Note: Descriptions are shown in the official language in which they were submitted.
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Background of the Invention
This invention is concerned with pull-type blind ~asteners,
that is to say with fasteners of a kind comprising a push-part having
a head for engagement with the exposed side of a workpiece and a
pull-part which passes through said head and projects as a pulling
5 stem therefrom, a shank provided by one of said parts being effective
when the shank has been inserted through aligned holes in a workpiece
and the stem is pulled to engage the workpiece at the blind side to
clamp it against sald head. The fastener also has means for efIecting
inter-engagement between the two parts to lock them in set relationship
lû and to hold them together on removal of the pulling stem.
Metal pull-type blind rivets have been known for many years,
one brand having manufactured and widely marketed by the company
assignee of the present invention under the registered trademark
"POP" . Such rivets have a rivet body, or "push-part", and a mandrel
15 or "pull-part", which may be pulled right through the rivet body, or
broken to leave a head part in the set rivet, or may be subsequently
trimmed to remove the stem projecting from the rivet head after setting.
Metal pull-type blind rivets enable reliable and permanent riveted
joints to be made in workpieces comprising sheet metal panels, ror
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example, to which access is available from only one side, and may be
designed not only to give strong joints with the parts of the workpiece
tightly clamped together but also to afford a high degree of pulling
together of the parts of the workpiece if, as is very common, there is
a small gap between them at the beginning of the riveting operation.
Among the wide variety of applications for which blind rivets
are used are some for which metal is regarded as undesirable, if not
altogether unsuitable. Electrical insulation, lightness in weight, choice
of color, for example, are factors which have led to the introduction
of plastic blind fasteners. ~Iowever, such plastic fasteners, especially
those which resemble pull-type blind rivets in appearance, usually
suffer from a very low ability to pull parts of a workpiece together,
and very low residual clamping force in the set fastener.
An example of a two-piece plastic pull-type blind fastener
which has been proposed is one comprising a part which is pushed,
i.e. a "push-part", and which has an annular head with a hollow
- shank projecting forwardly from it for insertion in a hole in a
workpiece, and a pull-part accommodated in the shank and having
a stem projecting from the head of the push-part so that it can be
pulled. The push-part of this fastener has two dlametrically opposed
slots running along an intermediate portion of the shank between the
head and an annular wall at its tail end and the pull-part extends
beyond the shank and there, has a head of the same diameter as the
outer diameter of the annular wall so that, when the pull-part is pulled,
the head abuts the wall and the intermediate portion oE the shank
splays out like two elbows to engage the blind side of the workpiece.
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Teeth may be found on the pull-part so that they dig into the material
of the head of the push-part and lock the two parts of the fastener
together in set position more firmly than relying on friction, the two
parts thus remaining in their set condition when the portion of the pull-
part projecting from the head of the push-part is trimmed off.
The fastener can be made by injection molding the pull-part
first and then the push-part over it. Whereas this particular example
of a plastic blind fastener has generally adequate strength and an
ability of pull parts of a workpiece together, the range of workpiece
thickness with which it can be used is limited and it requires relatively
lO complex tooling for its manufacture.
It is an object of the present invention to provide an improved
blind fastener which can be made economically of plastic material and
which will yet exhibit a high degree of ability to pull together parts
of a workpiece, and hold them tightly clamped alter setting.
Summar of the Invention
Two pull-type blind fasteners in accordance with the invention
are hereinafter described in detail to illustrate the invention by
way of example, each of these illustrative fasteners comprising
two intercooperating parts, each of resilient plastic material of a
20 thermoplastic nature so that they can be injection molded. The
pull-part of each of the illustrative fasteners has an elongated shank
provided by a plurality, e . g. two, legs, the legs being joined at
rear ends to a pulling stem, which has a head at its rear end by
which is can be held by a pulling device of a æuitable setting tool.
25 Each leg of the pull-part, at its forward, free, end, has a shoulder
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which projects beyond the periphery of that part of the shank which
lies behind the shoulder so that the shoulder, after the leg has been
radially bent inwardly on insertion of the shank in a hole to permit
the shoulders of the legs to pass through can, on recovery of the legs
to a relaxed condition, overlie the workpiece around the hole at the
blind side.
The push-part of each of the illustrative fasteners has a head to
engage the workpiece around the hole at the accessible side from which
the shank is inserted and a plug which projects forwardly from the
head, part way along the shank, where it is accommodated between the
10 legs. The legs of the shank, in the case of each of the illustrative
fasteners, pass through apertures of complementarily shaped cross-
section in the head of the push-part, the arrangement being such that
the push-part can slide along the shank to advance the plug to a
position between the shoulders of the legs.
