Development and characteristics of extensible dipole antenna using deformable tubular metallic strip elemen

Hoblin, L. E.

English

NASA Technical Reports Server

REPLY TO 
ATTNOF: G P  
NATIONAL AERONAUTICS AND SPACE ADMINISTRATION 
WASHINGTON, D.C. 20546 
MEMORANDUM 
 TO : KSI/Scient i f ic  & Technical Information Divis ion ~, 
A t t n :  M i s s  Winnie M. Morgan 
FROM : GP/Office of A s s i s t a n t  General 
Counsel f o r  Patent Matters 
SUBJECT : Announcement of NASA-Owned 
U.S. Pa ten t s  i n  STAR 
I n  accordance with t h e  procedures contained i n  t h e  Code G P  
t o  code US1 memorandum on t h i s  sub jec t ,  dated June 8, 1970, 
t h e  a t tached  NASA-owned U.S. pa t en t  is being forwarded for  
abs t r ac t ing  and announcement i n  NASA STAR. 
The following information is  provided: 
U.S. Patent No .  : 3,299,431 
Corporate Source : Keltec Indus t r i e s ,  I n c ,  
Supplementary 
Corporate Source 
NASA Pa ten t  C a s e  No.  : 
Gayle Parker 
--. ~ - 
\ 
(THRU) A /  
Enclosure : 
Copy of Pa ten t  N 
0 
9 
I w 
0, 
' C  
(CATEGORY) $ (NASA CR OR TMX OR AD NUMBER) 
LL 
https://ntrs.nasa.gov/search.jsp?R=19710019503 2020-03-17T03:14:50+00:00Z
L. E. HOBLIN 3,299,43 1 
UNFURLABLE STRUCTURE INCLUDING COILED STRIPS 
THRUST LAUNCHED UPON TENSION RELEASE 
Filed Feb. 10, 1964 
Jan. 17, 1967 
i 
w 
21 
BY 
Fzy 2 
INVENTOR 
Lester E tloblzn 
AG€N 7 
3,299,43 1 United States Patent Office Jan. 17, 1967 
1 
3,299,431 
UNFURLABLE STRUCTURE INCLUDING COILED 
STRIPS THRUST LAUNCHED UPON TENSION 
RELEASE 
Lester E. Hoblh, Fairfax County, Va., granted to National 
Aeronautics and Space Administration under the pro- 
visions of 42 U.S.C. 2457(d) 
Filed Feb. 10, 1964, Ser. No. 343,760 
8 Claims. (Cl. 343-823) 
This invention relates in general to antennas of the 
whip variety and in particular to extensible whip antennas. 
Since the introduction of unfurlable whip antennas by 
R. B. Blackmore, to whom U.S. Patent No. 2,157,278 was 
granted on May 9, 1939, many have endeavoured to per- 
fect a metallic strip sufficiently resilient to permit exten- 
sive deformation of the strip over extended periods of 
time without deterioration of the resilient properties 
thereof. Now that a metallic strip having such resilient 
properties is available, unfurlable whip antennas have 
been recognized as practical mechanical structures and 
considerable effort has been expended to devise means 
for transposing the deformation and the extension. 
In many extensible antenna applications, particularly 
in spacecraft applications, weight, size and power re- 
quirements are especially critical. Often environmental 
factors must be controlled in such applications, and it may 
be necessary, for example, to employ nonmagnetic mate- 
rials exclusively. Moreover, it is generally essential that 
the structure afford a significant rigidity and durability in 
its extended state. Most prior art devices which require 
both extension and retraction anchor the deform reel in 
the manner disclosed by Blackmore, and the metal strip 
is extended and retracted by rotation of the reel, usually 
by means of an electrical motor system. In the case of 
an extension without retraction, either end may be an- 
chored, of course, and one prior are device anchors the 
deform unit, a hollow cylinder wherein the furled metallic 
element is stored and employs a sideways ejection such 
that the fully extended antenna is pivoted into final posi- 
tion. Another more complex prior art device anchors 
the free end of each of two metallic elements which are 
spun upon ejection and the deform unit, a unique reel 
with conical side cheeks is adapted to serve as a centrifugal 
brake acting differentially to control the rate of ejection. 
Each of these prior art extensible antenna ejection 
devices has found some utility in selected applications 
but few, if any, devices of this variety meet the demands 
of outer space. In particular, it has been found that the 
pivot features of one prior #art device often presents an 
electrical and a mechanical problem in reliability. Also, 
the unique reel assembly, necessary to the free extension 
unit described above, introduces a weight complication 
which precludes its application in many instances. 
I t  will be 'appreciated that a lightweight, reliable ex- 
tensible antenna is needed and woutd be welcomed as a 
significant advancement of the art. Accordingly: 
It is an object of this invention to provide an extensible 
dipole antenna which is relatively lightweight. 
It is another object of this invention to provide an ex- 
tensible dipole antenna in which the ejection means may 
be of nonmagnetic material. 
It is also an object of this invention to provide an ex- 
tensible dipole antenna wherein no readjustment of ele- 
ment orientation is required upon full extension of the 
antenna. 
It is a further object of this invention to provide an 
extensible dipole antenna with a rigid fixed electrical con- 
nection upon extension. 
It is still another object of this invention to provide an 
extensible dipole antenna wherein a positive ejection of 
the antenna elements is assured. 
2 
Other objects of the invention will become apparent 
upon a more comprehensive understanding of the inven- 
tion for which reference is had to the following specifica- 
tion and drawings wherein: 
FIGURE 1 is a detailed showing of one embodiment of 
this invention in readiness for unfurlment. 
