Note: Descriptions are shown in the official language in which they were submitted.
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ROBOTICALLY OPERATED LASER HEAD
CROSS-REFERENCE TO RELATED APPLICATIONS
This is a completion application of a co-pending, prior filed U.S. provisional
application S.N. 6U/099,547 entitled "Laser Cutting-Head with Adjustable Light
Source, Crash Avoidance System and Improved Gas Delivery System" filed
September
l0 9, 1998, the disclosure of which is herein incorporated by reference.
BACKGROUND OF THE >7WENTION
15 The present invention pertains to robotically operated laser cutting and
welding
devices. More particularly, the present invention pertains to a robotically
controlled
laser cutting or welding head that operates about the surface of a three
dimensional
workpiece.
2o II. PRIOR A_R~r
Present-day laser cutting or welding devices typically have a light source
that
directs light to one or more mirrors and lenses which in turn directs the
light to a focal
or condenser optic. The light source may be an optic fiber. The mirror and
lenses or
optics of the laser device are typically housed in a laser head. The laser
head has a
25 housing with a nozzle through which a laser beam is directed to impinge
upon a
workpiece. The operation or motion of the laser head about a workpiece may be
controlled by a robot and controller or the fike.
Robotically controlled laser devices are often operated under rugged
conditions.
The devices are subjected to jarring, bumping and vibrations. Continual use
under
3o these conditions often results in the light beam being other than optimally
aligned on
the laser optics.
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Centering the light beam on the laser optics is important where light
converges
from the focal lens through the nozzle onto a work piece to deliver large
amoums of
energy. A focal lens is often used to concentrate such light from the light
source into a
powerful beam to art or weld various materials. The most intense part of the
beam is
the apex or focal spot. The apex or focal spot impinges upon a workplace to
perform
much of the laser operation. It is therefor necessary to maintain an optimal
portion of
the incoming light beam upon the focal lens to thereby maximize the operation
of the
focal spot upon a workplace.
Additionally, replacement of the Iight source is not uncommon. Once a new
to light source is installed, the light beam is typically aligned upon each
mirror or lens in
the optic system. Care must be taken not to significamly alter the optimal
path length
of light diverging from the light source to avoid diminishing the intensity of
the
concentrated laser beam. Care must also be exercised to direct the
concentrated light
beam through the nozzle of the laser head. Thus, the installation of a new
light source
15 is often time consuming, laborious, and requires considerable care.
Realignment of the optics in many present day laser heads mandates that the
head be dismantled and each mirror or lens be individually adjusted. Laser
cutting
operations may not be performed in the cleanest environments. Thus, the laser
head
must be removed from the operation site to a clean location so that the laser
optics can
2o be adjusted in a contamination free environment. The realignment process,
like the
installation process, is also time-consuming, laborious and requires
considerable care so
as not to contaminate the optics with dirt and dust.
Some laser heads provide a way to realign the laser beam by adjusting the
focal
or condenser lens. In such laser heads, a mechanism for adjusting the
condenser lens is
2s disposed near or at the nozzle. A laser head having a mechanism for
adjusting the
condenser lens is disadvantageous for a number of reasons. One such reason is
that the
mechanism for adjusting the condenser lens results is a laser head having a
bulky
housing and nozzle. The bulky housing and nozzle is particularly
disadvantageous
where the laser head must be manipulated about the surface of a three-
dimensional
3o workplace having varying topography.
Furthermore, assist or make-up gases, such as oxygen, are used with lasers to
increase the laser's cutting efficiency and for removing debris from the
cutting surface.
2
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The assist gas is typically delivered from the nozzle of the laser head to the
surface of a
workpiece. The gas m&y be delivered to the nozzle via an external, Ioose tube
or hose
connected to a gas source. The gas delivery tubes of present day laser heads
are
deficient for a number of reasons including the fact that they create a point
or place for
a workpiece to catch upon. Additionally, these tubes frequently wear out or
become
damaged as a result of their external positioning next the laser head, thus
requiring
repeated replacement.
As is generally known to the skilled artisan, present day laser heads can be
operated by a robot. The robot controls the pattern and distance the laser
head operates
io about the surFace of a workpiece.
The surface topography of a workpiece can vary considerably. Similarly, the
thickness of a workgiece can also vary considerably. As a result, it has been
a long-
standing problem to have collisions between the laser head and a workpiece or
a
surrounding fixture that may damage either the Iaser head or the workpiece. To
further
15 complicate the problem, workpieces are pften cut in batch during industrial
operations.
As a robot moves the laser head from workpiece to workpiece collisions may
occur due
to the misplacement of the workpiece within a support structure.
One attempt to overcome the problem of collisions has been to provide present
day laser heads with breaker switches or micro switches that open to stop the
robot
2o after a laser head has collided with a workpiece. The force required to
open the breaker
switch may be a force sufficient to disconnect the laser head from the robot.
This force
can be sufficient to damage the laser head, optics or the robot.
