Note: Descriptions are shown in the official language in which they were submitted.
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1 The present invention relates in general to induct
live welding, and in particular to a method of and a device
for welding a laminated cup-shaped cover composed of a metal
layer and a thermoplastic layer to a shell ox a container which
is also coated with a thermoplastic layer.
In known welding devices of this kind, described for
example in DEMOS 27 I 711, the induction coil inserted during
welding in the recessed part of a cup-shaped cover, includes
three windings. The purpose of such a closed construction of
the induction coil is to ensure that the cover be continuously
welded to the container body along its entire circumference.
The disadvantage of this prior-art method and device
is the fact that the welding seam is relatively broad and con-
sequently and welding time and energy consumption are relatively
high.
It is therefore a general object of the present invent
lion to overcome the aforementioned disadvantages.
More particularly, it is an object of the invention
to provide an improved method of the aforedescribed type which
results in a relatively narrow and continuous welding seam which
can be made in a shorter time and at lower energy consumption.
Another object of this invention is to provide an
improved welding device of this kind which is simpler in con-
struction and can be readily accommodated in the recess of the
cover.
In keeping with these objects and others which will
become apparent hereafter, one feature of the invention resides,
in the method and device of the aforedescribed kind, in the pro-
vision of an inductive coil constituted by a single winding in-
sortable into the recess in the cover parallel to the upright
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1 wall of the latter, the single winding having its end surfaces
arranged at a minute distance opposite each other.
In welding by the single winding coil of this invent
lion, it has been found that the annular welding seam produced
between the cover and the shell of the container is completely
continuous, without any interruptions, and is perfectly leak-
proof. At the same time, due to the fact that the welding seam
is narrow, the operational time and the energy consumption are
reduced.
The novel features which are considered characteristic
for the invention are set forth in particular in the appended
claims. The invention itself, however, both as to its construe-
lion and its method of operation, together with additional ox-
jets and advantages thereof, will be best understood from the
following description of specific embodiments when read in con-
section with the accompanying drawing.
FIG. 1 is a section side view of the device of this
invention when used for welding a cup-shaped cover to a tubular
body of a container; and
FIG. 2 is a top view of the device of this invention.
Cover 1 to be welded to a tubular container body 6
has a cup-shaped configuration defining a flat bottom 2, an
upright flange 3 with a downwardly folder rim 4. The cover 1
is composed of a multi-layer material, of which the innermost
layer adjoining the inner wall of the container 6 is made of a
fusible thermoplastic material, such as polyethylene or polyp
propylene for example, and adjoining another layer of a thin
metal foil, preferably of aluminum. The outer supporting layer
is of a suitable synthetic material. The body of container
6 is also made of a laminated or multi-layer material, of which
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1 the inner layer, as mentioned before, is also made of a fusible
thermoplastic material, the intermediate layer is of metal sup-
ported on an outer layer.
In order to secure the cover 1 to the open end of the
container body 6, the flange 3 is inserted into the container
shell 6 to such an extent that the entire flange 3 is in contact
with the inner wall portion of the container shell 6, and the
folder rim 4 abuts against the end face of the container shell.
Thereafter, the flange 3 of the cover 1 and the con-
tatting rim of the container body 6 are compressed and heated for a short period of time whereby the heated inner thermos
plastic layers both of the cover 1 and of the container body 6
momentarily fuse in an annular area opposite the induction coil
15 and thereafter form an annular welding seam 7.
The welding device for producing the welding seam 7
includes a stepped plunger 10, the leading end 11 of which fits
the recess of the cover 1. The step 12 of the plunger 10 abuts
against the rim fold 4 of the cover. The end part 11 of plunger
10 cooperates with lateral open dies 14 movable against the down-
warmly bent part of rim 4 for compressing the same and the rim of contained body 6 against the flange 3 of the cover.
The end part 11 of plunger 10 is made of an electric
gaily insulating material and supports on its periphery a single
winding coil 15. The winding 15 is flush with the circumference
of the end part 11, and upon insertion of the plunger 10 in the
recess of the cover 1, the outer side surface of winding 15 is
brought in contact with the inner wall of flange 3 of cover 1.
The end surfaces 16 and 17 (FIG. 2) of the single winding 15
face each other at a distance of about 0.5 to 1 mm. Supply con-
dulls 13 undo 19 are connected to respective end portions of the
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1 winding 15 at an angle of about 75 to the plane of the coil 15.
Both conduits 18 and 19 pass through corresponding grooves 13
in the plunger 10. The end surfaces 16 and 17 of winding 15 are
separated from each other by an insulting foil 20.
The single winding 15 is made of a cooper tube of rectangular cross section which is bent in accordance with the
inner perimeter of the flange 3 which in this example has a
configuration of a square with rounded corners. The end sun-
faces 16 and 17 are situated in one straight side of the square
winding 15. The longer side of the rectangular copper -tube 15
facing the flange 3 of the cover 1, is shorter in length than
the latter.
During the welding operation, the end part 11, as
mentioned before, is introduced in recessed part of cover 1 so
that the outer surface of winding 15 is brought into contact with
the flange 3. The narrow lower side of winding 15 is flush with
the bottom of plunger part 11, and in the welding position is
spaced apart from the bottom 2 of the cover. The power supply
conduits 18 and 19 passing through the plunger 10 are coupled to
a non-illustrated high-frequency generator which energizes the
winding 15 for a time period of about 0.5 seconds with a high-
frequency current of about 2 megahertz. The resulting electron
magnetic field in the coil 15 induces in the range of the inter-
mediate metal layer in cover 1 opposite the coil 15 eddy currents
which heat up the metal foil. The generated heat is transferred
to the adjoining thermoplastic layers both of the cover 1 and of
the container body 6 and heats the same to a welding temperature.
Simultaneously, the open dies 14 compress the folded rim 4 of the
cover against the end part 11 of the plunger and the melted or
fused regions are united in the welding seam 7. This welding
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1 seam is continuous even in the region of the gap between the end
surfaces 16 and 17 of the winding 15, because the fused thermos
plastic layers of the cover and of the container body receive
enough heat to melt and fuse together the thermoplastic layer
around the entire circumference of -the cover. To prevent over-
heating of coil 15 and of plunger 10, a cooling agent is contain-
usual fed through the hollow channel in the coil 15. If desired,
by increasing the length of the hurricanes pulse, there is
generated a correspondingly increased amount of heat in the alum-
inum layer of flange 3 and of the folded rim 4 to melt the thermos
plastic layer in the fold 4 and fuse the same with the outer sun-
face of the container body 6.
It will be noted that each of the elements described
above, or two or more together, may also find a useful applique-
lion in other types of constructions differing from the types
described above.
While the invention has been illustrated and described
as embodied in a specific example o-E a welding device, it is not
intended to be limited to the details shown, since various mod-
fixations and structural changes may be made without departing inane way from the spirit of the present invention.
Without further analysis, the foregoing will so fully
reveal the gist of the present invention that others can, by apt
plying current knowledge, readily adapt it for various apply-
cations without omitting features that, from the standpoint of
prior art, fairly constitute essential characteristics of the
generic or specific aspects of this invention.
What is claimed as new and desired to be protected by
Letters Patent is set forth in the appended claims.
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