FIGURE 2 is a showing of the embodiment of FIG- 
URE 1 in its unfurled state. 
Briefly, the device of this invention is an extensible 
10 dipole antenna employing a naturally tubular metallic 
strip element which is deformable into a transverse coil 
form and is sufficiently resilient to revert back to its 
natural configuration. The device affords a positive action 
ejection of the strip element in coil form by release of a 
15 loaded compression spring means whereby the resilience 
of the strip is implemented. 
6 
Referring now to the drawings, 
The embodiment of this invention shown in FIGURE 1 
includes a base and center column section 11 which is 
20 secured by conventional means to the support member 
12 which may be, for example, the spear boom of a 
missile intended for satellite application. 
In accordance with the invention, at least three pairs 
of transverse members, the pair 13 and 14, the pair 15 
25 and 16, and the pair 17 and 18, having end sections, 13a 
and 14a, 1% and 16a, 17a and 18a, respectively, are dis- 
posed in parallel relation to substantially define a plane 
and are attached to the center column section 11 such 
that the end sections of each pair are substantially equi- 
30 distant the center column section 11 and each member is 
in substantially perpendicular relation with respect 
thereto. It will be appreciated, of course, that in the de- 
picted embodiment the pairs of members, 15 and 16, and 
17 and 18, may in actuality be ,a single continuous mem- 
35 ber of conductive or nonconductive material which passes 
through the center column section. The pairs of mem- 
bers 13 and 14, however, are connected to the dipole 
elements 21 and 22 which, of course, must be electrically 
isolated. Consequently, if a single continuous member is 
40 to be substituted for the pair 13 and 14, the member must 
be of a nonconductive material. 
As shown in the embodiment of FIGURE 1, the pair of 
members 15 and 16 may be longer than the pair of mem- 
bers 13 and 14, and the pair of members 17 and 18 may 
45 be longer than the pair of members 15 and 16. In this 
length relationship, the coiled dipole elements 21 and 22 
may be nested slightly beneath the respective member of 
pair 17 and 18 and substantially adjacent the respective 
end section of pair 15 and 16 by detent means 23 and 
It will be appreciated that various forms of detent 
means may be employed with the device of this invention 
to contain the dipole element in coiled form. In the illus- 
trative embodiment, each detent means comprises a string 
55 section secured at one end as indicated at 31 to the re- 
spective end sections 17a and 18a with the other end 
tied to an interrupter means 32 such that upon interrup- 
tion the string section no longer restrains the coiled dipole 
element, and it is free to unfurl. 
In this embodiment, the interrupter means 32 com- 
prises a link of fuseable wool 33 in contiguous relation 
with the fuseable wire. Firing means 34 may be an elec- 
trical source, as shown, which effectively ignites the WOO] 
65 to separate the loop and thus disable the detent means 23 
and 24 simultaneously upon the activation of switch 
means 34 by remote control means, not shown. 
In accordance with the invention compression springs 
35 and 36 are disposed about the transverse members 15 
Since the no ,load length of each 
of the springs 35 and 36 is substantially greater than the 
length of its respective transverse member, it will be seen 
50 24, respectively. 
6o 
70 and 16, respectively. 
3,299,431 
3 
that with the coiled dipole element in readiness as shown, 
the springs 35 and 36 are under considerable tension. 
Thus, when the detent means 23 and 24 are disabled, the 
force of the springs 35 and 36 ejects the coiled dipole 
elements simultaneously. 
The coiled dipole elements 21 and 22 are electrically 
and mechanically secured at their free end to respective 
members of the pair of transverse members 13 and 14. 
As in the device described by Blackmore in his afore- 
mentioned patent, the metallic strips, which form each 
of the dipole elements 21 and 22, have a natural circular 
cross-section with a substantial overlap. In addition, 
these metallic strips are characterized by a high resiliency 
which permits nonpermanent deformation into coil form. 
This type of material is generally of the alloy variety and 
may be formed by various manufacturing techniques gen- 
erally including heat treatment at one or more stages. 
FIGURE 2 is illustrative of the device of FIGURE 1 
after the detent means has been disabled and the elements 
21 and 22 have been unfurled. In this illustration, the 
unfurlable antenna device is disposed in the nose end of 
a rocket or other space vehicle and the elements 21 and 
22 are extended in substantially perpendicular relation to 
the general axis of the vehicle. It will ‘be noted that the 
compression spring means are missing in the embodiment 
depicted in FIGURE 2. These ejection means may be 
ejected in the course of the coiled member release or 
otherwise. It is, of course, within the purview of this dis- 
closure to employ suitable detaining means, not shown, 
in the event release of the ejection means would be un- 
desirable. Further, in this illustration the elements 21 
and 22 and the central support member to which they are 
attached are shown without electrical insulation means 
therebetween. It will be appreciated that some electrical 
