CA1111691A - Laser workpiece position and presence inspector and machine control governor - Google Patents

Abstract

A B S T R A C T

Vertically bored for horizontally swingable mounting on a vertical pivot pin fixed in a base is an upstanding mirror holder support post containing a horizontal part-ly-cyclindrical recess thereacross, the horizontal axis of which intersects the vertical axis of the pivot pin. Mating with the partly-cylindrical recess and coaxial therewith is a horizontal partly-cylindrical convex mirror holder with a flat front mirror mounting face thereon. A first set screw locks the post in its horizontally-adjustable position relatively to the pivot pin, whereas a second set screw locks the mirror holder in its vertically-adjusted position relatively to the mirror holder support post.

Description

This application is a division of an applica-tion Serial No. 307,166, filed July 11, 1978.
Hitherto, serious acciclents have occurred in workpiece shape-altering machines, such as stamping presses, when the workpiece 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. Previously, workpiece-positioning systems have been provided with limit switches in conjunction with an electrical circuit for attemptedly indicating when a workpiece blank has been improperly positioned in the press die-set but such limit switches have often failed as a result of their repeated operations, with the result that the lntendedly safeguarding system no longer operates successfully.
In one instance, for example, the inspection system did not indicate the improperly positioned workpiece, with the resul-t that the workpiece was hurled across the room by the improper contact of the punch therewith, causing serious danger to bystanders.
The invention described and claimed in the aforesaid application principally resides in the provision of the laser beam source transmitting its outgoing beam into the beam splitter for subsequent division into two beams, one of which notifies the control system of the workpiece shape-altering machine whether or not t:he workpiece has been properlypositioned in the die set and subsequen-tly is properly removed .

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therefrom. A further feature of the invention resides in the provision of means for transmitting to the machine control system the requisite 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 unintendedly adheres to the upper die of the die set and ascends with it, the laser beam reaches the laser beam detector prematurely, 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 removed from the upper die. The particular invention which forms the subject of thisapplication lies in the construction of a particular component, which is useful in the laser workpiece position and presence injector and machine control governor - namely a horizontally and vertically adjustable mirror mounting structure.
Thus accordiny to this invention, a horizontally ; and vertically adjustable mirror mounting structure, comprises a base, a vertical pivot element mounted on said base, an upstanding mirror holder support mounted on said pivot element for horizontal rotational adjustment relatively to said base and having a horizontal partly cylindrical recess disposed horizontally thereacross.
a mirror holder having on one side thereof a mirror mounting surface and haviny on the opposite side -thereof a horizontal partly cylindrical convex surface disposed in mating enyagement with said horizontal part].y cylindrical recess for vertical rota-tional adjustment relatively to said base, one arm for locking said mirror holder support in lts horizontally-rotated position of adjust-ment relatively to said base, and means for locking said mirror holder in its vertical-ly-rotated position of adjustment relatively to said base.
The invention will now be described further by way of example only and with reference to the accompanying drawings which, for the sake of completeness, illustrate the invention in the context of a complete system. Referring to the drawings:
Figure l is a diagrammatic perspective view of a laser workpiece position and presence inspector and machine control governor, showing a workpiece blank properly in 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;
Figure 2 is a central vertical section through a conventional trimming and piercing die-set and adjacent portions of a conventional stamping press, e~uipped with the laser workpiece-position inspector ancl machine control . governor looking in the direction of the arrows 2 ~2 in FigIre l;

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Figure 3 is a side eleva-tion, wi.th the cover in central vertical section, of an adjustable reflector employed in the arrangement of Figure l;
~igure 4 is a top plan view of the reflector, with the top of the cover removed as shown by the section li~es 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 axrangement shown in Figure 1, with the top o~ 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 tunnel therethrough.
Referrirlg to the drawings in detail, Figures 1 and 2 show a laser workpiece position and presence inspector and ma-chine control governor, generally designated 10, installecl in a workpiece shape-altering machine such as a stamping press, gen-erally designated 12, for determining the proper position or for detecting a departure therefrom of a workpiece 14 which is to be further formed by the workpiece shape-altering machine 12.
For convenience of illustration, the workpiece 14 is shown as an automobile bumper recluiring trimming and piercing before it is 6~3~

