Note: Descriptions are shown in the official language in which they were submitted.
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MET~OD ~iND APPA~U~TUS FOR BUTT WELDING
TO~1~K SHEET RT.~NR.C
SCOPE OF T~E INVENTION
The present invention relates to a method and
apparatus for aligning and welding together two or more
sheet blanks and, more particularly, to an apparatus
adapted to automatically align and butt weld together
proximal edge portions of two sheets along a common seam
line.
BACKGROUND OF THE INVENTION
Present day manufacturing requirements often
necessitate the formation of various workpiece components
by welding together two or more metal sheet blanks.
Typically, individual sheet blanks are joined by
conventional seam or butt welding equipment, such as high
energy CO2 lasers, or electric beam/plasma arc-welding
devices. To obtain an effective and complete weld, it is
necessary to ensure that the proximal edges of the sheets
to be joined are positioned and maintained in a directly
abutting orientation during the welding operation.
Where CO2 lasers are used to perform welding
operations, to ensure the formation of a complete weld
seam, it is necessary that the edges of the sheet blanks be
pre-finished and have a mirror-smooth finish.
Conventional welding apparatus used to join sheet
blanks incorporate mechanical clamps for holding the sheets
together. The use of mechanical clamps to secure the sheet
blanks during welding, however, leads to inefficiencies in
workpiece production. In particular, mechanical clamping
mechanisms require increased time to clamp and unclamp the
sheet blanks in position prior to and after welding. A
-
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further disadvantage of conventional apparatus is that the
increased clamping time resulting from the use of
mechanical clamps inhibits adjustment in the positioning of
the proximal edges of the sheets which are to be welded
together once the clamps are engaged.
Mechanical clamps which are used in conventional
welding apparatus are typically pneumatically or
hydraulically operated, re~uiring that the welding
apparatus include large rigid and expensive clamp
supporting frames to absorb the clamping forces.
In one attempt to overcome the disadvantages of
prior art welding apparatus, magnetic clamping devices have
been proposed, as for example, is disclosed in United
States Patent No. 5,023,427 which issued June 11, 1991 to
Neiheisel et al. The Neiheisel patent discloses an
apparatus for aligning steel sheets which are to be welded
together by a laser. In the apparatus of Neiheisel, an
electromagnet is used to support the sheets in such a
manner as to induce opposite magnetic polarities in the
proximal edges of adjacent sheets, drawing the sheets
together by creating a magnetic attraction therebetween.
While the apparatus of Neiheisel may be useful in
aligning proximal edge portions of iron or other
ferromagnetic sheets which are of a thickness sufficient to
m; n i m i ze magnetic reluctance therebetween, the apparatus of
Neiheisel is poorly suited for use in aligning thinner
steel sheet blanks, or sheet blanks which are plated or
coated or which are made from non-ferromagnetic materials
such as copper, aluminum, plastic and the like.
SUMMARY OF THE INVENTION
To at least partially overcome the difficulties
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of prior art welding apparatus, the present invention
incorporates a sheet clamping mechanism which clamps sheet
blanks in place between an electrically activated magnetic
sheet supporting surface, and at least one clamping shoe
which is magnetically attracted to the magnet. The shoe is
positioned above the magnetic surface and is vertically
movable theretowards with the activation of the magnetic
surface, whereby the magnetic attraction of the shoe
towards the magnetic surface pulls the shoe downwardly. In
this manner, part of the sheet blank which is sandwiched
between the shoe and magnetic surface is held in place at
least in part by the downward force applied by the magnetic
attraction of the shoe to the magnetic surface. The
electromagnetic clamping mechanism of the present invention
advantageously permits almost instant clamping and
unclamping of the sheets to be welded by activating and
deactivating the electromagnet. Further as clamping is
performed by the magnetic attraction of the shoe, the
apparatus may be used to weld non-ferromagnetic sheet
blanks.
Another object of the invention is to provide an
apparatus for accurately and quickly aligning the proximal
edge portions of two or more sheets which are to be welded
together in a position aligned with the path of a movable
welding apparatus.
It is another object of the invention to provide
an apparatus adapted to align and secure in an abutting
relationship the proximal edge portions of both
ferromagnetic sheet blanks and non-ferromagnetic sheet
blanks, as for example may be made from iron, steel,
copper, aluminum, nickel, metal alloys and/or plastics and
the like.
Another object is to provide an apparatus for
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laser butt welding two or more sheet blanks together,
without re~uiring that the edge portions of the blanks be
pre-~inished.
A ~urther object of the invention is to provide
a simplified apparatus for automatically aligning and
welding the proximal edges of sheet blanks to be joined,
which may easily be adapted to perform welding operations
on different sheet blanks to produce different finished
workpieces.
Another object of the invention is to provide an
apparatus having a clamping mechanism for clamping together
edge portions of workpiece blanks, and which does not
re~uire a large or cumbersome supporting frame to offset
and absorb clamping forces.
Another ob~ect of the invention is to provide an
apparatus for positioning and welding together proximal
edge portions of two or more sheet blanks having different
relative thicknesses.
To achieve at least some of the ~oregoing
objects, the present invention includes a laser or other
welding apparatus for welding together proximal edge
portions o~ two sheet blanks, and two clamping mechanisms,
each supporting thereon an associated respective one of the
sheet blanks to be joined in a desired orientation relative
to the other. Preferably, a high energy laser, such as a
yttrium aluminum garnet (YAG) laser, is used to weld the
blanks. The laser is movably provided in the apparatus so
as to move an emitted laser beam relative to the sheet
blanks along a sensed or predetermined linear and/or curved
path. In this manner, the laser is activated and moved
along its sensed/predetermined path to weld proximal edges
of the two sheet blanks together along a seam line aligned
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with the path of the laser beam.
