Note: Descriptions are shown in the official language in which they were submitted.
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INTRusIoN DETECTION_SYSTEM FOR OPERATING INDUSTRI~L MACHIN
Field Of The Invention
This invention relates to intrusion detection sys~ems in
general, and more particularly to intrusion detection systems of
the sort adapted to enable~disable the operation of an associated
trial machine when an appropria~e intrusion is detected.
:,.:
Background f ?he Invention
Certain industrial machines comprise moving parts which can
pose a danger to operators working around the machines. For
example, a press fo~ punching or Eorming metal stock typically
requireS that an operator work a~out successively opening an~
closing dies or other working members to fixst insert and then
move the stock being worked. It has been recognized that an
intrusion detection system can be positioned between the operator
and the industrial machine's moving parts to detect when the
operator intrudes into the area of danger. This intrusion
detection system may ~e adapted to shut down the machine if the
intrusion occurs at an inappropriate time, e.g. if the opera~or's
hands intrude between closing working members during the power
stroke of the press.
Optical intrusion detection systems o~ the type described
above are well ~nown in the industry. Such systems generally
comprise a "Light c~rtain" ~ormed by a pl~rali~y of parallel
spaced light heams. More particularly, su~h~optical intrusion
detection systems generally comprise light transmitter means
adapte~ to genera-te a plurality of parallel spaced light beams,
light receiver means adapted to sense the light beams generated
by the light transmitter means, and appropriate control circuitry
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adapt~d to operate the light transmitter means and light receiver
means and also to communicate with the industrial machine which
is being safeguarded. Whenever an opaque object o~ su~ficient
size passes through the area traversed by the light beams so as
to bloc~ one or more of the light heams, the system recognizes
that an intrusion has occurred. If the intrusion occurs at an
appropriate time, e.q. during the power stroke of the press,
the system~s control circuitry can immediately shut down the
~: associated machine to prevent operator injury. See, for example,
U.S. Patent No. 4,266,124 (Weber e~ al.) and the references cited
therein.
It has been recognized that different objects, having
different light-blocking profiles, may penetrate the light
curtain from time to time, with significantly different
implications. For example, an oversized piece of metal stock may
be properly posi~ioned between the jaws or other working members
of a press during the power stroke of the machine and yet still
penetrate the light curtain, or a moving ~ix~ure or an ejected
part may normally interrupt a portion of the light curtain; in
such cases it may be desirable for the machine to remain ena~led,
despite the intrusion, so it can operate through its power
stroke. However, an operator's hand may be improperly positioned
so as to penetrate the light curtain during the power stroke of
the machinei in this latter case it is obviously not desirable
for the machine to remain enabled so it can operate through its
power stroXe.
Accordingly~ some op ical in~rusion detec~ion systems are
designed to allow their associated industrial machines to operate
when no ligh~ ~eams are broken or when a single light beam is
bro~en, e.y. ~y a relatively thin piece o~ oversized metal stock
or by a relatively thin gripping or transfer tool, but to shut
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down the industrial machines when more than one light bea~ is
broken, e.g. by a relatively thick human hand. See, for exarnple,
U-S. Patents Nos. 3,551,683 tTotkillJ, 4,015,122 (Rubinstein),
and ~,249,074 (Zettler et al.). Inas~uch as the specific
conditions for enabling or disabling the industrial ~achi~es c~n
vary according to the particular application being undertaken, at
least one of the prior art systems described above, that of U.S.
Patent No. 4,015,122 (~ubinstein), includes manual switches which
-: allow the operator to initially instruct the optical intrusion
detection system to ignore specific repetitive light beam
obstructions~ such as those caused by "permanent" installations.
However, with this prior art system, as well as with all other
known prior art systems, the detection sensitivity of the system
remainS fixed as long as the sys~em is activated during the
operating cycle of the syste~'s associated industrial machine.
In this regard it should be no~ed tha~ some op~ical intrusion
detection systems are designed ~o be fully enabled during the
entire operating cycle of the machine. ~n such a situation, the
industrial machin~ can be adapted ~o either ignore penetrations
detected during "non-ha~ardous" portions of the machine's
operatiOn (e.g. ~he upstro~e) or it can allow itself to be shut
down ~y such penetrations. Other optical~in~rusion detection
systems are designed to be fully activated during "hazardous"
portionS of the machine's operation ~e~g. the downstroke) and
fully deactivated during non-hazardous portions o~ the mackinels
operation. In any case, even with optical intrusion detection
ystems of this latter~ype, the detection sensitivity o the
system remains ~ixed as long as the system is activated during
the operating cycle of the assoc~ated indus~rial machine. Por
the purposes of this description, all such systems shall be
considered to have a fixed detection sensitivity.
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r have recognized that in some situations it may be desirable
to have an optical intrusion detection systenl which can vary its
detection sensitivity in accordance with changes in the operatin~
cycle of the associated industrial machine. For example, it
might be desirable to have the optical intrusion detection system
set to respond to the intrusion of an object of size X or larger
during one phase of the machine's operation, and set to respond
to the intrusion of an object of size 1/3 X or larger during
another phase of the machine's operation. With prior art
device5~ it is necessary to preset the detection system to
respond during any perio~s the system may be activated to objects
of either size X or size 1/3 X throughout the entire operating
cycle of the system's associated industrial machine, since such
prior art detection systems are incapable of changing their
detection sensitivity automatically in accordance with changes in
i the operating cycle of the system's associated industrial
machine.
