Note: Descriptions are shown in the official language in which they were submitted.
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m is invention relates to a two-piece rivet comprising a shank member
and a collar, which collar is swaged onto a thread carried by the shank member.
Two-piece rivets of this class are known. One known rivet is shcwn in
Schuster United States patent No. 2,955,505 issued October 11, 1960, wherein a
collar is swaged onto an end of a shank me~ber. This end has a plurality of
ring-shaped ridges of diameters which decrease from a maximum at the tip end of
the shank member. Another known type is shown in Ruhl United States patent No.
3,915,053, issued October 28, 1975 wherein a collar is swaged into a plurality
of grooves of different axial lengths but identical diameters.
The Schuster patent exerts an axial force while being set which is
similar to that exerted by the instant invention in that its collar also makes
its first cor.tact with the shank member near its tip end. As a consequence, a
tensile force is generated in the shank member as the collar is progressively
swaged onto the shank member and pressed against the workpiece. However, in the
Schuster patent this is a step-wise function of engagement of ring after ring.
This is a disadvantage in that generation of pre-load only occurs in the flow of
the outer material of the collar which is being locked discontinuously in the
grooves. It is an object of this invention to provide a helical thread wherein
the engagement of the collar and the thread is a continuously progressive engage-
ment so that the mecha~ical advantage of the inclined plane due to the helical
angle will be utilized to uniformly pre-stress that portion of the fastener, as
well as the entire assembly.
The R~hl patent merely shows means for transferring loads at the base
threads and is not concerned with creating a tensile force in the shank member.
Furthermore, both the Schuster and Ruhl patents use ring-shaped ridges
~ich do not permit removal of the collar by exertion of sufficient torque.
While this device is a locking fastener, the lock can be overcome by a sufficient
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torque, which permits readier removal and replacement.
A two-piece rivet according to this invention comprises a shank
member having an axis, and a head, a shank, and a thread in that order along
the axis, said shank being cylindrical and having a shank diameter, the head
having greater radial dimensions than the shank, said thread being helical and
having a substantially constant pitch, but having a major diameter which de-
creases as it extends away from a maximum adjacent to its end farthest from
the shank, said maximum diameter being no greater than said shank diameter; and
a ring-like collar to be swaged onto said thread, said collar having an inner
wall and an outer wall, and a first and a second end, said inner wall defining
a passage between said ends to receive with a substantial radial clearance at
least a portion of said thread spaced from the end farthest from the shank, and
with a larger diameter portion of the thread closer to the end farthest from
the shank also received in said passage, whereby with said shank placed in an
aperture in a workpiece, with at least a portion of the thread projecting beyond
a surface of said workpiece, the collar may be placed over the thread, and with
the shank restrained to prevent its being thrust back into the aperture, a
swaging setting force having both axial and radial components can be exerted
on the outer wall of the collar near its end farthest from the shank, whereby
to force the other end of the collar against said surface of the workpiece, and
to swage said inner wall adjacent to said first-mentioned end into the thread
at its maximum diameter, and thereafter continuously moving said swaging force
axially along the outer wall toward said surface of the workpiece to progres-
sively and continuously swage the inner wall into engagement with the thread
and maintain the axial force component against the workpiece thereby to exert
through the thread a force on the shank member having an axial component direc-
ted away from said head.
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According to a preferred but optional feature of the invention, a
peripheral groove is formed in the outer wall of the collar which groove is
axially spaced from both of the ends of the collar. Alternative preferred
shapes of the collar for various materials may include a tapered exterior or a
short taper at each end of the collar.
Other useful collar configurations include a tapered exterior, or a
short taper at each end of the collar.
The above and other features of this invention will be more fully
understood from the following detailed description and the accompanying drawings,
in which:
Figure 1 is a side view of the presently preferred embodiment of the
invention;
Figure 2 is a cross-section taken at line 2-2 in Figure l;
Figure 3 is a side view of one embodiment of the collar for use with
the shank member of Figure l;
Figure 4 is a right hand end view of Figure 3;
Figure 5 is a side view of still another embodiment of collar;
Figure 6 is a right hand end view of Figure 5;
Figure 7 shows the shank member of Figure 1 provided with a pull-tail;
Figures 8, 9 and 10 are axial sections showing progressive stages in
setting the rivet;
Figure ll shows another embodiment of the collar for use with the
shank member of Figure l;
Figure 12 is a fragmentary axial section showing another thread con-
figuration according to the invention;
Figure 13 is an axial section of another useful collar configuration;
Figure 14 is a top view taken at line 14-14 in Figure 13;
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Figure 15 ls a side view of yet another useful collar configuration;
Figure 16 is a top view taken at line 16-16 in Figure 15;
Figure 17 is a side view of still another useful collar configuration;
and
Figure 18 is a top view of the collar of Figure 17.