At least one clamping mechanism includes an
electrically activated magnetic supporting surface which
supports a lower side of the associated sheet blank
thereon, and one or more vertically movable clamping shoes
spaced above the magnetic supporting surface. The magnetic
surface is preferably part of an electromagnet operated by
electric current. The electromagnet may comprise of one or
more conventional electromagnets, but more preferably
consists of one or a series of electronically switchable
permanent magnets which are arranged in an array and
contain electric coils, and which are electrically pulsed
to provide increased downward magnetic forces.
The clamping shoes are made from a ferromagnetic
material such as iron, or is otherwise constructed having
a high magnetic susceptibility so as to be magnetically
attracted and held down by the electromagnetic support when
the support is activated. By lowering the shoes of each
clamping mechanism onto the top of the sheet blank so it is
sandwiched between the support and shoes, the proximal
portions of the sheets are clamped in position. Clamping
is achieved by both the downward force applied ~y the shoe
as a result of its magnetic attraction to the corresponding
electromagnetic support as well as by any magnetic
attraction of the sheet blank to the support.
The electromagnetic support may be provided as an
elongated electromagnet which extends longitudinally along
and,supports the underside of a respective sheet, adjacent
the proximal edge to be joined. The shoe may also be
formed as a single elongate member which extends
longitudinally above the electromagnetic support, or for
ease of manufacture a number of smaller, longitudinally
spaced shoes are provided at spaced locations thereabove,
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The shoes are mounted to the apparatus, 50 as to
be reciprocally movable between a raised position spaced
slightly above the upper surface of the sheet, and a
lowered clamping position. In the clamping position, the
shoe is moved downwardly into engagement with the upper
surface of the sheet, clamping it against movement between
the shoe and the respective supporting electromagnet.
A positioning guide may also be provided to
ensure correct location of the sheet blanks. The guide
acts to locate the edge proximal portion of one of the
sheet blanks in a position aligned with the predetermined
seam line. When the proximal edge of the second other
sheet is moved against the other sheet, the proximal edge
portions of both sheets thus both orient in an abutting
relationship aligned with the predetermined seam line.
Accordingly in one aspect the present invention
resides in an apparatus for aligning and welding together
proximal edge portions of first and second sheets, said
apparatus including,
welding means for welding the proximal edge
portion of the first sheet to the proximal edge portion of
the second sheet along a seam line,
positioning means for positioning the proximal
edge portion of said first sheet in a welding position
substantially aligned with said seam line,
first sheet supporting means for supporting said
first sheet with said edge portion of said first sheet in
said welding position, the first sheet supporting means
including,
first clamping means for releasably retaining
said first sheet in said apparatus during welding, the
first clamping means comprising,
first magnetic hold-down means for engagingly
supporting a first side of said first sheet, and
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first shoe means for engaging the second other
side of said first sheet, the first shoe means
characterized by magnetic susceptibility and being movable
relative to said first hold-down means between a forward
position wherein said first shoe means is moved towards
said first hold-down means a distance selected to
substantially prevent movement of said first sheet
therebetween and a rearward position wherein said first
shoe means is moved away from said first hold-down means
to permit substantially unhindered movement of said first
sheet therebetween,
the first clamping means being activatable to
produce a magnetic field in the first hold-down means
sufficient to magnetically attract the first shoe means to
the forward position and clamp the first sheet
therebetween, and
second sheet supporting means for supporting said
second sheet with said proximal edge portion of said second
sheet in a generally abutting relationship with said
proximal edge portion of said first sheet.
In a further aspect the present invention resides
in an apparatus for forming a workpiece by welding together
proximal edge portions of first and second sheet blanks,
said apparatus including,
welding means for welding the proximal edge
portion of the first sheet to the proximal edge portion of
the second sheet along a seam line,
positioning means for maintaining the edge
portion of said first sheet in a position substantially
aligned with said seam line,
first sheet supporting means for supporting said
first sheet in a generally horizontal position thereon with
said edge portion of said first sheet in said position
aligned with said seam line, the first sheet supporting
means including,
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first clamping means for releasably retaining
said first sheet in said apparatus during welding the first
clamping means comprising,
first magnetic hold-down means for engagingly
supporting a first lower side of said first sheet, and
first shoe means for engaging the other upper
side of said first sheet, the first shoe means
characterized by magnetic susceptibility movable relative
to the first hold-down means between a sheet engaging
position, wherein the first shoe means is lowered towards
the first hold-down means to engage and clamp the first
sheet in position between the first shoe means and first
hold-down means, and a release position wherein the first
shoe means is raised above the first hold-down means a
distance selected to permit movement of the first sheet
therebetween,
wherein the clamping means is activatable to
produce a magnetic field in the first hold-down means to
magnetically attract the first shoe means and assist in
moving the first shoe means to the sheet engaging position,
second sheet supporting means for supporting said
second sheet thereon in a substantially horizontal
orientation with said edge portion of said second sheet in
an approximately abutting relationship with said edge
portion of said first sheet.
