Note: Descriptions are shown in the official language in which they were submitted.
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TWO PIECE FASTENER AND INSTALLATION TOnL
Background a~d Summary of the Invention
The present inven~ion relates generally to multiple
piece fasteners and more particularly to two piece fasteners of
the type comprising a pin and swageable collar designed for
installation by a pulling tool which exerts a pulling force on
the pin and reaction force on the collar so as to swage the
collar into engagement with the pin.
Conventional pull~type ~wo piece fasteners include
a pin and a collar adapted to be swaged thereon. The pin has an
elongated shank provided with a head a~ one end, a plurality of
lock grooves and a plurality of pull grooves defined by substan-
tially uniform diame~er crests alternating with valleys of sub-
stantially uniform diameter, These pull grooves are provided on
a separable pintail portion of the shank. The collar is applied -~
to the shank of the pin subsequent to insertion of the pin into a
prepared opening in workpieces to be joined. An installation tool
having a jaw assembly is applied to the pin with the jaws of the
installation tool having a plurality of teeth adapted to engage
a selected number of the pull grooves whereby a pulling force can
be exerted on the pin. The installation tool also has a swaging
anvil adapted to engage the collar and to swage the collar into
engagement with locking grooves on the shank portion of the pin
in reaction to the pulling force. As the pulling force continues ;
to increase in magnitude the pintail portlon of ~he shank is
separated at a breakneck groove provided on the pin shank between
the locking grooves and the pull grooves, The pintail portion is
discarded and the setting operation is complete. This pintail
portion, however, represents a cost factor in ~he fastener ~hich
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contributes nothing to the fastened joint as it serves only to aid
in the installation of the fastener.
Iypically these pintail portions have been fabricated
with a substantially grea~er number of pull grooves than that
required to properly set the ~astener. One of the reasons for this
excess number of pull grooves and hence extra length of the pintail
is to ensure that a sufficient number of pull grooves are engaged
by the jaws of the installation tool to develop the pull force
required to set the fastener If an insufficient nu~her of pull
grooves are engaged by the jaws, the engaged pull grooves may be
stripped before complete setting of the fastener thus requiring
removal of the partially installed fastener and installation of
a new fastener.
While present material costs attributable to this
lengthy pintail when such pull-type fasteners are fabricated from
low cost materials may no~ be significant enough to generate much
concern, this is not necessarily the case when the fasteners are
fabricated from more costly, exotic metals such as titanium which
are commonly used in the aerospace industry. In the latter case,
2Q it is very desirable to reduce to an absolute minimum the amount
of material required and hence the costs associated with the
fastener and particularly to reduce the amount of that material
and associated cost which does not contribute to the integrity or
strength of the fastener as installed i.e, the disposable pintail.
One problem, however, is to assure that the minimum number of
grooves are engaged by the tool jaws to preclude stripping.
Accordingly, the present invention provides a fastener
and associated installation tool jaw as~embly by which the amount
o~ disposable pintail material is minimized. In a preferred foxm
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of the invention, the pintail portion of the pin is reduced to
a minimum length required to provide only that number of pull
grooves necessary to provide sufficient strength to accept the
setting force to be exerted thereon by the installation tool when
all of the grooves are engaged. In a different form of the
invention, the pintail portion is totally eliminated, the pull
grooves being provided within an axially inwardly extending
opening provided in the pin portion of the fastener. In both of
these embodiments, the pull grooves are designed to cooperate
with the jaws of the installation tool in such a manner as to
preclude engagement of less than the minimum number of pull grooves
required before any pulling force can be generated thereby eliminating
the possibility of stripping of the grooves
Thus, the present invention provides a pull-type
fastener and associated installation tool jaw structure which
enables the length of the pintail to be substantially reduced or .
even eliminated while still precluding the possibility of stripping
the fastener The reduced length or complete elimination of the
pintail portion affords the advantage of cost savings which can
be significant where costly materlals are employed.