An optical intrusion deteotion system capable of adjusting
its sensitivity in response ~o varying machine states is
particularly desirabLe in ~he situa~ion where it is to be used to
both start and stop the operation o~ an associated industrial
machine. More particularly, ~uring the machine's initial "idle"
period, when the optical intrusion detection sys~em is to be used
as a trigger device to ini~iate op~ra~ion of the machine upon
detec~ing ~he int~usion and then withdrawal of ~he opera~or's
hand through -~he light curtain as the workpiece is placed on the
die, it is desi~able to have the system set to respond only to
the intrusion and then withdrawal o~ a relatively large o~ject,
i.e., the operator's han~, so that the machine will not be
started prematurely by minor accidental in~rusions. However,
during the machine's subsequent "rrn" period or cycle, when the
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optic21 intrusion detection system is to be used as a safety
device to halt operation o~ the industrial machine upon detecting
an appropriate intrusion, it is desirable to have the system set
so that it will err on the side oP caution and cause the machine
to stop immediately upon detecting the intrusion of an object of
allnost any size, thereby reducing the risk of operator injury.
It is noted that the term "presence sensing device
initiation~ or "PSDI", is fre~uently used in the industry to
: refer to the use of an optical intrusion detection system to both
start and stop the operation of an associated industrial machine.
Objects Of The Invention
Accordinglyr the primary ob~ect of the present invention is
to provide an improved optical intrusion detectiorl system for
controlling the operation of a cyclically operating manufacturiny
;. machine which has a variable detection sensitivity, in order that
the detection system can be se~ to respond to the intrusion of an
object oP a first size during one phase of the operation of the
associated machine and to an object of a second size during
another phase of the ma~hine's operation.
Another object of ~he invention is to pro~ide an optical
ntrusion detection sys~em of ~he type described which can be set
so as to be insensitive to relatively s~all objects during one
phase of operation of a machine an~ yet sensitive to the same
relatively small o~jec~s during ano~her phase of operation of the
same machine.
Still ano~her objec~ of ~he i~vention is ~o ~rovide an
optical intrusion detection sys~em o~ the type described which is
adapted to serYe as a trigger device ~o start the operation o~ an
associated industrial machine, and also as a saPety device to
stop the operation of the same machine.
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Summary Of The Invention
~ hese and other objects of th~ invention are achieved by a
novel optical intrusion detection system which comprises light
transmitter means adapted to generate a plurality of parallel
spaced light beams, light receiver means adapted to sense the
light beams generated by the light transmitter means, and
; appropriate control circuitry adapted to operate the light
transmitter means and light receiver means and also to
communicate with control elemen~s of the industrial machine which
is being safeguarded, wherein the appropriate control circuitry
is adapted to enable or disable ~he industrial machine when X or
more light beams are ~locked ~uring one phase of the operation of
the industrial machine, and to ena~le or disable the industrial
machine when Y or more light beams are blocked during another
-~ phase o~ the operation of the indus~rial machine.
In the preferred embodiment o the invention, the novel
Optical intrusion de~ection system is adapted to be used as both
a trigger device to ini~iate operation of the industrial machine
when X or more light beams are bloc~ed (and then restored) during
an initial "idle~' phase of the industrial machine, and as a
safet~ device ~o halt operation o~ the industrial machine when Y
or more light beams are bloc~ed during a subsequent "run" phase
of the indust~ial machine. By arranging the sys~em so that X is
a number grea~er ~han ~, it can ~e assured tha~ ~he system will
only start t~e "idlin~" industrial ma~hine when it senses ~he
intrusion (and ~hen wi~hdrawal) of a relati.vely large object
through the light curtain, i.e, the operator's hand placing the
workpiece on ~he die, and yet will automatically s~op the
running" industrial machine as soon as it senses any intrusion
at all through the light curtain. ~he control circuitry comprise
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Drog~2mmablc logic circuits" so that the particular
characteristics of the optical intrusion detection s~stem may ~e
software controlled.
Brief Description Of ~he Drawi~
Still other objects and features of the present invention
will ~e more ~ully disclosed or rendered obvious in the following
detailed description of the preferred embodiment o~ the
lnvention~ which is to be considered together with the
accompanying drawings wherein like numbers refer to like parts
and further wherein:
Pig. 1 is a schema~ic diagram illustrating a preferred
embodiment of the novel optical intrusion detection system;
~ ig. 2 is a ~lock diagram illustrating how the preferred
embodiment of the novel optical in~rusion detection system
!f~ interfaces with the various par~s of a representative industrial
machine such as an hydraulic or mechanical power metal forming
punch press;
: ~ig. 3 is a flow diagram illustrating the mode of operation
of a general form of the novel optical intrusion detection
system;
: ~ig. 4 is a 10w diagram illustrating the mode of operation
of a preferred embodiment of the novel optical intrusion
detection system; and
Fig. 5 is a flow diagram ill~strating the mode of operation
of an alternative embodimen~ of the novel optical intrusion
detection system.
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.
Detailed Descri~tion Of The P~eferred Embodiment
Looking first at Fig. 1, there is sho~l a novel optical
intrusion detection system 100 that generally comprises light
transmitter means lOS, light receiver means 110, and control
circuitry 115.
