are intended to cover all such modifications and adaptations which

fall within the true spirit and the scope of the present invention.

What is claimed is:
LAR 15136-I

Abstract of the Disclosure

PATENT APPLICATION

5

10

A joint and a method of constructing a joint for a variable geometry

truss having a variable number of planes of variable length battens connected

together in a triangular configuration, each plane being connected by six fixed

length longerons in a Stewart platform configuration. The variable length

battens allow the orientation of one end plane of the variable geometry truss

to be changed to the other end plane in a controlled manner by selectively

adjusting the lengths of the variable length battens. A main pivot joint

pivotally connects two battens about a pivotal axis. A universal joint is

pivotally connected to the main joint such that the pivotal axis of the universal

joint is coextensive with the pivotal axis at the main joint. Two longerons are

pivotally connected to the universal joint. Each longeron is thereby provided

with three intersecting axis of rotation. Each longeron may include a revolute

joint, allowing rotation about the longitudinal axis of the longeron.
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