Therefore, it is to be appreciated from the preceding that present day
robotically
operated laser heads are deficient in providing for precise manipulation about
a three-
25 dimensional workpiece having varying topography for a number of reasons.
For
example, present day laser heads require a bulky housing to accommodate
present day
optics and their support smrctures. Further, present day laser heads are
typically fitted
with an external assist gas delivery system that may catch upon a workpiece or
fixture
and may succumb to accelerated wear.
3o It is also to be appreciated from the preceding that present day
robotically
operated laser heads fail to provide a suitable means for adjusting the
optical path of a
CA 02343722 2001-03-08
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light source upon a condenser optic to focus a laser beam through a nozzle of
the laser
head.
It is also to be appreciated from the preceding that present day robotically
operated laser heads fail to provide an effective, yet durable, way of
delivering an assist
gas to the nozzle of a laser head.
It is also to be appreciated from the preceding that present day, robotically
olaser devices having a laser head attached to a robot are deficient in
providing
an effective means of avoiding a collision with a workpiece so as not to
substantially
disconnect the laser head from the robot attached thereto.
SLfMMARY OF THE INVENTION
As discussed hereinbelow, the present invention, to address the above stated
problems and others, as is detailed hereinafter, enables an improved laser
head for
manipulation about a three-dimensional workpiece having varying topography.
The
present invention also provides an improved laser device having means for
avoidiag a
collision with a workpiece by stopping the robot and laser head operation
before
damage to the laser head or robot occurs.
The laser head hereof has: a housing; a nozzle attached to the housing at a
distal
end thereof, the nozzle forming a tip, a light source which produces a light
beam
2o supported by the housing; at least one focal optic for receiving the light
beam and
focusing the Iight beam into a high density laser beam through the nozzle,
means for
adjusting the light path of the light beam from the light source within the
housing onto
the focal optic wherein the means for adjusting is adapted to center the
focusing beam
coaxial with the tip, and means for adjusting the means for receiving the
light beam.
2s The laser head may firrther include means for delivering an assist gas from
inside the housing, through the nozzle to the cutting surface of a workpiece.
Also, the
laser head may further comprise means for determining the proximity of the
laser head
to a workpiece.
By delivering an assist gas from within the housing and placing the means for
3o adjusting the means for receiving the Gght beam within a top portion of the
housing, the
nozzle and the laser head may be formed with a more streamlined design. By
making
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the housing and the nozzle more streamlined, the laser head can be operated
more
precisely about the surface of a three-dimensional workplace.
The present invention also provides means for avoiding a collision between a
laser head and a workplace. Robotic operation of the laser head may be
performed in
s several modes. The modes of operation may be determined by either the
proximity of
the laser head to a surface of a work piece or the operating condition of the
robotic unit
or both. The modes of operation may include, for example, an operation or run
made, a
park mode, a teach mode, and a hold mode. The modes of operation may further
be
controlled by the operating condition of the laser head, for instance, whether
the laser
1o head is operating at an extended or a retracted limit.
In use the laser head is mounted to a robot or robotic arm, which together,
function as a laser device that may operate upon a surface of a workplace in
one or
more of the above mentioned modes. The laser device has means for determining
~if the
laser head is in contact with or in close proximity to the surface of the
workplace.
15 Depending upon the mode of operation that the laser device is functioning
in, the
device, particularly the robot operation, will cease to operate when the laser
head is at a
predetermined distance from a workplace. Thus, by prohibiting the device from
operating in certain modes when the laser head is positioned above a surface
of a
workplace at a certain distance, the present invention provides a crash
avoidance
2o system whereby the laser head is less likely to be involved in a crash with
a workplace
to prevent damage and other problems that may therefor follow.
The laser head hereof may be telescopable. In operation, the telescopable
laser
head retracts and extends to follow the surface of a workplace and to correct
for minor
deviations therein. The crash avoidance system provides means for stopping the
laser
25 head and robot or the laser device when the telescopable laser head reaches
an extended
limit or a retracted limit.
The laser head will typically reach an extended limit when the laser head is
fully
telescoped and positioned at a maximum distance from a work piece such that
the laser
head can not extend fiuther to accommodate the distance from a workplace that
the
30 laser head is operating at. Even though the laser head is not likely to be
involved in a
collision with a work piece at this distance, such distance is likely to
result in inferior
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use of the laser. Therefore, the robot is better shut down or stopped then
left to
continued operation about a workpiece.
The laser head reaches a retracted limit when the laser head moves so close to
a
workpiece that the laser head may no longer retract within itself. The laser
head may
s reach a retracted limit for a number of reasons, for example as a result of
operating
programming which does not coincide with the variations among surface
topography
between workpieces. If a laser head is left to operate at a retracted limit,
the laser beam
may not optimally impinge upon the surface of the workpiece. Additionally, the
laser
head will be more prone to crashing when operating at a retracted limit.
