Note: Descriptions are shown in the official language in which they were submitted.
`` ~;z5-U~735
23~8-125
The present invention relates to a joining method in
which two sheet metal pieces lying side-by-side are joined. The
invention further relates to an apparatus adapted to implement the
method of the invention and of a ioint of two sheet .metals made
therewith.
Canadian Patent 1,1~2,665 discloses an apparatus for
joining sheet metal pieces in side-by-side relation. The
apparatus cornprises a female die having a central anvil member and
support members adjacent to the anvil rnember extending beyond the
anvil working face. The support members have cutting edges at
their distal ends and may flex resiliently outwards with respec-t
to the anvil member.
Further, the apparatus comprises a rnale die, which is
movable relative to the female die through the sheet metal pieces
towards the anvil Member's working face. In use the male die and
the female die co-operate such that both sheet metal pieces are
cut along congruent incisions and with the male die pressing
against the anvil member working surface of the female die, the
material is deformed through -the sheet metal pieces is la-terally
extruded to engage beyond -the edges o-E the incisions opposite the
sheet metal first pierced by the male die. For this purpose the
male die (or each of the rnale dies if there is a plurality of male
dies and female dies) has cutting edges so that the sheet metal
piece first engaged by the male die is properly cut as well as the
other sheet metal adjacent the female die.
Joints made by means of this known apparatus in general
73S
- 2 - 23448-125
have a strength sufficient for most practical applications. How-
ever, in some cases extreme joint strength is required, a strength
which cannot be acheived by using the method and apparatus dis-
closed in the referenced patent. It is the object of the present
invention to provide method and apparatus by means of which joints
of increased strength may be produced. "Increased strength", in
this context, means higher strength as compared with the strength
of joints made by use of the apparatus referred to above, under
circumstances which otherwise are the same (thickness and type of
the sheet metals to be joined, size of the joint, etc.).
According to the invention there is provided a method for
joining two overlapping sheet metal pieces wherein only one of said
pieces is provided with incisions proximate to each other to define
a joining area therebetween, comprising deforming said other piece
at a site congruent with said area substantially perpendicular to
the sheet plane thereof towards said one piece so as to deform
said area until material of said other piece protrudes beyond the
face of said one piece opposite said other piece, and compressing
said protruding material whereby the latter flows sidewards in
clamping engagement beyond the edges of said incisions opposite
said other piece.
The invention also provides an apparatus for joining two over-
lapping sheet metal pieces comprising a female die having a central
anvil member and support members adjacent said anvil member, each
support member projecting beyond a working surface of said anvil
member and having cutting edges at the ends of said projections,
~B~
lZ5~73S
3 - 23448-125
said support members being adapted to flex away from said anvil
member, and comprising further a male die adapted to be pressed
towards said working surface of said anvil thereby deforming sheet
metal pieces disposed between said dies, said male die having a
working surface opposite said anvil working surface, said male die
working surface being narrower than the distance spacing said
support member cutting edges.
Surprisingly it has been found that joints produced by
this method and apparatus have a strength exceeding that of the
known joints referred to above by at least 50~ and, in some cases
(shearing strength) by 75~. As a further advantage it is to be
noted that the non-cut sheet metal remains fluid-tight, a fact
which in some applications is of utmost importa~e. Frequently,
the sheet metals have a coating for purposes of corrosion protect-
ion, and if such coating (for example zinc plating on steel) is
plastically deformable, the coating of the non-cut sheet also will
remain intact.
A joining method and apparatus and a joint produced
therewith wherein the joint remains fluid-tight are disclosed in
the DE-A- 31 06 313. According to the teaching of this publication,
sheet metal pieces are joined by means of an apparatus having a
male die and a female die. Neither die has cutting edges with the
result that no incisions are produced. Instead, both sheet metal
pieces are bulged at the joint site so that material of both pieces
protrude to one side, and thereafter bo-th protruding material
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~ 3a - 23448-125
portions are laterally compressed. For this purpose the female die
may laterally open against spring bias. The deformed portion of
the piece adjacent the female die does not contribute to the
strength of the joint; on the contrary
~.,
l~S~35
it withstands the lateral deformation of the other sheet metal
portion so that the joint strength obtained is limited. Moreover,
all inte.rengaging surfaces of the two sheet metal pieces are
rounded, which fact fur-ther limits the joint strength. These
considerations, again, refer to joints produced from identical
materials and of comparable size.
