Note: Descriptions are shown in the official language in which they were submitted.
Mounted adjacent and in alignment with the workpiece sup-
porting portion of a wor]~piece-shape-altering machine, such as
the lower die of a stamping press, is a laser beam source, the
outgoing beam from which passes through a beam splitter which
divides the entering beam. One of the two emeryent beams from
the beam-splitter is a workpiece position-inspecting beam which
passes in a grazing direction across one portion of the top of
a workpiece resting upon the lower die for subsequent stamping
by the upper die of the press. This beam continues onward to
a mirror which reflects it in a grazing direction back across
another portion of the top of the workpiece to a workpiece pos-
sition detector. The other emergent beam from the beam split-
ter is a workpiece presence-inspecting beam which is obstruct-
ed by the workpiece, if presenton the lower die, so that it -
does not reach the workpiece presence detector therebeyond.
If~ however, the workpiece has not been ~livered to the lower
die, or if delivered and worked upon,~ has adheredto and has
been carried upward with the upper die, the workpiece presence ~ -
detector immediately transmits the absence of the workpiece
from the lower die to the electric control system of the press,
which prevents the operation of the press until a workpiece is
properly supplied -to a~d positioned upon the lower die. On
the other hand, even if the workpiece is in position on the
lower die but is improperly positioned, such as being tilted,
to that it obstructs the workpiece position-inspecting beam
with the result that the beam does not reach the workpiece
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detector, the improper position of the worl~piece is transmit
ted to the electric press control system which thereupon
prevents actuat:Lon of the press until -the workpiece has been
properly positioned upon the lower die by the operator.
~ ither-to, serious accidents have occurred in workpiece-
shape-altering machines, such as stamping presses, when the work-
piece has been improperly positioned in the die set thereof or
when the stamped workpiece sticks in the upper die or punch and
is carried upward while the new workpiece has been automatically
fed into the die-set by the conveyor mechanism. The result has
been that when the punch or upper die has again descended, the
workpiece adhering to it has clashed with the next workpiece,
which has meanwhile been fed to the die set, with dangerous
consequences to the operator as well as to the machine. Pre-
viously, workpiece~posit~oning systems have been ~rovided with
limit switches in conjunction with an electrical circuit for
attemptedly indicating when a workpiece blank has been improp-
erly positioned in the press die-set but such limit switches have
often falled as a result o~ their repeated operationsO with the
result that the intendedly safeguarding system no longer oper-
ates successfully. In one instance, for example, the inspect-
ion system did not indicate the improperly positioned workpiece,
with the result that the workpiece was hurled across the room
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by the improper conta~t of the punah therewith, causing serious
: da~g~r to bystanders.
.
The invention principally resides in the provision of the
: laser beam source transmitting its outgoing beam into the beam
splitter for subsequent division into two beamsO one o~ which
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notifies the con-trol system of the workpiece shape-al-tering rna-
chine whether or not the workpiece has been properly posltioned
in the die set and subsequently is properly removed therefrom.
A further feature of the invention resides in the provision of
means for transmitting to the machine control system the requis-
ite information either for proper operation or for halting the
machine or preventing its operation when proper information as
to the position and presence of the workpiece has not been
transmitted to the machine control system. If the workpiece un-
intendedly adheres to the upper die of the die set and ascendswith it, the laser beam reaches the laser ~eam detector pre-
maturely, i.e. before the predetermined time of operation of
the workpiece removal and resupply mechanisms, whereupon this
indication of improper and untimely removal of the workpiece
operates the safety control circuitry of the workpiece shape- ~ ;
altering operation until the improperly-lifted workpiece is re-
moved from the upper die.