Light transmitter means 105 comprises twelve light sources
12oA-l2oL connected to two driver ~odules 125A and 125B. Light
sources 120A-120L are conventional light emitting diodes ("LEDs")
of the sort adapted to emit a narrow infrared beam oP light in
response to an appropriate electrical impulse. Driver modules
125A and 125B are conventional solid state devices of the sort
)laving a plurality of output lines for providing electrical
signals to selectively energize in~ividuàl ones of light source
120A-120L in response to appropriate elec~rical control signals
;~ received from a microprocessor lS0, as will hereinafter be
described in further detail. Microprocessor 150 is of
conventional design and may be one o~ a variety of
rocessors well Xnown in the art. Microprocessor 150
includes a plurali~y of associated f lags or registers for
recording the occurrence o~ selected events, as will hereinafter
~e described in ~ur~her detail.
Light receiver means llO comprises twelve light sensors
30A-130L and two driver modules 135A and 135B. hight sensors
30A-130L are conventional photo~ransistors o~ the sort adapted
to amplify a given electrical impulse in response to the
recep-tion o~ ligh~. Light sensors 130A-130L are aligned with
their corresponding light sources l~OA-120L, and they are adapted
to have a pea~ sensitivity in the in~rared range so that they are
appropriately matched to the primary radiation emitted by light
source s 12 0A- 12 01, . Dr iver module s 13 5A ,~nd 13 5B a re conventiona l
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~1277397
solid state devices of the sort ha~ing a plurality oE output
lines for pro~iding electrical signals to selectively activate
individual ones o~ light sensors 130A-130L in response to
appropriate electrical control signa~s received from
microp~ocessor 150, as will hereina~ter be described in further
detail .
Control circuitry llS comprises a pair of amplifier circuits
l~OA and 140B, a pair of inverters or buf~ers 145A and 145B, and
computer means in the form of a microprocessor 150. Amplifier
circuitS 140R and 140~ are conventional operational amplifier
circuits of the sort adapted to produce a signal pulse when the
output of an analog input device reaches a selected level. The
outputS of ampli~iers 140A and 140B are connected to the inputs
of inverters 145A and 145B, respectively. Inverters 14SA and
145B are of ~he sort well known in the digital signal processing
art. The outputs of inverters 145A and 145~ are connected to two
different input ports of microprocessor 150 by lines 155 and 160
respectively~ By having two amplifier~inverter channels, one for
the 'odd-numbered" detectors 130A, 130C, 130E, 130G, 130I and
130A~, and the other for ~he "even-numbered~' channels 130B, 130D,
130~, 130~, 130J, and 130L, ~here is redundancy for increased
failsafing of the sys~em. Additionally, ~y using two
amplifier/inverter channels, i~ is possible to have two adjacent
light sources and th~ir corre~ponding light sensors activated
simultaneously~ or in time-oYerlapping relation, if this should
~e desired; however, in the ~re~erred embodiment the
'odd-numberedn and "even-num~e~edn dete¢~ors 130 are alternated
ln activatiOn sequence ~o eliminate any possibility of optical
crosstalk bett~een adjacent detectors~
Light transmit~er means 105, light receiver means 110 and
control circuitry 115 are interconnected as shown. More
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specificallv~ ~icroprocessor lS0 has twenty-four output lines,
twelve connec~ed to ~ne input ports of d~iver modules 125A and
125~, and twelve connected to the input ports of driver modules
135A and 135s. For convenience of illustration, lines 165, 170
l~S and 180 each represent six com~uter output lines. The
outputs or the ~'odd numbered" light sensors 130A, 130C, 130E,
130G, 130I and 130X ~re connected to the input of amplifier
circuit 140A by a line 185, and the outputs o~ the "even
numbered" light sensors 130B, 130D, I~OF, 130H, 130J and 130L are
Connected to the input o~ amplifier circuit l~OB by a line 190.
Microprocessor 150 is adapted to ge~erate four trains of clock
pulses at a common fixed frequency, with vne train of clock
pulses applied to driver module 125~, a second train applied to
driver module 125B, a third train applied to driver module 135A,
and the ~ourth train applied to driver module 135B. The pulse
trains are arranged so that ligh~ sources 120A-120L are energized
sequentially in the order named at the selected frequency, and
the correSpondin~ pho~otransistors 130~-130L are activated
simultaneously and in the same order as light sources 120A-120L
respectively. Thus, each time a light source is energized by
driver module 125A ox 12SB, i$s corresponding light sensor, i.e.,
phototransis~or~ is biased "on" by driver module 135A or 135B so
that it will respond to the ligh~ beam ~rom the corresponding
light source However, i~ a light beam is blocked, the
corresponding senso~ will no~ generate an output pulse even
though it is biased nOnn. Similarly, if no light beam is
produced by a light source when it receives a pulse from its
driver moduLe 125A or 125~, or i~ a light beam is produce~ but
~he Corresponding phototransistor does not respond in response to
a pulse from it~ driver module 135A or 135B (or gets no
energi~ing pulse ~rom its driver module), the signal input to
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amplifier 1~0~ or 140B, as the case may be, will show no light
beam, just as when a li~ht beam is blocked. It is to be
appr~ciated that while in the foregoing description it was stated
that a given light sensor is activated "simultaneously" with its
Corresponding light source whenever a given light channel is
activatedr in practice it is frequently desirable to activate a
given light sensor slightly before activating its corresponding
light source, in order to assure proper light sensor reponse.