Therefore, the
1o robot and laser head are preferably stopped until adjustments, such as
repmgramming
the robot or repositioning the work piece, may be preformed.
For a more complete understanding of the present invention, reference is made
to the following detailed description and accompanying drawings. In the
drawings like
reference characters refer to Iike parts throughout the several views.
is
BRIEF DESCRIPTION OF THE DRAWINtiS
Fig. 1 is a cross-sectional side view of a first embodiment of a laser head in
accordance herewith;
Fig. 2 is a cross-sectional top view of the laser head hereof taken along line
3-3
20 of Fig. 3 and line 1-1 of Fig. 1;
Fig. 3 is a second cross-sectional side view of the laser head in accordance
with
the present invention;
Fig. 4 is a cross-sectional view of a second embodiment of a laser head in
accordance with the present invention; and
25 Fig. 5 is a flow chart of a preferred method of crash avoidance of a
robotically
operated laser head in accordance with the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
At the outset, it is to be noted that the present invention is particularly
suited for
3o use in solid material cutting or welding, such as in metal cutting, sheet
metal cutting,
welding, lap welding or for the car manufacturing industry in general, etc.,
although
6
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WO 00/54925 PCT/US99/20820
other uses therefor will become apparent to the skilled artisan from the
ensuing
disclosure.
Now referring to Figs. 1, 2 and 3, a laser head 10 in accordance with the
present
invention is depicted therein as including a housing 12 containing laser
optics 13. The
s housing Z2 forms a hollow inner Chamber 20 to provide a light path and to
protect the
optics 13 from particulates anti abrasion during any laser cutting or welding
operation.
The housing 12; at a first end thereof, is connected to a mounting block 14 by
conventional means, such as fasteners or the like. The mounting block 14 may
be
formed separate from the housing 12 or made integral therewith. The mounting
block
14 provides a suitable attachment member for securing various components or
the laser
head thereto. The housing 12 tapers down at a second end to a nozzle 16.
Alternatively, the nozzle 16 may be attached to the second end using suitable
fastening
means. The nozzle 16 further tapers down to tip 90 having an exit or nozzle
port 17 to
provide a laser head that can direct assist gases and prevent debris or
spatter from
operation upon a workplace from entering the nozzle 16.
In a preferred embodiment, the nozzle 16 is an extended tubular member that is
narrower than the housing 12. Such a nozzle may have a first tapering conical
portion
followed by a second tapering portion, which also extends longitudinally to
provide an
extended member. The second tapering portion is then followed by a third
conical
2o tapering portion that terminates at a tip. The extended, narrower tubular
nozzle
provides a laser head capable of precisely operating about a three dimensional
workplace.
A light source 18 is connected to the mounting block 14 and is in optical
communication with the hollow inner chamber 20 of the housing 12. The light
source
18 provides a light beam for the laser head. The light source 18 can be any
suitable
laser light beam generating means, for example, an optical fiber or the like.
The light
source 18 is adapted to shine a beam of light through a chamber in the
mounting block
14 and is adjustably connected thereto, as discussed below.
The light source 18 generates and directs the light beam upon the laser optics
13
3o or means for receiving the light beam. The means for receiving may be any
type of
receiving optic, including a lens, mirror, prism, beam splitter, etc. As
shown, the
means for receiving the light beam comprises a first or receiving lens 22
disposed
CA 02343722 2001-03-08
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within the hollow inner chamber 20 of the housing 12. The receiving lens 22
may be a
collimating lens. The receiving lens 22 provides means for delivering a
suitable light
beam to a second or focal lens 26. As shown, the receiving lens 22 is
supported within
the inner chamber 20 of the housing 12, at the end opposite the mounting block
14, by a
first lens cartridge 24. The second Lens 26 is supported inside the housing
proximate a
top porrion of the noule 16 by a second lens cartridge 28. The second lens 26
is in
optical communication with the first lens and may receive a collimated light
beam from
the first lens 22 to focus the light beam through the nozzle 16 onto a
workplace.
The laser head 10, hereof; further includes means for adjusting the incoming
light beam upon a first receiving optic or the like, which is generally
depicted at 33. As
shown, the means 33 for adjusting the incoming light beam includea a fiber
adapter 42
adjustably seated within the mounting block 14. The means 33 for adjusting the
incoming light beam upon the first receiving optic provides for directing or
centering
the incoming light beam upon a desired light path. The desired light path is,
for
1s instance, an optical path in line with the focal or condensing lens 26.
Thus, upon
operation of the means 33 for adjusting, the incoming light beam can be
directed upon
the focal lens 26 in a manner suitable for delivering an~amount of light to
the focal lens
26 sufficient for farming a high-powered laser beam. The means 33 for
adjusting also
permits the focal point of a laser beam to be centered coaxial with the nozzle
port 17 or
2o hole without moving the focusing lens or the nozzle.