In another aspect the present invention resides
in a use of an apparatus to form a workpiece by welding
together proximal edge portions of first and second sheet
blanks, said apparatus including,
welding means for welding the proximal edge
portion of the first sheet to the proximal edge portion of
the second sheet along a predetermined or sensed seam line,
positioning means for positioning the edge
portion of said first sheet in a position substantially
aligned with said seam line,
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first sheet supporting means for supporting said
first sheet with said edge portion of said ~irst sheet in
. said position aligned with said seam line, the first sheet
supporting means including,
first clamping means activatably to releasably
retain said first sheet in said apparatus during welding,
the first clamping comprising,
first electromagnetic hold-down means for
engagingly supporting a first side of said first sheet, and
first shoe means for engaging the second other
side of said first sheet, the first shoe means
characterized by magnetic susceptibility and being movable
relative to said first hold-down mans between- a forward
clamping position wherein said first shoe means is moved
towards said first hold-down means to engage and clamp a
portion of said first sheet therebetween, and a rearward
position wherein said first shoe means is moved away from
said first hold-down means a distance sufficient to permit
movement of said first sheet therebetween, and
second sheet supporting means for supporting said
second sheet thereon with said edge portion of said second
sheet in an approximately abutting relationship with said
edge portion of said first sheet, said second sheet
supporting means including,
second clamping means activatable to releasably
retain said second sheet in said apparatus during welding,
the second clamping means comprising,
second electromagnetic hold-down means for
engagingly supporting a first side of said second sheet,
and
second shoe means for engaging the second other
side of said second sheet, the second shoe means
characterized by magnetic susceptibility and being movable
relative to said second hold-down means between a forward
clamping position, wherein said second shoe means is moved
towards said second hold-down means to engage and clamp a
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portion of said second sheet therebetween, and a rearward
position wherein said second shoe means is moved away from
said second hold-down means a distance sufficient to permit
movement of said second sheet therebetween,
wherein with each of said first and second means
positioned in said respective rearward positions, said
workpiece is formed by the steps of
moving said first sheet between said first shoe
means and said first hold-down means to engage said
positioning means and to position said edge portion of said
first sheet substantially in alignment with said seam line,
activating said first clamping means to product
a magnetic field in said first hold-down means and move the
first show means to the forward position to retain the
first sheet therebetween,
moving said second sheet between said first shoe
means and said second hold-down means to position the edge
portion of the second sheet in a position abutting the edge
portion of the first sheet,
activating the second clamping means to produce
a magnetic field in said second hold-down means and move
the second shoe means to the forward position to retain the
second sheet therebetween, and
activating said welding means to perform welding
along the seam line to weld together the edge portion of
the first sheet and the edge portion of the second sheet.
~RIEF DESCRIPTION OF THE DRAWINGS
Further objects and advantages of the invention
will appear from the following description taken together
with the accompanying drawings in which:
Figure 1 is a cross-sectional end view of a
welding apparatus in accordance with a first preferred
embodiment of the invention;
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Figure 2 is a top view of the apparatus of Figure
1 showing the formation of a workpiece composite blank
thereon;
Figure 3 is a cross-sectional view of the
apparatus as shown in Figure 2 taken along lines 3-3';
Figure 4 is an enlarged partial cross-sectional
view of the welding apparatus of Figure 1 taken along line
4-4', showing the insertion of a first sheet blank to be
welded;
Figure 5 is a cross-sectional view of the welding
apparatus as shown in Figure 4 with an edge portion of the
first sheet aligned at a predetermined seam line;
Figure 6 is a cross-sectional view of the welding
apparatus as shown in Figure 4 showing the insertion of the
second sheet blank thereto;
Figure 7 is a cross-sectional view of the welding
apparatus as shown in Figure 4 showing the proximal edge
portions of the first and second sheets in an abutting
position aligned with the predetermined seam line;
Figure 8 shows a partial schematic side view of
a clamping mechanism in accordance with a further
embodiment of the invention;
Figure 9 shows a schematic end view of the
welding apparatus in accordance with a second preferred
embodiment of the invention;
Figure 10 shows a schematic top view of the
apparatus of Figure 9 showing the formation of a composite
workpiece blank thereon;
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Figure 11 shows a schematic top view of a
production assembly line for ~orming composite workpieces
in accordance with a third embodiment of the invention;
Figure 12 is a partial sectional side view of the
welding apparatus shown in Figure 11 taken along line 13-
12' and showing the laser apparatus used to weld sheet
blanks;
Figure 13 shows a schematic top view of a
production assembly line for forming composite workpiece
blanks in accordance with a fourth embodiment of the
invention; and
Figure 14 shows a schematic side view of the
laser welding apparatus shown in Figure 13.
DETAILED DESCRIPTION OF THE INVENTION
Reference is made to Figure 1 which shows an
apparatus 10 for aligning and welding together two planar
steel sheets 12,14. The apparatus 10 joins the sheets
12,14 together along a longitudinally extending and
predetermined linear seam line 16 which is aligned with the
longitudinal axis A1 of the apparatus 10, to form a finished
composite workpiece 18 (shown best in Figure 2). As will
be described hereafter, the apparatus 10 joins the sheets
12,14 by welding their respective proximal or ~acing edge
portions 12',14' together. It is to be appreciated that
the sheets 12,14 are formed having generally linear
proximal edge portions 12',14' which are complementary to
each other so as to properly meet along the desired seam
line 16, with each edge portion 12',14' to be joined
extending generally in the direction of axis A1.
To move the sheet blanks 12,14 into the apparatus
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10 for welding, the apparatus 10 is provided with two
magnetic stepping conveyors 20,22 which extend
longitudinally along each side of the axis A1. A sheet
positioning assembly which includes three cylindrical weld
datum or locating pins 30 (shown best in Figures 4 to 7)
and a number of spaced pneumatically operated positioning
slide assemblies or rods 32,34 is used for the final
alignment of the blanks 12,14 prior to welding. As will be
described in detail hereafter, two independently operable
sheet clamping units 36,38 secure a respective sheet 12,14
in position during welding so that the proximal edge
portions 12',14' of the sheets 12,14 are maintained in the
proper orientation aligned with the predetermined seam
line. A Lumonics 2kW YAG laser is provided for welding the
sheets 12,14 together along the predetermined workpiece
seam line 16.