linished. In particular, Figure 2 sho~s the workpiece 14, af~
terit has been p~eviously subjected to forming and ~langing op-erations but before the peripheries OL the flanyes have been cut ~ff by the machine 12 and before the central'portion has been pierced.
The workpiece shape-altering machine 12 of Figure 2 is shown as a convent~onal stam~ing press having a press bed 16 upon ~hich is mounted a bolster 18 surmounted by a lower die shoe 20 which in turn supports the post 22 o~ a trimming and pierciny die-set, generally designated 24, haviny an upper die :
26 secured to a movable platen 28. The latter is moved upward and downward in a conventional manner, such as by a crank mech-anism or by hydraulic cylinder and piston 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 or cavity 32 in which an upper pad 34 is mounted for vertical reciproca~ion rel-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 die shoe 30 and,also guide che upper pad 34 which performs the function of holding down the workpiece 14 during the trimminy operation. In particular, the central su~stanti.ally flat po~-tion 40 of the workpiece 14 is held down hy the suhstantially flat bottom 42 of the cavity 44 in the upper pade 34, whereas : .
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the opposite sides 46, 48 of the workpiece 14 are retained in position respectively by the perpendic~llar side surface 50 and inclined side surface 52 of the cavity 44. ~ e upper pad 34 has a centxal bore 5~1s through which projects a piercing punch 56 seated in a bore S8 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 3~15 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 dra~ing. The compression coil springs 68 constantly urge the upper pad 34 downward relatively to the piercing punch 56 but yield to permit t:he piercing punch to form a hole 70 in the workpiece l~s (Fiyure 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 w~ich supports the central portion 76 of the wor]cpiece 14 in co-operation with the bottom surface 42 of the upper pad 34r 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 3~s 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 correspondingly formed horizontal portions 90 and 92 respectively of the lower die 22. Stationary cutoff members 94 and 96 are recessed into the p,ost 22 irnmediately below the hori-~ontal surfaces 90 and 92 and cooperate with the vertically-mov-able trimming cutters 36 and 38 to cut off the outer portions , .

ol the workpiece flanges 82 a~d i34.
The scrap edge portions 102 and 104 shown by the dotted lines in the lower portion of Figure 2 constitute the severed portions of the worXpiece 14 cut of~ by the mov~ble trimming cutters 36 and 38 cooperating with the stationary cu~of f member s 94 and 96 respectively. The severed portions 102 and 104 slide down inclined plates 106 and 108 to points of disposal. The post 22 o the die set 24 is formed with a post hore 110 alignecl 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 rrom 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 energization 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 ` 20 stanchion 128, the lower end Orc which rests upon and is secured - to the lower die show 20 (Figure 2). Also mounted on the plat-orm 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 worXpiece posi-tion indicating laser beam 136 and a workpiece presence-indicat-ing laser beam 138 (Figure 1.). Mounted on a platform 140 on an upright post or stanchion 1~1 is a laser beam ~eflector 142.
The details of the laser beam splitter 132 and laser beam re-.

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flec~or 1~ are set ro~th ln more detail below.
Aligned with the reflected compon~nt of ~he wor~piece position-indicating laser beam 136 is a workpiece pGsition detector 144 ~Fiqure 1) whereas aligned with ~he workpiece pres-ence-indicating laser beam 138 is a workpiece presence detector 146. From the detectors ].44 and 146, the conductor cables 148 and 150 run back to the laser energization and control unit 120 which is electrically connected in governing relationship to the press control circuit by the cable 158. The laser beam ~en-erator 124, beam splitter 132, reflector 142 and workpiece-position detector 144 are so mounted ancl 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 yrazing relationship when the workpiece 14 is pxoperly 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 ~igure 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 indident 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 indicate the direc-tion which the workpiece presence~indicating laser beam 13~3 would have taken toward the workpiece presence detector 146 if the workpiece 14 had not been present in ~he die set 24, and the ac t~al portion of the workpiece presence-indicating laser beam 133 itself is proceeding unobstructedly to the workpiece pres-ence detector 146 in the even'~ that the workpiece 14 is absent from its proper position on top OL the post 22 of the die set 24 or has not been delivered thereto by the workpiece conveying 10 mechanism.
The laser beam source or generator 124, the wor~piece - position detector 144 and the workpiece presence cletector 146 are conventional and their details are beyondl'~he 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 suhstantially without diffusion throughout their paths of travel. As their widths are of only a few thousandths of an inch, they maintain their substantially original intensity over their entire path of ~0 travel Thus, an ordinarily insiynificant displacement or the workpiece 14 shows up instantly when that displacement inter-~` cepts the laser beam 136 or 138 rnore accurately and~more depend-ably than would be indicated by limit switches.
The beam splitter 132 (Figure 5) and the re1ector 142 (Figures 3 and 4) are ~30vided wi.th similar moun~s, yenerall~
designated 160 and 162 respectively, and differ only in the pos-itioning o~ their respective mirrors, hence a srLng1.e description will suffice for both. Both also are provided with similar in-` , _ g _ verted cup-shaped metal or plastic protective covers 161 and 163 respectively, therefore also requirin~ onl~ a sinyle descripti.on.
~rhe covers 151 and 163 provide p~o-tection against mechanical dam-age and oil or other vapors near such machines 12. The mounts 160 and 162 (Fi~ures 3, 4 and 5) are provided with cylindrical bases 164 which are bored and counterbored at clrcumferentially-spaced locations 165 to receive bolts or soc~et head screws 166 by ~hich they are secured to their respective supports 126 or 140.
The basé 164 is provided with a vertical bore 168 which receives a vertical shaft or pin 170 firmly and immovably secured in its bore 168. The upper end o~ ~he 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 i~to 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 horizontal and therefore perpendic-..la~ to the axis of the vertical bore172.
Mounted in the cutaway cylindrical por-tion 180 for swinginy mo-tion around the axis 182 thereof is a semi-cylindrical mirror support 184 havi~g a flat f.ront mirror-mounting surface 186 co~
incident with the axis 182. Secured to the flat surface 186 as by a suitable adhesive (not shown~ is a xear-surface mirror 188 The mirror support 184 is provided with a cylindrical rear sur-face 190 of the same curvature as the cylindrical cutaway portion 180 and arcuately slidable relatively thereto. The upper portion of the post 174 is provided with an arc~ate slot or groove 192, .. .. . . . ...

