Note: Descriptions are shown in the official language in which they were submitted.
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P-302
WELD NUT
TECHN~C~I FIELD
This invention relates to wela nuts which
are secured to an apertured support.member by a welding
.process t~ permit the support member to receive a
complementary ~astener~
BACKGROUND ART
A weld nut is welded to sheet metal or
similar type supporting material to permit the sheet
metal to receive a complementar,y fastener, The sheet
metal alone is ordinarily insufficient to support the
fastener, and the weld nut.provides the required
supporti~lg strength.
A typical weld nut is formed from a piece of
flat metal stock and has a central tapped hole ~ormed
therethrough ~or the receipt of.a threaded bolt. The
surface of the weld nut which is to bear against the
sheet,metal or supporting material includes a plurality of
raised integral projections or~nibs. The nut can be
secured to the supporting material by xesistance welding
which causes the projections to ~low and'alloy with
the supporting materi~l.
One concern in the use of weld nuts is
that the weld be se¢ure. This requires a fusion of su~fi-
cient material to maintain the weld throu~h all typesof normal use. Of particular concern is the pro~lem of
the weld nut not sea~ing flush against the supporting
material. Where a rectangular weld nut is usea with four
pxo jections, i.e. one at each Yertex~ t~ere is th,e
possihility that the nut will not seat flush with the
supportin~ material if there is an~ discrepancy in the
heiyht o~ the projections~ This c~n be'especially
troublesome if resistance weIdin~ is used to join the 'nut
to the supporting material and there is an air gap
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between ~ projectio~ ~nd the supporting material. Moxe-
over, the misorientation of the nut m~y cause cross-
threading with the bolt which it receives~
Another concern is that the fusion must not be
so extensive that weld flash or splatter reaches into the
tapped hole or aperture in the weId nut and interferes
with the entr~ of the bolt~
In addition, the weld nut must be given to high
volume manufacture at relatively low cost in order to
be cost-effective with competing forms of fasteners,
It is, therefore, an objective o~ -khe invention
to provide a weld nut which will form a secure weld
with a supporting material.
It is another objective of the invention to pro-
vide a weld nut which is designed to be free of weld; flash or splatter in the aperture of the weld nut.
It is yet another objec:tive of the invention to
provide a weld nut design which is relatively low cost
to manufacture.
DISCLOSURE OF THE IN~IENTION
A weld nut in accordance with the present inven-
tion includes a nut bod~ defined by a flat metal plate.
The 1at metal plate has the shape of an equilateral tri-
angle with its vertices truncated by flat-tening or round-
ing. A central opening is formed through the nut bod~ toreceive a complementary fastener. In a typical embodiment~
the central opening is a tapped hole.
One of the surfaces of the nut body is adapted
to bear against the supporting material after welding and
is termed a mating surface. A set o ~ixst, second and
third integral projections or ~ibs are raised from the
mating sur~acet The raised projections are spaced about
the central opening in equila~eral relation with respect to
one another. Each projection has a rusto-conical body
with a rounded top. In -the preferred em~odiment, one
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raised projection is formed near each truncated vertex
- of the triangular shaped flat plate defining the n~t body.
Each of the raised projectîons is surrounded by
- an annular channel. The annular channeI serves to
accommodate metal flow when ~he projections are welded
to the supporting material. In this regard the annular
channels contain the flow a.nd pre~ent weld flash or
splatter from reaching the central opening through the
nut. In addition, the channels permit the mating surface
of the weld nut to se~t against the supportin~ material
without an air gap in between. B~ forming each channel
` to intersect with a flattened or rounded vertex it
provides a path for material to flow outwardly and form
an external fillet.
Other advantages of the present invention will
be readily appreciated as the same becomes better under-
stood by reference to the followi.ng detailed descri.ption
when considered in connection with the accompan~ing
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIGURE 1 is a plan view o the matin~ surface of
a weld nut embodying the present invention;
FIGURE 2 is a cross-sect.ional view ta~en along
line 2-2 of FIGURE 1 and which shows the weld nut ready
to be welded to a sheet of suppor~in~ material; and
. FIGURE 3 is an enlarged cross-sectional view o~
a portion of the we~d nut showing it welded to the sheet
of supporting material.