Additional advantages and features of the present
invention will become apparent from the subsequent description and
the appended claims taken in conjunction with the accompanying
drawings,
Brief Description of the Draw~ngs
Figure 1 is an elevational view of a fastener partially
in section with the fastener assembled to workpieces to be joined
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and a portion of an installation tool ready for application thereto
all in accordance with the present invention;
Figure 2 is a view similar to Figure 1 but showing the
installation tool in initial engaging relationship with the fastener;
Figure 3 is a view similar to that of Figure 1 but
showing the fastener in a set condition with the pintail portion
separated therefrom;
Figure 4 is an enlarged fragmentary view shown partially
in section of the pintail portion of the fastener of Figures 1
through 3 with the installation tool jaws shown in engaging
relationship therewith;
Figure S is a view similar to Figure 4 but showing an
improper relationship between the installation tool jaws and the
pintail portion; and
Figure 6 is a view similar to that of Figure 2 but
illustrating a different form of the present invention.
Description of the Preferred Emhodiments
Referring now to the drawings and specifically to
Figures 1 through 3, there is shown a pull-type two piece fastener
in accordance with the present invention indicated generally at 10
and comprising a pin 12 installed within aligned openings 14 and 16 :~
of workpieces 18 and 20 respectively and a swage collar 22 assembled
thereto,
Pin 12 includes a shank portion 24 having a head 26
provided at one end thereof~ a pintail portion 28 at the other
end thereof and a plurality of locking grooves 30 disposed there-
between. A breakneck groove 32 is also provided on shank portion
24 between locking grooves 30 and pintail portion 28. It should
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be noted that head 26 of pin 12 may be of either a shear or tension
type and further of either a pro~ruding type as shown or of a
countersunk type if desired. Also, locking grooves 30 may be of
any suitable construction such as of the type illustrated and
described in Patent No. 3,915,053 issued ~ctober 28, 1975 for
example. Similarly, collar 22 may be of any suitable type desired.
Pintail portion 28 of pin 12 is of a generally conical
shape and has a plurality of pull grooves 34 provided therealong,
each of said pull grooves being defined by successively alternating
crests 36 ~hrough 42 and valleys 44 through 50. As shown, each
of the successive crests 36 through 42 proceeding outwardly away
from breakneck groove 32 has a diameter less than any of the
preceding crests Similarly, each of the valleys 44 through 50
has a diameter less than the diameter of any of the preceding
valleys.
A portion of an installation tool assembly 52 is
also shown in Figures 1 through 3 and comprises an anvil 54 having
a bore 56 extending inwardly from end 58 thereof through which a
collet assembly 60 extends, collet assembly 60 normally extending
outwardly beyond end 58. A collet assembly carrying member 62
is reciprocably disposed within an enlarged diameter bore 64
provided within anvil 54, into which bore 56 opens. The outer
end of bore 56 has an outwardly flared generally frusto conically
shaped surface portion 66 provided thereon.
Collet assembly 60 comprises a tubular collet jaw
structure 67 terminating in a longitudinally split or segmented
jaw portion 68 having a plurality of radially inwardly extending
teeth 70; the jaw structure 67 has a longitudinally extending
central bore 72 extending inwardly, The jaw portion 68 has three
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jaw segments normally resilicntly located in an open position.
Collet assembly 60 includes a spring loaded ejection pin or
mandrel 74 which is movably disposed within bore 72 and which
is urged outwardly between teeth 70 of jaw portion 68 by a spring
78. Ejection pin 74 has a flange portion 76 provided on its
inner end, one surface 77 of which provides a sea~ for one end
of the biasing spring 78, the opposite surface 79 of which engages
an annular shoulder 81 provided within the jaw structure 67 so
as to retain ejection pin 74 therein. The other end of spring
1~ 78 is seated on a retaining ring 80 seated within a groove 82
provided at the inner end of collet jaw structure 67,
Jaw portion 68, as previously mentioned~ is comprised
of a plurality of resilient fingers or sections which may be formed
by providing a plurality of axially inwardly extending slits 83
which extend for only a portion of the length of collet jaw
structure 67. Alternatively the fingers could be provided by
fabricating collet jaw structure 67 from a plurality of separately
machined segments, In any event, the Quter surface of collet j~w
portion 68 is provided wi~h an inclined or frusto conical surface
portion 84 which is engageable with surface 66 of anvil assembly 54.