As seen best in Figures 1 and 2, the magnetic
conveyors 20,22 are provided in a spaced apart arrangement
each extending parallel to and on each side of the seam
line 16. The conveyors 20,22 are independently operable to
move a respective sheet blank 12,14 in the longitudinal
direction of arrow 42 (Figure 2) into the apparatus 10 to
a workstation for welding; as well as moving the finished
workpiece 18 outwardly therefrom. Although not essential,
the use of magnetic conveyors 20,22 in conveying steel or
other ferromagnetic sheets advantageously min;mizes the
likelihood that the sheets 12,14 will move out of alignment
or slide off of the conveyors 20, 22 as they are moved.
Figures 1 and 3 show the YAG laser as including
a laser head ~hereinafter generally referred to as the
laser 40) which is movably mounted on a gantry robot 44
provided on an overhead support 46. The support 46 is
suspended at each of its ends by a pair of horizontal steel
beams 48a,48b in a position extending generally parallel to
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the axis A1 and conveyors 20,22. The laser 40 is moved
along the support 46 in the direction of axis A1 and above
the seam line 16 by the robot 44. The robot 44 is driven
in movement through the engagement of a motor driven pinion
with a rack (not shown) extending horizontally along the
support 46. The rack extends a distance along the support
46 so as to permit movement of the laser 40 along
approximately 3 metres of the support 46. In this manner,
a laser beam 56 (Figure 7) may be emitted along a
predetermined longitudinally extending pathline which is
aligned with the seam line 16 to be formed.
- Figures 4 to 7 show best the sheet clamping units
3 6, 38 which are used to maintain the sheets 12,14 in a
fixed position within the apparatus 10 during welding by
the laser 40. The clamping units 3 6, 38 are independently
operable with unit 3 6 activatable to first clamp a
respective sheet 12, and unit 38 activatable to clamp sheet
14. Clamping unit 36 and clamping unit 38 have essentially
the identical construction with like re~erence numbers used
to identify like components. For clarity and brevity,
clamping unit 36 is described in detail herebelow. It is
to be appreciated from Figures 4 to 7 that clamping unit 38
is provided having a mirror structural arrangement to
clamping unit 36 and operates in a like manner.
Clamping unit 36 includes an elongated
electrically operated magnet 54 about 0.3 metres wide and
3 metres in length which extends longitudinally parallel to
and adjacent the axis A1, and a number steel clamping shoes
55 provided above the magnet 54 at longitudinally spaced
locations. Figure 4 shows best the electromagnet 54 as
having a flat horizontal upper surface 58. The
electromagnet 54 shown in Figures 1 to 7 has a straight
elongated structure and is formed by joining a number of
generally rectangular magnet modules 53 end to end in a
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straight line. I~ desired, the modular construction of the
electromagnet 54 advantageously also enables the
electromagnet 54 to curve. In this manner, the
electromagnet 54 may also be positioned following curved or
bent seam lines, by incorporating one or more curved
modules 53 or by simply rearranging the positioning of the
modules 53. The modules 53 each consist of a permanent
magnet which contains an electric coil. When electrically
pulsed, the coils in the modules 53 produce variable
magnetic fields to provide the required downward magnetic
forces along the length of the electromagnet 54. The use
of modules 53 in the construction of the magnet 54
advantageously enables the modification of the clamping
units 36,38 to achieve optimal clamping of different shaped
blanks.
The upper surface 58 of the electromagnet 54 acts
both as a support upon which an associated one of the
sheets to be joined rests, and as a hold-down mechanism for
retaining the clamping shoes 55 in a sheet-clamping
position. The electromagnet 54 extends along a horizontal
support beam 57. The beam 57 in turn is mounted at each of
its ends to two vertical beams 64a,64b (see Figure 3) which
are spaced apart a sufficient distance to enable the sheets
12,14 and finished workpiece 18 to move substantially
unhindered therebetween. Although not essential, a servo-
motor drive unit 66 is preferably also provided to
vertically raise or lower the beam 57 and electromagnet 54
o~ cla-~ ng un ~ ~& o~ ~e b~ar,s 64a,64~, re~t~-v2 t~ t~
electromagnet 54 of clamping unit 36. It is to be
appreciated, that the servo-motor drive unit 66
advantageously permits vertical adjustment in the relative
positioning of the sheets 12,14, as for example, to permit
sheets of different thicknesses to be welded together.
In the embodiment shown in Figure 3, nine
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identical steel shoes 55 are provided in each clamping unit
36,38. The shoes 55 are each formed from cast iron and
extend laterally across almost the entire width of the
electromagnet 54, and longitudinally a distance of between
about 0.2 to 0.4 metres. Each of the shoes 55 includes a
generally flat horizontal bottom surface 68 which, when the
clamping units 36,38 are activated, moves against the upper
surface of a sheet therein to sandwich it ~etween the
bottom of the shoe 55 and the electromagnet 54. A rearward
edge portion 70 o~ the shoe 55, spaced furthest away from
the axis A1 and seam line 16 slopes upwardly from the bottom
surface 68. As will be described later, the upward slope
of the rearward edge portion 70 acts to assist in
flattening and directing the sheets 12,14 between the
respective electromagnets 54 and shoes 55 as they are slid
into position moving the edge portions 12',14' towards
alignment with the seam line 16.
The shoes 55 of each clamping unit 36,38 are
mounted on associated vertically movable pneumatic piston
cylinders 72 positioned on sides of the overhead support
46. By activating the piston cylinders 72, the shoes 55
are vertically moved between a lowered position, where the
bottom surface 68 of the shoe 55 engages the upper surface
of a sheet thereunder, and a raised position spaced a
distance above the electromagnet 54, which is sufficient to
enable movement of a sheet between the electromagnet 54 and
shoes 55.
