Note: Descriptions are shown in the official language in which they were submitted.
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Self-Lockin~ Threaded Connectin~ l)e.vicc
F~An~rnnn~1 of thf~ TnvP.nti~n
I . Field of the Invention
The present invention relates to self-locking threads and threaded c~."..- ~;. ..~, and
more particularly to seTf-locking threaded connection devices that may be discrete fasteners
intended to secure two or more work pieces together and comprised of a comhinAtir n of a
threaded bolt, cylinder, stud, shank or screw mated with a conlpl;.~ y threaded nut or
hole, or that also may be an integral part of some other deviGe, such as the threads on the
end of the arrn that screws into the threaded ...:... ,I,lin, ,1 A- y hole in the torso of a toy
soldier.
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i2~ 94 ~ 64
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2. I)~cnription of r h~ !lt~l Art
Locking threaded fasteners and tbreaded çonnecting devices of a wide variety of
types are available which reduce the tendency of male, generally cylindrical, threaded
c. .."~ n. .a~ from altering their position in relation to their ~VII~IJVI~dillg female threaded
~omron~.nf, thereby reducing the tendency of such threaded fasteners and threaded
connecting devices to loosen and come apart in response to vibration, expansion,
contraction amd other movement. Many such fasteners function in this regard by increasing
friction between the otherwise mated threads of the male and female çr.mr~ nte or
between the fastener and the parts joined by the fastener. Examples include: loçk washers,
tooth washers, blind thread bores filled with resilient inserts such as disclose.d in U.S. Pat.
No. 5,078,562 issued to DeMaitre on January 7, 1992, and screw thread profiles that jam or
deform when tightened such as disclosed in U.S. Pat. No. 5,242,252 issued to Harle on
September 7, 1993. Other such fasteners and cv ~ c function by increasing the friction
between the engaging surfaces of the head of the male component and worl:. pieçe, or
beh~een the female component and work piece such as disclosed in U.S. Pat. No.
4,290,4~9 issued to Nakae on September 22, 1981. In all such al~ , the increased
friction makes rotation more difficult between the male and female ~,vll.lJon~ , thereb
preventing inadvertent releare or loosening of the male and female r~f~mpnnente A
drawback of all these approaches is that the male and female ~ n. ~ can loosen at aoy
axial pressure or tension less than that required to strip the male component out of the
~ WO96101379 r~ U.~ o20
9'4164
female component. Since the threads in each case fall away in the direction of a~ial pressure
or tension, a portion of such pressure or tension is translated into a rotational force tending
to loosen the r~ Also, fasteners using these approaches generally require high or
increased torque to install, or mar the joint surface, or are not reusable, or require greater
loads to be effective than is desirable to apply to some joints. Self-locking a~ such
as cotter pins, lock wires, and nut assemblies comprising a first working nut and a second
locking nut part as disclosed in U.S. Pat. No. ~,154,~60 issued to Copito on October 13,
1992, have the drawback of requiring additional installation effort.
Therefore, there is a need for threads, threaded fasteners, and threaded devices: (i)
that will not come loose under loads equal or less than the fastener supports, (ii) that can be
easily installed using cv~ iull~l tools, (iii) that employ torque values appreciably closer to
those torque values only necessary to clamp together the wu~k,~ (as opposed to
requiring higher torque values to provide increased resistance against loosening), and (iv)
that can be installed as easily as standard fasteners. The present invention addresses these
drawbacks in known prior threaded fasteners and threaded devices and meets these needs
with a novel thread design which can be forged, rolled, stamped, or otherwise applied to
threaded fasteners and threaded devices using c~ ..io.lol techniques. Improved threaded
fasteners and threaded devices may therefore be lu~ uL~,lul~d at close to the cost of
traditional locking threaded fasteners and devices.
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Brief D~c~ri,ption of the Drawin~e
Figure lA is a side view of the invention in an assembled state.
Figure lB is a bottom view of the invention in an assembled state showing the
flexible thread projections of the female component interacting with the thread recesses of
the male ~
Figure 2A is a side view of adjacent thread rotations of the invention in an
assembled state and showing one fiexible thread projection in an un ocked state as applied
to maie and female fastening c.~
Figure 2B is a side view of adjacent rotations of the invention irL an assembled state
increased in size to show detaiis of one flexible thread projection of the female component
meshed with a recess of the ma'e component.
