Electronic shutter incorporated in automated laser safety system

Abstract

A fully automated laser safety system is configured to monitor the operation of a high- power laser which outputs a laser beam within a work cell having an openable door for robotically delivering workpieces i< be beam treated inside the cell. The automated safety system includes an electronic shutter logic provided with a two-channel logic block configured to meet the redundancy and diversification requirements. The logic block-receives input data from multiple input devices including. among others, multiple door interlocks, start button, and shudder control, and is operative to check the status oral! input devices. If the input devices are satisfied, the logic block operates as an electronic shutter making the current source change its operation in a high current output regime to a safe, tow current output regime, 'Thereafter, the door automatically opens, a workpiece is delivered into the cell and the door is then closed. With the electronic shutter subsequently opened, the current source switches to the high current output regime without human intervention..

Description

[0001] r ELECTRONIC SHUTTER INCORPORATED IN

[0002] AUTOMATED LASER SAFETY SYSTEM

[0003] BACKGROUND OF THE DISCLOSURE Field of the Disclosure The present invention relates to laser safetv systems. In particular, the invention relates to a folly automated laser safety system provided with an elechonie shatter logic which controls the operation of the laser s power source in nigh- and low-power regimes without human intervention.

[0004] Prior Art Discussion Laser safety standards are well established and relatively harmonized internationally. These standards establish few broad classifications of laser safety for laser sources. The classifications range from relatively low power devices of Class 1 to high power laser source of Class 4. The primary goal of any laser safety system is to minimize the risk of exposing humans to the laser radiation which obviously increases with the increased output laser power. Typically, any safety system meeting this goal is cmfilguted with at least three main fonutionally uodependeat parts. The input of the safety system inchtoes one or more sensing logical devices, such as interlock(s). Ley switches, and etc., with respective outputs in Boolean, i.e. true or talse. Following the input part is a safety instrumental. system which is a logic block or circuit evaluating the stow of the input devices and, based oo the e valuation, making a decision, such as whether the shutdown or change of operational regime of the laser power source is warranted. Completing the safety system is an actuator which executes the logic's decision.

[0005] Most governments have safety regulations for laser systems la order to insure that the undeslred operation of the laser does not occur. These minirnally include laser work cell enclosnm, a door to access the work cell, a switch to sense the integrity of the enclosure, a momentary start button, and a method to prevent tire operation of the laser. The laser has interfaces built in to moni tor the door interlocks, start bottom laser interlocks and methods to prevent the laser operation white the customer provides the enclosure and switches. 1 0ven the most tax laser legutatiom: state that a single component failure will not allow unsafe opemifon. For this reason, the logic of the safety system is based on the redundancy principle providing for redundant sensors used to detect the slate of enclosure 12, and multiple methods are used to prevent laser operation. For higher levels of safety, these redmfeam iepm

[0006] Referring to FIG. 1 , a safety system 10 is configured to prevent a human from being exposed to laser radiation emission 18 generated by a high power solid state laser 29 with a fiber-delivered laser emission 'fhe system 10 includes mr enclosure 12 surromiding a work cell 14. Within, the latten a processing or laser head of fiber laser system 20 focuses a laser beam 18, which is guided along a delivery fiber 22 from laser 20 to the laser head, on a workpiece 16 to be laser treated. The laser operation, be it welding, cutting or other laser applications, requites periodic trips of the human inside cell 14 for a variety of reasons. Before the human opens a door 24 of enclosure 12 which is wired to the safety system by means of multiple cables 22, the power source, energizing laser 20, is shut down.