It is preferred that when the electromagnet 54 is
not activated, the shoes 55 are automatically returned to
the raised position, as for example, by means of the servo-
control of the cylinders 72, permitting substantially
unhindered sliding movement of the sheets 12,14 between
associated shoes 55 and electromagnet 54; and whereby the
activation of the electromagnets 54 deactivates the
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- 17
cylinders 72, resulting in the lowering of the shoes 55 to
return to the lowered sheet engaging position.
.
The shoes 55 are each provided with a generally
horizontal flat upper shoulder 74 extending approximately
one-half o~ its width. The upper shoulder 74
advantageously permits placement of one or more rectangular
iron bars 76 or other ferromagnetic weights (seen best in
Figure 8) to be placed on the shoe 55. The addition of
iron bars 76 may advantageously be used to decrease
magnetic reluctance with respect to the electromagnet 54,
where thinner sheets 12,14 are to be welded.
Figures 4 to 7 show best an elongated 0.25 inch
wide la~er dump 59 aligned beneath the axis A1 and recessed
beneath the upper surfaces 58 of the magnets 54. The laser
dump 59 is preferably copper-lined to absorb excess YAG
laser energy, and is liquid cooled by pumping cooling water
along a longitudinally extending coolant channel 61 which
extends beneath the bottom of the dump 59.
The locating pins 30 of the sheet positioning
assembly are provided in alignment at longitudinally spaced
locations under the support 46. The pins 30 are located in
the apparatus 10 with one circumferential edge portion of
each pin 30 tangentially aligned with the laser dump 59 and
axis A1. In this manner, when the edge portion 12' of the
steel sheet 12 is moved against the pins 30, the edge
portion 12' aligns with each of the laser dump 59, the
pathline of an emitted laser beam 56 and the desired seam
line 16 of the workpiece 18. As seen best in Figures 4 to
7, each locating pin 30 is vertically movable within a
corresponding pneumatically operated cylinder 60 which is
secured to a vertical side of the electromagnet 54 of
clamping unit 36 by bolts 62. Ry the selective activation
or deactivation of the associated cylinders 60, the pins 30
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are moved between a raised position, where the pins 30
engage and contact the proximal edge portion 12' of sheet
12, and a lowered position moved vertically a distance
below the lower surface of the sheets 12,14.
The positioning rods 32,34 are provided in sets
of ten rods on each side of the axis A1. ~ach set of rods
32,34 is used to move a respective one of the sheets 12,14
to a position so that the proximal edge portions 12',14'
are aligned with the predetermined seam line 16. As will
be described later, the positioning rods 32,34 are
activatable to engage the non-proximate edge portions of
the respective sheets 12,14 and slide the sheets 12,14 to
a position with their proximal edge portions 12',14' in
abutting engagement under the path line of the laser beam
56 for welding.
The overall operation of the laser 40, gantry
robot 44 and clamping units 36,38 may be performed
manually, but more preferably a microprocessor control 78
(see Figure 2) is provided. The microprocessor control 78
may be equipped with software whereby the laser 40, gantry
robot 44, and clamping unit 36,38 operations may be either
pre-set or taught for repeated workpiece 18 production.
The use of the apparatus 10 is best described
with reference to Figures 2 and 4 to 7. Initially, the
servo-motor drive unit 66 is activated to raise or lower
the electromagnet 54 of clamping unit 38 relative to the
electromagnet 54 of clamping unit 36. The clamping unit 38
is moved so the upper surfaces 58 of the electromagnets 54
of both units 36,38 are at the desired relative vertical
position, having regard to the thicknesses of the steel
sheets 12,14 to be joined.
The two sheets 12,14 which are to be welded
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together along their respective proximal edges 12',14' are
then placed on a respective conveyor 20,22 with the edge
portions 12',14 each oriented towards the axis A1. The
conveyors 20,22 are then operated either simultaneously or
separately, to move the sheets 12,14 in the direction of
arrow 42 into the apparatus 10.
The pneumatic cylinders 60 are next activated to
raise the locating pins 30 to a height so as to engage the
proximal edge portion 12' of the sheet 12 as it rests on
the surface of the electromagnet 54 of clamping unit 36.
The set of locating rods 34 are then individually
extended, whereby the rods 34 engage the non-proximal edge
portions of the sheet 12. The engagement of the rods 34
with the non-proximal edge portions of the sheet lZ slides
the sheet 12 within the apparatus 10. The sheet 12 is
moved so that the lower surface of part of the sheet 12
adjacent the edge portion 12' rests upon and is supported
by the surface 58 of the clamping unit 36 electromagnet,
and the proximal edge portion 12' is moved in the direction
of arrow 80 (seen in Figure 4) against the pins 30 into
alignment with the axis A1 and seam line 16. As the sheet
12 moves towards the pins 30, the sheet 12 is moved between
the upper surface 58 of electromagnet 54 and shoes 55 of
the clamping unit 36 and into engagement with each of the
locating pins 30. The engagement of the edge portion 12'
o~ sheet 12 with the pins 30 thereby aligns the edge
portion 12' precisely under the path line of the laser beam
56 and seam line 16 in the optimum position for welding.
In addition, the movement of the sheet 12 between the shoes
55 and electromagnet 54 of clamping unit 36 acts to flatten
the sheet 12, removing any warp or bends from the sheet 12.
.
With the proximal edge portion 12' engaging each
of the locating pins 30, the electromagnet 54 of the
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clamping unit 36 is activated and the associated shoes 55
are lowered onto the upper surface of the sheet 12. The
lowering of the shoes 55 sandwiches the sheet 12 in place
between the shoes 55 and electromagnet 54. When activated,
the increased magnetic attraction between the electromagnet
54 and its associated shoes 54 pu115 the shoes 55
downwardly onto the sheet 12 with a sufficient force
selected to preventing movement of the edge portion 12' out
of alignment with the predetermined seam line 16. It is to
be further appreciated that where sheets of ferromagnetic
materials are clamped in place, the magnetic attraction of
the sheet 12 directly to the supporting electromagnet 54
further assists in holding the sheet 12 in place.