Looking next at Fig. 2, the novel optical intrusion detection
system 100 is intended to be connected to a representative
industrial manufacturing machine 200 that, for example, comprises
a press 205 for punching or reforming metal stock, operator
station controls 210 that allow the machine operator to input
power on/power off commands to the industria~ machine, and press
controls 215 for controlling operation of the press.
By way of example, operator station con~rols 210 may take the
form of an on/o~ switch and a latching relay for coupling the
system to an electrical power supply.
Press controls 215 comprise means ox determining t~e
operating state o~ punch press 205 and means for starting and
Stopping punch press 20S in response to selected control signals,
e.g. a control signal generated by light curtain control
circuitry llS. Typical press controls are exemplified by U. S.
Patent ~os. 3,80S,061 and 4,266,1Z4 and the re~erences cited ~.
therein. Press controls 215 are o~ the sort well known in the
art and are therefore not shown in detailu
Still referring to ~ig. 2, ope~ator station controls 210 are
connected to press controls 215 as represen~ed ~y line 220, and
press contro1s 215 a~e connected to the electric drive motor (not
shown) of press 205, as represented by line 225.
Although not shown, it is to be understood that light
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transmitter me~ns 105, liql~t receiver means 110, ~nd the light
curtain control circuitry 115 are coupled to a suita~le power
supply (not shown) whe~ operator station controls 210 are turned
"on". Optical intrusion detection system 100 is at~ached to the
manufacturing machine 200 by positioning its light transmitter
means 105 and light receiver means 110 adjacent the portion of
the press which is to be monitored, so that the detection
system'5 light curtain extends across the area between the
machine'5 operator and stock-receiving section o~ the press that
is the danger area for the operator. In addition, press controls
215 are connected to an input port of microprocessor 150 of light
curtain control circuitry 115 by a "select" line 230 (Fig. 1~,
and an output port of microprocessor 150 is connected to an input
terminal of press controls 215 by a "control" line 235.
~ y appropriately programming microprocessor 150 in ways well
known in the art, the novel optical intrusion detection system
100 can be made to ~perate in conjunction with machine 200 so
that the intrusion detection system will enable or disable the
industrial machine when ~ or more light beams are blocked during
one phase of the operation of the indus~rial machine, and so that
the intrusiOn detection system will enable or disable the
industrial machine when Y or more light beams are bloc~ed during
another phase of the operation of the industrial machine. It is
to be appreciated that the description which immediately follows
reflects the mode of opera-tion of a general form of the invention
and is not limited to a specific ernbodiment. Reference should be
had to ~ig. 3, which illustrates the mode o~ operation of this
general form of the invention in flow chart form.
Initially the machine operator will use operator station
controls 210 to apply power to press con~rols 215. Press
controls 215 respond by putting press 205 in a first phas of
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operation and, simultaneously, press controls 215 advise light
curtain control circuitry llS of this fact by sendi.ng it a signal
via "select" line 230. This signal serves to advise the
microprocessorr by virtue of its p.re-programmed instructions, as
to how many consecutive li~ht beams mus~ be broken during this
phase of the machine's operation in order to constitute the
threshold intrusion. Thus, for example, if press controls 215
send micrOprocessor 150 a "hiqh" signal along "select" line 230,
the microprocessor~s pre-programmed instruc~ions might cause the
microprocessor to ~atch for and act upon the interruption of at
least three adjacent light beams during this phase of the
machine's operation, and to ignore all lesser intrusions.
Microprocessor lS0 would activate a first one o~ the light
sensors 130A-130L (typically phototransistors, or "PTs"~, and
then activate a corresponding one of light sources 120A-120L
: (typically "LEDs"). As such activation occurs, the
microprocessor would monitor the output o~ inverters 145A and
145B via lines 155 and 160, respectively, for signal outputs
representative of the occurrence o~ light ~lockages.
Microprocessor 150 will interpret the signals ~rom inverters 145A
and 145B as indicative of either the absence or presence of an
opaque object in the path o~ a ligh~ bea~ generated by one of the
light sources 120A-120L. If this irst pulse was received, the
microprocessor would be sure that any flags it had dedicated to
tracking blocked light beams were cleared (they should all be
clear at this ~oint, since this was ~he first light beam pulsed),
and then the microprocessor would ~est to see i~ the channel ~ust
pulsed was the last channel in the se~uence to be checked (againt
this should not be the last channel in the sequence to be
checked~ since it was the first channel pulsed). Assuming that
this was not the last channel in the sequence to be checked, the
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~ILZ773g7
microproceSSOr would move on to the neY.t adjoining channel and
repeat the foregoing process. In the event that the
microprocessor checked every channel in the sequence without
detecting any light bloc~ages whatsoever, ~he microprocessor
would advise press controls 215 of this ~act by sending them an
appropriate signal along "control" line 235, and then the
microproceSSor would resume its cycle of polling the light
channels .