separation fs essential to most applications of the device 
of this invention and that this may be accomplished as 
shown in the embodiment of FIGURE 1 or otherwise. 
The dipole elements 21 and 22 may be coiled either in 
the direction relative to  the natural circular cross-section 
shown in the drawing or in the opposite direction, pro- 
vided, of course, the strip material has sufficient resiliency. 
It has been found, however, that coiling in the direction 
shown in the drawing is to be preferred in most applica- 
tions. 
It will be appreciated that the depicted compression 
sprinlg means for initial ejection of the coiled elements 21 
and 22 is not essential to the operation of the device and 
that various other spring loaded means for ejection se- 
cured by the detent means shown or by other suitable 
means, for example, a cooperative latching meohanism, 
are within the purview of this disclosure. 
Likewise, it is not essential that the detent means be 
released by remote control. In the event direct control 
means are employed, it will be appreciated that a wide 
variety of means may be employed to release the detent 
means. 
Furthermore, it is not essential to this invention that 
two members be released or that the release of members 
occurs simultaneously. Thus it is within the purview of 
this disclosure to employ a separate detent means for each 
coiled member and to cause the release of members in 
any selected order, if desired. 
Moreover, the device of this invention is not restricted 
to  extensible antennas nor to electrical applications in 
general, and the unique concept embodied therein is ap- 
plicable to a wide variety of uses including decorative dis- 
play systems, direction indicator means and the like. 
Finally, this invention is to be limited only by the scope 
of the claims appended hereto. 
4 
What is claimed is: 
1. An unfurlable structure comprising a central sup- 
port member, a plurality of ribbon like flexible strip ele- 
ments each having a coiled portion and a free end portion 
5 disposed with the free end thereof directed toward said 
central support member; a like plurality of rod means 
extended from said central support member in selected 
directions; means for attaching said free end of each of 
said strip elements to a respective rod means in said plu- 
10 rality thereof such that the axis of each coiled portion and 
its respective rod means are in a transverse relation; each 
of said elements having a selected length and width and 
characterized by a stable circular cross-section with a 
substantial overlap and by a resiliency such that said 
15 stable circular cross-section may be readily restored sub- 
sequent to deformation of said strip element into coil 
form; detent means adapted to maintain said coiled por- 
tion of said elements at a selected distance from said cen- 
tral support member; tension loaded ejection means inter- 
20 posed said coiled portion of each of said strip elements 
and said central support member and adapted to provide a 
thrust force therebetween upon tension release; and de- 
tent release means adapted to free said coiled portion of 
said strip element such that said tension release occurs. 
2. An unfurlable structure as defined in claim 1 where- 
in sard flexible strip elements are adapted as antenna ele- 
ments. 
3. An unfurlable structure as defined in claim 2 where- 
in said plurality of flexible strip elements is an even num- 
30 ber plurality, said strip elements are paired and each pair 
is disposed in opposite relation about said central support 
member and said detent release means are adapted to re- 
lease respective elements of each of said pairs thereof in 
time coincidence such that said thrust force of respective 
35 ejection means directed toward said central support means 
is substantially counter-balanced. 
4. An unfurlable structure as defined in claim 2 where- 
in at least a portion of said tension loaded ejection means 
are compression spring means and said detent means are 
40 adapted to maintain said spring means under compres- 
sion. 
5. An unfurlable structure as defined in claim 3 where- 
in at least a portion of said tension loaded ejection means 
are compression spring means and said detent means are 
45 adapted to maintain said spring means under compres- 
sion. 
6. An unfurlable structure as defined in claim 5 where- 
in said detent means are strap means. 
7. An unfurlable structure as defined in claim 6 where- 
60 in respective strap means of respective strip elements in 
each pair thereof are interlinked and said detent release 
means is operative to interrupt the linking therebetween. 
8. An unfurlable structure as defined in claim 7 where- 
in said detent release means is a fuseable material in close 
65 proximity to said strap means of respective strip elements 
in each pair such that ignition of said fuseable material 
affords interruption of said linking therebetween. 
References Cited by the Examiner 
UNITED STATES PATENTS 
2,085,585 6/1937 Hamilton _ _ _ _ _ _ _ _ _ _ _  343-877 
2,212,128 8/1940 Richter _ _ _ _ _ _ _ _ _ _ _ _  343-902 
2,569,810 10/1951 Hamel et ai. _ _ _ _ _ _ _ _  343-877 
25 
60 
65 FOREIGN PATENTS 
800,738 5/1936 France. 
ELI LIEBERMAN, Primary Examiner. 
R. F, HUNT, JR., ExurniKr? 


Unfurlable structure including coiled strips thrust launched upon tension release Patent

Abstract

Similar works

Full text

Available Versions

NASA Technical Reports Server