The means 33 for adjusting may comprise a fiber adapter 42. The fiber adapter
provides means for adjustably supporting an optical fiber. As shown, the fiber
adapter
42 is a hollow member having an outer wall 48 for supporting an optical fiber
within
the mounting block i4. The outer wall 48 is adapted to extend into the
mounting block
25 14 and terminate at a tip 44 of the fiber adapter 42. The tip 44 has a
central opening or
is open at a first end for directing light from the optical fiber there
through. A support
ridge 46 extends circumferencially from the outer wall 48 to slidably support
the fiber
adapter 42 upon a ledge or shelf 32 of the mounting block 14. The outer wall
48
longitudinally extends beyond the support ridge 46 where the wall 48 has at
least one
3o notch 50 circumferencially disposed thereabout. The notch 50 is used to
secure or fix
the position of the fiber adapter 42 within the mounting block 14. The wall 48
8
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WO 00/54925 PCT/US99/20820
terminates at a second open end 52. The second open end 52 is adapted to
receive an
optical fiber there thmugh.
An optic or optical fiber 34 is seated in the fiber adapter 42 and extends to
approximately the tip 44 of the fiber adapter 42. The optical fiber 34 is
secured or
s removably fixed within the fiber adapter 42 using any suitable fastening
means, for
example, a screw 58 impinging upon a tapered portion 56. The use of the
optical fiber
34 for producing a light beam is generally known and includes any type of
long, thin
thread of fused silica, or other transparent material used to transmit light.
The mounting block 14 provides a support for the fiber adapter 42 and a
to mechanism to shear upon the occurrence of a violent or uncontrolled crash
between the
laser head sad a workplace or other fixture. The mounting block 14 has a first
throughbore 91 and a second bore 93 concentric therewith, the bores 91, 93
cooperate
to form a ledge 32. The fiber adapter 42 has a ridge 46 adapted to set upon
the ledge 32
of the mounting block 14. The second bore 93 has a radius substantially
greater than
is both the ridge 46 of the fiber adapter and the first bore 91 of the
mounting block 14.
The fiber adapter 42 is disposed tip 44 first in the first throughbore 91 of
the mounting
block such that the ridge 46 of the fiber adapter comacts the ledge 32 of the
mounting
block and is translatable or is slidably seated thereon. Thus, the fiber
adapter 42 is
adapted to translate or slidably move upon the ledge 32. The slidability or
translation
20 of the fiber adapter 42 provides for adjustment of the light beam upon the
focal lens 26
to center the focused laser beam through the tip 90 of the nozzle 16.
The mounting block 14, may also provide a support to attach the laser head to
a
robot 35 (shown in part). The laser head may be attached to the robot 35 using
any
suitable fastening means, such as magnetic attachment, break-away tabs, etc.
The
2s fastening means preferably provides a safety release mechanism, which
disconnects the
laser head from the robot upon a violent or uncontrolled collision.
As shown in Fig. 3, the mounting block is a two piece structure that acts as a
safety relief mechanism adapted to shear upon the laser head uncontrollably
colliding
with another object to separate the laser head containing the optics from the
robot 35.
3o The safety relief mechanism comprises an upper break-away flange 36 and a
lower
break away flange 40. The upper break-away flange 36 is secured to the robot
35 using
suitable fastening means, such as screws, bolts or the like. The lower break-
away
9
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WO 00/54925 PCT/US99/20820
flange 40 is secured to the mounting block 14 using suitable fastening means,
such as a
screw 60, bolt or the like. The lower break-away flange is seCUred to the
upper break-
away flange by a suitable break-away means. The break-away means is effected
by at
least one break-away plate 62 and a plurality of pins 98, 99 connecting the
upper break-
s away flange 36 to the lower break-away flange 40. A break-away ring 38 is
disposed
between the upper and lower break-away flanges to provide means for aligning
the
flanges. The break-away ring 38 conforms to the inner shape of the upper and
lower
flanges and rests upon the lower flange to effectuate the alignment.
The break-away plate 62 may be formed of any material that provides a suitable
to shearing mechanism to disconnect the upper flange 36 from the lower flange
in the
event of an uncontrolled collision between the laser head and a workplace or
other
object to thereby separate the laser head from the robot 35. Such a mechanism
protects
the robot and the laser head from major damage should a collision be
unavoidable.
The lower break-away flange 40 has a bore with a radius substantially wider
15 than the outer wall 48 of the fiber adapter 42 to allow for unrestricted
movement of the
fiber adapter 42 As discussed below, movement of the fiber adapter 42 may be
restricted by one or more fasteners.
Referring now to Fig. 2, the fiber adapter 42 is adjustably attached to the
mounting block 14 with a plurality of fasteners 66, 66', 66", 66"'. Preferably
the fiber
2o adapter 42 is adjustably mounted within the mounting block with at least
three
fasteners, and preferably four fasteners, diametrically disposed radially
about the lower
break away flange and contacting the notch 50 of the fiber adapter 42. As
shown in
Fig. I, a screw 66 mounted through the lower break-away flange 40 contacts the
notch
50 in the outer wall 48. The screw 66 cooperates with at least one other screw
to
25 restrict the slidable movement of the fiber adapter 42 about a horizontal
or a x-y axis.
