US 3739538 A
The mast is extendible along its axis from a collapsed position to a fully extended position and is useful as an antenna mast or boom, such as may be used to support an electromagnetic wave energy reflecting surface and/or to support transmitting and receiving equipment. The mast comprises three or more longitudinal members of spring material which have been preformed with a curvature in their transverse direction and are supported by a plurality of spaced platforms. The separation between platforms is determined by the buckling load required for the longitudinal members and the material is selected as to type and size to obtain the desired spring bias. Packaging is achieved by buckling each of the longitudinal members inwardly to permit the platforms to be brought together. Mechanical stops between the platforms prevent the introduction of excessive curvature into the buckled longitudinal members. Deployment occurs by releasing the collapsed mast. The stored internal energy in the bent longitudinal members is sufficient to completely erect the mast to its fully extended position.
Description (OCR text may contain errors)
[ June 19, 1973 Rubin NON-ROTATABLY EXTENDIBLE MAST  Inventor: Charles P. Rubin, Los Angeles,
 Assignee: Hughes Aircraft Company, Culver City, Calif.
 Filed: Apr. 29, 1970  Appl. No.: 32,946
343/881, 343/DIG. 2  Int. Cl. E04h 12/10, H01q 1/00  Field of Search 52/108, 632, 641;
 References Cited UNITED STATES PATENTS 3,107,712 10/1963 Bergeretto 150/49 3,381,923 5/1968 Berry 343/881 3,564,789 2/1971 Vyvyan et a1... 52/108 1,283,152 10/1918 Gleeson et aL. 248/350 2,315,640 4/1943 Morse et al 52/108 513,269 1/1894 Knop 150/49 1,533,636 4/1925 Day 150/49 608,998 8/1898 Apthorp... 150/49 2,150,620 3/1939 Frost 150/49 2,422,913 6/1947 Leach 46/146 2,521,126 9/1950 Price 248/350 3,474,488 10/1969 Kruzich.... 52/108 3,507,485 4/1970 Bright 267/182 1,650,762 11/1927 Machin 46/146 FOREIGN PATENTS OR APPLICATIONS 659,434 3/1963 Canada 267/164 Primary ExaminerFrank L. Abbott Assistant Examiner-Leslie A. Braun Attorney-James K. Haskell and Lewis B. Sternfels  ABSTRACT The mast is extendible along its axis from a collapsed position to a fully extended position and is useful as an antenna mast or boom, such as may be used to support an electromagnetic wave energy reflecting surface and- /or to support transmitting and receiving equipment. The mast comprises three or more longitudinal mem bers of spring material which have been preformed with a curvature in their transverse direction and are supported by a plurality of spaced platforms. The sepa ration between platforms is determined by the buckling load required for the longitudinal members and the material is selected as to type and size to obtain the desired spring bias. Packaging is achieved by buckling each of the longitudinal members inwardly to permit the platforms to be brought together. Mechanical stops between the platforms prevent the introduction of excessive curvature into the buckled longitudinal members. Deployment occurs by releasing the collapsed mast. The stored internal energy in the bent longitudinal members is sufficient to completely erect the mast to its fully extended position.
2 Claims, 7 Drawing Figures PATENIEDJWS 3.739.538
SHEEIl or 2 Charles P. Rubin,
NON-ROTATABLY EXTENDIBLE MAST The present invention relates to a mast which may be extended from a collapsed position to a fully extended position without rotation or twist and which has great stiffness and extreme deployment accuracy. Such a mast is specifically useful as the central support structure on a deployable antenna (such as may be used to support an electromagnetic wave energy reflecting surface and/or to support electronic equipment, e.g., one or more feeds), an extendible boom to separate an experimental package from a spacecraft, one of several elements in a deployable complex space truss structure, and a deployable reentry decoy, although the present invention has general use as an extendible pole, boom, rod, etc., wherever such extension may be required or desired.
Extendible booms are known. One tubular construction comprises a metallic strip preformed into a circular cross-sectional shape. In its flattened condition, the strips are rolled into or onto a drum for storage and are deployed generally by some motorized mechanism. One serious disadvantage of such a tubular boom is that the outermost tip position cannot be reliably predicated and that the boom has a low tortional stiffness. Another configuration utilizes rods of Fiberglas material as the longitudinal support members and is packaged by rotating the mast which causes buckling of the rods. Crossed wires between the rods provide torsional stiffness. Upon deployment, the mast rotates, which is generally a disadvantage, especially for space anten nae, because rotation creates an undesired gyroscopic effect, such as precession and because there are elements which may be secured to the mast and which should not be rotated. To overcome this rotational problem, a relatively complex deployment mechanism is required; however, for spacecraft purposes, such a mechanism adds nonstructural weight to the entire system.
The present invention overcomes these and other problems by providinga simple structure which comprises a plurality of curved longitudinally extending elements of spring material either of a dielectric or a metal. The shape of each element is generally that of a carpenters tape. Each element is connected to the other element by platforms which are spaced along the length of the elements. To stow the mast in its collapsed position, the elements are buckled and the platforms are brought close to one another. Complete touching between the platforms is avoided by means of spacing pins to prevent bending of the elements beyond the elastic limit. To deploy the mast, the stored spring energy in the buckled elements is released. Controlled deployment is effected such as by a feeder wire secured between the ends of the mast. The deployed mast resists shear and bending loads because of the resistance of the arced transverse section of the elements to flatten out. It also resists torsion due to the shear stiffness of each element, singly and in combination.
It is, therefore, an object'of the present invention to provide an extendible mast.
Another object is the provision of such a mast which does not rotate during extension thereof.
