US3875403A - Light beam apparatus - Google Patents

Light beam apparatus Download PDF

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Publication number
US3875403A
US3875403A US446423A US44642374A US3875403A US 3875403 A US3875403 A US 3875403A US 446423 A US446423 A US 446423A US 44642374 A US44642374 A US 44642374A US 3875403 A US3875403 A US 3875403A
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light
pulse
circuits
circuit
light source
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US446423A
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English (en)
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Lars Erik Svensson
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    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16P—SAFETY DEVICES IN GENERAL; SAFETY DEVICES FOR PRESSES
    • F16P3/00—Safety devices acting in conjunction with the control or operation of a machine; Control arrangements requiring the simultaneous use of two or more parts of the body
    • F16P3/12—Safety devices acting in conjunction with the control or operation of a machine; Control arrangements requiring the simultaneous use of two or more parts of the body with means, e.g. feelers, which in case of the presence of a body part of a person in or near the danger zone influence the control or operation of the machine
    • F16P3/14—Safety devices acting in conjunction with the control or operation of a machine; Control arrangements requiring the simultaneous use of two or more parts of the body with means, e.g. feelers, which in case of the presence of a body part of a person in or near the danger zone influence the control or operation of the machine the means being photocells or other devices sensitive without mechanical contact
    • F16P3/144—Safety devices acting in conjunction with the control or operation of a machine; Control arrangements requiring the simultaneous use of two or more parts of the body with means, e.g. feelers, which in case of the presence of a body part of a person in or near the danger zone influence the control or operation of the machine the means being photocells or other devices sensitive without mechanical contact using light grids