The actuation mechanism portion of installation tool 52 may be of
any suitable conventional construction such as the type illustrated
in U,S, Patent No. 3,329S000, the disclosure of which is hereby
incorporated by reference, As will be seen the tool 52 can be
actuated by an operator to a pulling stroke during which the
~astener 10 is set and then deactuated whereby the tool 52 ~ill
be acti~ated to a return stroke.
As seen in Figure 2, when installation tool 52 is
applied to fastener 10, the terminal end surface 86 of pintail
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portion 28 will engage rounded end portion 88 of ejection pin 74
thereby moving ejection pin 74 longitudinally into bore 72 and
compressin~ spring 78. l~ereafter, the tool 52 is actuated to
its pulling stroke causing collet carrying member 62 to move
longitudinally relative to the anvil assembly 54. As jaw portion
68 moves longitudinally or axially inwardly with respect to anvil
54, the engagement of surface 66 with inclined surface 84 causes
the separate fingers of collet jaw portion 68 to move radially
inwardly and the teeth 70 to move into engaging relationship wi~h
pull grooves 34 of pintail portion 24. When jaw portion 68 is
in a fully closed position, outer surface 89 engages the sidewall
of bore 56 along its length axially outwardly from inclined surface
84 holding the fingers of jaw portion 68 closed as a pulling force
is exerted on pin 12.
Thereafter, continued relative movement between the
anvil 54 and collet carrying member 62 will cause surface 66 and -
a portion of bore 56 thereof to move into engagement wlth and
swage collar 22 into engagement with locking grooves 30 of pin 12,
Thereafter, increased pulling force is applied to pintail portion
24 until breakneck groove 32 fractures thereby separating pintail
portion 28 from the set fastener. It should be noted that bore 56
will be of a sufficient length to insure full engagement with surface
89 over the entire length of travel of collet assembly 60. The
installation tool 52 is then deactuated from its pulling stroke by
the operator whereby the installation tool 52 is activated to its
return stroke causing the collet assembly 60 to n~ove axially
outwardly relative to anvil assembly 54 to return tool 52 to its
ready position as shown in Figure 1. At the same time on the
return stroke the swaging anvil 54 is retracted from the swaged
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collar 22. Jaw portion 68 will then move radially outward into an
open position and separated pintail portion 28 will be ejected
therefrom by outward movement of ejec~ion pin 74. Installation
tool 52 is then ready for application to the next fastener to be
set.