In the drawings,
Pigure 1 is a diagrammatic perspective view of a laser - -
workpiece position and presence inspector and machine control
governor, according to one form of the inven~ion, showing a
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workpiece blank properly ln position for proper utilization of
the two laser beam portions from the beam splitter permitting
work operation of the workpiece shape-altering machine, such as
a trimming and piercing die-set in a stamping press (not shown)~
upon a partially-completed workpiece;
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Figure 2 is a central vertical section through a conven-
tional trimming and piercing die-set and adjacent portions of a
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conven-tional stamping press, equlpped with the laser ~orkpiece- ~-
pOSitiOIl inspector and machine control gov~rnor o:E the present
invention, looking in the direction o~ the arrows 2--2 in Fiy-
ure l;
Figure 3 is a side elevation, with the cover in central
vertical section, of an ad~ustable reflector employed in the
arrangement of Figure 1,
Figure 4 is a top plan view o~ the reflector, with khe
top of the cover removed as shown by the section lines 4--4
in Figure 3,
Figure 5 is a section similar to Figure 4 but showing
in top plan view a beam splitter and its mount employed in the
arrangement shown in Figure 1, with the top of the cover removed;
and
Figure ~ is a diagrammatic central vertical section
through a stamping press equipped with a trimming and piercing
die-set having a laser workpiece position and presence inspect-
or and machine control governor wherein the lower die is provided
with a laser beam tunne~ therethrough.
Referring to the drawings in detail~ Figures 1 and 2
show a laser workpiece posltlon and presence inspector and ma-
chine control governor~ generally designated 10, installed in a
~: workpiece shape~-altering machine such as a stamping press, gen-
erally designated 12~ for determining the proper position or ~or
detecting a departure therefrom of a workpiece 1~ which is to
be further formed by the workpiece shape-altering machine 12. .:
For convenlence of illustration, the warkpiece 14 is shown as a~
automobile bumper requirinq trimming and piercing before it is ..
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finished. In particular, Figure 2 shows the workpiece 14, afe
terit has been previously subjected to forming and flanging op-
erations but before the peripheries of the flanges have been
cut off by the machine 12 and before the central portion has
been pierced.
The workpiece shape-alter:ing machine 12 of Figure 2 is
shown as a convent~onal stamping press having a press bed 16
upon which is mounted a bolster 18 surmounted by a lower die
shoe 20 which in turn supports the post 22 of a trimming and
piercing die-set, generally designated 24, having an upper die ;
26 secured to a movable platen 28. The latter is moved upward
and downward in a conventional manner, such as ~y a crank mech-
anism or by hydraulic cylinder and p~ston motors (not shown).
Such stamping presses 12 are conventional,are controlled by con-
ventional electric control circuits, and their ~etails form no
part of the present invention.
The upper die 26 consists of an upper die shoe 30 which
is flanged at its upper end for securing it to the platen 28.
The upper die shoe 30 is provided with a recess o~ cavity 32 in
which an upper pad 34 is mounted for vertical reciproca~i
on rel-
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atively to the upper die show 30 in which it is mounted. Later-
ally-spaced elongated trimmoing cutters 36 and 38 are secured to
and depend from a plate 39 ~hich in turn is secured to the upper
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die shoe 30 and~lso guide the upper pad 34 which performs the
function of holding down the workpiece 14 during the trimming
operation. In~particular, the central substantially flat por-
tion 40 of the workpiece 14 is held down by the substantially
flat bottom 42 of the cavity 44 in the upper pad~ 34r whereas
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the opposite sides 46, 48 of the workpiece 14 are retained in
position respect~vely by the perpendicular side surface 50 and
inclined side surface 52 of the cavity 44. T~le upper pad 34 has
a central bore 54 throuyh which projects a piercing punch 56
seated in a bore 53 of a mount 60 secured to a plate 62 which
in turn is secured to the bottom 64 of the cavity 32. The upper
pad 34 is recessed at 66 to receive the lower ends of a plural~
ity of helical compression springs 68, only one of which is
shown in Figure 2 as lying in the plane of the drawing. The
compression coil springs 68 constantly urye the upper pad 34
downward relatively to the pi.ercing punch 56 but yield to permit
the piercing punch to form a hole 70 in the workpiece 14 (Figure
1). For this purpose the punch 56 is provided with a reduced
diameter nose 72.
The post 22 has a substantially flat upper surface 74
which supports the central portion 76 of the workpiece 14 in co-
operation with the bottom surface 42 of the upper pad 34p and
has respectively perpendicular and inclined opposite side sur-
faces 78 and 80 cooperating with the opposite side surfaces 50
and 52 respectively of the upper pad 34 to hold down the opposite
side portions 46 and 48 of the workpiece 14. The horizontal
flanges 82 and 84 are held down by the cooperation of the hori-
zontal lower peripheral surfaces 86 and 88 of the upper pad 34
with the correspomdingly formed horizontal portions 90 and 92
respectively of the lower die 22. Stationary cutoff members 94 ~:
and 96 are recessed into the ~pst 22 immediately below the hori-
zontal su~faces 90 and 92 and cooperate with the vertically-mov-
able trimming cutters 36 and 38 to ~ut off the outer portions .