In using the illustrative fasteners for securing two parts of a
workpiece together, the shank of the fastener is inserted through aligned
holes in the parts of the workpiece, the shoulder portions of the legs
being resiliently urged inwardly to permit the shoulders to pass right
through the workpiece, and, on recovery of the legs to a relaxed condition
20 when the shoulders are beyond the blind side, to overlie the periphery
of the hole. The legs of the shanks of the illustrative fasteners at
their free ends are close enough together ;n their relaxed condition to
engage one another and provide an axis about which the shoulders
pivot ~,vhen they are constrained to pass through the hole. By means
25 of a suitable blind-rivet setting tool, the pull-part is then pulled by
a chuck of the tool while a nosepiece of the tool pushes against the
head of the push-part thus to cause the shoulders of the shank legs
and the head of the push-part to be urged together first to draw
together the parts of the workpiece (if there is a gap between them)
and then clamp them tightly, with the plug of the push-part now
S sufficiently advanced along the shank to lie between the shoulders
and hold them apart in overlying relationship with the workpiece
around the hole at the blind side.
Each of the illustrative fasteners comprises means for effecting
such inter-engagement of the two parts that movement of separation
10 of the head of the push-part and the shoulders of the shank legs, after
the fastener has clamped the workpiece, is prevented, such means
being so incorporated in the fastener that such separation will not
occur even though the portion of the pull-part projecting from the
head of the push-part is removed. In one of the illustrative fasteners
15 such means comprises teeth on the plug of the push-part which
inter-engage with the inner walls of the legs of the pull-part.
In the other of the illustrative fasteners, such means comprises teeth
on the outer wall of the legs of the shank, which inter-engage with
the outer walls of the apertures in the head of the push-part through
20 which the legs pass. In each case, the por~ion of the pull-part
` projecting from the head of the locking member is cut off, preferably
by cutting means of the setting tool, to sever the legs flush with the
head of the push-part and thus leave a fastener of pleasing appearance
at the accessible side of the workpiece. Severing of two relatively
~5 thin legs is usually easier than severing a solid stem of similar
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material and cross sectional area.
The illustrative fasteners are simple and quick to insert and
set, ~ot electrically conductive, light in weight and, besides being of
pleasing appearance, can readily be molded in selected colors, the
two parts being of the same color, or, if preferred, of different
S colors. They can be set in workpieces of widely varylng thickness.
The illustrative fasteners can be made economically by injection
molding, the part provided with the teeth first, and then the other part
molded directly onto it. Thus, the said other part may readily be
molded with grooves complementary to at least some of the teeth.
The invention provides, in one of its several aspects, a
two-part pull-type blind fastener comprising a pull-part having a
shank provided by a plurality of legs, the legs being Joined at rear
ends to a pulling stem and at their other, free, forward ends having
external, rearwardly facing, shoulders, and a push-part axially
15 slidable on said shank and comprising both a head which surrounds
the shank, the shank legs passing through apertures in the push-part
and a plug projecting forwardly from said head~ the plug being
accommodated in, and extending part way along, the shank and
capable, after the shank has been in6erted through a hole in a
20 workpiece and the plug has been advanced to a position between
said shoulders, of holding the legs apart with the shoulders overlying
the workpiece around the hole at the blind side. The fastener also
comprises means for effecting such inter-engagement of the two parts
that movement of separation of the head of the push-part and the
25 shoulders of the shanks legs is prevented, after they have been
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urged towards one another to clamp the workpiece therebetween and
the portion of the pull-part projecting from the head of the push-part
has been removed.
The two parts of a blind fastener in accordance with the invention
may be made of the same material, or they may be made of diEferent
S materials, whether plastic or metal. To facilitate injection molding
of one part directly onto the other, the parts are preEerably of
different thermoplastic materials, that part molded first having a
higher softening temperature than the second. The shank member is
desirably resilient, and essentially so where, as in the case of the
10 illustrative fasteners, the legs have to yield inwardly as they pass
through a hole in the workpiece; the locking member may be of a
harder material, especially if it has teeth on it to inter-engage with
the other parts. Nylon ff6 and "DELRIN", a brand of acetal resin,
are sutable materials of similar hardness to one another, the
15 nylon having the higher softening point. Polycarbonate is a suitable
harder material for the locking member, where this is desired.
Where, as is the intended use of the illustrative fasteners,
fasteners in accordance with the invention are used merely to fasten
parts of a workpiece together, the heads of the locking members may
20 be round and smooth or of any other desirable shape for ornamental
purposes. The locking members of fasteners in accordance with
the invention may, however, be shaped to serve functional purposes,
for example as retaining devices or clips for trims, pipes, electrical
~` leads, etc., or as hooks.