The plurality of fasteners 66, 66', 66", 66"' are equally distanced around the
fiber adapter 42. Adjustment of the light beam is accomplished by loosening
specific
fasteners 66, 66', 66", 66"' followed by the tightening of other fasteners 66,
66', 66",
66"' whereby the optic fiber or the fiber adapter 42 may be incrementally
moved. This
3o movement of the optic fiber, in turn moves the light beam emitted from the
light source
to incrementally alter the light path of the beam along the x-y axis of the
laser head.
to
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When the correct position of the light beam is reached, all fasteners 66, 66',
66", 66"'
are re-tightened.
In use, the laser head travels along a surface of a workpiece at a
predetermined
speed. As the present invention contemplates, the laser head is adapted to
operate upon
a three dimensional surface having varying topography. Such a laser head is
adapted to
continuously alter the position or distance that the tip 90 or nozzle 16 of
the laser head
operates at in relation to the changing surface topography of the workpiece.
A laser head adapted to contimrously alter the operating height is now
described
in a preferred embodiment. The housing 12 in this preferred embodiment is a
1o telescopable two-part assembly comprising a first body or upper eye-induced
tube 70
and a second body or lower tube 72 retractable and extendable irno and out of
the first
body 70.
The teiescopable housing 70, 72 provides a laser head that may precisely track
the surface of a workpiece in relation to the changing topography of said
surface. The
1s telescopable housing also provides an improved or faster means for
adjusting the
distance or height that the laser head operates at above a workpiece as
compared to a
laser head adjusted solely by a robot or robotic arm.
The first and second bodies 70, 72 may be formed of any suitable material,
inchrding stainless steel, brass, alloys, ceramics, etc. Suitable materials
are resistant to
2o wear and heat and provide adequate support for the optics. The bodies 70,
72 are
preferably rigid, cylindrical structures that are sized to fit one within the
other. The
telescopable housing thereby provides a housing less prone to wear, as opposed
to for
example, an accordion or a flexible housing design.
The laser head, as shown in Fig. 3, includes means 21 for continuously
2s adjusting the distance or height that the nozzle or laser head operates at
above the
surface of a workpiece. The means 21 for continuously adjusting is any
suitable device
for extending and contracting the housing within itself or the mounting block.
Such
means may include one or more of the following, for example, an electric
motor, rack
and pinion, hydraulic means, pulley and cable, opposing springs, etc.
3o As shown, the means 21 for adjusting includes a motor 76, a flange 75, a
pulley
74, a cable 80, and at least one spring 82 that are connected to drive the
telescopable
housing. As stated above, the lower tube or second body 72 has an outer
diameter
11
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smaller than the upper tube or first body 70 and is telescopable therein. The
flange 75
is connected to or made integral with the top of the lower tube 72. The pulley
74
having a cable 80 associated with it is rotatably mounted within the mounting
block 14.
The cable 80 is wound upon the pulley 74 with one end extending through the
mounting block 14 and connected to the flange 75. The motor 76 is mounted to
the
mounting block and is functionally connected to the pulley 74. The motor 76 is
controlled electronically through a controller (not shown). The motor 76
provides
rotational motion to the pulley 74 for winding and unwinding the cable 80
about the
pulley 74. The cable 80 in turn moves the flange 75 and the corresponding
lower tube
l0 72 into the upper tube 70.
As shown in Fig. l, a spring 82 and is seated between the upper tube 70 and
the
lower tube 72 and acts to oppose the retraction of the lower tube 72 within
the upper
tube 70, thereby opposing the motion of the pulley 74. As shown, the spring 82
is
supported at one end by the lower tube ?2 with a spring shield 84. The
opposite end of
is the spring 82 is attached to the mounting block 14 at a spring post 86.
Operation of the
pulley 74 to wind the cable 80 retracts the lower tube 72 within the upper
tube 70.
Likewise but in a reverse manner, opooration of the pulley 74 to unwind the
cable 80
extends the lower tube 72 from the upper tube 70.
The laser head may ftuther include means for determining the distance the
laser
2o head is positioned at above a surface of a workgiece. The means for
determining may
be any suitable distance sensing device or means, including but not limited to
various
electrical devices, capacitive sensing, laser reflection, variable resistance
sensors, a
linear potertiometer, etc. As shown, the means for determining is means 97 for
capacitive sensing. The means 97 for capacitive sensing includes an
electrically
2s conductive tip 90 disposed at the free or distal end of the nozzle 16 and a
capacitive
sensing cable 94 (shown in part) attac>~d thereto.
