Deployable geodesic truss structure

A deployable geodesic truss structure can be deployed from a stowed state to an erected state. The truss structure includes a series of bays, each bay having sets of battens connected by longitudinal cross members which give the bay its axial and torsional stiffness. The cross members are hinged at their mid point by a joint so that the cross members are foldable for deployment or collapsing. The bays are deployed and stabilized by actuator means connected between the mid point joints of the cross members. Hinged longerons may be provided to also connect the sets of battens and to collapse for stowing with the rest of the truss structure.

BACKGROUND OF THE INVENTION 
This invention relates to a truss structure for deployment from a collapsed 
state to an elongated erected state. 
DESCRIPTION OF THE PRIOR ART 
Truss structures which can be carried or stowed as a relatively small 
package and deployed to a full erected state are required in many 
applications. For example, efficiently packaged deployable boom structures 
are necessary for many space satellite applications, especially large area 
space structures. Other typical applications for deployable boom 
structures include space cranes, remote manipulator arms, masts to support 
and accurately position feed horns for large antennas, to deploy and 
provide tension in large solar arrays, or to serve as structural 
components of a space operations center. Deployable truss structures may 
also find use in scaffolding, light service deployable bridges, 
cherry-picker or fire truck uses, among others. 
Various deployable structures are known but only a few such structures have 
the capability of serving a structural function when only partially 
deployed. Moreover, the known structures must be deployed and retracted 
parallel to the longitudinal axis of the truss structure. 
SUMMARY OF THE INVENTION 
Accordingly, one object of the present invention is to provide a deployable 
geodesic truss structure which is efficiently packaged yet can be deployed 
or retracted in a serpentinous manner so as to be highly maneuverable. 
Another object of the present invention is to provide a deployable geodesic 
truss structure which has the capacity of acting as an articulating 
structure, remote manipulator arm, or the like. 
Another object of the present invention is to provide a deployable geodesic 
truss structure having foldable axial longerons for providing axial 
stiffness to the truss which is automatically deployable along the axis 
without articulation. 
A still further object of the present invention is to provide a deployable 
geodesic truss structure which uses deployment energy stored in actuators 
during the collapsed or stowed state. 
In accordance to one aspect of the present invention, we provide a 
deployable geodesic truss structure for movement between a collapsed or 
stowed state and an elongated erected state. The structure comprises a 
series of bays. Each bay is formed by connecting sets of battens by 
longitudinal cross members which give a bay its axial and torsional 
stiffness. The cross members are hinged at their mid point by a joint so 
that the cross members are foldable for deployment or collapsing. The bays 
are deployed and stabilized by actuator members connected between the mid 
point joints of the cross members. The truss structure can be formed using 
a number of geometrical relations for the battens, actuators and cross 
members, but, according to this aspect of the invention, the battens and 
actuators each form the legs of an equilateral triangle and the cross 
members join the sets of battens so that two intersecting cross members 
form two isoceles triangles with the battens. 
According to another aspect of the invention, we provide a deployable truss 
structure having a first equilateral triangle formed by three battens 
connected at their ends by first, second and third joint means; a second 
equilateral triangle similar to the first but spaced from the first 
triangle and having fourth, fifth and sixth joint means; six cross members 
connected so that a first cross member extends from the first to the sixth 
joint means, a second cross member extends from the third to the fourth 
joint means, a third cross member extends from the first to the fifth 
joint means, a fourth cross member extends from the second to the fourth 
joint means, a fifth cross member extends from the second to the sixth 
joint means and a sixth cross member extends from the third to the fifth 
joint means; the first and second, third and fourth and fifth and sixth 
cross members being connected by seventh, eighth and ninth joint means, 
respectively; three actuator means connected at their ends by said seventh 
through ninth joint means, the actuator means each having an elongated 
member and means to vary the length of the member whereby the position in 
space of the first through ninth joint means can be varied from a compact 
stowed position to an erected position. 
In one embodiment of the invention, the first through sixth joint means 
each comprise a joint body, means for connecting from two to four batten 
ends to the joint body and means for connecting the ends of two cross 
members to the body. Further, the seventh through ninth joint means each 
comprise a hinge body, ball and socket joint means at opposite ends of the 
body, means on said ball and socket for movably connecting with the 
intermediate ends of the cross members, and means for movably connecting 
the ends of two actuator means to the hinge body. Further, the battens and 
cross members are hollow and tubular and each actuator means has a rod 
telescoped within a tubular section. 
In another embodiment of the invention, three hinged longerons are 
connected respectively between the first and fourth, third and sixth and 
second and fifth joint means. Further, hinge means are provided at the mid 
point of the length of the longerons so that the longerons can fold at the 
hinge means for stowing or erecting the structure. 
Other objects and advantages of the invention will be evident to those 
skilled in the art from the following description taken in connection with 
the accompanying drawings wherein there is shown by way of illustration 
preferred embodiments of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 illustrates a two bay deployed geodesic truss structure 10 according 
to one embodiment of the present invention. Each bay B is formed by 
connecting sets of battens 11 by longitudinal cross members 12 which give 
the bay its axial and torsional stiffness. The cross members 12 are hinged 
at their midpoint at points 14, 15 and 16. The bays are deployed and 
stabilized by actuator means 13 connected between the mid point joint 
means 17 of the cross members 12. In FIG. 1, the battens 11 form an 
equilateral triangle and the cross members 12 that control the deployed 
height are hinged at their center. The cross members are connected so that 
a first cross member extends from the first joint means J1 to the sixth 
joint means J6, a second cross member extends from the third joint means 
J3 to the fourth joint means J4, a third cross member extends from the 
first joint means J1 to the fifth joint means J5, a fourth cross member 
extends from the second joint means J2 to the fourth joint means J4, a 
fifth cross member extends from the second joint means J2 to the sixth 
joint means J6 and a sixth cross member extends from the third joint means 
J3 to the fifth joint means. As seen in FIG. 1, nine joint means (J1-J9) 
are used in the bay. 