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the bottom 194 of which is concentric i~ith the a~is 162 and the c~lindrical surfaces 180 and 190. The mirror support 18~ is pro-vided ~ith a drilled and threaded bore 196 which receives the correspondingly-threaded shank of a set screw 198. The head of the set screw 198 i.s 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 s~pport 194 may be rocXed vertically around its horizontal axis 182 and the~ost 174 can be swung horizon~ally around the shaft or pin 170, the vertical axis of which, if ex-tended, passes through the horizontal axis 182 of the cylindri-~al surfaces 180 and 190. Each cover 163, a~s previously stated, is of inverted cup-shaped form with a hollow cylindrical side wall 200 mating with the cylindrical base 164, the former of ~hich is drilled and the latter drilled and threaded to receive a locking screw 202. A disc-shaped top 20~ 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 :l62 of the ~0 reflector 142. The beam splitter 132, however, is provided with a beam spiittin~ rearr~silvered mirror 206 which is semi-transpar-ent so that the outgoing l.aser beam 13~ has a portion 136 which proc~eds 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-offse~ posi tion relatively to the mirror support 184. The cons-truction is otherwise the same as khat described above for the refle.ctor 142.
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During the installation o~ the laser ~orkpiece posi~ion and presence inspe.ctor and machine control governor, :let it be assumed that the laser light source 124, beam splitter 132, re-flector 142, workpiece position detector 144 and workpiece pres-ence detector 146 have been mounted without their respective cov-ers 163 and adjusted with respect to the lower die 22 of the t~orkpiece shape-altering machine 12, so that a workpiece 14 prop-erly positioned upon the latter will be properly oriented for the re~uired passage or interception of the laser beams 134, 136 and 138, as explained above. Before the inspection arxange-ment 10 can be operated, however, the protective covers 161 and 163 must be drilled to provide a laser beam inlet aper-ture 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 1~2.
If the.cover 161 is of transparent plastic material, 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 o-f the resulting spots of liyht are marked and aubsequently drilled to provide the apertures 209, 211 and 213. After these apertures are drilled, the transparent plastic cover 163 of the reflector 142 is similarlyp 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-sequently 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 spra~-ing, to prevent undesired entry, reflection or di.ffusion of out-.. . ~ .. . .. .. . .~