As shown, the nozzle 16 is connected to the bottom of the lower tube 72 of the
housing. The nozzle preferably has an electricaliy conductive tip 90. The
nozzle 16
may be made of any metal or alloy that is conductive and heat resistant. An
insulating
3o insert 89 is disposed between the tip 90 and the rest of the nozzle or
housing. The
insert prohibits undesirable electric cxrrrent from traveling through the
nozzle or tip to
the housing. The tip 90 is connected to the nozzle 16 with a conductive
threaded insert
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WO 00/54925 PCT/US99/20820
87. The insert 87 also provides a connection from the tip 90 to the capacitive
sensing
cable 94.
Thus, the tip 90 is in electrical communication with a capacitive sensing
cable
94. The capacitive sensing cable 94 has an inner conductive core 104. The
inner
s conductive core 104 is surrounded by an insulated outer coating or
dielectric 110. The
capacitive sensing cable may be connected to the tip 90 in any suitable
manner, such as
spot welding, fasteners, etc. The inner conductive core 104 is a conductive
metal, such
as copper, silver, etc. A second insert 92 may be used to separate the tip 90
from the
nozzle 16. As with the first insert above, the second insert 92 prohibits
undesirable
to electric current from traveling through the nozzle to the housing.
In use, an electric charge is applied to the insutative tip 90 through the
capacitive sensing cable 94, whereby an electrical discharge to the workpiece
in
relation to the distance from the tip 90 occurs. The electrical discharge is
measured or
monitored by a controller or any other suitable device (not shown), such as a
PLC,
15 computer analogue to digital converter, analogue electrical circuit, etc.
The controller
may also operate to keep the distance between the tip 90 and the workpioce
constant,
such as by controlling the motor 76 operation. As will be discussed below, the
cornroller may also be used as part of a crash avoidance system.
Operation of the motor 76 is controlled by a cornroller (not shown), such as a
2o PLC, electric circuit, computer or the like which may have a program. The
controller
determines the motor 76 operation by processing signals sent from a
poterniometer 102,
means 97 for capacitive sensing or the like. As shown the potentiometer 102 is
disposed between the mounting block 14 and the lower tube 72. The
potentiometer 102
is electronically connected to the controller. The potentiometer 102 senses
the amount
25 of compression / retraction the housing has undergone and sends an
electronic signal to
the controller. The signals may then be processed with any suitable device,
for
example, an AID converter, computer software loaded into the computer, etc.
The
signals are then used to determine the extension/retraction the housing has
undergone.
The laser head may also include an assist gas delivery system, wherein the
3o system, preferably, is disposed within the housing and adapted to deliver
an assist gas
to the nozzle 16. As shown, the assist gas delivery system is a telescopable,
two-part
conduit 96 which extends along the inside of the housing 12 through the
mounting
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block 14 and is connected to a gas inlet connector 30. The gas inlet connector
30 is
mourned to the top of the mounting block 14 and extends into the housing 12.
The gas
inlet connector 30 is connected to the conduit 96 disposed within the housing
12 by any
suitable fastening means. The conduit 96 runs the length of the housing 12
tapering at
the nozzle 16. The conduit 96 has a rigid inner tube 98 collapsible into a
rigid outer
tube 100, wherein the outer tube 100 has an inner diameter greater than that
of the outer
diameter of the inner tube 98, thereby allowing the conduit 96 to
retract/extend within
itself. The retractable, extendable gas assist delivery system provides a
durable way to
deliver an assist gas to the nozzle and provides a laser head more capable of
operating
1o about a three dimensional surface.
In a preferred embodiment, the laser head and robot form a laser unit having a
crash avoidance system. The crash avoidance system includes means for
determining
the operating mode of the laser head; means for determining the distance the
laser head
is operating at above a surface of a workpiece; and means for stopping the
operation of
1s the laser unit to avoid a collision when the laser head is detected at a
predetermined
distance above a surface of a workpiece.
Referring now to Fig. 5, shown therein is a flow chart depicting the operation
of
a crash avoidance system in accordance with the present invention generally
shown at
524. Operation of the laser head and robot is performed as a unit. The unit
may be
20 operated in several different modes. The modes of operation may be
determined by
either the position of the laser head about a workpiece or by an operating
condition of
the robot or by both. The modes of operation may include, for example, an
operating
or run mode, a park mode 510, a teach mode 512, and a hold mode 514.
Each mode of operation may be a discrete operating mode. The nui mode is the
2s actual operation of the unit. The park mode 510 is a mode of operation
where the unit
is in a standing or latent position. The teach mode 5I2 is a mode of operation
where
the unit masks or traces the desired motions and actions of operation in order
to
program the unit. The hold mode 514 is a mode of operation where the unit
operates
upon a portion of a workpiece at an edge or hole of the workpiece. During
operation,
3o the laser head normally tracks the surface of a workpiece by rising and
falling
therewith. Rather than having the height of the laser head drop dramatically
upon
reaching an edge or hole in the workpiece, in the hold mode 514 the laser head
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maintains it's current operating axis or height irrespective of the surface it
is operating
upon to properly perform the laser operation.