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of the workpiece flanges 82 a~d 84.
The scrap eclge portions 102 and 104 ~hown by the dotted
lines in the lower portion of Figure 2 consti-tute the severed
portions of the workpiece 14 cut off by the mov~ble trimming
cutters 36 and 38 cooperating wit:h the stationary cutoff members
94 and 96 respectively. The severed portions 102 and 104 slide
down inclined plates 106 and 108 to points of disposal. The
post 22 of the die set 24 is formed with a post bore 110 aligned
with the punch 56 and with the central bore 53 of the upper pad
34 to receive the severed scrap portion shown b~ the do~ted
lines 116 resulting from the punch 56 producing the hole 70 in
the workpiece 14 (Figure 1)~ This severed scrap portion 116
slides down an inclined chute 112 onto an inclined plate 114
and thence to a point of disposal.
The laser workpiece position inspector 10 ~Figure 1~ is
provided with a laser energizatlon and control unit 120 from --
which a conductor cable 122 proceeds downward to a conventional
laser beam generator or coherent light source 124 mounted on a
platcorm 126 which in turn is mounted on an inclined post or
stanchion 128, the lower end of which rests upon a~d is secured
to the lower die show 20 (Figure 2j. ~lso mounted on the plat-
form 126 in optical alignment with the outgoing laser beam 134
from the laser beam outlet 130 is a laser beam splitter 132
which divides the outgoing laser beam 134 into a workpiece posi-
tion indicating laser beam 136 and a workpiece presence-indicat-
ing laser beam :L38 (~igure l). Mounted on a platform I40 on an
upright post or stanchion 141 is a laser beam ~eflector 142.
The details of the laser beam splitter 132 and laser beam re-
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flector 142 are set forth in more detail below.
Aligned with -the r~flected component of the workpiece
position-indicating laser beam 136 is a workpiece position
de-tector 144 (Figure 1) whereas aligned with the workpiece pres-
ence-indicating laser beam 138 is a workpiece presence detector
146. From the detectors 144 and 146, the conductor cables 148
and 150 run back to the laser ene:rgizatiGn and control unit
120 which is electri~ally connected in governing relationship to
the press control circuit by the cable 158. The laser beam gen-
erator 124, beam splitter 132, reflector 142 and workpiece-
position detector 144 are so mounted and oriented that the in-
cident and reflected components of the workpiece position-indi-
cating beam 136 cross and recross the opposite end portions 152
and 154 respectively of the workpiece 14 in grazing relationship
when the workpiece 14 is properly positioned upon the lower die
22, i.e. without being tilted or otherwise misaligned, as ex-
plained below in connection with the operation of the invention.
When the workpiece 14 is thus properly positioned, both
the incident and reflected components of the workpiece position-
indicating laser beam 136 pass unobstructedly to the workpieceposition detector 144, hence are shown in solid lines in Figure
1. If, on the other hand, the workpiece 14 is present in the
die set 24 upon the post 22, it obstructs the workpiece presence-
indicating laser beam 138 so that the irldident component thereof
encounters, as an obstruction, the side 46 of the workpiece 14
and does not pass beyond it. Accordingly, the incident component
of the workpiece presence-indicating laser beam 138 is shown in
solid lines up to the point 156 of laser beam obst~uction and
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in dashed lines therebeyond. The dashed :Lines inclica-te the direc-
tion which the workp~ece presence-indicating laser beam 138 would
have taken toward the workpiece presence detector 146 if the
workpiece 1~ had not been present in the die set 24, and the ac-
tual portion of the workpiece presence-indicating laser beam
138 itself is proceeding unobstructedly to the workpiece pres-
ence detector 146 in the event th3t the workpiece 14 is absent
from its proper position on top of the post 22 of the die set
24 or has not been delivered thereto by the workpiece conveying
mechanism~
The laser beam source or generator 124, the workpiece
positinn detector 144 and the workpiece presence detector 146
are conventional and their details are beyo~dl ~h~ scope of
the present invention. The laser beams 134, 136 and 138 consti-
tute narrow weightless and absolutely rectilinear rods or point-
ers which, being of coherent light, are substantially without
diffusion throughout their paths of travel~ ~s their widths
are of only a few thousandths of an inch, they maintain their
s~bstantially original intensity over their entire path of
travel. Thus, an ordinarily insignificant displacement of the
workpiece 14 shows up instantly when that displacement inter-
cepts the laser beam 136 or 138 more accurately and~more depend-
ably than would be indicated by limit ~witches.