When the microprocessor detected a first light beam being
blocked, the microprocessor~s pre-programmed instructions would
cause the microprocessor to test to see if the current light beam
being blocked was the last one re~uired to be blocked during this
phase of the machine's operation in order to constitute the
required threshold intrusion. If the microprocessor's
pre-programmed instructions indicated that an intrusion of only
one light beam were necessary ~o constitute the threshold
intrusion during this phase of the operation of the industrial
machine, the microprocessor would immediately advise press
controls 215 ~via "control" lin~ 235) that the threshold
intrusion h~d occurred, whereupon press controls 215 would
initia~e the desired ac~tion, e.g. stop the press. If, on the
o~her hand, the microprocessor's pre-programmed instructions
indicated that an intrusion o~ more than one light beam was
required to be blocked at this stage of the machine's vperation
in order to constitute the requisite threshold intrusion, the
microprOcessor would simply set a ~lag to record the current
detected intrusion, a~d then it would re~ume polling the light
curtain with the next channel. If the following channel is
clear, ~he microprocessor clears the flag jus~ set (since the
occurrence of the clear channel indicates the intrusion
previously detected was too few consecu~ive light beams to
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constitute the requisi~e threshold intrusion) and then resumes
polling~ If the following channel is not clear, the
microprocessor would test to see if the current light heam being
blocked was the last one required to be broken during this phase
of the machine's operation and, if the current broken beam was
the last broken beam necessary to constitute the requisite
intrusion~ microprocessor 150 would advise press controls 215 of
this fact via "control" line 235. If, on the other hand, the
current bro~en beam was not the last broken beam necessary to
constitute the requisite intrusion during this phase of the
machine's operation, the microprocessor would set another flag to
record the current detected intrusion and then continue pollin~
the light curtain to see if the next beam was broken. The
roregoing process is continued over and over.
By way of example, suppose the microprocessOr's
'~ pre-programmed ins~ructions re~uire three consecu~ive beams to be
bro~en during this phase of the operation of the industrial
machine in order to constitu~e the requisite intrusion. Then, so
long as a~ least three consecutive beams are not blocked,
mic~oprocessor 150 would advise press controls 215 that there was
no requisite thresh~ld penetration via "control" line 235; as
soon as the three consecutive beams were blocked, microprocessor
150 would advise press controls 215 of the threshold penetration
via 'lcontroll~ line 235, whereupon press controls 215 can initiata
the ~esired ac~ion, e.g~ staxt or s~op ~he press.
~ hen the industrial machine thereafter enters a subsequent
phase of its operation, press controls 215 will advise light
curtain control circuitry llS o~ this ~act by sending a new
signal to microprocessor 150 via "sel~c~" line 230, in which
event light curtain control circuitry llS will modify its
detection criteria, i.e., the number o light beams required to
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be blocked to cause a change in machine operation, according to
the microprOceSSOr~s pre-programmed instructions. ~or example,
press controls 215 might send microprocessor 150 a "low" signal
along 'Iselect" line 230, whereby the microprocessor's
pre-programmed instructions might cause the microprocessor to
watch for and act upon the interruption of at least two adjacent
light beams during this phase of the machine's operation. Once
again, the microprocessor would opera~e in accordance with the
flow chart shown in Fig. 3. For example, suppose the
microprocessor~s pre-programmed instructions require two
consecutive light beams to be broken during this new phase of the
operation o~ the industrial machine in order to constitute the
requisite intrusion. Then, so long as at least two consecutive
beams are not blocked, microprocessor 150 would advise press
controls 215 that there was no requisite threshold penetration
via "control" line 235; as soon as the two consecutive beams were
~locked, microprocessor 150 would advise press controls 215 of
the threshold penetration via "control" line 235, whereupon press
control5 215 can initiate the desired action, e.g. start or stop
the press.
In this way, sys~em 100 can have a light curtain sensitivity
which varies according to cartain pre-programmed instructions and
certain independent even~ts, e.g. varying machine phases . By
providing sufficient means ~or allowing press controIs 215 to
appropriately signal microprocessor 21S and by providing
sufficient memory to hold the microprocessor's instru~tions,
system 100 can be made to adjust its li~ht curtain sensitivity
according to many different machine states.
In the flow chart of Fig. 3, as well as in the other flow
charts of Figs. 4 and S, the block "ini~ialize" is meant to
symbolize any preliminary activities required by the
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microprocessor and its associated hardware prior to beginninq a
sc~nning sequence, e.g. clearing all flags, any self-diagnostics,
etc.
In the pre~erred embodiment, optical intrusion detection
system 100 is adapted to be used as a trigger device to
automatically initiate operation oE industrial machine 200 when
two or more light beams are firs~ blocked and then restored
during the initial "idle" phase o~ the industrial machine, and as
a safety device to automatically halt operation of the industrial
machine if a single light beam is blocked during the subsequent
"run" phase of the industrial machine. By requiring that two or
more light beams be broken to trigger the industrial machine from
its "idle" state to its "run" state, it is assured that only the
intrusiOn and then withdrawal of a relatively large object, i.e.,
the operator~s hand, will activate the machine; on the other
hand, by requiring tha~ only one light beam need be broken to
stop the industrial machine during its "run" phase, it is assured
tha~ the system will respond to the lntrusion of an object of
almost any size, so as to prevent injury to the operator. Fig. 4
llustrates this preferred mode of operation in flow chart form.