The means 522 for determining the distance the laser head is operating at
above
a surface of a workpiece is any device or means that allows the approximate
space
between the distal end of the tip of a laser head and a surface of a workpiece
to be
measured. The laser head and robot function as a unit which operates upon a
surface of
a work piece in one or more of the above mentioned modes. The means 522 for
determining the distance may be any suitable means or device, such as the
means 97 for
capacitive sensing or the linear potentiometer 102 as described above. The
means 522
1o for determining may also be either a single device or separate devices
522', 522" for
determining the distance.
As mentioned above and shown in Fig. 3, the means 97 for capacitive sensing
comprises a nozzle or tip 90 and means for electrically determining if the
laser head is
in contact with or in close proximity to the surface of the workpiece.
Depending upon
is the mode of operation that the unit is functioning in, the unit will not
operate or will
cease to operate when the laser head is at a predetermined distance from a
work piece.
The predetermined distance is normally from 0 mm to about lmm and preferably
less
than 0.5 mm between the laser head and a workpiece. A crash is considered
avoided
even if the predetermined distance is set to 0 mm as long as damage does not
occur to
2o the laser head or robotic unit upon contact. Thus, by prohibiting the unit
from operating
in certain modes when the laser head is positioned at certain heights or in
contact with a
workpiece, the present invention provides a laser head less likely to be
involved in a
crash with a workpiece or damaged, thereby preventing problems that may
therefor
follow.
2s The laser head and robot or the unit may further be controlled by the
operating
condition of the laser head. For instance, operating conditions of the laser
head include
but are not limited to the laser head reaching an extended limit 516 or a
retracted limit
518. As the present invention also provides a laser head that is telescopable
or
extendable, the crash avoidance system may provide means for stopping the unit
when
3o the laser head reaches the extended limit 516 or the retracted limit 518. A
laser head
will typically reach an extended limit 516 when the laser head is at a maximum
distance from a workpiece and the telescoping housing is fully extended. Even
though
CA 02343722 2001-03-08
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the laser head is not likely to be involved in a collision with a workpiece,
such
operating condition is likely to result in inferior use of the laser beam.
Therefore, the
laser unit is better shut down or left idle for adjustment than left to
continued operation
on a workplace.
The laser head reaches a retracted limit 518 when the laser head operates or
moves close to or is in such proximity to a workplace that the telescopable
housing of
the laser head may no longer retract within itself. A laser head may reach a
retracted
limit 518 as a result of preprogramming the operation of the laser head,
wherein the
programming does not coincide with unexpected variations of workplace surface
1o topography. If a laser head is left to operate at a retracted limit 5 i 8,
the focused laser
beam may not properly impinge upon the surface of the workplace, or the laser
head
may be prose to increased collisions. Therefore, the unit is preferably
stopped or left
idle until adjustment to the unit or reprogramming may be preformed.
For example, as a laser cuts a workplace, the laser head may operate at about
1
mm from the cutting surface. In movement from workplace to workplace, the
laser
cutting heed may momentarily reach a parked position, being as much as 10 mm
from
the workplace. As the head then moves from workplace to workplace, the means
522
for avoiding a collision detects if the workplace comes within a 3 mm to 6 mm
range of
the surface of a work piece and shuts the laser head and robot off before a
collision
occurs.
The means 520 for stopping the operation of the laser head to avoid a
collision
when the laser head is detected at a predetermined distance above a surface of
a
workplace may be any suitable means or device that stops or prohibits the
movement of
the laser head and robotic unit when a "crash" condition is met. Suitable
devices
comprise for example, a controller that receives a signal from a linear
potentiometer,
the controller in turn sending a signal to open a crash interlock to stop the
laser head
and the robot. The controller can be any suitable controlling device that may
receive a
signal and send a signal when a "crash" condition is met. Suitable controlling
devices
include a PLC, a computer driven by software, a circuit board with a
controller chip, an
3o electric circuit, an analogue electric circuit, PROM, etc.
Referring now to Fig. 4, there is depicted therein a second embodiment of the
present invention, generally depicted at 200, wherein an optical fiber 224 is
connected
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to a laser head 200 at an angle, preferably normal to the cutting axis. In
this
embodiment, the laser head comprises a housing 201, an optical fiber 224 and
means
215 for adjusting the light path of light beam produced from a light source.
As shown,
the means 215 for adjusting is an adjustable optic or mirror assembly disposed
within
the housing 201 for adjusting the incoming light beam along the y-axis of the
laser head
and a translatable or slidable carriage to adjust the incoming light beam
along the x-axis
of the laser head.
Positioning the optical fiber 224 at an angle provides for attachment of a
camera
202 or other viewing device at the top of a mounting block 204, directly above
the
io focused laser beam. As shown, a receiving mirror 206 or optic is disposed
within the
housing 201 and is adapted to deflect or bend the incoming light beam onto a
first lens
208 to provide a light beam that enters the housing at an angle in relation to
the exiting
laser beam. The light beam is passed to a second or focal lens 210 from which
the light
beam is focused through a nozzle 212 onto a workpiece (not shown).