With the sheet 12 clamped in a welding position
with the edge portion 12' aligned with the seam line 16,
the cylinders 60 are deactivated to retract the locating
pins 30 to the lowered position shown in Figure 6, wherein
the pins 30 are moved beneath both the lower surfaces of
the sheets 12,14, and the upper surface 58 of the
electromagnet 54 of the clamping unit 38.
The locating rods 36 are then activated to engage
the non-proximal edges of sheet 14, and move the sheet 14
towards the axis Al in the direction of arrow 81 lshown in
Figure 6) so that the proximal edge portion 14' of the
sheet blank 14 is moved into abutting engagement with the
proximal edge portion 12' of sheet 12. The movement of the
sheet 14 by the locating rods 36, similarly slides the
lower surface of part of the sheet 14 which is adjacent the
edge portion 14' onto the electromagnet 54 of clamping unit
38, so that it is supported thereby. Once the edge
portions 12',14' are positioned in the proper abutting
engagement, the electromagnet 54 of the clamping unit 38 is
activated, and the associated shoes 55 are lowered onto the
upper surface of the sheet 14. As with clamping unit 36,
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the magnetic attraction of the shoes 55 towards the
electromagnet 54, pulls the shoes downwardly with
sufficient force as to substantially prevent further
movement of the sheet 14.
With each of the sheets 12,14 clamped in abutting
engagement by the respective clamping units 36,38, the
computer control 78 automatically activates the laser 40
and gantry robot 44, to move the head of the laser 40 along
the support 46 by the motor driven pinion engaging the rack
(not shown). The movement of the laser 40 thereto moves an
emitted laser beam 56 along the path line welding the
proximal edge portions 12',14' together along the
predetermined seam line 16. By the length of travel of the
laser 40 along the support 46, weld seams may be formed
which are 3 or more metres in length.
The use of the YAG laser 40 has several
advantages over conventional CO2 lasers. In particular, the
YAG laser 40 is more suited to welding aluminum and
aluminum alloys. The YAG laser additionally permits faster
weld times of 3 metres per minute and enables simplified
fibre optic beam delivery to a comparatively small laser
head. In addition, to achieve effective butt welding with
conventional CO2 lasers, it is necessary that the edge
portions 12',14' of the blanks 12,14 have a highly pre-
finished, minor smooth surface. This has heretofore proven
to be a significant drawback in the large scale
implementation of CO2 lasers in continuous butt-welding
processes. In contrast, the YAG laser 40 effectively welds
sheets 12,14 having normal sheared edges, without requiring
specialized edge treatment of the sheets 12,14.
It is to be appreciated that as the sheets 12,14
are clamped in place by the attraction of respective shoes
55 and electromagnets 54, there is no need to provide the
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apparatus 10 with a cumbersome and expensive clamp
supporting frame to absorb opposing clamping forces
associated with conventional welding apparatus. Further,
the permanent magnets used in the modules 53 are selected
so that when the electromagnet 54 is not activated, the
sheets 12,14 and workpiece 18 may be moved into and out of
the apparatus lO.
Following welding, the electromagnets 54 of both
clamping units 36,38 are deactivated and the associated
shoes 55 are raised by their respective piston cylinders 72
to unclamp the finished workpiece 18. The conveyors 20,22
are then activated to simultaneously move the ~inished
workpiece 18 out of the apparatus 10 in the direction o~
arrow 42 (shown in Figure 2~ while simultaneously moving
two new sheets to be joined therein.
The foregoing construction advantageously permits
sheets made of non-ferromagnetic materials, such as tin or
aluminum, to be securely clamped in place during welding,
by their being sandwiched between the magnetically
attracted associated shoes and electromagnets.
While the YAG laser 40 is disclosed as being
moved along the support 46 by the engagement of a rack by
a motor driven pinion, other drive mechanisms to be used
with the gantry robot 44 are also possible and will become
apparent. Depending on the workpiece 18 to be formed, the
laser 40 may be operated to emit a continuous laser beam 56
which performs continuous welding along the whole of the
seam line 16, or alternately, the laser 40 may be pulsed to
~orm welds at longitudinally spaced locations. Similarly,
while the laser 40 disclosed with reference to Figures 1 to
7 is preprogrammed to travel along a predetermined seam
line, the laser could also include a seam line sensor which
automatically senses the spacing between two sheet blanks
CA 02239079 1998-0~-28
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and guides the laser 40 in movement along the sensed seam
line.
An alternate embodiment of the present invention
is illustrated in Figures 9 and 10 wherein like reference
numerals are used to identify like components. The
apparatus lO shown in Figures 9 and 10 has all of the
components as that shown in Figure 1, however, a third
magnetic stepping conveyor 85, two additional clamping
units 86,88 and a second YAG laser 90 are additionally
provided. The clamping units 86,88, and laser 90 are used
to weld not only sheets 12 and 14 together in the manner
described with reference to Figures 4 to 7, but also weld
an edge portion 92' of third steel sheet 92 to an edge
portion 14" of steel sheet 14 which is remote ~rom edge
portion 14'.
The apparatus 10 welds the sheet 92 to sheet 14
along a second seam line 94, aligned with an axis A2 which
is parallel to axis A1 and seam line 16. As in the
embodiment shown in Figures 1 to 7, servo-motor drive units
66 are provided to permit not only vertical adjustment of
the height of the electromagnet 54 of unit 38 relative to
that of unit 36, but also vertical adjustment of the
electromagnet 54 of units 86 and 88. The laser 90 is
movably provided on a second overhead support 91 which
extends parallel to support 46 in essentially the same
manner as laser 40.