Figure 3A is a top view of the female fastening ~,UlLl~ 'Li flexible thread
according to a preferred ~ ,l ,o~i; . ,1 of the present invention.
Figure 3B is a side view of the female fastening ~ JV..~ flexible thread
according to a preferred . . . ,1"~ ,. . s of the present invention.
Figure 3 C is a bottom view of the femaie fastening component with its flexible
thread according to a preferred ~ "l,o~ of the present invention.
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1 7 ~ 1 6~
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Figuse 3D is a half cut away side view of tile female fastening component with its
flexible thread according to a preferred -- S,o~l S of the present invention~
Figure 4A is a side view of adjacent rotations of an altemative r~ oll 11 of the
invention in an assembled and unlocked state, where the recesses are located at the root of
the recess locking thread, and extending into the core of the male fastening component
between adjacent thread rotations of the male comrl-n~.nt and the projections ara located
on the crest of the internal flexible thread segment.
Figure 4B is a side view of adjacent rotations of an alternative ~Illbod;..~ t of the
present invention in an assembled and urlocked state as applied to male and female
fastening .":.. "1 ,.,.... ,1 ~ where the projections of the flexible thread segment press axially
against the recesses of the male thread. .
Reference ~ rnl~riqlc jn thP l::)rawin~pc
11-- male component
12 -- female component
21-- fernale ~U~ UII~ flexible thread segment
22 -- projections of the flexible thread segment
25 -- voids in flexible thread segment
26 -- poshioning tabs of the flexible thread segment
31 -- recess locking thread
32 -- recesses of the recess locking thread
wo 96/0~379
"J4 1 l~4
Drt~ Description of the Preferred E."l~od;,...,.,l
Figure I A shows a side view of a setf-locking threaded conn~rt;nn~ in an assembled
state, comprising a male component (I l) having a first novelly formed thread (31)
~hereafter referred to as the "recess locking thread") and a female component (12) having
applied to it a second novelly formed thread (31) (hereafter referred to as the "projection
locking thread," more fuliy shown in Figure 2A). The projection locking thread is aligned
on the female component so that its flexible projections (22) press up against the thread of
the male component. The projection locking thread is either attached to the female
component in a manner tbat enables its projections to rdex axially or radially, or the
projections are formed in a manner that enables them to flex axially or radially. The female
component is typically a threaded nut, bore, or hole. The male component is typically a
threaded bolt, cylinder, stud, shank or screw. The projection locking thread and the recess
locking thread are designed to work together so that, as the male component is being
screwed into or out of the female component, the two threads engage each other in a slovel
ma~mer (hereafter referred to as "meshing") and thereby lock~ In the drswings, dashed lines
indicate that a feature appears only 1~ u~t~ ly from the given perspective.
Figllre lB shows an end view of the self-locking threaded connection of Figure lA
in a meshed state. Meshing occurs when any of the projections (22) of the fiexible thread
segment (21) aiign with any of the recesses (32~ of the recess locking thread (31). When
such alignment occurs, the tension pressing the female's internal flexible thread se~ment's
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projections up against the male's thread (21) forces the aligned projection into the
~ UI ~ Ulldi;llg a.igned recess thereby meshing the threads. Once meshed, sufficient
additiona'. higher torque in either the loosenhlg or tightening direction unmeshes the
threads. The sides of the projections and recesses have a gentle enough slope so that torque
can urge the projections to slide up and out of the recesses, and thereby unmesh the threads
~hen the torque is suf.~icient to overcome the friction between the faces of the engaged
proiections and recesses and to overcome the tension pressing the fema.e's interna. flexible
thread segment up against the recess loc.;ing thread (in addition to overcoming friction
between the female's standard thread and the ma.e's thread as with standard thread
cu..fl,~... dtiO.Is~, the threads unmesh and the fastener is in an un.ocked state until a
pro~ection and a recess again a'.ign and mesh In Figures IA and IB, the flexible thread
segment (21~ flexes p~,. ,U~ I;..uk.. ly to the axis of the fastener
Figures 2A is a side view of one projection of the flexible thread segment in an
un.ocked state In Figure 2B, the projection appearing in l igure 2A is shown in greater
detail and is meshed with a recess of ~he recess locking th.ead. In the drawings, dashed lines
indicate that a feature appears only intermittently from a given perspective.