A mounting block 204 in conjunction with the housing 201 is used to fix the
laser head to a robot or robotic arm 235 (shown in Part). As shown, the
mounting
block 204 also provides a suitable support for a light source 224, for optics
208, 206,
210 and for a camera 202. The mounting block 204 has an internal chamber 218;
a first
hole 220 passing through the bottom of the mounting block which bisects the
chamber
218; and a second hole 222 extending from the side of the chamber to a back
wall.
The means 215 for adjusting may include an adjustable mirror assembly. As
shown, the adjustable mirror assembly is disposed within the mounting block
204. The
adjustable mirror assembly includes a mirror 206, a mirror mount 214, and a
pair of
biased adjustment fasteners 250 (one of which is shown). The mirror 206 is
seated on
2s the mirror mount 214 and is rotatably disposed within the internal chamber
218 with
the pair of biased adjustment fasteners 250. The fasteners 250 may be any
suitable
securing members that are adjustable, such as screws, bolts, clips, clamps,
etc. As
shown, the fasteners 250 are screws extending through the mounting block to
adjustably hold the mirror mount 214 in place.
3o The mirror mount 214 has a machined side to tightly fit against or butt the
front
surface of a fiber adapter 230. A spring 216 is compressed between the mirror
mount
214 and the back of the chamber 218 to keep the mirror mount 214 butted to or
pressed
i7
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against the fiber adapter 230. Butting the mirror mount 214 to the fiber
adapter 230
provides an assembly that may translate or slide in unison, yet forms a two
piece
assembly or a carriage 231 wherein the mirror mount 214 or mirror may
independently
rotate about an axis.
s An optical fiber 224 or other light source is connected to the mounting
block by
a fiber adapter 230. The optical fiber 224 is attached to the fiber adapter
230 by any
suitable means, for example and as shown, a butt plate 228. The optical fiber
224 is
positioned to shine a light beam through the second hole 222 to a receiving
optic or
mirror 206. The mirror 206 is positioned on the mirror mount 214 to form the
mirror
1o assembly. The mirror 206 may be of such design as to reflect only desired
wavelengths.
The mirror 206 is positioned at an angle, preferably about 45 degrees, to
provide optical
communication between the optical fiber 224 and a first lens 208.
A pair of fasteners, such as adjustment screws 250 (one of which is shown),
rotatably support the mirror mount 214 within the mounting block. The
adjustment
1s screws 250 extend fibm the outside of the mounting block 204 to the mirror
mount 214.
The adjustment screws 250 function to adjust the light beam from the optical
fiber 224
along the y axis of the laser head onto the first lens 208 without changing
the length the
light beam travels from the optic fiber 224 to the first lens 208.
The carriage 231, as shown, comprises the mirror assembly and the fiber
2o adapter 230, wherein the mirror assembly diametrically opposes the fiber
adapter at
machined surfaces to form the carriage 231. The carriage 23 i is slidably
seated in the
mounting block 204. A guide pin 232 fixed to the mounting block rides within a
guide
channel 234 formed in the carriage 231 to prohibit rotational movement of the
fiber
adapter 230 within the mounting block 204.
25 The carriage 231 is translatable along an axis of the laser head.
Translation of
the caniage 231 is limited by any suitable means or fastening device. As
shown, a pair
of set screws 244, 246 limit the translation of the carriage. The set screws
244, 246
extend through the mounting block 204 to contact a second groove 248 formed on
the
slidable carriage 231, whereby tightening the set screws fixes the position of
the
3o slidable carriage 231.
The set screws 244, 246 operate in a synergist manner to incrementally move
the carriage 231 along an axis of the laser head. To incrementally move the
carriage,
~s
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the set screws 244, 246 are seated in a groove of the mounting block wherein
the
groove 248 terminates on either end at an inclining wall. The screws 244, 246
and
groove 248 are adapted to move the carriage along the x-axis when loosening
one
screw 244 followed by the tightening of the other 246. Moving the carriage
along the
x-axis thereby moves the optic fiber and mirror mount in unison to reposition
the light
beam on a lens 208 without changing the length of the light path between the
optic fiber
224 and the lens 208.
in practicing the present invention, preferably, the housing 201 is sealed and
generally kept under positive pressure to keep the internal components of the
housing
l0 201, including optics, dust fi-ee. Also, the optical system, preferably,
comprises a
plurality of lenses such that a first receiving lens 208 or optic directs a
parallel or
collimated light beam to a second focusing lens 210.
While the invention has been illustrated in detail in the drawings and the
foregoing description, the same is to be considered as illustrative and not
restrictive in
1s character, it is understood that only the preferred embodiment has been
shown and
described fully and that all changes and modifications that come within the
spirit of the
invention are desired to be protected.
Having thus described the above several embodimerns of the present invention,
what is claimed is:
19