Another object is to provide such a mast with high accuracy of deployment from a stowed or collapsed position to an extended position.
Another object is the provision of such a mast having high stiffness and a resistance to collapse.
Another object is the provision of such a mast which is simple in construction.
Other aims and objects as well as a more complete understanding of the present invention will appear from the following explanation of exemplary embodi ments and the accompanying drawings thereof, in which:
FIG. 1 is a view of one section or bay of the mast in its collapsed position;
FIG. 2 is another view of such a section in its partially extended position;
FIG. 3 is a view of the section or bay in its fully ex tended position;
FIGS. 4-6 are cross-sectional views of three different embodiments of the mast of FIGS. 1-3, FIG. 5 bein the cross-section of FIGS. 1-3; and I FIG. 7 is a perspective view of the mast useful as the central portion of an antenna having an electromagnetic wave energy reflecting surface.
Accordingly, with reference to FIGS. 1-3, 5 and 7 a mast 10 comprises a plurality of bays or sections 12, each one of which includes a plurality of elements 14 which longitudinally extend along the mast axis when the mast is in its extended position shown in FIGS. 3
- and 7 and which are secured to one another by a plurality of platforms l6 and bounded by end platforms l8 and 20. Connection between the platforms and the longitudinal elements may be by any convenient method, such as rivets, screws, adhesives, and welding and the platforms may comprise any convenient stabilizing elements, such as struts. Each element has a curvature in its transverse direction as indicated by radius 22 (see FIGS. 1-6) to provide an arced cross-section, preferably throughout its length.
A plurality of spacing pins 24 are secured to each platform and extend axially of the mast in order to prevent creasing or folding of the elements beyond their elastic limit when the mast is in its collapsed portion.
To obtain a stowed or collapsed position of the mast, each element 14 is buckled inwardly and platforms 16 are brought towards each other, the separation therebetween being maintained by pins 24. FIG. 1 represents such a collapsed position of one bay 12. Extension of the mast is shown in two steps in FIGS. 2 and 3 whereby the stored energy of the buckled longitudinal elements is released to enable each element to straighten out.
FIGS. 4 and 6 show two other configurations of the elements in quadrature and triangulation, respectively, the preferable minimum number of three being required to prevent twisting or bending of the extended mast.
FIG. 7 depicts one use of mast 10 as the central element of an unfoldable antenna. One end platform 18 is secured to a portion of a spacecraft, schematically represented by numeral 26. Secured also to a spacecraft 26 is a winding mechanism 28, such as a winch,
provided with a central opening 46 to permit extension of the mast therethrough.
Ring 40 may be of the type disclosed in copending patent application Ser. No. 590,561, filed Oct. 31, 1966, now US. Pat. No. 3,576,566, patented Apr. 27, 1971, the mesh may be of the type disclosed in copending patent application Ser. No. 9,132, filed Feb. 11, 1970 continuation of Ser. No. 590,571, filed Oct. 31, 1966, while the deployment of the mesh may be made by the inventions described in Ser. No. 590,593, filed Oct. 31, 1966, now US. Pat. No. 3,546,706, patented Dec. 8, 1970, or in Ser. No. 842,525, filed July 17, 1969, all assigned to the assignee of the present invention. It is to be understood, however, that other antennas and antenna constructions may be utilized.
In the embodiment described above, elements 14 are shown as disposed parallel to the mast axis; however, the elements may be inclined to the axis to configure the mast in a tapered disposition. In this instance, platforms 16 would be consecutively decreased in size.
Although the invention has been described with reference to particular embodiments thereof, it should be realized that various changes and modifications may be made therein without departing from the spirit and scope of the invention.
What is claimed is:
l. A foldable and unfoldable antenna mast foldable into a collapsed position and unfoldable and selfdeployable in a linear non-rotatable extension along an axis to a fully extended position comprising a plurality of bays connected in tandem, and including:
a plurality of rigid platforms spaced from each other,
the planes of said platforms positioned at right angles to the axis;
at least three elongated elements secured to said platforms, said elements positioned generally parallel to the axis when said mast is in the mast extended position to provide the linear, non-rotatable extension of the mast during deployment thereof, each of said elements being formed of a spring material and capable of being folded and buckled inwardly between adjacent ones of said platforms, said elements having a curvature normal to the axis in a cross-sectional plane in the mast extended position and being folded and buckled and under sufficient spring bias in the mast collapsed position to enable self-deployment of said mast from the collapsed position to the extended position; each said platform having a width and distance from adjacent ones of said platforms sufficient to completely enclose said elements within the widths of said platforms when said elements are folded and buckled in the mast collapsed position; and
stops secured to and between said platforms and extending parallel to the axis, said stops contacting adjacent ones of said platforms in the mast collapsed position to space said adjacent platforms from one another in the mast collapsed position and to provide space means, said stops being so positioned on said platforms as to permit folding and buckling of said elements and said space means providing space for said elements when folded and buckled.
2. An erectable member capable of non-rotatably elongating along an axis from a collapsed position to a fully extended position, comprising:
a plurality of elements of spring material, each said element having a curved cross-section and foldable into a general E-shape generally towards one another for storage of spring energy when said member is in the collapsed position and unfoldable to lie generally parallel to the axis when said member'is in the fully extended position, each said element having first portions maintained equidistant from the axis and having second portions movable towards the axis when said member is in its collapsed position and into the general Z-shape;
a plurality of stabilizing means connected to said elements at said first portions to interconnect the elements; and
spacers secured to said stabilizing means to space each of said stabilizing means from the adjacent one when said member is in the collapsed position.