A particularly simple embodimant of the aloparatus
according to the invention comprises a female die having only two
support members, each having a cutting edge, the cutting edges of
~0 the two support members being parallel to each other. This embod-
iment is not only simple in manllfacture but also easy to adjust on
a press because the alignment of male and female die must be
effected only in direction perpendicular to -the cutting edges,
alignment in the direction orthogonal thereto being non-cri-tical.
Embodiments of apparatus according -to the invention will
be explained hereunder with reference to the accompanying
drawings. These drawings are simplified in an attempt to illus-
trate only the features of importance for the implementation of
the invention; for further details reference may be made to the
disclosure of the Canadian Patent 1,182,665.
Figure 1 shows in partial side view a first embodiment, the
two sheet metal pieces to be joined being shown in section;
Figure 2 shows in similar manner the elemen-ts after termi-
nation of the joining stro]~e;
Figure 3 iLlustrates in an isometric view, par-tially in sect-
ion, a joint according to the invention as produced by the appar-
atus shown in Figure 1 and 2;
~2S~?'735
Figure 4 is an illustration similar to Figure 3 but seen in
direction of the arrows 4-~ of Figure 3;
Figure 5 is a plan view of the joint o Figure 3, 4;
Figure 6, 7 and 8 show plan views of the female dies of fur-
ther embodiments of the apparatus;
Figure 9 shows in side-view a male clie of a Eurther embodi-
ment.
Figure 10 is similar to Figure 1 and shows a female die oE
different desicJn; and,
Figure 11 is a sectional view of the female dle of Figure 10
in the direction oE ~QW~ 11.
The press on which the co-operating tool parts, i.e.
male die and female die, are mounted aligned to each other is not
shown in the drawings. The operating direction of the press
results readily from the combination of Figure 1 and 2 which show
the two possible relative positions of male and female dies at the
beginning and at the end of the press stro~e.
At first Figure 1 through 5 are referred to.
The Eemale die comprises a stationary anvil member 10
supported at its bottom in the press. The anvil member 10 has a
substantially rectangular elongated section shape; Figure 1 shows
the side view on -the narrower side. Support members 12 extend
along the larger sides of the anvil member, the support members
12 being mounted to resiliently yield sidewards (cf. Figure 2),
the -free edges of the support members adjacent the anvil member
acting as cutting edges. The plane deEined by the two cutting
edges is somewhat elevated with respect to the somewha-t convex
~IZ~735
working face 16 of the anvil member lO, this elevation being
smaller than the sum of the thicknesses of the two sheet metal
pieces l8, 20 but the elevation exceeds the thickness o-f the
sheet 1~ acljacent to the female die.
The male die 22 has a working surface 24 which as illus-
trated in Figure 1 is narrower than -the distance spacing the
cutting edges of the two support members oE the female die. The
male die section tapers outwards from its working surface so that
the die-portion which penetrates into the sheets h~s a trunco-
pyramidal shape with a rectanyular base. The pyramid sides areinclined with respect to the die-axes at about 20; this corre-
sponds to an apex angle of 40. The difference between the wid-th
oE male die working surface 24 and the spacing of the two cutting
edges from each other depends upon the -thickness of the sheets, in
particular upon the thickness of the sheet 20, and preferably is
dimensioned such -that this sheet 20 during the joining operation
is just not cut. The edge surrounding working sur-face 24 is
rounded (in the illustrated embodiment the rounding radius is in
the order of magnitude of 0,5mm) and polished thereafter. The
side faces of the trunco-pyramidal die portion are designated 26.
The contour of the male die at the sides extending orthogonal to
the cutting edyes of the female die is not illustrated in Figure 1
and 2, however, is seen in Figure 9 whlch shows a male die
comprising two die members similar -to the male die of Figures 1
and 2. It is to be noted that here again the con~our has about
the same apex, pyramidal angle as the other sides extending
parallel to the cutting edges.
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~ hile Figure 1 shows the si-tuation prior to the joining,
Figure 2 illustrates the result of the press stroke. It is to be
noted that the press is adjusted either with respec-t to the pres-
sure applied or with respect to its stro]ce.