side light or of the laser beam.
f, on ~he other hand, the covers 161 and 163 are to be o metal.:, such as is desirable where there is danger from llying objects and other materials which miyht damage or dest~ plastic covers, there is provided a correspondingly-shaped transparen~
cup-shaped plastic templet of inside diameter adap-ted 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 138,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 over the s-teel covers 161 or 163 and their apertures used as d~lling guides ko 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 for use.
In the operation of the workpiece position and presence inspector and machine control governor 10, with the various com-ponents thereof adjusted in khe manner described above, let it ~` be assumed that a workpiece 14, such as a stamped but untrimmed sutomobile bumper, has been placed in position up~n the post 22 o~ the workpieee shape-altering machine 12, either manually or by a eonveyor and workpiece handling s~stem fr~entl~ used in such installations. Let it also be assumed that the workpiece 14 is properly positioned upon the post 22 and that the laser li~ht source 124 is energized to produce the outgoing laser ~eam 134 which in turn is divided by the beam splitter 132 into emergent beams 136 and 138. When the workpiece 14 is thus prop-erly positioned, the workpiece position indicating beam 136 pro-ceeds uninterruptedly at grazin~ i.ncidence over both the locations 152 and 154 near ~he opposite ends of the workpiece 14. As a re-sult, the workcpiece position detector 144 operates to indicate ~
that ~he workpiece 14 has been properly positio~.ed and transmits this information through the cable 146 to the control unit 120, whieh in turn transmits it through the cable 158 to the eontrol eireuit of 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 lt is obstructed by the latter and fails to reach the workpiece presence indicating deteetor 146. As a result, the information that the workpiece 14 is present onthe post 22 is transmitted through the cable 150 baek to the control unit 120 which in turn transmits it thLough the cable 158 to the control circuit o~ the wor]cpiece shape~
altering machine 12 that the workpiece 14 is both present and in its proper position, releaaes the o-therwise conventional machine control circuit to cause the pl.aten 28 and upper die 34 to des-eend and carry out the forming oper~ion~ upon the workpiece 14.
If, on the other hand, the workpiece 14 is improperly positioned, such as, for example, being tilted so that the pOillt .~ - 14 -152 is higher than the point l.54, the portion o~ the workpiece 14 adjacent the point 152 interrupts the workpiece posi.tion indi-cating laser beam 136-so that it does not reach the reflector 142, whereupon the workpieae positioning detector 1~4 does no-t receive the beam 136 and transmits this information to the con-trol unit 120 by way o~ 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 1~2 but its reflected .- 10 component 136 is obstructed b~ the workpiece 14 at the point 154, the same result occurs in that the workpiece position in-dicating detector 144 does not recelve the laser beam 136 and transmits this information along the cable 148 to the control unit 120. In either event, t~e equipment in the control unit 120 through the cable 158 to the control cir~uit of the workpiece shape-altering machine 12 prevents the operation of the workpiece shape-altering machine 12, such as a stamping press (Figure 2).
and consequently the platen 28 and the upper die 26 axe pre-- 20 vented from moviny downward until the improper position of the ~ - workpiece 14.is corrected.
: . If, now, th~r,e happens to be no workpiece 14 at all on . the post ~2, such as i~ none has been delivered thereto by the workpiece conveying and supplying mechanism, the workpiece pres-ence indicating laser beam 138 is no lonyer obstructed by any workpiece 12 at the point 15~ but passes directly onward into the workpiece presence detector 146, wh.ich thereupon transmits this ~orkpiece absence information throu~h the cable 150 to -the ' '7., .
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control un.it 120, and then~e through the ca~le 158 to the other- -wise conventional press control circuit to again prevent opera-tion o~ the wor~piece shape-altering machine 12 until the fore-going condition is corrected by properly posit.ioning a workpiece blanX 14 upon the post 22.
If/ on the other hand, 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 con-trol unit 120 for its ejection and resupply, the upper workpiece presence indicator, generally 10 designa~e~ 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 except that the beam splitter 132 is omitted. The equipment and arrangement are otherwise similar, hence similar parts bear the sam~eference numerals.
The upper wor~pi.ece 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 127 from ~ plate 3g and i its laser beam 136 passes at grazing incidence past'the hori-zontal peripheral surfaces 86 and 88 of the upper pad 34 to a 20 detector 146 also mounted on a bracket 1.29 likewise secured to ;
a detector 146 also mounted on a bracket 129 likewise secured to and depending from th~plate 3g. As a consequence, if 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 46 or 48 interrupt the laser beam 136 so that it no lon~er reaches the detector 146, whereupon the press control systern is caused to halt the press until the improperly adheri.ng workpiece 14 has been removed from the upper punch 56 and/or the cavit~