[0007] Having completed rhe task at hand dining the safe regime, the itumari exits cell 14 through door 24 having a door interlock 26 winch senses the integrity of enclosure 12, The data indicative of lite desired door state and other controlled inputs of the safety system and the laser me received and interpreted by a logic. If all input de vices are satisfied, the laser po wer source may be energized again. However, the laci that interlock 26 (and other input devices) is satisfied is only a necessary condition. To meet the sufficiency requirement for the restart of the lasers the human must momentarily depress a momentary start button 28 located outside cell 14,

[0008] Ths above-disclosed operation of system 10 works perfectly well when the humaa's presence inside enclosure 12 of FIG. 1 is indispensable. Yet, with the advance of automated laser-based industrial processes including, for example, the automated delivery of workpieces into cell 14 of FIG. 1 , the interruption of laser radiation emission with the obligatory subsequent human intervention introduce inevitable process interruptions which detrimentally affect the process efficiency. To adjust the safety system for a fully automated operation with minimal human intervention, two levels of enclosures are needed including an inner enclosure which blocks the laser output or flic entire laser, and outer enclosure 12 placed around the inner one.

[0009] FIG. 2 illustrates a folly automated safety system 25. The safety system is configured to co tenuously contain the laser emission within one of tire inner and outer enclosures without turning off laser 20. Like system 10 of FIG. 1. system 25 is configured with cell 14 which receives workpieces 16 robotically delivered through open door 24 for further thermal treatment by laser beam 18. In addition to the above-discussed components of safety system 10 of FIG. 1, safety system 25 is configured with an inner enclosure 62 which surrounds area 60 around the processing head (and possibly laser 20} and has a door 64.

[0010] The inner enclosure 62 may be configured as a simple mechanical blocking device which is sufficient for low power laser sources. For higher powers, an electro-optical devices, such as a single channel switch beam, can function as inner enclosure 62. Located along the beam path anywhere between laser 20 and the laser's output, the beam switch is configured with redundant sensors to detect the state of the mirrors mounted within its housing, redundant thermal sensors, inputs for work cell doors, and all the control electronics for satisfying the requirements for fully automated laser operations.

[0011] For the safe regime of the laser power source to be realized, first door 64, such as the mirror beam switch 62 is closed, thereby blocking beam 18 at a predetermined time prior to the opening of door 24 of outer enclosure 12. Then door 24 can be opened, new workpiece 16 is delivered and then door 24 is closed. Only after that inner door 64 is open and a high power regime of laser 20 is resumed. Ihe whole process is automated to repeat with a human required to start it only after tire laser radiation emission has been interrupted for the required period of time.

[0012] The beams switches are not without the known disadvantages. For example, beam 18 propagates through free space inside the switch between the input and output fibers which involves precise mechanical alignment as well as an increase in fiber size which in certain cases, such as single transverse mode fibers, may be impractical. In summary, beam switches are mechanically and optically delicate devices requiring frequent maintenance operations and imposing certain restriction on the environment in cell 14 and beyond. These considerations drive tire cost of laser source 20 and entire protections system 25 up.

[0013] Accordingly, what is needed is a simple, reliable and cost-effective fully automatic laser safety system configured with an electronic shutter and operating without human intervention.

[0014] SUMMARY OF THE DISCLOSURE

[0015] This need is met by the inventive laser safety system. Conceptually, the inventive safety system with the electronic shutter is configured to augment, the safety circuitry of the laser to give the same functionality as an external beam switch or mechanical safety shutter without the need for additional optics or hardware.

[0016] This concept is realized by the inventive safety system in which the electronic shutter enables the current source of the laser power supply to reduce its output power to a safe level during automatic delivery' of workpieces into tire work cell. Once the electronic shudder is ‘‘open”, the current source automatically reverts to its high-power regime in which the cell's door prevents a high-power laser beam from escaping outside the cell. 'fhu$, the operation of the inventive system ensures that the laser radiation emission is continuously blocked by either die outer door or electronic shutter in respective high-power and safe regimes of the current source. Hence there is no need for a human being to fiddle with the start button for enabling the high power regime of the current source.