Looking next at Figs. 1, 2 and 4 collectively, the preferred
embodiment o~ the optical intrusion detection system is adapted
to operate in conjunction with industrial machine 200 as follows. -
The machine's opera~or ~irst uses opera~or station controls 210
to instruct press controls 215 ~o power up press 205 and make it
ready to run. Press controls 215 do this by sending an
appropriate signal to press ~OS via line 225. ~s the machine
settles into its initial "idle" mode, waiting to be automatically
started by ~he operator's hand ~reaking and then unbreaking the
light ~urtain as ~he wor~piece is placed on the die of the press,
press controls 215 simul~aneously send a "high" signal to
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microprocessor 150 of ligh~ curtain control circuitry 115 via the
'~select~ line 230. This "hiqh" signal instructs the
microprocessor~ by virtue of its pre-programmed instructions, to
monitor the light curtain for any intrusions large enouyh to
block two or more adjacent light beams, and to ignore all lesser
intrusions~ As a safety precaution, press controls 215 are also
typically adapted so that they will automatically disarm the
; press if the operator's hand does not brea~ and then unbreak the
light curtain within some predetermined time period, e.g. 5
seconds, after the operator instructs press controls 215 to power
up the press, or after the press has completed a full operating
cycle This feature pre~ents the operator from leaving a press
fully armed during a period when ~he press is not being actively
worked If press controls ~15 do automatically shut down the
press due to the fact that ~he operator's hand does not break and
unbreak the light curtain within the prescribed time period, the
operator must then ~ypically rearm the machinery using operator
station controls 210.
Microprocessor 150 energizes light sources 120A-120L in a
predetermined sequence and simultaneously activates light sensors
13oA-l3oL in a corresponding sequence. As this is done, the
microprocessor monitors the outputs of inverters 145A and 145B~
So long as signals indicative of unbroken light beams are applied
to micro~rocessor 15~ by buf~ers 145A and 145B at the same
frequency as the light sour~es are ac~ivated, microprocessor 150
will maintain the signal output on ~control" line 235 at the
"high" lavel and keep the "channel blocked~ flag clear.
When a light beam ~rom one of light sources 120A-120L is not
received by its associated light sensor, the "high" signal on
"select" line 230 causes ~he microprocessor to check if its
associated "channel blocked" flag is set. ~f ~hat light beam is
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the first light beam to be ~locked, the "channel blocked" flag
will be clear and, since the "control" line is then "high", the
microprocessor will take no action other than to set the "channel
blocked" flag, whereupon polling of the light curtain continues
with the neY~t light beam. If the next light beam is successfully
received ti.e., it is not blocked), the microprocessor will
respond by clearing the "channel blocked" flag before continuing
polling of the light curtain with the next light beam.
If and when a light beam is blocked while the "channel
blocked" flag is set, signifying that the current light beam
being blocked is the requisite second consecutive light beam to
be blocked, the microprocessor will respond by clearing the
"channel blocked" flag and sending a "low" signal to press
controls 215 on "control" line 235 ~o signal that the threshold
"two beam" intrusion has been detected. Press controls 215 do
not yet activate press 205, however, since the intrusion beincJ
sensed is the operator's hand placing a workpiece in the press,
without the requisite withdrawal of the operator's hand. The
microprocessor~ by vir~ue of its preprogrammed instructions~
continues monitoring the light curtain, waiting for all of the
blocked light beams ~o be unblocked, i.e~, for the intrusion ~the
operator's hand~ to be withdrawn. ~s long as a~ least one ligh~
beam remains ~locked whil~ the 'Iselect" line is "high" and the
ncontrol n line is "low", the microprocessor will continue sending
a nlow" signal to press controls 215 on "control" line 235 to
a~vise the press eon~rols ~hat some intru~ion is still oc~urring.
As soon as the intrusion is completely withdrawnf so tha~ none of
the light beams is then blocked, bu~ers 14S~ and 145B will
proYide signals to microprocessor lS0 indicating that fact,
whereupon microprocessor lS0 will respond by sending press
controls 215 a "high" signal on "cont~ol~ line 235. Press
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controls 215 thereupon reset the signal on "select" line 230 from
"high" to "low". Press controls 215 thereupon initiate operation
of press 205.
As the machine settles into its subsequent "run" mode, ready
to be automatically stopped by any detectable intrusion, press
controls 215 continue to send a "low" signal to microprocessor
150 via "select" line ~30. This "low" signal instruc~s the
microprocessor~ by uirtue of its pre-programmed instructions, to
monitor the light curtain Eor any intrusions large enough to
block even one light beam. In the event tha~ such an intrusion
is detected, the microprocessor will respond by changing the
"high" signal on "control" line 235 to a "low" signal. Press
controls 215 will thereupon immediately stop operation of the
press. In the event that no such intrusion is detected, the
microprocessor will maintain the "high" signal on "control" line
235 and press controls 215 will permit press 205 ~o complete its
power stro~e wi~hout interruption. Thereafter, the punch press
will prepare itsel~ for its next power stroke by opening its
working memhers.
In some circumstances punch press 205 will be provided with
means for automatically ejecting the ~inished workpiece Erom the
press. I~ this is the case, the press will automatically eject
~he finished workpiece as its wor~ing members open in preparation
~or its next power stroke. Additionally, punch press controls
~lS will send a new "high'~ signal to microprocessor 150 via the
"sele-ctn line 230. At this point, the punch press will ha~e
resumed its original nidle" sta~e once more, waiting to be
automatically star~ed by the operator's hand breaking and then
unbreaking the ligh~t curtain as a new workpiece is placed on the
die. Such a mode oE operation is sometimes re~erred to in the
industry as "one break" operation. On~e again, press controls
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215 may be adapted 50 that they will automatically disarm the
press if the operator's hand does not break and then unbreak the
light curtain within some predetermined period, e.g. 5 seconds.