In use of the apparatus 10 o~ Figure 9 and 10,
the sheet blanks 12 and 14 are joined together in the
identical manner as that described with re~erence to
Figures 4 to 7. Following the welding o~ sheets 12,14, the
third conveyor 85 is operated to move the sheet 92 in the
direction of arrow 42 into the apparatus 10, so that the
edge portion 92' of the sheet 92 which is proximate to edge
-
CA 02239079 1998-0~-28
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portion 14" is positioned facing theretowards. The
clamping unit 86 is activated to clamp the sheet 14 in the
same manner as clamping units 36,38. In the same manner as
clamping unit 38, clamping unit 86 is activated to clamp
the sheet 14, with sheet 12 having been welded thereto, in
position with the edge portion 14" aligned with the
predetermined seam line 94. The third sheet 92 is then
moved so that its proximal edge portion 92' which is
proximate edge portion 14" is positioned in abutting
relationship therewith. Once the sheets 14,92 are so
positioned, the fourth clamping unit 88 is activated to
clamp the sheet 92 in position with the edge portions
14',92' abutting and aligned with seam line 94. ~he second
laser 90 is then activated and moved by a gantry robot
along the support 91 to weld sheets 14 and 92 together
along the second seam line 94.
It is contemplated that the sheet positioning
assembly shown in Figures 9 and 10 could also include
additional locating pins and/or positioning rods (not
shown~ to assist in orienting the proximate edge portions
14" and 92' in the correct alignment with the seam line 94.
Where a second set of locating pins is used, it is to be
appreciated that following the welding of the sheet 12 to
the sheet 14, the clamping units 36,38 are deactivated and
the locating rods 34,36 further adjusted to move the welded
sheets 12,14 to a corrected position prior to welding sheet
92.
While Figures 9 and lO show the apparatus 10 as
including two lasers 40,90 which each travel along parallel
path lines, the invention is not so limited. Depending on
the workpiece which is to be produced, additional lasers
and clamping units could also be provided. The lasers
40,90 may also be movable along perpendicular horizontal
and/or vertical directions, or alternately along curved or
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irregular non-linear path lines, as for example, to produce
workpieces having curved or irregular seam lines or the
like.
Another embodiment of the present invention is
illustrated in Figures ll and 12, wherein like reference
numerals are used to identify like components. Figures 11
and 12 show the apparatus 10 used in a production line 100
~or the continuous manufacture of composite workpieces 18.
The production line 100 is configured for the
concurrent manufacture of two completed workpieces 18a,18b,
and includes a single laser 40, which is configured for 3
axis movement. As seen best in Figure 12, the entire laser
and support 124 is movable in a first horizontal
direction via a gantry robot 44 along an overhead support
46 and a slave support 146. As in the embodiments shown in
Figures 1 to 7, the laser 40 is movable via a gantry robot
44 along a rack provided on overhead support 46. The
supports 46,146 are further slidable in a second horizontal
direction perpendicular to the first on parallel spaced end
supports 114a,114b which support each end of the support
46, and slave support 146. A servo-drive motor 120 is
provided at the end of support 46 engaging a rack 122
extending along one support 114 thereby permitting the
laser beam 56 movement in any horizontal direction. In
this manner, by moving the laser 40 along the support 46,
and moving the support 46 along supports 114a,114b, the
laser beam 56 may be moved along substantially any path.
In addition, it is preferable that the laser 40 be
vertically movable, thereby permitting its movement along
all three axes and provide increased adaptability to the
apparatus 10.
In use, pairs of component sheets 12a,14a and
12b,14b are moved 5equentially via robotic vacuum lifts
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- - 26 -
106a,106b from respective supply stacks 108a,108b, and are
positioned on parallel magnetic feed conveyors 110. The
robotic vacuum lifts 106a,106b are used to move each
component sheet 12a,14a and 12b,14b, respectively through
an initial qualifying procedure, to ensure correct initial
positioning of the sheets on the feed conveyors 110. In
this regard, sets of locating pins 130, which are
substantially identical to pins 30, are provided at spaced
locations between the conveyors 110 to position the sheets
in the desired initial position.
Each robotic vacuum lift 106a,106b operates with
suction cups used to initially pick up the sheets 12 and 14
under a high vacuum pressure, so as to fixedly retain each
sheet as it is raised from the supply stac~ 108. As the
sheet is moved to a position immediately above the
conveyors 110, the suction pressure used to hold the sheet
is reduced. The reduction suction pressure is chosen so
that the retained sheet continues to be suspended by the
vacuum force of the lift 106, while permitting the sheet to
be slid laterally relative to the vacuum lift 106. The
lift 106 is then moved to bring the retained sheet against
one set of pins 130 which have been extended above the top
surface of the conveyors 110. By moving the edges of the
sheets against the pins 130, the sheets may be slid on the
lift 106 into the desired initial position on the conveyors
110. Following the positioning of the sheets, the vacuum
lift 106 is deactivated to release the sheet, and the pins
130 are lowered to permit the sheets to be conveyed for
welding.
Once the respective pairs of sheets 12a,14a and
12b,14b are in the desired initial position, the feed
conveyors 110 move the pairs of sheets 12a,14a and 12b,14b
in the direction of arrow 42, into a laser operations room
112 in which the apparatus 10 is housed. The laser
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- - 27 -
operations room 112 provides an added safety feature
whereby plant workers are shielded by the room 112 from YAG
laser energy emitted by the laser 40. In this regard, the
room may be provided with mail box or sliding doors (not
shown) which close to optically isolate the apparatus 10
during welding operations.
The conveyors 120 in turn convey the respective
pairs of component sheets 12a,14a and 12b,14b into
respective clamping units 36a,38a and 36b,38b which
straddle one of the parallel paths along which the laser
moves.