Traditional threaded fasteners subjected to dynamic loads, stress reversals or
vibration are susceptible to loosening Tightening such fasteners develops axial tensile stress
that creates frictiona. resistance to loosening between mated threads and i~etween bolt and
nut surfaces bearing against the joined materials This same tensile stress in the bolt also
encourages the mating threads to slip due to the "downward" slope of their helix angle In
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4 1 ~1 4
the current invention, for the mating threads to slip even as vibration reduces resistance, the
axial tensile stress must also lift or force the fle cible thread segment's projections out of the
male thread's recesses and to overcome any remaining friction. To push or lift a projection
out of a recers, the loosening torque resulting from tensile stress must be great enough to
overcome the naturai spring retum action pushing the flexible thread seginent's projections
into the male thread's projections. To ensure that the loosening torque is less than these
resistive forces, the combination of the flexible thread segment's projection tension, the
slope of the sides of the recesses, and the shape of the projections are in C~
engineered to create sufricient resistance to prevent inadvertently ioosening of the fastener.
In aiternative ~ . a ~, the faces of the recesses and projections can be formed
so that the projections dig into the recesses when torque is spplied in either the tightening
or loosering directions. In such ~ bod~ , the fasteners cannot be either further
tightened or loosened once meshing occurs without damaging the projection or the recess.
When the female component is used with a traditional bolt or other male component
without recesses, the fiexible thread segment presses up against the maies t'hread creating
additional resistance to loosening. When the 'dexible thread is engineered to press with
sufficient force against the thread of the male, the additional resistance prevents inadvertent
loosening in the same manner as prevailing toroue nuts such as those with nylon inserts.
Figure 3A is a bottom view and Figure 3B is a side view of the female cu~ o~ .L'~
flexible thread segment (21 of Figure IB). In the preferred r~ lo.l;.~ .1, the female's flexible
thread segment is not solid from its root to its crest for its full length A selies of voids in
~ WO96101379 ~ l q1~ r~
the filexible thread segment (2=t), formed extending from the thread crest toward the thread
root, facilitate each projection (22) ;"~ ly meshing fuliy with any recess ~32 in
Figure IB) when they aiign irrespective of the meshing state and position of the other
projections and recesses. In the preferred rll.l,o.l;.,...a the individual projections align
radialiy with the recesses, but the projections as a whole do not need to be arranged
~y~ liy with the recesses. In the preferred embodiment there are a prime number of
recesses on e.ach thread rotation, seventeen, and six projections on the flexible thread
segment. The fexible thread segment can be attached to the female component (12) in any
manner so long as the flexible thread segment aiways rotates with the female component
and cannot rotate ;".lrl,r.,fi.. ~l ly of the femaie comr~-n~nt In the preferred, r~ o~ ....t
positioning tabs (26 of Figure 3A and 3C) prevent the flexible thread segment from rotating
in relation to the rest ofthe femaie component (12) and position the flexible thread segment
so that it's projections continue in the helix path formed by the standard thread of the thread
of the female cnmr-~n~n~
Figure 4A is a side view of adjacent rotations of an aitemative ~ bo ihll~.lL of the
invention in an assembled and unlocked state. The recesses (32) are located at the root and
extend into the male CUIll~Joll~..lt ~ ~11) core between adjacent thread rotations of the recess
locking thread (31).
Figure 4B is a side view of adjacent rotations of an aitemative t mho~iml~nt of the
present invention in an assennbled and unlocked state where the projections of the internal
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-10-
flexible thread segment press axially against the recesses of the male thread. In the
~.~,.l.o ~ shown, the }ecesses (32) and the project;ons are on the following flanks. In
alternative ~IlLodi ~ they can be on the leading flanks.
While the present invention has been described with reference to certain preferred
lbodil~ 4 those skilled in the art will recogniae that various l..odirl~L;~ may be
provided. For example, there are many other embodiments ha~ing a variety of
c~,lrl~ ~ dLi("ls for the shape, angle and si~e of the projections and recesses. The recesses
can be located in the center of the thread flank instead of at or near the root. Instead of
recesses on the e:~ternal thread, projections on the external thread can be used to mesh with
the projections of the flexibls thread segment. The flexible thread segment can be more or
less than one full rotation. These and other variations upon, and mr~tl;fi~ti~ns to, the
preferred ~ "" .n are provided for by the present invention ~hich is only limited by the
following claims..