The beam splitter 132 (Figure S) and the reflector 142
(Figures 3 and 4) are p30vlded with similar mounts, generally
designated 160 and 162 respectively~ and dlffer only in the pos-
itioning of their respective mirror~s, hence a s~ngle description
~will suffice for both. Both also are provided with similar in-
: , _ 9 _
verted cup-shaped metal or plastic protective covers 161 and 163
respectively~ therefore also requlring only a single description.
The covers 161 and 163 provide p~otection ayainst mechanical dam-
age and oil or other vapors near .such machines 12. The mounts
160 and 162 (Figures 3, 4 and 5) are provided with cylindrical
bases 164 which are bored and counterbored at circumferentially-
spaced locations 165 to receive bolts or socket head screws 166
by which they are secured to their respecti~e supports 126 or 140.
The base 164 is provided with a vertical bore 168 which receives
a vertical shaft or pin 170 ~irmly and immovably secured in its
bore 168. The upper end of the shaft or pin 170 passes into a
bore 172 in an upstanding post 174. The post 174 is adapted to
be adjustably rotated by its bore 172 relatively to the shaft or
pin 170 and fixed in its adjusted position by a headless set
screw 176 threaded ihto a transverse or horizontal bore 178 com-
municating with the vertical bore 172.
The upper portion of the post 174 is provided with a cyl-
indrical cutaway portion 180 disposed with its axis hoxizontal
and therefore perpendictt~r to the axis o~ the vertical bore172.
Mounted in the cutaway cylindrical portion 180 for swinging mo-
tion around the axis 182 thereof is a semi-cylindrical mirror
: ~ support 184 havi~g a flat front mirror-mounting surface I86 co-
incident with the axis 182. Secured to the flat surface 186 as
by a sultable adhesive (not shown) is a rear-surface mirror 188.
The mirror support 184 is provided with a cylindrical rear sur-
face 190 of the same curvature as the cylindrlcal cutaway portion
180 and arcuately slidable relatively thereto. The upper portion
of the post 17~ is provided with an arcaate slot or groove 1920
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the bottom 194 oE which :is concentric with the axis 162 and the
cylindrical surfaces 180 and 190. The mirror support 184 is pro-
vided with a drilled and threaded bore 196 which receives the
correspondingly-threaded shank of a set screw 198. The head of
the set screw 198 is of less diameter than the width of the slot
or groove 192 so that when the screw 198 is tightened~ it engages
the cylindrical bottom surface 194 of the groove 192 In this
manner, the mirror support 194 may be rocked vertically around
its horizontal axis 182 and the~post 174 can be swung horizontally
around the shaft or pin 170, the vertical axis of which, if ex-
tended, passes through the horizont~l axis 182 of the cylindri- .
cal surfaces 180 and 190. Each cover 163, as previously statedO
is of inverted cup-shaped form with a hollow cylindrical side
wall 200 matlng with the cylindrical base 164, the former of
which is drilled and the latter drilled and threaded to receive -
a locking screw 202. A disc-shaped top 204 closes the upper
end of the hollow cylindrical side wall 200.
The beam splitter 132 (Figure 5), as previously stated,
has a mount 160 of similar construction to the mount 162 of the
reflector 142. The beam splitter 132, however, is provided with
a beam splitting rearr~silvered mirror 206 which is semi-transpar-
ent so that the outgoing laser beam 13~ has a portion 136 which
proceeds through it and a portion 138 of preferably equal intens-
: ity which is reflected by it. In order that the laser beams 134,
136 and 138 shall avoid being obstructed by the mount 160, the
beam splitter mirror 206 is secured in a laterally-offset posi-
tion relatively to the mirror support 184. The construction is
otherwise the same as ~hat described above for the reflector ~42.