The geodesic truss structure is fabricated from tubular members and, in the 
collapsed state (See FIG. 5), the stack height of the package is nominally 
controlled by the diameter of the cross members and the members of the 
actuator means. The packaging efficiency (ratio of deployed height to 
stowed height) is a function of design requirements. However, packaging 
efficiencies of twenty or greater should be easily obtainable. 
FIG. 2 illustrates a typical joint means 18 for connecting the ends of two 
battens 11 and the ends of four cross members 12. The battens 11 are fixed 
to the joint means and are not required to rotate. The cross members 12 
are rotatably mounted to rotate (as shown by arrows) about a line along 
the batten axis. As best seen in FIG. 2, the joint means has a joint body 
19, means 20 for connecting two batten ends to the body and means 21 for 
connecting the ends of four cross members to the body. As illustrated, the 
means for connecting the batten and cross member ends are cylindrical 
members adapted to be insertable into the hollow interior of the ends of 
the battens 11 and cross members 12. 
FIG. 3 illustrates a typical joint means 22 for connecting the intermediate 
ends of the cross members 12 and the ends of two of the actuator means 13. 
The necessary mobility of the cross members 12 is obtained by a ball and 
socket 23 and the actuators are hinged at 24 on the socket body 25. 
Loading eccentricities to the joint means 22 which are introduced through 
the top and bottom cross members are reacted by bending of the actuator 
means 13. FIG. 3 shows the joint means 22 including a hinge body 25, ball 
and socket joint means 23 at opposite ends of the body, means 26 attached 
to the ball and socket joint means for connecting with the intermediate 
ends of the cross members 12, and means 27 for movably connecting the ends 
of two actuator means 13 to said hinge body by way of hinges 24. In the 
figure, the means for connecting the cross members and actuator means are 
cylindrical members 26 and 27 adapted to be insertable into the hollow 
interior of the ends of the cross members 12 and the tubular end of the 
actuator means 13. 
FIG. 4 is a view similar to FIG. 1 of a deployed geodesic truss structure 
of one embodiment of the present invention. FIG. 4 demonstrates the 
maneuverability of the present invention. In the figure, a plane P1 
through the three battens 11 at the top is canted about 60' to the plane 
P2 through the three battens 11 at the base resting on the ground. By 
changing the length of the actuator means 13, a point in the center of the 
equilateral triangle formed by the battens at the top of the two bay 
structure may be placed at virtually any position within the conical 
region where the vertex of the cone is at the base. When the actuator 
means 13 are locked, the truss structure 10 has a high axial and torsional 
stiffness at any position within the same conical region. The 
maneuverability of the disclosed embodiment provides the advantage that 
the embodiment may be used as part of an articulating structure or remote 
manipulator. 
FIG. 5 is an illustration of the embodiment of FIG. 1 when it is in the 
collapsed or stowed state. As illustrated, the actuator means 13 have been 
extended to the full length L, and the equilateral triangles defined by 
the battens 11 overlie one another. Finally, the cross members 12 have 
been rotated and pivoted into a substantially adjacent plane with the 
battens 11 and other cross-members 12. For the sake of clarity, like joint 
means in comparison to FIG. 1 have been marked with a prime to show the 
substantial change in the location of the first through ninth joint means 
between the deployed and stowed state. 
FIG. 6 is a diagramatic view of another embodiment of the present 
invention. The embodiment follows the one shown in FIGS. 1-5 but also 
includes hinged longerons 28 along the length of the structure. By using 
the longerons 28, the truss deploys automatically along the truss axis and 
does not articulate. The use of longerons along the truss axis contribute 
substantially to the axial stiffness. The longerons 28 hinge at their mid 
point 29 to fold for collapsing the truss structure. The truss may be 
deployed by releasing energy stored in elastic bands within the actuator 
means 13. When the longerons 28 are fully deployed with the hinges locked, 
the actuator means 13 also latch to form a stiff, stable structure. With 
the cross members straight (cross members lie in the plane formed by the 
longerons and battens) the alternate embodiment is similar to the double 
laced lattice column but differs from that column by the use of stored 
energy in the actuator means. An additional advantage results if the cross 
members are not straight (e.g. the cross members are slightly longer so 
that the mid point joints lie outside the plane formed by the longerons 
and battens). In that case, the distribution of axial load between the 
longerons and cross members can be controlled. Also, any free play in the 
truss structure due to joint tolerances will be removed if the actuator 
means have sufficient stored energy to pretension the longerons. The 
latter will result in a truss structure that can be deployed repeatedly in 
a gravity-free environment and the position of the end of the truss 
structure relative to the base will be the same after each deployment. 
Although particular embodiments of the invention have been described and 
illustrated herein, it is recognized that modifictions and variations may 
readily occur to those skilled in the art, and, thus, it is intended that 
the claims be interpreted to cover such modifications and equivalents.