The blanks 12a,14a and 12b,14b are positioned in
the clamping units 36a,38a and 36b,38b in the same manner
as described in Figures 1 to 7 aligned on a respective pair
of electromagnets 54. In the manner described, once
positioned, the sheets 12a,14a and 12b,14b are secured in
place by clamping shoes 55 (Figure 12). The laser 40 is
then activated to first weld blank 12a to blank 14a, and
then by moving the laser 40 and supports 46,146 relative to
supports 114, to weld blank 12b to blank 14b.
The feed conveyors 110 may be used to
simultaneously feed the pairs of sheets 12a,14a and 12b,14b
into the laser operations room 112 and onto aligned
magnetic conveyors 120. Preferably, however, the
production line 100 is computer controlled so that the
right half of the line 100, which is shown as the top half
of Figure 11, operates independently of the left half. In
this manner, the conveyors 100 may be used to independently
convey the pairs of sheets 12a,14a and 12b,14b into laser
operations room 112. The applicant has appreciated that
independent left and right operations advantageously enable
maximum production efficiency. In particular, while
clamping units 36,38 are used to position one pair of
CA 02239079 1998-0~-28
097126110 PCT/CA96/00737
- - 28 -
sheets 12a,14a, the laser 40 can be used to weld the other
pair 12b,14b along the seam line.
Once the completed workpieces 18a,18b have been
formed, the conveyors 120 move the workpieces 18a,18b out
of the laser operations room 112 onto aligned exit
conveyors 118 which convey the composite workpieces 18a,18b
to robotic lifts 125a,125b for placement in finished
composite stacks 127a,127b.
Figure 12 shows the shoes 55 as being mounted on
a second steel beam 119, which is spaced above a
corresponding electromagnet 54, and below the support 46.
The shoes 55 are movably coupled to the beam 119 by pistons
(not shown) in essentially the same manner as the coupling
of the shoes 55 to the support 46 shown in Figures 4 to 7.
The electromagnets 54 and beams 119 are movable along
respective slides 121,123. The slides 121, 123 extend
perpendicularly to each respective magnet 54 and beam 119
and allow adjustment of the lateral positioning of the
clamping units 36,38, for welding different workpieces 18.
A further embodiment of the present invention is
illustrated in Figures 13 and 14 wherein like reference
numerals are used to identify like components. Figure 13
shows a component production line 100 adapted for the
simultaneous manufacture of completed composite workpieces
18a-f using a laser 40 which is rotatably mounted within an
overhead support 124 shown best in Figure 14. As in the
embodiment shown in Figure 11, the laser 40 is adapted for
3 axis movement on supports 46,146 and 114a,114b. The
laser 40 is, however, additionally provided on an arm
assembly 126 which is journalled in rotational movement
along an inner edge portion of a hollow supporting cylinder
130.
The production line of Figure 13 operates in a
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- 29 -
similar manner to that shown in Figure 11, with the
exception that six pairs of component sheets 12a,14a,
12b,14b, 12c,14c, 12d,14d, 12e,14e, 12f,14f are welded
within the laser operations room 112 at any one time. In
addition, with the apparatus 10 shown in Figure 13 welding
of the sheets 12,14 occurs along a curved line. In this
regard, the configuration of the magnet modules 53 and
shoes 55 are modified to reflect the curved path of the
laser beam 56.
In the production line Figure 13 and 14, a single
laser 40 may be used to sequentially weld each pair of
sheet components 12,14 or, additional lasers (shown in
phantom) may further be provided. The path of laser beam
56 movement may be preprogrammed to follow a precise
repetitive path which is preset having regard to the blank
12,14 configuration and the weld seam 16. More preferably,
however, the laser 40 is provided with a seam tracking
optic sensor which automatically follows any spacing
between the blanks 12,14 and centres the laser beam 56
thereon to perform welding operation.
While Figure 3 illustrates the clamping unit 36
as including a number of individual shoes 55 spaced
longitudinally over a corresponding electromagnet 54, fewer
larger, or even a single elongated shoe could alternately
be provided without departing from the scope of the present
invention.
Although the preferred embodiment of the
invention discloses the use of a YAG laser to weld the
sheet blanks together, depending on the sheet material to
be joined, other welding apparatus, including plasma arc or
electron beam welding apparatus, arc welding apparatus or
the like could also be used and will now become apparent.
CA 02239079 1998-0~-28
O 97126110 PCT/CA96/00737
_ 30
The use of cast iron shoes 55 advantageously
provide an economical and easily manufactured construction
which has a high degree of magnetic susceptibility, so as
to ~xi~;ze the magnetic attraction between the shoe 55 and
electromagnet 54. If desired, however, the shoes may also
be formed from steel or other ferromagnetic materials.
Alternately, in another possible construction, the shoe may
itself be provided with an electromagnetic insert or coil
for inducing a magnetic polarity therein which is opposite
to that of the underlining portion o~ the supporting
electromagnet.
While the preferred embodiment describes the use
of the present invention in butt welding two or more sheets
12,14 other applications are also possible. For example,
by inclining the laser beam relative to the vertical axis,
the present invention may also be used to mash weld two or
more sheet blanks together.
Although Figures 4 to 7 show the locating pins 30
as being movable in a cylinder 60 secured to electromagnet
54, other constructions are also possible. The pins 30
could, for example, be mounted to a support suspended above
one or both magnets 54, and move downwardly into bores
formed in the upper magnet surface 58. In such a
configuration the magnets 54 would be separated only by the
laser dump 59 and advantageously support the portions of
the blanks 12,14 closest to the edge portions 12',14' to be
welded.
While the detailed description of the invention
describes and illustrates preferred embodiments of the
invention, the invention is not so limited. Many
modifications and variations will now appear to persons
skilled in this art. For a definition of the invention,
reference may be had to the attached claims.
