Note: Descriptions are shown in the official language in which they were submitted.
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M~THOD ~D APPARATUS FOR JOINING WORKPIECES TO(~
The invention relates to a method for joining
workpieces together by welding by means of a welding energy
source in a welding station, and also to an apparatus for
carrying out the method.
- Various welding processes are known for joining
workpieces together, particularly for the fabrication of
body components for motor vehicles. Especially worthy of
note are mash roller seam welding, laser welding, etc.
For all welding processes, it is essential that
the welding operation be conducted as economically as
posRible. It is important to note that a specific time is
required for the actual welding operation, since a specific
rate of travel has to be maintained. In the present state
of the art this lies somewhere below 15 m/min.
Furthermore, the workpieces which are to be
joined together have to be positioned before welding can
take place, and they have to be transported, loaded on
carriers and unloaded from carriers, dressed, cooled, and
subjected to quality inspection. These operations take up
a considerable time, which is nonproductive time during
which no welding can take place.
The object underlying the present invention is to
develop a method and an apparatus of the abovementioned
kind which allow two workpieces to be joined together in a
more economical way and the productivity of the line to be
increased through a reduction in nonproductive time.
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This object is achieved by using a common welding
energy source to join together, in succession, a plurality
of workpieces in a plurality of welding stations.
This means that several welding stations can be
served by a single welding energy source, which is normally
the most expensive part of the apparatus. This is known as
duplex operation, in which those elements which are
responsible for nonproductive time in single operation are
multiplied. As a result costs can be reduced. It is also
possible according to the invention, while a welding
operation iæ taking place in one welding station, to remove
workpieces which have already been joined together f~om
another station in order to load that other station with
new workpieces and to position those workpieces. All that
then remains is to divert tne welding energy æou~ce to the
newly supplied welding station in turn. As a result, very
little time i9 lost.
In one way of carrying out the method according
to the invention, the workpieces can be fixed and a welding
beam, in particular a laser beam, traversed in relation to
the workpieces to effect the welding. In the other way of
carrying out the method, however, the welding energy source
and the laser beam are fixed during welding and the
workpieceæ are traversed with respect to the welding beam.
Obviously, the workpieces are secured during the welding
operation, by means of suitable clamping tables, clamping
elements or the like. Alternatively, roller conveyors with
securing arrangements may be used.
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If a laser is used as the welding energy source,
better possibilities may be obtained by the interposition
of deflector devices into the laser beam. With the present
state of laser technology, it can be arranged that the
laser remains stationary, transmitting a beam always in one
direction. Deflector devices can then be interposed into
the path of the beam as required, to suit the positions of
the welding stations, so as to deflect the beam to a
focussing unit and to the welding station desired.
However, if the workpieces are to remain
stationary during the welding operation, the possibility
also exists of traversing the focussing units togeth~r with
the deflector devices within the welding stations.
Possible deflector devices will normally be mirrors, but
glass fibre cables can also be used.
There are also a large number of possible
arrangements for the welding stations. They may be
arranged in line or in parallel, or aligned in a sandwich
arrangement. Moreover, the individual welding stations may
be positioned at any desired angle in space with respect to
each other.
The efficiency achievable by the present
invention lies first of all in a duplication of the simpler
components, minimising non-productive times for the costly
welding energy source. The welding energy source can be
permAne~tly utilized, which iB particularly important: at a
given rate of travel (determined by the state of the art or
other criteria), it is possible to achieve the maximum
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production rate that can be attained by the use of a single
welding energy source. It i9 also possible to cater for
more than two welding stations with a single energy source.
Further advantages, features and particulars of
the invention will become apparent from the following
description of preferred embodiments given by way of
example and with reference to the drawings, in which:
Fig. 1 is a diagrammatic side view of an
apparatus according to the invention for joining two
workpieces together;
Fig. 2 is a plan view of the apparatus according
to Fig. 1;
Fig. 3 is a plan view of a further embodiment of
an apparatus according to the invention;
Figs. 4 and 5 are diagrammatic views of further
embodiments of an apparatus according to the invention;
Fig. 6 is a diagrammatic plan view of part of the
apparatus shown in Fig. 2;
Fig. 7 is a cross-section through an apparatus
according to the invention which uses a shuttle for welding
several sheet-pairs;
Fig. 8 is a plan view of the apparatus shown in
Fig. 8.
In an apparatus R according to the invention, two
workpieces 1.1 and 1.2 (see Fig. 2) are to be joined
together by laser welding. This apparatus R has feed units
Fl and F2 on either side of a portal 2, and welding stations
Sl and S2 inside the portal. The actual welding is
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performed by means of a laser beam 3 produced by a laser 4.
In order that the laser beam 3 can be directed
either to the welding station S1 or to the welding station
S2, deflector devices 15.1 and 15.2 are provided in the
laser beam 3, each able to deflect the la9er beam 3 from a
horizontal direction to a vertical direction.