Definitions

  • ABSTRACT [30] Foreign Application Priority Data I Feb 1973 Sweden WSW/73 A hght curtain for supervlslng or controlling the operation of machines comprising a series of electrical [52] U S Cl 250/209 250/221 317/177 light sources arranged to give light pulses which are 40/258 short in relation to the repetition frequency. After the [51] Int CL". G06m 7/8 60% 13/00 Holh 47/24 light pulses have spanned the supervlsed region they [58] Field of Search 250/2521 208 are detected by one or more pulse detectors for each "340/258 317/1273 light source.
  • the present invention relates to apparatuses in connection with so-called light curtains or light beam apparatus.
  • Such apparatus is especially used for guarding dangerous machines or installations from unintentional access. This is arranged by the opening which allows access being monitored by light beams placed side by side or sweeping light beams which, when they are interrupted. cause the immediate stoppage of the machine which is being guarded.
  • Special sensing devices are therefore connected to a light curtain apparatus, for stopping the machine both when an object is introduced into the opening of the light curtain apparatus and when some predictable fault arises in the supervising equipment.
  • a problem here has been to make the sensing devices with the right degree of sensitivity. If there is great sensitivity there is the risk of emergency stoppages even for completely irrelevant disturbances. Such disturbances can be occasional variations in the electric power supply voltage, natural alterations or reasonable wear of the participating components and details in the sensing devices. Light or smoke can also be disturbing and cause interruptions in operation. Too low sensitivity, on the other hand, brings with it the risk of malfunction when function is absolutely required.
  • Previously known light curtains are preferably arranged according to two main principles.
  • the one works with a row of combined lamp and photo-electric cells, the light from the lamps spanning the opening in the light curtain in parallel beams, either being reflected back again by a mirror or directly transferred to the photocells which, in their turn, are connected to electrical amplifiers and relays by the help of which the arresting function is carried out, when one or several light beams are interrupted or weakened by a previ ously determined amount.
  • the other principle utilizes a single lamp and photocell instead of several lamps and photocells, the light from the lamp being given a sweeping movement over the light curtain opening by means of a rotating mirror.
  • the sweeping movement which has a parallel course over the opening, is provided by a mirror arrangement containing a plane and a parabolic mirror in the center of which the rotating mirror is placed.
  • the scanning speed is limited by the sluggishness of the mechanical system.
  • special controlling means in the shape of extra photocells are required to indicate when the light beam leaves and reenters the light curtain opening. Both the devices mentioned suffer from sensitivity to outside light. The spread of light can further cause light to strike the photocell associated with a certain beam although the beam has been blocked, thus triggering the protecting mechanism.
  • the use of so-called light diodes or light-emitting semiconductors, as light sources has been proposed and these can be fed with voltages pulses. It has been found that operational reliability has thereby been able to be increased.
  • the requirement of double safety is put on such installations these days, i.e., at least two operating means independent of each other shall be switched on for the machine in question to be started. This has naturally had repercussions on the construction of the light curtain circuit.
  • the object of the present invention is to put right the weaknesses accounted for above and to provide light curtains having large tolerance against variations of sensitivity and high functional reliability and which work solely with cheap and operationally reliable electronic components.
  • FIG. 1 is a principle diagram over the electronic circuiting of a suitable embodiment of the invention.
  • a pulsing source 1 for electrical pulses is arranged.
  • the source 1 which can be a pulse generator known per se, works with a suitably selected pulse repetition frequency, e.g., lkl-Iz, and feeds a rapid light supply 3 via a pulse amplifier 2, the light supply being a light diode or a gas discharge lamp.
  • the light pulse obtained in this way is concentrated by suitable optical means on a mirror 4 arranged on the far side of the area to be supervised, and which reflects the light pulse back again in the present case to two light pulse detectors 5 of photodiode or phototransistor type, mounted on each side of the light source in the plane of the light curtain.
  • the output signal obtained in the light pulse detectors 5 is an electrical pulse representing light pulses and is taken to a special pulse control circuit 6, which is in its turn arranged to give a further electrical impulse only on the condition that the reflected light pulse has the right amplitude and arrives within a time period determined by pulse source 1, or the feeding pulse to light diode 3. In the present example, this is done so that a portion of the feeding pulse is portioned off and used as a control pulse. In this connection it should be pointed out that the propagation time of the pulses is negligable, and for this reason the control pulse and the output pulse from the light pulse detectors 5 occur in the pulse control device 6 practically simultaneously. If the light pulse has now not met any obstacle, the pulse control device 6 gives an output pulse as mentioned, which in principle is a copy of the one obtained from the pulse source 1.