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During the installation of the laser workpiece position
and presence inspec-tor and machine control governorO let it be
assumed that the laser light source 124, beam splitter 1320 re-
flector 142, workpieee position detector 144 and workpiece pres-
ence detector 146 have been mounted without their respective cov-
ers 163 and adjust~ with respect to the lower die 22 of the
workpiece shape-altering machine 12, so that a workpiece 14 prop-
erly positioned upon the latter will be properly oriented for
the required passage or interception of the laser beams 134,
136 and 138, as explained above. Before the inspection arranye-
ment 10 can be operated, however, the protective covers 161 and
163 must be drilled to provide a laser beam inlet aperture 209
and laser beam outlet apertures 211 and 213 for the beam split-
ter 132, and laser beam inlet and outlet apertures 215 and 217
respectively for the reflector 142.
If the cover 161 is of transparent plastic materialO
these apertures are positioned properly therein by causing the
laser light source 124 to project it~ outgoing beam 134 onto the
side wall of the plastic cover of the beam splitter 132, where-
upon the locations of the resulting spots of light are markedand subse~uently drilled to provide the apertures 209, 211 and
213. After these apertures are drilled, the transparent plastic
cover 163 of the reflector 142 is similarly~.- positioned and the
locations of the spots of light on the cover created by the
emergent beam 136 from the beam splitter 132 are marked and sub-
se~uently drilled to provide the apertures 215 and 217. The in- .
terior surface of the transparent plastic covers 161 and 163
are then coated with an opaque black material, such as by spray-
ing, to prevent undesired entry, reflection or diffusion of out- . : -
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side light or of the laser beam.
If, on the other hand, the covers 161 and 163 are to be
of meta~;, such as is desirable where there is danger from flying
objects and other materials which might damage or des~ plastic
covers, there is provided a correspondingly-shaped transparent
cup-shaped plastic templet of inside diameter adapted to snugly
receive and slide in telescoping :relationship over the stee.~ or
other metal cover to be drilled. This templet is placed in the
position ultimately to be occupied by the steel cover 161 or
163. The sameprocedure is them followed to cause the laser beam
134, 136 or 133,as the case may be, to project spots of light on-
to the plastic covers 163. The locations of these spots are
then marked on the plastic templets, which are subsequently
drilled in these locations. The cup-shaped transparent plastic
templets are then telescoped ovex the steel covers 161 or 163
and their apertures used as dF lling guides ~o drill the nec-
essary apertures 219, 211 and 213 in the beam splitter 132
and the apertures 215 and:217 in the reflector cover 163. The
steel or other metal covers 161 and 163 with their respective
apertures thus provided, are then mounted on their respective
bases 164, and adjusted by rotating them horizontally until
their respective apertures are aligned with the laser beams 134,
136 and 138, whereupon the inspector 10 is ready ~or use.
In the operation of the workpiece position and presence
: inspector and machine control governor 10, with the various com-
ponents thereo~ adjusted in the manner described above, let it
be assumed that a workpiece 14j such as a stamped but untrimmed
sutomobile bumper, has been placed in position:upon the post 22
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of the wor]cpieee shape-altering machine 12, either manually or
by a conveyor and wor]~piece handling system ~requently used i.n
such installa-tions. Let it also be assumed that the workpiece
1~ is properly positioned upon the p~st 22 and that the laser
light source 124 is energized to p:roduce the outgoing laser
beam 134 which in turn is divided by the beam splitter 132 into
emergent beams 136 and 138. When the workpiece 1~ is thus prop-
erly positioned, the workpiece position indicating beam 136 pro-
ceeds uninterruptedly at gra~in~ incidence over both the locations
152 and 154 near the opposite ends of the workpiece 14. As a re-
sult, the workpiece positinn detector 144 operates to indicate t
that the workpiece 14 has been properly positi3~ed and transmits
this information through the cable 14~ to the control unit 1200
which in turn transmits it through the.cable 158 -to the control
circuit o~ the workpiece shape-altering machine 12. At the same
time, the workpiece presence indicating laser beam 138 proceeds
to the point 156 on the workpiece 14 where it is obstructed by
the latter and ~ails to reach the workpiece presence indicating
detector 146. As a result, the information that the workpiece
14 is present on ~e post 22 is transmitted through the cable 150
back to the control un~t 120 which in turn transmits it through
the cable 158 to the control circuit of the workpiece shape~
altering machine 12 that the workpiece 14 is both pre~ent and in
its proper position, releases the otherwise conventional machine
control circuit to cause the platen 28 and upper die 34 to des-
: : cend and carry out the ~or~ming oper~ions upon the workpiece 14.