In Figure 1 there is shown a shank member 20 having an axis 21, and a
head 22, shank 23 and thread 24 in that order from the head. The shank is
cylindrical and has a diameter 25. The head has greater radial dimensions than
the shank.
The thread joins the shank section at a reduced portion 26 thereof.
It is a helical thread, preferably having a sloping faoe facing toward the head
end although it may if desired be a square thread or other shape. It has a
pitch dimension 28 which is oonstant for the full length of the thread. Its
major diameter 29 changes by an amount on the order of approximately 0.025 inches
per inch as shown by angle 30. The maximun major diameter is near to the end 31
farthest from the head.
m e presently preferred embodlment of collar 35 for use with shank
member 20 is shown in Figure 3. mis collar includes an inner wall 36, an outer
wall 37, a first end 38 and a second end 39. Inner wall 36 forms a passage 40
which extends from end to end. A peripheral groove 41 extends around the collar
in the outer wall spaoe d from the said two ends. The collar has an axis 42.
Another embodiment of collar 45 is shcwn in Figure 5. It also in-
cludes an inner wall 46, an outer wall 47, first end 48 and second end 49.
Inner wall 46 forms a passage 50 from end to end. The outer walls of both of
the embcdiments of Flgures 3 and 5 are cylindrical except for the grcove 41 in
Figure 3. The ends are preferably square to axes 42 and 51 of the collars.
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In Figure 7 there is shown an alternate embodiment of shank member
55. It includes a head 56, a cylindrical shank 57 and a thread 58, all of
which are identical to those of shank member 20. In addition it has a pull-
tail 59 with a head 60 by means of which an axial pull can be exerted on the
threaded end of the shank member as a convenience in setting. After the setting
operation is completed the pull-tail can be clipped off, or will be pulled off
in tension at the conclusion of the driving cycle, or otherwise removed.
Figure 11 illustrates another embodiment of collar 65 which has an
inner wall 66, outer wall 67, first end 68 and second end 69. Inner wall 66
forms passage 70 between the two ends. These are all concentric around axis
71. In contrast to the embodiments of Figures 3 and 5, a thread 72 is formed
in the inner wall. The thread has a constant diameter 73 which engages but
does not interfere with the maximum diameter of thread 24 as shown in Figure
11. An increasing clearance 74 is formed between them along the axial dimen-
sion for purposes yet to be described.
Figure 12 shows another thread shape 100 for use with this invention.
It may be directly substituted for thread 24 in shank member 20. This thread
also has a constant pitch 101, but instead of being formed as a uniform thread
shape and an enlarging minor diameter, it is a conventional thread with uniform
minor diameter 102 and uniform pitch, but with its crest ground off along a
conical path to form a major diameter 103 which is at a maximum at the free
end, and decreases as it extends toward the shank. This forms a flat 104 of
increasing width as it extends toward the shank. The taper is about 0.025
inches per inch, as in Figure 1.
Figure 13 shows a collar 110 with an internally threaded passage 111
and a tapered conical outer wall 112. One effect of the taper is to provide
additional material to be swaged into the decreasing-diameter thread. If
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preferred, the taper could extend part way from both ends so the collar would
not be a one-way part.
Figure 15 shows a collar 120 identical to collar 110) except for
four wrench-engaging recesses 121. When the collar is to be unthreaded, it is
convenient to have these recesses for the wrench to engage.
Figure 17 shows still another useful collar 130 which is basically
identical to collar 65 in Figure 11. It could also have the external groove
of the collar shown in Figure 3. Its external wall is basically cylindrical,
rather than tapered. T]le inside passage is threaded~ and wrench-engaging sur-
faces 131 are formed for the wrench to engage if the collar is to be removed.
In general J a thread will be provided in the collar when relativelyhard material such as steel is used to form the collar. The softer materials
such as aluminum alloys readily form thread shapes when they are swaged onto
the thread of the shank member. Therefore, wrench-engaging surfaces may use-
fully be provided even when the passage is unthreaded. For example, in Figures
15 and 17 if the collar material readily flows to form threads and later un-
threading is contemplated, then the wrench-engaging surfaces could be provided
in these collars, but the passage would not be initially threaded.
The setting of these fasteners is illustrated in Figure 8, together
with a tool 75 for accomplishing it. Tool 75 is a swaging tool intended to
exert an axial force as a consequence of being driven by a force indicated by
arrows 76. An opposing force is indicated by arrow 77. Force 77 could be
exerted by means such as a bucking bar or a clamp, or by pulling on a pull-tail.
The tool may be percussively driven or may be pressed by a hydraulic tool, such
as in opposition to a pull on the pull-tail. Setting techniques of these types
are well-known and require no further description here.
The tool is formed as a tubular body 79. The tubular body has an
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internal wall 80 which defines a passage 81. It has a setting end 82 where
the passage opens. The internal wall includes a deflection surface 83 in the
form of a surface of revolution which decreases in diameter as it extends away
from the setting end. The wall also preferably has a cylindrical portion 84
which "wipes" along the collar as it is formed.