In the event that punch press 205 is not provided with means
for automatically ejecting the finished workpiece from the press,
a slightly different mode of operation (sometimes re~erred to as
a "two break" operation in the industry) is utilized. More
particularlyr as the press' working members open in preparation
for the nex~ power stro~e, punch press controls 215 will send a
new "high" signal to microprcessor 150 via the "selec~" line 230,
thus advising the microprocessor that the punch press is in its
"idle" period and instructing it to monitor the light curtain for
the occurrence of any intrusions large enough to block two or
~ore light beams, and to ignore all lesser intrusions. When the
operator therea~ter reaches into the press to remove a finished
I workpiece~ ~he ligh~ curtain is broken by the requisite threshold
intrUsion. Microprocessor 150 advises punch press controls 215
of this intruSion by sending them a "low" signal on the "control"
line 235 The microprocessor, by virtue o~ its pre-programmed
instructionsr continues to monitor the light curt~in for any
intrUsions large enough to block even one light beam. As long as
any portion o~ the operator's hand continues to penetrate the
light curtain so as to break even one light beam, the
microprocessor will ~ontinue sending a "low" signal to press
control5 215 on control line ~35. W~en the operator is finished
removing the finished workpiece from the press, so that none of
~he liqht ~eams of the light curtain are blocked, microprocessor
150 will advise press contrvls 215 of this fact by raising a
"high" signal on "control" line 235~ Press controls take no
action at this point, however, since the press is then empty. At
this point, the punch press has essentially returned to its
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original "idle" state once more, waiting to be automatic~lly
started by the operator's hand breaking and then unbreaking the
light curtain as a new workpiece is placed on the die. Once
again, press controls 215 may be adapted so that they will
automatically disarm the press if the operator's hand does not
break and then unbreak the light curtain within some
predetermined period, e.g. 5 seconds.
. It is to be noted that the length of time the machine will
: remain in its idle state before being disarmed (assuming no
interruption of the light curtain during that time period) may be
established by the microprocessor ox by press controls 215.
It is to be appreciated that in the preceding description
relating to Fig. 4, on account of the fact that press controls
215 require a "high" signal on "control" line 235 to start the
press (signifying complete removal of the operator's hand) after
they first receive a "low" signal on that line (signifying
insertion of the operator's hand ), microprocessor 150 was
effectively programmed to alter the light curtain's detection
sensitivity from ntwo beams" to "one beam" after the operator's
hand ~as been detected brea~ing the light curtain and before it
is withdrawn~ Alterna~ively, press controls 21S could use the
"select" line ~30 to instruct microprocessor 150 to change the
light curtain's sensitivity from "-two ~beams" to none beam~ after
the operator'S hand has been detec~e~ breaking the light curtain
and before it is withdrawn.
It is also possible ~o ~esign the system so that
microprocessor 150 does not al~er i~s dete~tion sensitivity ~rom
~two beams n to "on~ ~eam" a~ter the operator's hand has been
detected breaking the light curtain and be~ore it is withdrawn.
In this event, the microprocessor will simply continue monitoring
the light curtain for any intrusions large enough to bloc~ two or
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more li~ht beams (and to ignore all lesser intrusion~), rather
than monitoring the light curtain for intrusions larqe enough to
block even one light beam. 0f course, such an opera~ion is
generally not preferred, since it is conceivable that after an
initial "two beam" penetration, the opera~or might adjus~ the
position of his hand so ~hat it was thereafter still intruding
acrOSS the light curtain but only interrupting one light beam,
whereupon the microprocessor would indicate to press controls 215
that the intrusion had been completely removed. On account of
this potentially disastrous possibility, it is generally
preferred to have the device operate as previously described,
whereby microprocessor lS0 effectively alters its intrusion
sensitivity from "two beams" to "one beam" as soon as the
operator~s hand has been detected breaking the light curtain.
- Alternative Embodiment
In the preferred embodiment described above, all decisions on
press status and press mode are made directly in punch press
controls 215, and microprocessor 150 is only us-ed to control the
light curtain~ ~ore speci~icall~, in the preferred embodiment
described above, punch press controls 215 determine the press
status and press mode and, depending on ~he same, press controls
215 send an a~propriate signal to microprocessor 150 on "select"
line 230. Microprocessor 150 utiLizes this signal to set its
sensitivity level and then serves only ~o scan t~e light curtain
for the occur-rence o~ a threshold penetration. When s~ch a
penetration occurs, microprocessor 150 signals punch press
controls 21~ on "control" lina Z35 and punch press oontrols 21S
~hen decide whe~her or not to shut down the press.
As an alternative arrangement, it is possible to use
microprocessor 150 to make some or all o~ ~he decisions on press
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status and press mode, as well as to control the light curtain.
For example, with such an ~rrangement, punch press controls
215 might be used simply to advise microprocessor 150 of when
punch press 205 changes operating status. In such case,
microproceSsor 150 could be pre-programmed to decide whether the
light curtain is activated during a particular state and, if it
is, microprocessor 150 could be pre--programmed as to what the
detection criteria is to be during ~:ha~ press state.