In this case the laser 4 i9 fixed and is located
for example in the corner region of the portal 2. The
laser 4 transmits a single laser beam towards the deflector
devices 15.1 and 15.2. Focussing units 16.1 and 16.2 are
associated with the deflector devices 15.1 and 15.2. When
the deflector device 15.2 is interposed in the path ~f the
laser beam 3, the focussing unit 16.2 is utilized. When
the deflector device 15.2 is swung clear, the laser beam 3
is able to pass to the deflector device 15.1 whe~e it is
deflected into the focussing unit 16.1. Both deflector
devices 15.1 and 15.2 move together with their respective
focussing units 16.1 and 16.2.
A discharge unit 5 is provided between the two
welding stations S1 and S2 for transporting the workpieces
1.1 and 1.2 away, in the direction y, after they have been
welded together to form a compound panel. The discharge
unit 5 may for example have a corresponding roller conveyor
6 as indicated in Fig. 1.
Since the construction of the feed units F1 and F2
and the welding stations S1 and S2 is identical, only one
example will now be described.
The feed unit F has a gripping manipulator 7
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which is capable of traversing in the direction xl. The
manipulator 7 has a horizontal slit 8 which is adjoined on
both sides by receiving rollers 9. The workpieces 1.1 and
1.2 are laid on these receiving rollers 9 and are propelled
towards one another and into the horizontal slit 8 by any
desired mechanical handling means. They are then clamped
in the horizontal slit 8 by means of any desired clamping
elements.
The manipulator 7 is then traversed into the
welding station S between two clamping tables 10.
Meanwhile the receiving rollers 9 remain in their position
outside the portal 2.
The manipulator 7 then lays the workpieces 1.1
and 1.2 on the clamping tables 10 so that the workpieces
1.1 and 1.2 are each held between a clamping tab~e 10 and a
pressure plate 11.1 and 11.2 respectively. These pressure
plates 11 are subjected to pressure, which may be
hydraulic, pneumatic or mechanical as desired, so that the
workpieces 1.1 and 1.2 are fixed as securely as possible.
The clamping pressure acting on the workpieces
1.1 and 1.2 in the horizontal slit 8 is then released! and
the manipulator 7 is traversed out of the welding station S
in the opposite direction to the direction x1. This
exposes a butt joint (not shown) between the two workpieces
1.1 and 1.2, and the laser beam 3 is now guided along it,
producing a welded seam and thus joining the two workpieces
together.
The feed unit F is reloaded with workpieces while
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the welding operation i8 being performed. When the feed
unit F is then traversed into the welding station S, these
further workpieces can expel the welded workpiece out of
the welding station S and onto the discharge unit 5.
In a further embodiment of the invention shown in
Fig. 3, clamping tables 10.1,10.2 and 10.3,10.4 are
arranged to run parall`el with and alongside one another on
corresponding rails 17.1 to 17.4. In this embodiment, the
clamping tables 10.1 to 10.4 are traversable, while the
laser 4 is stationary. The laser could also be made
pivotable about an axis of rotation through a predetermined
angle, in the preferred embodiment through an angle af
180, so that it can reach both the clamping tables
10.1,10.2 and the clamping tables 10.3,10.4, although with
preRent-day industrial-type l~sers this i8 not r~alistic
owing to their size and weight. In principle, it would
also be possible to make the laser rotatable so that it
could activate separate deflector devices provided on the
left and on the right over the clamping tables 10.1,10.2
and 10.3,10.4, respectively. This embodiment should also
be deemed to be included within the present invention, even
though it cannot be realised with present-day lasers.
Fig. 3 shows instead how the laser beam 3 can be
directed by a deflector device 15.3 ta prismatic mirror) to
the left or to the right as desired, towards the focussing
units 16.1 or 16.2. The focussing units 16.1 and 16.2
direct the beam 3 on to a butt joint 21 between the
workpieces 1.1 and 1.2, which are welded together by the
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laser beam 3. The clamping tables 10.1 and 10.2 are
traversed in the direction Y1 until the two workpieces 1.1
and 1.2 are joined together. The clamping tables are now
close to an ejector unit 19.1, which is in the form of an
industrial robot for example. As indicated in broken lines
at top right, this bears against the rear edge of the
welded workpieces and pushes them onto the discharge unit
5. The clamping tables 10.1 and 10.2, which are coupled
together to be driven jointly, then travel back to a
position as 5hown for the clamping tables 10.3 and 10.4.
Fig. 3 shows the clamping tables 10.3 and 10.4 in a loading
position, in which workpieces 1.3 and 1.4 are pushed
laterally on to the clamping tables so that they lie under
the pressure plates 11.3 and 11.4. At the same time, it is
possible to position the two workpiece~ 1.3 and 1.4, and in
particular to apply edgewise pressure to close the butt
joint between them.