As best shown in Figure 8, the shank member 20 is inserted into
aligned apertures 85, 86 in continuous workpieces 87, 88 which are to be held
together by this rivet. The head bears against one surface of one of the work-
piece and the shank makes whatever class of fit is desired in the apertures.
At least a portion of thread 24 projects beyond surface 89 of the workpiece.
The collar being used (in the illustrated case, collar 35) is placed
over the threaded section. There is a relatively close fit or a very minor
clearance between the inner wall and the maximum thread diameter. Now with
the setting forces exerted, the material of the collar will be swaged inwardly
to make contact with the thread, first at its maximum diameter.
As can be seen in Figure 9 this swaging movement is a continuous
situation as the tool moves along the outside of the outer wall. The groove
41, when used, gives some relief when the tool passes over it to give room for
some of the wave of material which precedes the setting tool. As can be seen
in Figure 9, the wall material continuously and progressively enters the thread
as the tool moves along.
In Figure 10 the tool has moved completely to the surface 89 where it
stops. In some installations, the tool might be stopped by a ring or protrusion
of displaced collar metal itself. The inner wall material will preferably, but
not necessarily, have engaged all convolutions of the thread, but it may or may
not have filled them entirely, depending on the volumetric relationships which
are used. What is important to this invention is that the engagement will have
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been a continuous and progressive one along the helical thread as contrasted
with the effect in the Schuster patent of a step-wise function from ring-to-
ring.
The foregoing collar arrangement is especially suitable for use with
relatively soft collars when the collars of Figures 3 and 5 are made of an
aluminum alloy, for example. If, however, it is desired to make the collar of
stronger materials such as steel, then a collar such as collar 65 should be
provided which is initially threaded and which makes a nearly net fit with the
thread 24 at the maximum diameter. Now a suitably modified swaging tool can
be moved along the outer wall and need only deflect the material the relative-
ly small amount required to fill clearance 74, and the material will not have
to flow as appreciably to form thread-like shapes to engage the thread on the
shank member. This will reduce the setting forces required for a strong steel
collar such as collar 65.
Once set, the collar is locked to the shank member. Because of the
reverse nature of the thread, that is because the thread diameter enlarges as
it extends away from the shank, the collar cannot be unthreaded without sub-
stantial deflection of material. It is, however, an advantage of this invention
that the collar can be unthreaded, but this requires a very strong wrench such
as an impact wrench, and significant difficulty will be encountered in the re-
moval. Nevertheless it can be done, which is not the situation in the Schuster
patent. One would not expect to reuse a fastener which had been disassembled
in this manner. The wrench-engaging surfaces shown iTI Figures 15 and 17 assist
the removal. Instead of recesses, these could be lugs or other shapes, but the
illustrated recesses are very convenient to make, and work well.
Also of interest in th s invention is the fact that while the rivet
is being set, the swaging tool exerts a compressive force on the thread. How-
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ever, this force also has an axial component 93 as a consequence in part ofthe reaction between the first end of the collar and surface 89 of the work-
piece. Also, when a sloping face is provided on the thread, the component is
emphasized, This reaction is known and described in Schuster patent No.
2,955,505. The primary distinction between the previous Schuster patent and
this disclosure is that in the instant invention, the engagement is continuous
and progressive along a helix instead of step-wise in a group of shoulders and
this provides a mechanical advantage in pre-loading the fastener. Also, this
device can with sufficient force be unthreaded by overcoming the locking fea-
ture.
The dimensions of this device may readily be selected by personsskilled in the art without undue experimentation. A relatively conventional
thread size for the shank diameter should be provided, and the maximum diameter
of the thread should be no greater than the cylindrical diameter of the shank
in order that they may pass through the same hole in a workpiece. The materials
of construction of the shank member may be any suitable rivet or bolt material,
and the collar any suitable material to achieve the necessary deformation and
deflection, and to have the strength required for the intended installation.
The engagemen1. and retention of the collar to the thread of Figure
12 is the same as that ~lescribed above, except~ of course, the thread has a
different crest shape. Still, the collar is swaged to form an engagement which
resists removal as the consequence of an enlarging major diameter.
All of the illustrated collars can be used interchangeably on the
shank members of Figures ] and 12.
In this sp~ification, the internal thread in the collar shown in
Figure 11 is regarded as part of the inner wall.
The term "substantial radial clearance" as used herein to describe
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the radial relationship between the inner wall of the collar and at least a
portion of the thread is intended to distinguish from a typical threaded en-
gagement of a nut and bolt. A clearance between the collar and a portion of
the thread spaced from the end of the thread farthest from the shank is pro-
vided so that a larger diameter portion closer to that end can make first
engagement with the collar.
This invention is not to be limited by the embodiments shown in the
drawings and described in the description which are given by way of example
and not of limitation) but only in accordance with the scope of the appended
claims.
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