BEST MODE FOR CARRYING O~T THE INVENTION
- 30 A weld nut embodying the present invention is
shown generally at 10 in the drawinys. With combined
reference to FIGURES 1 and 2, tlle weld nut 10 comprises
a body 1~ formed of a flat triangular steel plate of
sufficient thickness to support a threaded bolt or similar
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type fastener. The triangular shape of the body 12
is preferably modeled a~ter an equilateral triangle,
i.e. each side is of equal len~th. A modification
. from the triangular shape occurs at the vertices which
are trunca~ed to ~orm ends 14; in this context the term
"truncated" is meant to include both rounded and
flattened. In the pre~erred em~odiment, ~he width W
between the points 22a and b, which represent the transi-
tion points between the triangular shape of the plate
12 and the truncated end 14, is no less than the thickness
D of the plate; i,e. the ratio W:D is > 1.
. A central opening 16 is ~ormed through the nut
body 12. The central opening 16 is typicall~ tapped to
receive a threaded bolt, It has chamers 18 and 20 ~ormed
at its opposite ends to fac.ilitate engagement of he nut
10 with a threaded bolt.:
E.ither side of the weld nut 10 can ha~e a local
extrusion (not shown) formed about the periphery of the
central opening 16. The extrusion can be used as a
pilot if formed on the same side as the projections. The
wall thickness of the extrusion will be less than or .
equal to the thickness D of the plate 12 depending on
specific requirements;
The surface of the weld nut 10 which is to be
: 25 mated with a sheet of supporting material r e . g. as indi-
cated by the phantom lines 40 in FIGU~E 2, is termed .
a mating surace 24 and is substantially planar. The
mating surface 24 has formed in i~ a set of first, .
second and third integral raised projections ox nibs 26, .
28, and 30, respectively. The projections 26, 28 and
30 are spaced about the central opening 16 in equilateral
relation to one another. More particularly, each of the
projections 26, 28 and 30 is formed in proximity to a
flattened end 14, and includes a generally frusto~conical
body 32 which terminate~ in a rounded top 34, The
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rounded top 34 provides good contact resistance with the
supporting material 40 for resistance welding, yet is
not so pointed as to puncture t~e ~upporting material
~hen pressure ~s applied to join the nut-to the material
in the welding process. Accordingly, the rounded top 34
requires a relatively small amount of in~tial current to
begin the melting process and the frusto~conical body 32
continues t~is e~f~cient mel~ process~ The energy
efficiency is greater as compared with other shapes of
projections or nibs.
It is preferred that for each projection, the
smaller, outer end of the rusto~conical portion, where
it joins to the rounded portion 34, have a diameter
approximately one-half the diameter of the larger, inner
end of the frusto-conical portion. Additionally, it is
preferred thàt the angle of taper of the ~rusto-conical
portion be from 60-90, such angle being 70 in the pre-
ferred embodiment shown~
An annular channel is -Eormed in the mating
surface 24 in surrounding relation to each of the pro-
jections 26, 28 and 30. The annular channel i5 defined
by a lower waIl 36 and a flared side wall 38. Each of
` the channels preferably intersects an adjacent truncated
end 14 to provide a path for material to flow outwardly
and form an external fillet. However, if no fillet is
-; desired, the channel can be formed to completely sur~
round t~e projection.
A blind hole 42 is formed in the surface of
the nut body 12 opposite the bearing surface 24. The
blind hole 42 results from stamping the body 12 to form
the raised projections 26, 28 and 30 and annular chan-
nels in the ~earing surface. As a consequence, a blind
hole such as 42 complements each of the projections 26,
28 and 30.
With reference to FIGURE 3, the manner in
which the weld nut 10 is secured to the supporting
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material 40 is next described. By resistan~e welding
the weld nut 10 to the supporting material 40, the
projections are caused to flow and alloy with the sup-
porting material to form a weld. The extruded material
44 forming the projections flows radially outward and
fills the annular channel surroundin~ the original
projection. An external fillet 46 is formed adjacent
the point where the flattened end 14 and annular channel
intersect. The extruded material 44 is contained at the
diametrically opposed side of the channel to prevent
~eld flash or splatter from reaching the central open-
ing 16.
As a result, the weld nut 10 is secured to
the supporting material 40 by at least three welds sym-
metrically spaced around the central opening. The nut10 is seated against the supporting material 40 such
that the mating surface 24 is flush therewith without
an intervening air gap.
The invention has been described in an i~lus-
trative manner, and it is to ~e understood that theterminology that has been used is intended to be in the
nature of word description rather than limitation.
- Many modifications and variations of the
present invention are possible in light of the above
teachings. It is, therefore, ~o be understood that
within the scope of the appended claims, the invention
may be ~racticed otherwise than as specifically
described.
