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ment has not, in the past, seemed consistent with a struc- FIGURE 4 is a sectional view transverse to the axis of
ture which would be reliably bolted prior to release. In the bolt and nut system, taken at the transverse plane
the present invention, however, the segments are so housed indicated in FIGURE 2 by the arrows 4-4; and,
within a ·hollow actuating piston that they form a struc- FIGURE 5 is a perspective view of the conical tele-
turally rigid system with the telescoping conical system, 5 scoping system, only two segments out of four being
but, upon actuation, are able to move radially from a shown, in order to make the illustration more revealing.
thread-engaging position to a position in which the seg- In FIGURE 1, a bolted structure indicated generally
ments nest with the structure of the interior of the piston. by the numeral 10 is seen to be comprised of a lower plate
The foregoing type of operation is achieved by a re- or bolt-head part 11 surmounted by an upper plate or nut-
lease system which operates in a two-step sequence, al- IO held part 12, which are attached to one another by means
though even more steps can be added in more complex of an ordinary soc~et head bolt 13 (see FIGURES 2 and
systems. The conical telesooping system is not acted upon 3), which sets into an explosive nut 14.
until there has been sufficient longitudinal actuation to The explosive nut 14 has housed within its principal
permit the segments to be moved outward into nesting part a body 15 which may be considered as having an
position by this telescoping action. After said initial longi- 15 axis in its structure co-axial with the bolt 13 and extending
tudinal actuation, and only after it, does the telescoping from a ,release end 16 (see FIGURE 2) to a pressure
action begin. end 17.
As a result of the novel structure outlined in a general As already mentioned, it is usually desired to mount
way in these introductory paragraphs, the invention the explosive nut 14 permanently on the nut-held part
achieves the following and other objects and advantages. 20 12, usually by a mounting flange 18 held in position by
The device may be constructed as either reusable or screws 19 received in threaded bores 20.
not reusable. Where economy or some such consideration The outer or upstream end of the housing 14 which
may dictate, it can be made so that the segments are de- has been designated herein as pressure end 17 is
formed in the process of being both radially outward and designed to accommodate a suitable pressure source,
locked out. On the other hand, if a reusable device is 25 such as the explosive squib 21, which would ordinarily
desired, a few changes in the design, obvious to those be electrically actuated by wires 22, connecting to foot
skilled in the art of strength of materials, makes it pos- receptacle 23. Inside the squib means 21, the charge is
sible to design segments which are moved outwardly into hermetically sealed, by solder, or by other suitable seal-
a nesting position without any deformation. Of course, ing means, for protection against moisture, etc. Also, if
careful control over the charge employed in the explosive 30 desired, the squib may be encircled by a squib O ring
squib must be exercised. 24, seen in section in FIGURE 2, for resisting escape of
The present invention is not concerned with the partic- explosion gases from within the housing 15 by way of
ular types of propulsive charges, burning initiation space around the squib 21.
char:ges, electrical ignition means, electrical bridge wires, The sectional views of FIGURES 2 and 3, taken in
hermetic sealing, or the like, which may be employed, 35 connection with transverse sectional view of FIGURE 4,
although the present development of the explosive nut and the perspective view of FIGURE 5, reveal that the
art provides the designer with almost any set of character- bolt threads 29 are engaged by an internally threaded
istics he may desire, and the limits are mostly upon the sleeve identified generally by the numeral 30, but seen
abilities of the mechanical design which he pmduces. to be comprised of four quarter segments 31, 32, 33, and
In the present design, any choice of a variety of squibs 40 34, only segments 31 and 32 being shown in the perspec-
may be threadably mounted in the pressure end of the tive view of FIGURE 5.
body of the device. The interior of the body 15 is seen, in FIGURES 2
In the device of the present invention, an explosion pre- and 3, to provide a cylindrical chamber 40 which is
senting a peak pressure of 2500 lbs. or more may be co-axial with bolt 13, of substantially large; diameter
readily contained. The amount of explosion gases required 45 than bolt 13, and extends from a bolt receiving opening
for actuation are so small that complete actuation can be 42 at the release end, to an enclosed pressure chamber
achieved by only a short movement of the actuation piston 43 at the pressure end.
within the cylindrical chamber of the explosive nut body. A piston 44 is reciprocable within the cylinder 40
In a typical space application, for example, these gates between an upstream bolted position in which pressure
are extremely hot at the moment of actuation; however, 50 chamber 40 is relatively small, as seen in FIGURE 2,
in the low temperatures of outer space, they quickly cool to a downstream release position in which the pressure
down and the escape pressure rapidly falls off. It may be chamber volume has increased as indicated by 40a in
that sealing is not ahsolutely perfect; however, the amount FIGURE 3.
of gas which escapes at the moment of peak pressure is A locking ring 45 is threadably received in the release
extremely trivial, and as cooling takes place, the pressure 55 end 42 of the cylinder 40, and serves several purposes
falls and an equilibrium condition is reached without any to be described hereinafter, but including limiting the
gas discharge sufficient to damage solar cells in the vicini- release movement of piston 44 as indicated in FIGURE
ty. Or, if the explosion takes place inside of a sealed cabin, 3. It will be noted that piston 44 is comprised of a pres-
very little of the explosion gases leak out to contaminate sure end 46 with a downwardly depending sleeve 47,
the air therein. 60 within which the building and release conditions are
The foregoing and other features of the invention, and established. Also, piston 44 is preferably provided with
its general and preferred form of construction may be sealing means such as an O ring 48 housed in exterior
best understood from the following description of one annular groove 48a.
specific embodiment. It will be seen from the sectional view of FIGURE
The described embodiment is illustrated in the accom- 65 2 that the threaded segment assembly 30 is held into
panying drawings, in which: engagement with the bolt threads 29 by mating abutting
FIGURE 1 is a perspective view of fragments of a nut- structures on the exterior walls of the segments 31 to
held part attached to the upper surface of a bolt-held part, 34, and the interior walls of sleeve 47. In this particular
the explosive nut being seen from the exterior, mounted embodiment, this structure is comprised of a pair of
on said nut-held part by screws; 70 annular external shoulders 51 and 52 on the threaded
FIGURE 2 is a partial section taken through the ex- segment assembly 30, and a mating pair of internal
plosive nut and the bolted structure at the longitudinal annular shoulders 53 tnd 54 in the interior wall of piston
axial plane indicated by the arrows 2-2 in FIGURE 1; sleeve 47.
FIGURE 3 is the same view as FIGURE 2, but as seen However, it will be appreciated that variations in this
after explosion and release has ocourred; 75 abutting structure can be used, so long as it is capable