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According to a still further broad aspect of the present
invention there is provided a two-part pull-type blind
fastener comprising a pull-part having a shank provided
by a plurality of legs. The legs are joined at rear ends
to a pulling stem and at their other, free, forward ends
having external, rearwardly facing shoulders lying in a plane
at right angles to a longitudinal axis of the shank. A push
part is axially slidable on the shank and the shank legs
pass through apertures in the push-part. ~ pïug projects
forwardly from the head and is accommodated in, and extending
part-way along the shank and capàble, a~ter the shank has
been inserted through a hole in a workpiece and the plug has
been àdvanced to a position between the shoulders, of holding
the legs apart with the shoulders overlying the workpiece
around the hole at the blind side. The fastener also
comprises means for effecting such interengagement of the
two parts that movement of separation of the head of the
push-part and the shoulders o~ the shank legs, after they
have been urged towards one another to clamp the workpiece
therebetween and the portion of the pull-part projects -from
the head of the push-part has been removed, is prevented.
Brief Description o:E the Drawing
There now follows a detailed description, to be read with
reference to the accompanying drawing, of the illustrative fasteners
aforementioned. It will be realized that these illustrative fasteners
have been selected for description by way of example and not of
5 limitation of the invention~
In the accompanying drawing:
Figure 1 is a view, partly in longitudinal section, of the first
illustrative fastener, viewed from a position normal to its axis;
Figure 2 is a view, similar to Figure 1, but from a position at
lO 90 around the axis of the fastener;
Figure 3 is a view of the illustrative fastener from its tail
or leading, end (at the left of Figure 1);
Figure 4 is a view of the first illustrati.ve fastener in cross-section
on the line IV-IV of Figure 1;
Figures 5 and 6 are views of the first illustrative fastener in
cross-section on the lines V-V and VI-VI of Figure 2;
Figure 7 is a view, similar to Figure 1, but of the second illustrative
fastener;
Figure 8 is a view in cross-section of the second lllustratlve
20 fastener on the line VIII-VIII of Figure 7; and
Figure ~ is a view, similar to Figure 7, but showing the second
illustrative fastener installed in a workpiece.
Description of the Preferred Embodiments
The first illustrative blind fastener (Fig. 1-6) consists of a
25 pull-part 10 and a push-part 12. The pull-part 10 comprises a shank
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14 formed by two resilient legs 16 joined at their rear ends to a pulling
stem 18 of the pull-part 10. The stem 18 has a head 20.
Each of the legs 16 of the first illustrative fastener has, at its
free, leading, end a thickened portion 22 with a forwardly tapering
surface 24 and a rearwardly facing external shoulder 26 lying in a
5 plane at right angles to a longitudinal axis of the shank. Outer
surfaces 28 of the legs behind the shoulders are part cylindrical and
smool;h and pass through complementarily shaped apertures 30 (Fig. 6)
in the push-part 12. The push-part 12 of the first illustrative Eastener
has a head 32, in which the apertures 30 are provided, the head thus
l0 surrounding the shank 14, and also comprises a plug 34 which projects
forwardly from the head 32 and is accommodated between the legs 16
along which it extends part way towards the shoulders 26. The plug
34 has two opposing flat sides 36 (Fig 5) joined by symmetrically
disposed part cylindrical surfaces 38. On the surfaces 38 are formed
15 three ratchet shaped arcuate teeth aS0 (Figs. 1 and 2~, their inclined
sides facing forwardly, their rear sides being normal to the axis of
the plug.
The plug 34 of the push-part 12 of the first illustrative fastener
e.~tends about half way along the shank 12 from the head 32. In front
20 of the plug, inner walls 42 of the legs 16 o:E the shank are flat and
`~ converge towards one another in the direction of the free ends of
the legs. At their free ends, the legs are close enough together that,
when the shank 14 is inserted in a hole in a workpiece of a diameter
which will receive, and be substantially filled by, the part of the
25 shank Iying between the shoulders 2B and the head 32, the end~ of
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the walls 42 will meet and provide a pivotal axis about which the
shoulders 26 will pivot as the legs 16 resiliently yield more towards
each other to allow the thickened portions 22 to pass right through the
hole. After so passing right through, the legs relax and the shoulders
26 overlie the periphery of the hole of the blind side of the workpiece.
5 The foregoing feature that the shoulders 26 pivot about the point of
contact of the free end of the legs on inserting the shank 14 into the
hole, provides effective safeguard against accidential withdrawal
of the shoulders through the hole before the plug 34 has been
advanced between them.
