Note: Descriptions are shown in the official language in which they were submitted.
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BACKGROUND ~ND SUMMARY OF THE INVENTION
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The present invention relates to a fluid-sealing nut
and in particular to an improved method of making the same.
Sealing nuts of the present type are commonly used
in the aircraft industry wherein many aircraf-t are designed with
"wet" wings which require that the fasteners utilized in the wings
form a fluid-tight seal. Currently, the most widely used type
of sealing nut in the aircraft industry comprises a nut having
an annular deformable sealing ring inserted into a counterbore
cut into the bearing surface of the nut. Typically, the sealing
ring is designed to protrude above the bearing surface of the
nut so that when the nut is torqued down against the workpiece,
the sealing ring is deformed inwardly into the threads on the
shank of the bolt thereby formin~ a fluid-tight seal.
Sealing nuts oE this type are generally made by a process
whereby a counterbore is cold formed into the bearing surface of
the nut and then an undercut is machined into the side walls of
the counterbore to provide a means for retaining the sealing ring
in place. The disadvantage of this process is that the undercut
requires a separate machining operation which slows the production
rate of the sealing nuts and hence significantly increases cost.
Moreover, as with all cutting operations, the undercut surface
creates a weakened stress point in the nut which restricts the
torque and load limits of the nut.
The present invention seeks to eliminate these disadvantages
by providing a new and improved method of making the above-described
sealing nut. In particular, utilizing the method of the present
28 invention, when the nut is initially cold formed according to
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conventional practice, a protruding ridge of excess material
is purposefully retained around the periphery o the counter-
bore. When the nut is then cold formed a second time ko
smooth the bearing surface of the nut, the excess material
is forced inwardly, thereby reducing slightly the surface
diameter of the counterbore. In this manner, a means for
retaining the sealing ring is created without requirinq a
separate machining operation and without weakening the
structure of the nut. In fact, as will subsequently be
10~ explained in greater detail, the cold forminq process of the
present invention actually strengthens the load bearing
surface of the nut. Thus, the resulting sealinq nut
produced is not only less costly to manufacture but is also
a better quality nut.
The present invention is defined as a method of
making a seal nut comprising a body having a load bearing
surface and a sealing ring disposed within a counterbore in
the bearing surface of said body, the method comprising the
steps of: forming the body of the nut; cold forming the
counterbore in the bearing surface of the body so as to retain
a circular ridge of excess material protruding above the
bearing surface around the periphery of the counterbore,
cold forming the bearing surface to 1atten the surface and
force the excess material radially inwardly; and thereafter
inserting the sealing ring into the counterbore.
Additional objects and advantages of the present
invention will become apparent from a readinq of the detailed
28 description of the
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prc~crrc~l cmbo~llmcnt whlch m:~lce rcfcrcncc to thc followlng ~ot
of dr;lwln~ In w hlch: , ,
nRlET~' D~3SCI~Ir-'TlON OIi' TTIE' l~RAWINC:S 'i
Flgurcs 1-4 illustrate the various stagcs in the manu~
facture,of a sealing nut according to the teachings of the pres~ent
~nvention;
Figure 5 is a partial cutaway o.f a complete sealing nut
manufnctured according to the present invcntion;
Fig~lre 6 is an enlargcd view of the counterbore of a
nut blank made according to conventional practice; and .
Figure 7 is an enlarged view of the counterbore of a
nut blank ma.de according to the teachings of the present invention. .
DETAIL'ED VESCE~IPTION OF TETE PREF~RRE:D EMBODIMENT
A complete sealing nut 10 made according to the present .
invention is illustrated in Figure 5. The sealing nut 10 includes a body .
comprising a base section 12 and a torque receiving section or ~Iwrench .,
pad" 14. The torque-receiving section 14 typically bears a plurality
of driving surfaces 20 which are adapted to'be engaged by a conventional
wrench. The base section 12 of the nut 10 includes a flat annular .
bearing surface 16 of expande,d dia~neter relative to the torque-receiving ,
section 14, and a taperecl portion 18 which joins the base section 12 ,
to the torque-receiving section 14. , .
-~' ~ ~~ Thc sealing nut 10 has for~necl therein a central bore . 22 having an intcrnal thread 2~. The threadcd portion 2~ of the ccntralbore 22 is substanti~llly limitcd to the torquc-receiving section 14
of the scaling nut 10, with tllc ccntral bore 22 bcm~ cnlargcd by a
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countorborc 2G 3t thc b;~sc Cn(] 12 of thc nut 10. Tl~c countcrbol ~ 2&
18 actually a two-sLep countcrborc with tha dlamctcr oî thc ccntral
borc 22 bcing Incrcased initially frora thc threadcd diamcter 24 to a .
first cnlargcd diamctcr 28 and then furthcr lncrcased to a second
S enlargcd diamctcr 30 at the base end 12 of the nut 10. Import:mtly,
it will bc noted that the final enlarged counterbore diameter 30 is
reduccd slightly at the bearing surface 16 of the nut 10 as indicated
at 32. Thc purposc of the "lip" 32, as noted prcvio~sly, is to provide
a means for retaining the sealing ring 3~1 in place. .