As previously mentioned and bes~ seen with reference
to Figures 4 and 5, jaw teeth 70 are preferably contoured to
complement crests 36 through 42 and alternating valleys 44 through
50 of pintail portion 28 and are defined by crests 90 through 96
and alternating valleys 98 through 104. The diameter "A" of
pintail portion 28, as measured at valley 44, is substantially
equal to OT slightly greater than diameter "B" of pintail portion
28 as measured at crest 38. Similarly, the respective diameters
of pintail portion 28 as measured at valleys 46 and 48 are
approximately equal to or slightly greater than the diameters at
~` crests 40 and 42, respectively. Similarly, as jaw teeth 70 of
collet assembly 60 preferably have a shape complementary to the
shape of pintail portion 28, the diameter of the opening defined
by and measured at valley 100 wilI be less than or equal to the
diameter of the opening defined by and measured at crest 90 thereof
when jaw portions 68 are in a fully closed position. Similarly,
the diameter of the respective openings defined by and measured
at valleys 102 and 104 will be less than or approximately equal to
the respective diameters of the openings defined by and measured
at crests 92 and 94, respectively. Accordingly, proper and full ;
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Ipplication of installatiorl tool 52 to pintail por-tion 28 will result
in full mutual engagement of jaw teeth 70 with pull grcoves 34. It
is imp~rtant to no~e that with this structure the diameter of jaw
crest 90 in its closed position is greater than that of each of the
pintail crests 38, 40, and 42. The same is true with jaw crest 92
relative to pintail cres-ts 40 and 42 and with jaw crest 94 relative to
pintail crest 42. r~hus the jaw crests 90, 92, 94 and 96 will engage
pintail crests 36, 38, 40 and 42 only when both sets oE crests are in
proper alignment thereby assuring gripping of all of the pintail crests
by all of -the jaw crests or gripping of none. Thus, should for some
reason the operator fail -to fully or completely apply installation
tool 52 to pintail portion 28 prior to actuation of the tool so that
jaw portion 68 closes before pintail portion is properly axially
positioned, the tool will cycle without strippiny the pull grooves 34.
This situation can be seen in Figure 5 where the results of improper
align~ent are shown. Thus, when jaw portion 68 is in a fully closed
position, the opening defined by crest 90 will clear any of the axially
outwardly disposed crests 38, 40, or 42 and the same is true with regard
to jaw crest 92 as compared to pintail crests 40 and 42, and with regard
to jaw crest 94 as compared to pintail crest 42. Thus, the present
invention provides an effective disabling feature which allows the pintail
leng~h to be reduced to a minimum without concern as to stripping of
the pull grooves should the tool be positioned thereon so as to provide
less than full engagement of ]aw teeth 70 with all of the pull grooves 34.
While the present invention has been illustrated and
described with reference to a p m having a pintail portion provided
wlth four pull grooves 34, the specific number is not critical.
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It is important, however, to provide a number of pull grooves,
each having a shear area such ~hat the sun total of shear areas
of the pull grooves ~hich ~ill be engaged by the installation tool
is capable of supporting the pulling froce necessary to fully
set the fastener. Note that in order to optimize material usage
and minimize the amount of material required the effective total
shear area is selected to be a preselected minimum magnitude.
Ideally the minimum effective shear area would be that jus~
sufficient to accept the maximum shear stress imposed by the
maximum anticipated loads. This minimum shear area, however, is
set greater than the ideal in order to accommodate variations in
manufacturing, dimensional and material tolerances. With the
above construction and by providing the minimum number of pull
grooves having the minimum requIred total effective shear area,
it is possible to reduce the length of the pintail portion 28 to
a minimum; this can ~e a length generally equal to approximately
the nominal diameter of the smooth shank portion of the pin 12.
It should also be noted that each of crests 36 through
42 of pintail portion 28, as well as each of the ~aw crests 90
through 96 are sufficiently radiused at their peaks so as to assist
the tool 52 to be cammed into OT out of full engagement with all
of the pull grooves 34 should tool 52 be actuated when, for
example, pintail crest 36 and jaw crest 90 are positioned in radial
alignment. This arrangement will reduce the possibility of jaw
~` portions 6B being damaged or broken should crests 36 and 90 be
so aligned upon actuation of tool 52
Further~ while the present invention is illus*rated
as including a pin 12 having a breakneck groove 32 provided thereon,
in some applications it may be possible to eliminate this breakneck
and to allow pintail portion to remain attached to pin member 12.
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Note that the diameter of the bore 56 represents the
final swage diameter of the collar 22. This, of course, limits
the maximum diameter of the surface 89 of the jaw portion 68.
At the same time the wall thickness of the jaw portion 68 will
be limited by ~he contour of the tee~h 70. By utilizing the
generally conical shape for the pintail portion 34 and hence for
the area of teeth 70 an increase in wall thickness in the jaw
portion 68 across the valley 104 will provide an increase in
strength as contrasted to that resulting if a uniform diamter
pintail portion 34 and teeth 70 were provided. Thus an additional
advantage of the conical shape lies in an increase in strength of
the jaw portion 68.