If, on the other hand, the workpiece 14 is improperly
positioned, such:~as, for example, bei~ng tilted so that the point
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152 is highex than the point 154, the portion o~ the workpiece
14 adjacent the point 152 interrupts the workpiece posi-tion i.ndi-
cating laser beam 136 so that it does not reach the reflec-tor
142, whereupon the workpiece positioning detector 144 does not
receive the beam 136 and transmits this information to the con--
trol unit 120 by way of the cable 148. If, on the other hand,the workpiece 14 is tilted in the opposite direction so -that
the incident workpiece position indicating laser beam 136 is
transmitted unobstructed to the reflector 142 but its reflected
component 136 is obstructed by the workpiece 14 at the point
154, the same result occurs in that the workpiece position in-
dica~ing detector 144 does not receive the laser beam 136 and
transmits this information along the cable 148 to the control
unit 120. In either event, the equipment in the control unit 120
through the cable 158 to the control cir~`uit o~ the workpiece
shape-altering machine 12 prevents the operation of the wo~kpiece
shape-altering machine 12, such as a stamping press (Figure 2).
and conseguently the platen 28 and the upper die 26 are pre-
vented rom moving downward until the improper position of theworkpiece 14 is corrected.
If`, now, t~e happens to be no workpiece 14 at all on
the post 22, such as i none has been delivered thereto by the
workpiece conveying and supplying mechanism, the workpiece pres-
ence lndicating laser beam 138 is no longer obstructed by any
workpiece 12 at the point 156 but passes directly onward into
the workpiece presence detector 146, which thereupon transmits
this w~rkpiece absence inormation throu~h the cable 150 to the
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control unit 120, and then~e throuyh the cable 158 to the other-
wise conventional press control clrcuit to again prevent opera-
tion of -the workpiece shape-altering machine 12 until the fore-
going condition is corrected by proper]y positioning a workpiece
blank 14 upon the post 22.
If, on the other handl a previously-formed workpiece
has adhered to the upper punch 56 and has been carried upward with
it prior to the time set by the control unit 120 for its ejection
and resupply, the upper workpiece pres~nce indicator, generally
designated 125 (Figure 2) comes into operation. This is of sim-
ilar construction and operation to the workpiece presence indi-
cator 10 of Figures 1 and 2 e~cept that the beam splitter 132
is omitted. The e~uipment and arrangement are otherwise similar,
hence similar parts bear the sam~e.ference numerals.
The upper workpiece presence detector thus ~s provided
with a laser beam generatir or source 124 like the lower indicat-
or but this is suspended by a bracket 12; from ~ plate 39 and i
its laser beam 136 passes at grazing incidence past7the hori-
zontal peripheral surfaces 86 and 88 of the upper pad 34 to a
detector 146 also mounted on a bracket 129 likewise secured to ~
a detector 146 also mounted on a bracket 129 likewise secured to
and depending ~rom th~plate 39. As a conse~uence, i~ a previous-
ly-ormed workpiece 14 adheres to and is carried upward by the
upper punch 56, its lower flanges 82 and 84 or its side wall por-
tions ~6 or 48 i:ntexrupt the laser beam I3~ so that it no longer :
reaches the detector 146, whereupon the press control system is :
caused to halt the press until the improperly adhering workpiece
14 has been removed from the upper punch 56 and~or the cavity
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44 o~ the upper pad 34.