'~;`' ; 44 o~ the upper pacl 34.
The modified workpiece position and presence inspector and machine control governor, generally designated 210 (Figure 6) is larg~ similar to the workpiece presence inspector portions 124, 132, 142, 144, 1~7 of the workpiece posi-tion and presence inspector 10 sh~,wn in Figures 1 and 2, except that its installa-tiOIl is some~hat different.- Like parts are accordingly designat-ed with the same reference numerals as in Figures 1 and 2, paxt-icularl~ as they refer to portions of the post 22 o~ the work-piece shape-altering machine 12 in connection with which the installation is made. Thus a laser beam generator or source 216 is connected by the cable 122 of Figure 1 to the laser con-trol unit 120. In particular, in Figure 6, the post 22 is pro-vided with a downwardly and obli~uely inclined laser beam tunnel or passageway 212 through which,in the absellce of a workpiece ; 14, the laser outgoing beam 214 proceeds from the laser beam generator.or source 216 by way of the beam splitter 218 and di-verted beam 228 to the woxkpiece presence detector 230, these . heing inclined correspondingl~ with the inclination of the las-er beam tunnel 212. The direct beam 224 proceeds ~rom the ~eam splitter 216 close to but above the point 152 (Figure 1) on the far end of the workpiece 14 to the reflector 226 and thence close to but above the point 154 on the near end of the work-piece 14 to the workpiece position detect~ ~not shown),identical ` t.o the detector 144 in Figure 1.
In the operation of the rrlodified workpiece position and . presence inspector 210 of Eligure 6, let it be assumed that a work-piece 14 is pxoperl~ mounted upon the post 22 and that the las-.: .

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er beam generator 216 has been eneryized. Tne outyoing laser beam 214 from the laser beam generator 216 proceeds to the beam splitter 218, whence the divexted beam 228 travels onl~ as far as the side portion 46 of the workpiece 1~ 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 thxough 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~laten 28 , punch 56 and pad 34 to descend and carry out their trimming operations upon the worXpiece 14, as described above in connection with the opera-tion OL the wo1kpiece position and presence inspecLor 10 of Figures 1 and 2.
In the event, however, that no wo~piece 14 is restlng upon the lower die 20, the portion of the diver-ted 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 information through the cable 158 to the machine control circuit, whereupon the platen 28 of the p.ress 12 is according-1~ prevented from descending until a workpiece 1~ has actually been delivered to and properly rnounted upon the lower die 20.
If, on the other hand, t'ne workpiece 1~ has been properly trim-`` ' ' .

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med but has adhered to the punch 56 and/or to the eutters 36 and 38 and has been carried undesiredly upward prior to the time set by the control unit 120 for its proper ~ection and resupply of another workpiece 14, the premature unblocking of the laser beam 22~ so informs the control unit 120, which thereupon halts the press 12 as described above until the improperly-adhering workpiece 1~ has been removed.
The advantages o~ the single laser beam generator 1~4 or ~16 in combination with the beam splitter 218 over the use of two separate laser beam generators lies in the fact that failure of the sinyle laser beam generator 12~ or 216 in the sys-tem of tlle present invention is a "fail-safe" device in that such ~ail-ure SllUtS down and renders inoperative the press control circuit In contrast to this, failure of one of the two separate laser beam g~nerators would indicate to the 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 woxkpiece 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, seriously damaying the dies and poss-ibl~ also injuring any bystander.
A similar advantage results from the use of crossiny and recrossing laser beams at separate locations on the work-piece from a beam splitter and a sinyle laser beam generator rather than from two separate laser beam yenerators without the beam splitter, ... -- 19 --.

Claims (5)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE PROPERTY OR
PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A horizontally and vertically adjustable mirror mounting structure, comprising a base, a vertical pivot element mounted on said base, an upstanding mirror holder support mounted on said pivot element for horizontal rotational adjustment relatively to said base and having a horizontal partly cylindrical recess disposed horizontally thereacross, a mirror holder having on one side thereof a mirror mounting surface and having on the opposite side thereof a horizontal partly cylindrical convex surface disposed in mating engagement with said horizontal partly cylindrical recess for vertical rotational adjustment relatively to said base, one arm for locking said mirror holder support in its horizontally-rotated position of adjustment relatively to said base, and means for locking said mirror holder in its vertically-rotated position of adjustment relatively to said base.

2. A horizontally and vertically adjustable mirror mounting structure, according to claim 1, wherein said means for locking said mirror holder relatively to said mirror holder support includes a cylindrically arcuate slot in said mirror holder support on the opposite side thereof and coaxial with said partly cylindrical recess.

3. A horizontally and vertically adjustable mirror mounting structure, according to claim 2, wherein said locking means comprises a threaded hole in said partly cylindrical convex surface and a fastener having a threaded shank passing through said arcuate slot into threaded engagement with said threaded hole and having a head clampingly engaging the surfaces of said mirror holder support adjacent said slot.

4. A horizontally and vertically adjustable mirror mounting structure, according to claim 3, wherein said surface of said mirror holder support adjacent said slot is partly cylindrical and disposed coaxial with said partly cylindrical recess.

5. A horizontally and vertically adjustable mirror mounting structure, according to claim 2, wherein a hollow cover is disposed over said mirror holder support and mirror holder and has apertures therein opposite said mirror holder for the passage of optical beams and wherein fastening means is disposed between said cover and said base for securing said cover to said base.