  • the output pulse now feeds a second combination of amplifier 7, light source 8, mirror 9, photodetector and pulse control device 11, completely in agreement with the arrangement described before, and having the same working principle and a special supervisory circuit 12, the task of which is to ensure that the output pulse from the control circuit 6 is actually present.
  • the supervisory circuit 12 is designed with two inputs and that in the present case two further combinations of light source/detectors and pulse controlling devices, 13-16 and 17-20 resp. are connected in series.
  • the inputs of the supervisory circuit 12 are connected to alternate links in the chain, i.e., to 26 and 13-16.
  • a further supervisory circuit 21 is arranged in conjunction with units 7-11 and 17-20.
  • An operating relay 22,23 is respectively connected to each supervisory circuit. Said relays are suitably arranged in the operating circuit of a machine, e.g., the operating circuit for a press, whereat the connection is arranged to take place between terminals 24,25. Terminals 26,27 can be connected to a signal circuit.
  • both the relays 22,25 must be in circuit for the line between 24 and 25 to be closed, i.e., for the operating circuit of the machine to be closed. In its turn, this means that all the pulse sequences have gone undisturbed from unit 'to unit, and that the supervisory circuits 12,21 have been regularly actuated for putting in circuit their respective relays 22,23. If any disturbance should occur in any of the light beam paths, e.g., the one starting from the light diode 3, no light pulse is received in the appropriate manner by any of the detectors 5, whereon neither is there a pulse the next step 7-11 in sequence or to the supervisory circuit 12. Both relays 22,23 will then cut out, making it impossible to operate the machine. Safety is thus complete.
  • said pulse control circuit 6 is so designed that its output pulse is delayed in relation to the feeding pulse which controls the respective light diode. Scanning is hereby obtained along the whole of the light curtain ramp, line for line.
  • the pulse length and the pulse repetition frequency of pulse source 1 is therefore adjusted so that the whole of the light ramp can be scanned line for line between two consequent pulses from said pulse source. If, for example, the light curtain shown, which includes four light diodes 2,7,13,17, is supplied with a pulse repetition frequency of lkl-lz the pulse length is arranged to be less than 0.25 milliseconds. Further, embodiments are possible, where the number of light detectors may be varied as well as their placing. Instead of the mirrors which are normally used, the detectors can be put in the place of the mirrors.
  • a light curtain or light beam apparatus is obtained, built from simple reliable electronic components which may preferably be built together in a single solid mechanical unit. Thanks to the rapid development of techniques in the fields of optical-electrical semiconductors and integrated circuits, an apparatus according to the invention can be made very small and efficient. As scanning of the light curtain opening takes place in steps, resonance between the circuits is eliminated completely. It is further possible arbitrarily to graduate sensitivity by arranging more photodetectors for each light diode. Certain narrow objects can thereby be passed through the light curtain without the machine stopping. Thanks to the use of AC. amplifiers sensitivity can be further kept very constant and very high. It is thus possible to span large distances, the insensitivity to general lighting contributing to this possibility. As is usual in connection with light curtains, it is also possible to connect means for single, double or triple sequences, whereby intentional interruption of the light beams is used to start the machine, after the introduction of one or more objects during its working cycle.
  • a light curtain apparatus for supervising and/or operation of machines comprising a series of electrical light sources (3) arranged to give, through a periodic pulse source (1) light pulses which are short in relation to the repetition frequency of the pulse source, said light pulses after having spanned the opening in the light curtain being detected by one or more light pulse detectors (5) arranged for each light source (3), wherein the light detectors (5) for each light source control a pulse control circuit (6) which, on receiving essentially simultaneous pulses on its inputs, releases a starting pulse for the light source (7) next in sequence in the series, and simultaneously gives a supervisory circuit (12) an acknowledgement pulse.
  • a light curtain apparatus wherein the starting pulse for each light source is also arranged to feed an input of the respective pulse control circuits (6,11,16,20).
  • a light curtain apparatus wherein at least two supervisory circuits (12,21) are arranged, each having a number of inputs corresponding to half the number of light source circuits (26, 13-16, etc.), each input being connected to an appropriate pulse control circuit (6,16).
  • a light curtain apparatus according to claim 3 wherein alternate pulse control circuits (6,16 and 11,20 respectively) are connected to one and the same supervisory circuit (12 and 21 respectively).
  • each of the supervisory circuits (12 and 21 respectively) controls its own operating circuit (22 and 23 respectively) for the machine which is to be supervised and/or operated.
  • a light curtain apparatus according to claim 5 wherein the operating circuits comprise relays (22,23) the contacts of which are co-actively arranged to control the controlling circuits of the machine in question.
  • each pulse control circuit (6) contains a time delay means, a pulse being taken off said time delay means to feed the appropriate supervisory circuit (12).