Furthermore, if a threshold detection is detected during a
particular press state, microprocessox 150 could then decide
whether the press should be started or stopped, or neither,
depending on the current state of the press.
Where microprocessor lS0 is being used in such an alternative
manner and where punch press 205 is provided with means for
automatically ejecting the finished workpiece from the press
("one ~reak" operation), the 10wchar~ shown in Fig. 4 will still
apply. However, in ~e case where microprocessor lS0 is being
used in such an al~ernative manner and where punch press ~OS is
not provided with means ~or a,~~omatically ejecting the finished
wor~pie~e from the press ("two brea~" operatior-), the flowchart
shown in ~ig. 4 will no longer apply and opera~ion may take place
in accordance with the flow char~ shown in Fig. 5.
Thus, with re&rence~to Fig. ~, microprocessor 150 may ~e
pre-programmed so that the press wil~ a~toma~ically start another
"run" cycle only ater the operator has first cleared i~ of a
finished wor~piece and then ins~alled a new workpiece in its
place. In such a case, the microp~oces~or will ma~e use of a
number o~ additional ~lags ~o record the various ligh~ beam
bloc~ages which Wil l occur~in the course of placing and removing
the various workpieces on the die o~ the press. More
specifically, the microprocessor is arranged ~o utilize a
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1~77~9~
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"channel blocked" ~lag, an "interrupted scan" flag, a "first
brea~" flag, and a "second brea~" ~lag.
~ or the purposes of the following description, it will be
assumed that the press has just completed a power stroke and is
in its "idle" mode waiting for the worked part to be removed and
a new part to be inserted in the press. When the press has
completed its power stroke, the signal on "select" line 230 will
be "low", the signal on "control" line 235 will be "high", and
all the ~lags will be clear. Press controls 215 then apply the
"hiyh" signal on "select" line 235, causing the microprocessor to
monitOr the light curtain for the interruption of at least two
adjacent liqht beams caused by the operator's hand as he reaches
in to remove the punched workpiece. When such ~n intrusion
OCcurs, the "interrupted scan" flag and the "first break" flag
are set an~ the "control" line is sent to "low". When the
operator~S hand is thereafter completely withdrawn, the
"interrupted scan" flag is cleared. Thereafter, since the
"select" line is still "high", the device continues to monitor
for the interruption o at Ieast two adjacent light beams, caused
by the intrUsion of the operator's hand as he reaches in to place
the new workpiece on the die of the press~
~ his new intrusion causes the "interrupted scan" flag and
also the "second break" flag ~o be set. The "select~ line stays
"high" and the "control" line s~ays "lown. As soon as the
operatorlS hand is completely removed ~rom the curtain, ~he
microprocessor resets ~he "cgntrol" line 235 to "high" and clears
all flags When press controls 215 see the ~'high" signal on
"control" line 235, they respond by ac~iva~ing the press.
Simultaneously~ press controls 215 reset the "select" line to
"low" so as to cause the microprocessor to monitor for the
interruption of a single light beam during this "run" cycle of
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.
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the press. If such an intrusion is detected, micxoprocessor 150
will immediately change the "high" signal on "control" line 235
to a "low" signal, causing punch press controls 215 to shut down
the press. If no such intrusion is detected, the press will
complete its power stroke without interruption. Operation then
repeats as described above.
In this alternative embodiment, microprocessor 150 (rather
than punch press controls 215) may be programmed to disarm the
press in the event that two large intrusions do not occur within
a fixed time period following completion of an operating cycle,
e.g., within ten seconds.
Other Modificatlons of the Invention
It is, of course, possible to modify the invention in other
ways.
Thus, for exa~ple, the number o light sources 120, light
sensors 130, drivers 1~5, and drivers 130 may be varied. Also,
the program controlling microprocessor 150 may be changed so that
three (or more) light beams are required to be broken to staxt
~he press when it is in i~s initial ~idle" mode. SimilarLy, the
program controlling microprocessor lS0 could be modified so that
two ~or more~ lig~ beams are required to be ~ro-~en to stop the ~
press when it is in its "run" mode. I~ is also contemplated that
the light beams may be activated in a sequence other than purely
a~cending~ e.g. instead o~ activating light beam ~2 after ligh~
beam ~1 and light beam~3 after ligh~ beam t2, etc., one might
activate the odd-numbered light beams (i~e., numbers 1, 3, 5,
e~c.) in ascending order, and then actiYate the even-numbered
light beams ~i.e., numbers ~, 4, 6, ~tc.) in ascending order or a
totally different activation sequence may be utilized.
Still other modifications will be obvious to one skilled in
. ~ ,
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the art.
Advan~a ~s 0~ The Invention
A number o~ advantages are obtained by the present invention.
~ irst, the invention provides an optical intrusion detection
System which has a variable sensitivity, enabling it to be set to
respond to the intrusion o~ an object of a first size during one
~;, phase of its associated machine's operation and to a object o~ a
second size during another phase o~ the machine's operation.
Second, the invention provides an optical intrusion detection
System which can be set so as ~o be insensitive to relatively
small objects during one phase of its associated industrial
machinels operation and yet sensitive to the same relatively
small objects during another phase of the machine's operation.
Third, the invention provides an optical intrusion detection
system which can be used as both a trigger device to start the
operation o its associated industr~al machine, and as a safety
device to stop the operation of it~ associated machine.
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