While the present invention has been illustrated and
described above with regard to a fastener having a minimum length
pintail portion, it is possible in some cases to totally eliminate
the pintail portion, To this end a different form of invention
is illustrated and will be described with reference to Figure 6.
: A fastener 105 is shown therein and comprises a pin 106 haYing a
shank portion 108 with a head 110 provided on one end thereof.
Pin 106 is shown installed within prepared openings 112 and 114
of workpieces 116 and 118, respectively~ and has a swageable collar
120 assembled thereto. Shank portion 108 has a plurality of
annular lock grooves 122 provided thereon adjacent end 124 into
which collar 120 is swaged during $etting of the fastener,
Pin 106 is proyided with an opening extending axially
inwardly from end 124 thereof, which opening has a plurality of
pull grooves 128 provided therein which are defined by crests
130, 132 and 134 and alternating valleys 136, 138, and 140.
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A pulling tool 142 comprises an anvil portion 144
having an axially extending bore 146 provided therein opening
ou~wardly through end portion 148 and provided with a generally
frusto conically shaped surface 150 immediately adjacent thereto.
A collet assembly 152 includes a mandrel 153 movably disposed
within bore 146 and has a forward expandable nose portion 154
having a multitoothed outer surface contoured to correspond to
the contour of pull grooves 128 and engageable therewith. Nose
portion 154 is co~prised of a plurality of axially extending
fingers or segments and has a bore 156 extending axially there-
through within which is disposed an expansion pin 158 which
operates to cause the axially extending segments of nose portion
154 to move radially outwardly as it moves into bore 156.
Thus, in order to set fastener 105, nose portion 154
is inserted into the opening in end 124 of pin 106. At this time
the fingers or segments of nose portion 154 can move radially
inwardly permitting the noted insertion Thereafter, the tool
142 is actuated and pin 158 is caused to move axially into bore
156 thereby causing the axially extending segments of nose portion
154 to be radially expanded into engagement with pull grooves
128 and thereby enable installation tool 142 to exert a pulling
force on pin 106 and effect relative movement of anvil portion
144 so as to swage collar 120 into engagement with locking grooves ;~-~
122,
It~should be noted that the specific number of pull
grooves provided within end portion 124 ~f pin 106 will be selected
so as to ensure a sufficient total shear area thereof to withstand
the forcesnecessary to set the fastenert In order to ensure that
all of the crests 130-134 will be engaged by the corresponding
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teeth in nose portion 154, the relative diameters of alternating
crests 130 through 13~ and valleys 136 through 140 and the
corresponding valleys and crests of nose portion 154 are controlled
to incorporate the disabling go, no-go feature described above with
reference to Figures 1 through S thereby precluding the possibility
of engagement of less than all o the pull grooves by the nose
portion 154 of the installation tool and thereby reducing the
likelihood of stripping.
Thus, the present invention provides a pull-type
fastener which enables the length of the pintail to be substantially
reduced to a minimum length just necessary to accept the pulling
force necessary for installation of the fastener; in a different
form of the inventlon the pintail is eliminated entirely, Reducing
the length of the pintail affords significant cost savings
particularly in fasteners fabricated from exotic metals such as
titanium without any reduction of strength or ease of installation.
~urther, the pull grooves and associated jaw portions of the
installatio~ tools are designed so as to effectively reduce the
likelihood of the pull grooves being stripped due to improper
positioning of or premature actuation of the installation tool.
While it will be apparent that the preferred embodiments
of the invention disclosed are well calculated to provide the
advantages and features above stated, it ~ill be appreciated that
the invention is susceptible to modification, variation and change
without departing from the proper sc~pe or ,fair meaning of the '~
: subjoined claims.
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