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Geophysics And Detection Of Objects (AREA)
US446423A 1973-02-27 1974-02-27 Light beam apparatus Expired - Lifetime US3875403A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
SE7302757A SE372085B (enrdf_load_stackoverflow) 1973-02-27 1973-02-27

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US3875403A true US3875403A (en) 1975-04-01

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US446423A Expired - Lifetime US3875403A (en) 1973-02-27 1974-02-27 Light beam apparatus

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DE (1) DE2409113B2 (enrdf_load_stackoverflow)
SE (1) SE372085B (enrdf_load_stackoverflow)

Cited By (18)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4179623A (en) * 1976-09-02 1979-12-18 Honeywell Ltd. Pulsed level sensor
US4224608A (en) * 1978-11-13 1980-09-23 Detection Systems, Inc. Single terminal detection system
WO1981000750A1 (en) * 1979-09-10 1981-03-19 Ambler K Improvements relating to safety mechanisms for industrial machinery
US4317992A (en) * 1979-12-10 1982-03-02 Honeywell Inc. Object detecting apparatus
US4403142A (en) * 1980-05-20 1983-09-06 Matsushita Electric Works, Ltd. Moving object detecting apparatus
US4467251A (en) * 1979-05-31 1984-08-21 Besam Ab Object sensing apparatus
US4851746A (en) * 1987-04-15 1989-07-25 Republic Industries, Inc. Sensing apparatus for automatic door
US4903009A (en) * 1988-05-18 1990-02-20 Eastman Kodak Company Intrusion detection device
US4959805A (en) * 1987-03-17 1990-09-25 Alps Electric Co., Ltd. Coordinate detecting device
US5420430A (en) * 1991-04-15 1995-05-30 Formula Systems Ltd. Detection systems for detecting obstructions in doorways
US5504325A (en) * 1993-04-28 1996-04-02 Elisra Electronic Systems Ltd. System for monitoring a multiplicity of doors using multiple optical transceivers mounted on each door
EP0772166A1 (en) 1995-10-27 1997-05-07 Elisra Electronic Systems Ltd. A system for monitoring a multiplicity of doors
EP0793154A1 (en) * 1996-01-25 1997-09-03 RWL Consultants Ltd Fail safe system
US5900598A (en) * 1994-09-16 1999-05-04 T L Jones Limited Lift sensor
US6166371A (en) * 1999-04-30 2000-12-26 Beckman Coulter, Inc. Diffuse reflective light curtain system
EP0874383A3 (fr) * 1997-04-11 2004-06-23 Schneider Electric Industries SAS Circuit de surveillance
US20060010601A1 (en) * 2002-04-19 2006-01-19 Riley Carl W Hospital bed obstacle detection device and method
US11406548B2 (en) 2018-09-27 2022-08-09 Hill-Rom Services, Inc. Obstacle detection IR beam filter

Families Citing this family (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
FR2283494A2 (fr) * 1974-09-02 1976-03-26 Cometa Procede et dispositif de balayage photoelectrique
DE3509096A1 (de) * 1985-03-14 1986-09-25 Heinrich 3550 Marburg Sälzer Verfahren und einrichtung zur ueberwachung einer oeffnung
DE3803033A1 (de) * 1988-02-02 1989-08-10 Sick Erwin Gmbh Lichtschrankengitter
DE4338978C2 (de) * 1993-11-15 1998-05-07 Sick Ag Verfahren zur Feststellung defekter Lichtsender und/oder Lichtempfänger eines Lichtgitters und Lichtgitter
DE4344321C2 (de) * 1993-12-23 1997-04-30 Siemens Ag Betriebsverfahren eines Lichtschrankenmoduls für automatisch arbeitende Türsysteme und hierfür geeignetes Lichtschrankenmodul
DE19605102A1 (de) * 1996-02-12 1997-08-14 Siemens Nixdorf Inf Syst Infrarot-Sicherungssystem
DE19912142A1 (de) * 1999-03-18 2000-10-19 Fotoelektrik Pauly Gmbh & Co K Lichtschranke mit Überwachungsschaltung

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3742222A (en) * 1970-02-20 1973-06-26 Endl Elektronik Gmbh Co Photoelectric sensing system
US3746863A (en) * 1972-03-15 1973-07-17 Exotron Ind Ltd Light curtain control for a switch
US3805061A (en) * 1973-04-23 1974-04-16 Tyco Laboratories Inc Object detecting apparatus