In particular, sealing ring 34 comprises an annular-
shaped deformable plastic material, such as teflon, that has an inner
diameter 34 slihtly larger than the threaded diameter 24 of the
central bore 22 and an outer diameter 38 substantially equivalent
to the second enlarged counterbore diameter 30. In this ma~ner, the ;
sealing ring 34 is adapted to be press-fitted into the second enlarged
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counterbore 30 so that it seats against the ledge 40 and is frictionally
secured in place by the reduced diameter of the lip 32. . .
In addition, it will be noted that the thickness of the
sealing ring 34 is substarltially greater than the depth of the second
20 enlarged counterbore 30 so that the sealing ring 3~ protrudes above
the bcaring surface 16 of the nut 10 when properly secured within
the counterbore 30. In this manner, whcn the nut 10 is torqued
down to the point where the bcaring surface 1~ contacts the workpicce, .
the protruding portion of the sealing ring 34 is deformcd inwardly .,
25 lnto thc thrcads of the bolt on wbich the nut 10 is fastened, thercby
forminL~ a fluid-tigl1t scal along thc shaoli of thc bolt. Thc dcformation
of thc ~caling ring 3~ also scrvcs thc ~ddcd purposc of locking the
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nut 10 to thc l~olt to rcaJYt looscnln~ duo to vlbr3tlon, ete.
l~cfcrr1ng now to Ii'igurcs 1-~L, thC prcfcrrcd l~ctho~l
of m~klng tho nbovc dcscribctl scallng nut 10 accord1ng to thc prcsent
lnvcntlon will now bc expl3incd. The nut blt~nks ~ uscd to matcc the
scaling nuts I0 dcscribed hcrcin arc m:lde from a metal slu¢ ~0,
herein comprised of aluminum. The slug 40 is initially cold formed
into the Sasic confi~uration of the nut blank 44 111ustrated in Figure 2
with a torque-receiving end 14 and a flanged basc section 12. The nut
blank ~1~ is thcn cold formed a second time to form the colmtcrborc 26
I0 , in the base end 12 of the nut. The bearing surface lG of the nut is also
formed during thè step so as to leave an annular ring or "lip" 42 of
- excess material protruding above the bearing surface 16 around the
periphery of the counterbore 26, 5'ypically, the driving surfaces 20
on the torque-receiving end I4 (Figure 5) are formed during this step
as well. The nut blank 4~ is then cold formed a third time to flatten
the bearing surface 16 of the nut, thereby causing the excess material
in the "lip'! 42 to flow radially inwardiy as indicated at 32, thereby
reducing slightly the diameter of the counterbore 2~ at the bearing
surface 16 of the nut. The central bore 22 is then machined through
the torque-receiving end 14 of the nut and an appropriate internal
thread formed therein. The annular s0aling ring 36 is subsequently
snap~fittcd into the counterbore 26 to complete the sealing nut I0
illustrated in Figure 5.
Referring to Figures 6 and 7, the advantages of producing .
thc sealing nut 10 according to the prcsent invenlion will now be 4
explained. In Figure 6, an enlarged vicw of a scction of thc countcr-
borc 2G of a nut bl;mlc 4~ formcd according to conYcntion~l practic~
ls sllown. l~s 1s wcll known to thoso skillc~! in tllc art, thc cold forming
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proeess creates rnet:ll flow llnes ~1~' ln the nut blanlc ~ whlell sut~s~tantintly
- follow tlle contour of the cotd formed counterl)ore 2~', ilowcvcr, wllcn
the undercut ~G is machine(l into the counterbore 2G' according to ` .
prlor art practice, flow lines 4~' are brolcen by the machining operation,
thus ereating a 3tress point or stress "riser" 50 in the vicinity o~ the
bend at the base of the undereut 46. The effeet of the stress riser 50
.
is to eoncentrate stress forces at this point, thereby reducing the
integrity of the nut and restricting the torque and load limits of the nut.
In :Figure 7, however it can be seen that a nut blank
4'L made ptlrsuant to the teachings of the present invention results
in metal flow lines which substantially follow the contour of the "lip"
32. Specifically, when the lip 32 is bent over from the position
indicated by the dotted line 42, the cold forming process causes the
flow lines 48 to follow the movement of metal radially inwardly creating
the slightly reduced diameter in the counterbore 26 at the bearing
surface 16. Thus, the disadvantage of breaking flow lines caused .
by the undercutting opcration is eliminated.
Accordingly, as will be appreciated by those skilled
~n the art, the nut blank 44 made according to the process of the
present invention possesses superior load bearing characteristics
than a nut manuhctured pursuant to prior known methods. Moreover,
as noted~ in the background and summary, because the lip 32 is .
cold formed rather than undercut by a separate machining operation, .
the cost of manufacturing the nut according to the proccss c>f the
present invcntion is si~nificantly rcduced.
While the above description constitutes the preferred
e~l~odimellt of the invention, lt will be llppreclated that the invention
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1~ fJu~ccptll~lc to modiSlc~tlon, v~rl~tlon ilnd ch~nL~c wl~hout dcpi~r~ln~
Irom tllo propcr NCOpC or lulr mF:~nln~ o~ Ihc ~ccoml~nnyln~ cl~lm~, ¦
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