While loading of the clamping tables 10.3 and
10.4 has been taking place, the laser beam 3 has joined the
workpieces 1.1 and 1.2 together, in the position shown. On
completion of this welding operation, the laser beam 3 is
turned round, preferably through 180, into the position
shown in broken lines, by which time the clamping tables
10.3 and 10.4 have traversed forwards ln the direction Y
so that the laser beam 3 can continue welding in this
position. The workpieces 1.3 and 1.4 are then welded
together, while the clamping tables 10.1 and 10.2 can be
unloaded and reloaded. When the welding operation on the
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gworkpieces 1.3 and 1.4 is complete, the clamping tables
10.1 and 10.2 are once again in the position shown in Fig.
3 with newly loaded workpieces, 80 that the laser beam 3 i9
able, after having been turned round again through 180, to
continue welding on the clamping tables 10.1 and 10.2.
The schematic illustration of an apparatus
according to the invention in Fig. 4 iæ mainly intended to
show that the siting of the laser 4 is completely
independent of the location and arrangement of the welding
0 station, or of the workpieces. In this case an additional
deflector device 15.1 is interposed in the laser beam path
to one of the welding stations. Obviously, the workpieces
are fixed on corresponding clamping tables.
The apparatus R4 shown in Fig. 5 differs from the
forms cf apparatus shown in Figs. 1 to 4 in that a sandwich
type arrangement has been set up. Here, the laser 4 is
positioned between clamping tables 10.1 and 10.2 which are
traversed horizontally. To weld the workpieces on the
clamping tables 10.1 or 10.2 as the case may be, the laser
beam 3 is deflected accordingly.
With the embodiments shown in Figs. 3 and 5, it
is possible either to traverse the clamping tables in
relation to the focussing units or to traverse the
focussing units together with their deflector devices in
relation to the clamping tables.
In Fig. 6 the two workpieces 1.1 and 1.2 are
shown on corresponding clamping tables which together form
a shuttle 22 on which a plurality of workpiece-pairs are
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transported through a welding station S, for example from a
loading station to an unloading station. During transport,
the workpieces are secured to the clamping tables 10.1 and
10.2 by the pressure plates 11.1 and 11.2.
In the welding station S, the workpieces 1.1 and
1.2 are first of all dressed in the region of the butt
joint, as described in EP-A 0565846. A dressing unit to
carry out this operation is indicated at 23.
The dressing unit 23 is followed by a gap monitor
24 whose main function is to check the line of the gap to
be tracked by the laser beam 3.
After welding, it has proved advisable for the
welded seam to be treated in a brushing unit 25. This is
preferably followed by oiling, which also has the effect of
cooling the weld seam. This treatment takes place in a
cooling unit 26. This is followed by a quality inspection
27 and, if necessary, further-dressing in a post-dressing
unit 28.
This set-up suggeQted schematically in Fig. 6 is
illustrated more graphically in Figs. 7 and 8:
Fig. 7 shows a cross-section through a machine
with the functions illustrated in Fig. 6.
A plan view of the machine illustrated in Fig. 7
is shown in Fig. 8.
Fig. 7 shows a cross-section through an apparatus
for carrying out the invention. The drawing shows a
machine frame 16.1,30, with limbs of the part 16.1 of the
frame specifically designated 10.1 and 10.2. A clamping
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table or shuttle 20 runs on the frame 16.1,30, and is
supported thereon by C-shaped elements 20.1,20.2,29.1,29.2.
Magnets 23 form the supporting surface for the sheets 1.1
and 1.2. Press shoes 25, preferably of ferromagnetic
material, are pressed against the sheets 1.1,1.2 by
pressure elements 27. The pressure due to the pressure
elements 27 combines with that of the magnets 23 with more
than proportionate effect, with the result that the
arrangement is able to sustain more than proportionately
greater lateral forces. Dissipation of heat due to the
welding in the joint 3 is assisted by the cooling ducts
24.1 and 24.2.
From Fig. 8 it can be seen that the shuttle, of
which only the two yokes 29.1 and 29.2 are visible, runs
the whole length of the apparatus. At present it is in a
loading station F, from which it passes to a welding
station S, and thence to an unloading station E from which
the welded workpieces are removed.
In the welding station, the butt joint is
preferably dressed by a dressing unit 31 as described in
EP-A 565846. The dressing unit 31 is preferably followed
by a gap monitor 32 allowing a laser beam 2 located next
along the machine to track the line of the gap.
After the butt joint has been welded by the laser
33, the weld seam is preferably treated in a brushing unit
34 and oiled in a cooling station 35. These treatments are
followed by a quality inspection 36 and, if necessary,
further dressing 37.
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The workpieces 1.1 and 1.2 pass through all these
treatments while clamped to the shuttle.