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3742222A (en) * 1970-02-20 1973-06-26 Endl Elektronik Gmbh Co Photoelectric sensing system
US3746863A (en) * 1972-03-15 1973-07-17 Exotron Ind Ltd Light curtain control for a switch
US3805061A (en) * 1973-04-23 1974-04-16 Tyco Laboratories Inc Object detecting apparatus

Cited By (27)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4179623A (en) * 1976-09-02 1979-12-18 Honeywell Ltd. Pulsed level sensor
US4224608A (en) * 1978-11-13 1980-09-23 Detection Systems, Inc. Single terminal detection system
US4467251A (en) * 1979-05-31 1984-08-21 Besam Ab Object sensing apparatus
US4560912A (en) * 1979-05-31 1985-12-24 Bert O. Jonsson Object sensing apparatus for an automatic door
US4590410A (en) * 1979-05-31 1986-05-20 Joensson Bert Ove Object sensing apparatus
US4888532A (en) * 1979-05-31 1989-12-19 Besam Ab Object sensing apparatus
WO1981000750A1 (en) * 1979-09-10 1981-03-19 Ambler K Improvements relating to safety mechanisms for industrial machinery
US4317992A (en) * 1979-12-10 1982-03-02 Honeywell Inc. Object detecting apparatus
US4403142A (en) * 1980-05-20 1983-09-06 Matsushita Electric Works, Ltd. Moving object detecting apparatus
US4959805A (en) * 1987-03-17 1990-09-25 Alps Electric Co., Ltd. Coordinate detecting device
US4851746A (en) * 1987-04-15 1989-07-25 Republic Industries, Inc. Sensing apparatus for automatic door
US4903009A (en) * 1988-05-18 1990-02-20 Eastman Kodak Company Intrusion detection device
US5420430A (en) * 1991-04-15 1995-05-30 Formula Systems Ltd. Detection systems for detecting obstructions in doorways
US5504325A (en) * 1993-04-28 1996-04-02 Elisra Electronic Systems Ltd. System for monitoring a multiplicity of doors using multiple optical transceivers mounted on each door
US5900598A (en) * 1994-09-16 1999-05-04 T L Jones Limited Lift sensor
EP0772166A1 (en) 1995-10-27 1997-05-07 Elisra Electronic Systems Ltd. A system for monitoring a multiplicity of doors
EP0793154A1 (en) * 1996-01-25 1997-09-03 RWL Consultants Ltd Fail safe system
EP0874383A3 (fr) * 1997-04-11 2004-06-23 Schneider Electric Industries SAS Circuit de surveillance
US6166371A (en) * 1999-04-30 2000-12-26 Beckman Coulter, Inc. Diffuse reflective light curtain system
US20060010601A1 (en) * 2002-04-19 2006-01-19 Riley Carl W Hospital bed obstacle detection device and method
US7472437B2 (en) * 2002-04-19 2009-01-06 Hill-Rom Services, Inc. Hospital bed obstacle detection device and method
US20090109025A1 (en) * 2002-04-19 2009-04-30 Carl William Riley Hospital bed obstacle detection device and method
US8258944B2 (en) 2002-04-19 2012-09-04 Hill-Rom Services, Inc. Hospital bed obstacle detection device and method
US8502663B2 (en) 2002-04-19 2013-08-06 Hill-Rom Services, Inc. Hospital bed obstacle detection apparatus
US8866610B2 (en) 2002-04-19 2014-10-21 Hill-Rom Services, Inc. Hospital bed obstacle detection apparatus
US9655796B2 (en) 2002-04-19 2017-05-23 Hill-Rom Services, Inc. Hospital bed obstacle detection apparatus
US11406548B2 (en) 2018-09-27 2022-08-09 Hill-Rom Services, Inc. Obstacle detection IR beam filter

Also Published As

Publication number Publication date
DE2409113B2 (de) 1977-06-02
DE2409113A1 (de) 1974-08-29
SE372085B (enrdf_load_stackoverflow) 1974-12-09

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