The modified workpiece position and presence inspector
and machi.ne control governor, generally desiynated 210 (Figure
6) is larg~ slmilar to the workpiece presence lnspector portions
124, 132, 142, 144, 147 of the wo:rkpiece position and presence
inspector 10 shr,wn in Figures 1 and 2, exce~k that its installa-
tion is somewhat di~ferent. Like parts are accordingly designat-
ed with the same re~erence numerals as in Figures 1 and 2, part-
icularly as they re~er to portions of the post 22 of the work-
piece shape-altering machine 12 in connection with ~hich the
installation is made. Thus a laser beam generator or source
216 is connected by the cable 122 o~ Figure 1 to the laser con-
trol unit 120. In particular, in Figure 6, the post 22 is pro-
vided with a downwardly and obliquely inclined laser beam tunnel
or passageway 212 through which,in the ahsence of a workpiece
14, the laser outgoing beam 214 proceeds from the laser beam
generator or source 216 by way of the ~eam splitter 218 and di-
verted beam 228 to the workpiece presence detector 230, these
being inclined correspondingly with the inclination o~ the las-
er beam tunnel 212. The direct beam 224 proceeds from the beam
splitter 216 close to but above t~e point 152 (Figure 1) on the
~ar end of the workpiece 14 to the .reflector 226 and thence
close to but above the point 154 on the near end o~ the work-
piece 14 to the workpiece position detect~ (not shown3,identical
to the detector 144 in Figure 1.
In the operation o~ the modi~ied workpiece position and
presence inspector 210 of Figure 6, let it be assumed that a work-
piece 14 is properly mounted upon the post 22 and that the las-
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er beam generator 216 has been enercJized. The outgoiny laser
beam 214 from the laser beam generator 216 proceeds to the beam
splitter 218, whence the diverted beam 228 travels only as far
as the side portion 46 of -the workpiece 14 where it is obstruct-
ed thereby and is either diffused or reflected as shown by the
solid line portion of the diverted beam 228 when the workpiece
14 is present on the post 22, therefore the diverted beam 228
cannot reach the workpieee presence detector 230, as indicated
by the dashed line 228. This information is transmitted
through the cable 150 (Figure 1~ from the workpiece presence
detector 230 to the laser control unit 120. The latter there-
upon transmits it through the cable 158 to the press control
circuit which then permits th~platen 28 , punch 56 and pad 34
to descend and carry out their trimming operations upon the
workpiece 14, as described above in connection with the opera-
tion of the wo~kpiece position and presence inspe~tor 10 of
Figures 1 and 2.
In the event, however, that no wo~piece 14 is resting
upon the lower die 20, the portion of the diverted laser beam
228 indicated by the dashed lines passes unimpededly downward
through the inclined tunnel 212 and reaches the workpiece pres-
ence detector 230, whereupon the laser control unit 120 (Figure
1) is notified of that fact through the cable 150 and transmits
: this lnformation through the cable 158 to the machine control
circuit, whereupon the platen 28 of the press 12 is according-
ly prevented from descending until a workpiece 14 has actually
been delivered to and properly mounted upon the lower die 20.
If, on the other hand, the workpiece ~ has been properly trim-
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med but has adhered to the punch 56 and/or to the c~tters 36 and
38 and has been carried undesiredly upw~rd prior to the time
set by -the control unit 120 for its proper ejection and resupply
of another workpiece 14, the premature unblocking of the laser
beam 228 so informs the control unlt 120, which thereupon halts
the press 12 as described above until the improperl~-adhering
workpiece 14 has been removed.
The advantages of the sing:Le laser ~eam generator ~4
or 216 in combination with the beam splitter 218 over the use of
two separate laser beam generators lies in the fact that failure
of the single laser beam generator 124 or 216 in the system of
the present invention is a "fail-safe" device in that such ~ail-
ure shuts down and renders inoperati.ve the press control circuit.
In contrast to this, failure of one of the two separate laser
beam g~nerators would indicate to t~e press control circuit that
a workpiece was present on the workpiece forming support or die,
whereas no workpiece was actually present, and the press would
be permitted to operate. This would be disastrous if, for ex-
ample, an already formed workpiece had adhered to the upper die
and a new workpiece was permitted to be fed to the lower die, so
~; that upon operation of the press the upper workpiece would clash
with the lower workpiece, serlously damaging the dies and poss-
ibly also injuring any bystander.
;A similar advantage results from the use o crossing
and recrossing laser beams at separate locations on the work- -
piece from a beam splitter and a single laFer beam generator
rather than from two separate laser beam generators without the
~ beam splitter.
:~ , : - 19 - '
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