In Figure 2 sheet 18 has been cut along the cutting
edges 14 which extend orthogonal to the plane of the drawing, due
to the co-operation of these cutting edges with the male die 22
and the sheet portion 30 between the incisions is deEormed through
to the working face 16 of the anvil member. Upon further pressure
(and thus fur-ther stroke) o male die 22 the deformed portion 32
of shee-t 20 which was not cut is extruded such that its material
is plastically deformed laterally beyond the edges 3~ which have
been cut free so to ridgidly engage thereon. The portion 30
remains connected to sheet 1~ at its ends 36 because there was no
cutting operation. The joint so produced is illustrated in detail
in Figure 3 to 5.
In the first embodiment described above there were only
two incisions in the sheet 18. The female die and the male die
for this purpose have a very simple design to be manufactured at
low cost. If particular design considerations are to be met with
regard to the appearance of the joints, for example if the joints
are visible in household appliances, an embodiment of the appa-
ratus according to the invention may be preferred as illustrated
in Figure 6 to 8. I`hese embodiments are shown only as plan views
on the female die. The anvil member 10' (Figure 6) and 10"
(Figure 7) is cylindrical, and tlle support members 12' and 12"
respec-tively have cutting edges ~hich cut into the adjacent sheet
l~S~'73S
respec-tively along four (Figure 5) and three (Figure 7) arcs
having the same xadius and a common centre. Between the incisions
there is always a connection performin~ the same function as -the
connections 36 in Figure 3. 1'he working surface of the respec-tive
male die is indicated in dashed lines at 24' and 24" respectively;
the contour of these male dies will then be truncated conical wi-th
an apex angle of preferably 40, similar to Figure 1.
In the embodiment of Figure 8 there are four support
members 12"' disposed about an anvil member lO"' having a square
section shape. The connections will then be provided in the cor-
ners. It is to be noted that under certain circumstances the
connecting portions may be eliminated. This would mean in Figure
6 and 7 a closecl circular incision and in Figure 8 a closed square
incision with the result that a small plate portion would be
stamped fro~ the sheet adjacent the female die having the respec-
tive contour. The appearance of the joint would then be very
similar to a rivet head, however, after each joining operation the
stamped out plate portion would have to be ejected from -the female
die.
The male die according to Figure 9 is a twin die wherein
two male dies according to Figure 1 are disposed side by side and
are manufactured in an integral piece. One will see the two
working faces 24a, 2~b and t`he respectively allocated flanges 28
extending or-thogonal to the cutting edges of the female die (not
shown) and also define an apex angle of ~0. The cutting edges of
the respective female die are similar to Figure 1 but somewhat
-- 8 --
~25~73~
longer so that with one press stroke only two juxtaposed joints
are produced.
Figure 10 and ll show a female die in which the support
members are replacable.
The female die comprises a socket 118 having a planar
bottom 120 parallel to the table of a press (not shown) and a
planar clamping surface 122 which extends orthogonal to the bottom
120. A threaded hole 12~ extends into the socket from the
clamping surface 122.
Support members 126, 128 and anvil member :l30 are sepa-
rately produced components. Anvil member 130 is a stamped steel
part while the support members are cut from spring steel and have
each two cutting edges on both sides with respect to the anvil
member. In the area of the cutting edges the support members are
hardened or hard-coated and ground. Anvil member and support
members have through-'noles which when assembled are aligned with
the threaded bore 124, forces acting upon the components during
the joining operation being transmitted to the socket because the
support members and the anvil member engage the bottom Eace 120.
On the side of the support member 126 facing away from
clamping surface 122 there is a clamping disc 13~ which also has
an aligned through-hole. The entire assembly is clamped by
means of a screw 136. Figure 10 illustrates the situa-tion prior
to the final fastening of the screw so that it may be seen that
the disc 13~ is outwardly bulged so to act as a resilient disc.
Its lower edge also abuts the bo-ttom face 120.
This embodiment has the advantage that the support
members may be turned outside-in after t'neir cutting edges become
worn and when the second pair of cutting edges also has become
worn may be replaced. Moreover, -the anvil member also may be
exchanged. Such an exchange will most probably not become due to
the anvil member being worn, but another anvil member will permi-t
the joining of sheet metal pieces having di-Eferent thicknesses,
which requires a different spacing between cutting edges 132 and
anvil working face l38.
The upper edge 140 of the disc is dispose~ on the same
level as the upper edge 142 of clampiny surface 122 so that there
are identical clamping conditions for both support ~embers.
As may be seen from ~igure 11 the support members have
laterally cut off contour so that the bending tension duriny the
lateral yielding is distributed in uniform manner over the length
of the support members.
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