The shank 14 of the first illustrative fastener may be inserted
in a hole in a workpiece as just described and the head 20 of the pull-
part 10 is pulled and the head 32 of the push-part 12 pushed, by means
of a suitable blind rivet setting tool, to urge the head 32 and shoulders
26 towards one another, such action first drawing together parts of
15 the workpiece (if the shank has been inserted through aligned holes
in parts which are not touching) and finally clamping the workpiece
firmly. At such stage, the teeth 40 of the plug 34, embedded in the
inner walls of the legs (or accommodated in complementary grooves
in the walls 42) prevent movement of separation of the shoulders 26
20 and head 32. The portion of the pull-part 10 (including the stem 18)
then projecting from the head 32 of the push-part 12 now may be
removed by severing the legs 16 flush with the head 32 by cutting
means incorporated in the setting tool. Such severance is facilitated
by the relatively thin cross-section of the two legs where they pass
25 through the apertures 30, thus to leave a fastener which is of
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pleasing appearance on the accessible side of the workpiece.
The first illustrative fastener is made by injection molding
thermoplastic resinous material, for example the push-part 12 of
Nylon 66 and the pull-part 10 of "DELRIN" acetal resin. The push-
part is molded first and introduced into the mold into which the
S acetal resin is injected to form the pull-part directly on the push-
part. Made in this way, surfaces of the pull-part in contact with
those of the push-part are complementary in shape, which results,
inter alia, in the formation of the grooves (already mentioned) on
the inner walls 42 of the legs 16 complementary to the teeth ~0
lO on the plug 34> and an overall internal configuration of the shank
complementary to the surface of the plug except for the longitudinal
slots which separate the legs 16. Thus the walls 42 are part
cylindrical where they are in contact with the surfaces 28 of the
locking member; such cylindrical surfaces, or eonieal surfaces, can be
lS provided on the converging portions of the walls beyond the plug,
if preferred to the walls being flat as already deseribed. ~lternatively,
the plug could be a square cross-section with straight teeth on
- opposite walls, though arcuate teeth engaging cylindrical walls,
as already described, are preferred to effeet good filling of the hole
20 in the workpiece and reliable locking-together of the two parts of
the fastener. If a fastener having a plug with a flat sided shank is
selected, however, it is preferably of rectangular cross-section,
its broader faces extending across the whole complementary flat
inner faees of the legs and filling the gap between them.
The second illustrative fastener (~igs. 7,8 and 9) is in many
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respects similar to the first one, but the locking teeth are provided
on the legs of the pull-part instead of on the plug of the push-part.
Like reference numerals, suffixed by a dash, are used in Figs. 7,
8 and 9 for parts corresponding to those of the first illustrative
fastener .
Referring to Fig. 7, the teeth 40' are on the outside of the legs
16' and face the opposite way to the teeth 40 of the plug 4 of the first
illustrative fastener, their sides normal to the axis of the shank facing
the free ends of the legs. The inside walls 42' of the shank legs 16'
are flat and parallel right up to the tail end of the fastener, the plug 34'
being rectangular in cross-section. Such configuration of the legs and
plug simplifies the tooling for injection molding.
The second illustrative fastener is made by a similar two-stage
injection molding procedure as the first one, but the shank member 10'
is molded first. Thus, grooves complementary to the teeth 40' are
lS formed in the walls of the aperture 30' in the head 32' of the push-part.
The teeth a~o' extend over most of the length of the shank legs 16', and
locking is achieved, on clamping a workpiece, by inter-engagement of
the grooves in the head of the push-part with whichever of the teeth
on the legs they have come into engagement with. (If teeth are not
.l 20 provided on that part of the legs onto which the push-part is molded,
the teeth on setting of the fastener, will dig into the material of the
head of the push-part) .
It ~,vill be observed that the head 32' of the push-part 12' of
the second illustrative fastener is thinner than the head 32 of the
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first illustrative fastener. This is because, since the teeth 40' are
engaged directly by the head 32', less load has to be transmitted
by the head to the plug when advancing the plug along the shank
than is the case with the first illustrative fastener.
Fig. 9 shows the second illu,strative fastener installed in a
5 workpiece consisting of two plates P,Pl after the stem 18' has been
removed flush with the head 32' .
It will be realized that both illustrative fasteners can be
made with legs of any desired length and are capable of being set
in workpieces of any thickness which can be accommodated bet~,veen
lO the heads 32,32' of the push-parts and the shoulders 26,26' of
the legs.
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