[0017] In accordance with another salient feature of the invention, the logic performs two essential functions: (1) monitoring the state of input devices with door 24 closed, and (2) controlling the regime of Operation of the current source reducing its output before the door opens. During the latter, the logic functions as ah electronic shutter operative to periodically reduce the current source output to permissible safe levels.

[0018] Still another salient feature of the inventive logic includes receiving and evaluating feedback signals from the current source. The feedback signals are used to indicate tire state of the current source. If the internal failure of the source is detected, the safety system shits down the laser, To restart the laser after the interruption the laser radiation emission, the start button should be momentarily depressed by the operator. Thereafter, the- safety system operates without human intervention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and other structurally and conceptually complementary features will become more apparent with reference to the accompanying figures, which are not drawn to scale. The figures provide an illustration and a further understanding of the various intertwined aspects and schematics, and constitute a part of this specification, but do not represent the limits of any particular schematic or aspect. In the drawings, each identical or nearly identical component that appears in various figures is denoted by a like numeral. For purposes of clarity, not every component may have the same reference numeral. In lite figures:

[0020] FIG. 1 is an exemplary laser-based industrial system of the known prior art incorporating a safety system which requires human intervention.

[0021] FIG. 2 is an exemplary laser-based industrial system with a fully automated safety system of the known prior art;

[0022] FIG. 3 is an industrial laser-based system configured with the inventive, fblly automated safely system;

[0023] FIG. 4 is an exemplary schematic of the safety system gf FIG. 3.

[0024] SPECIFIC DESCRIPTION

[0025] Referring to FIGs. 3 and 4, a laser safety system 65 of FIG. 3 incorporates a fully automated electronic shudder 70 that controls the power supply to laser 72 so as io minimize the environmental hazard posed by the laser emission. Like the above-disclosed configurations of the known prior art, safety system 65 is configured with outer enclosure 12 provided with door 24 monitored by two door interlocks which are wired to the laser interface of laser 72 by means of redundant cables 32. In addition, the laser interfaces monitor start button 28 and other laser input devices and switches, and methods to prevent the laser operation. The laser 72 can be installed inside enclosure 12 or, as shown, outside it. Configured as a solid state laser, the latter includes, among others, a high-power fiber laser outputting akW and higher single transverse mode or multimode output and operating in a continuous, quasi-continuous or pulsed regime. Ilte configuration of laser 72 further includes a power source 61 of FIG. 4, control electronics and all other well-known laser source components. Ihe operation of laser 72 and system 65 is controlled by a controller 66. The main function of safety system 65 is to prevent laser beam 18 from escaping work cell 14 while the system operates fully automatically without human intervention. Since the delivery of workpieces 16 into cell 14 is automated, such a possibility is limited, but not fully excluded. To enhance die safety, electronic shutter 70 is configured with an electronic shutter logic 55 of FIG. 4 operable to input a signa! into a current source 58 - an electronic circuit within power source 61- which in response changes its operation between high -power and low- power regimes. The high-power regime corresponds to a high current output, whereas the safe regime corresponds to a low-current output.

[0026] To begin the automated process for laser treating workpieces, manual start button 28 must be momentarily depressed once. After that, barring any emergency situations, such as malfunction of laser 72, power source 61 and / or input devices 38 - 44 of FIG. 4, safety- system 65 operates continuously without the need for pushing button 28 during a transitional period between the normal, high-power regime and the safe regime of current source 58.

[0027] During the normal, high-power regime of the current source door 24 of FIG. 3 is closed and electronic shutter 70 is “open” so that current source 58 of FIG. 4 outputs the high-current signal energizing pump laser diodes 59, The latter, in turn, pump the gain medium of laser 72 outputting high-power beam 18 which is focused on workpiece 16ofFIG. 3. The main function of safety system 55 of FIG. 5, i.e., environmental protection from laser emission, is realized by controlling an electric current signal to the laser diodes.

[0028] To transition from the normal high-power regime to the safe regime of the current source, controller 66 of FIG. 3 generates a sequence of commands including first '‘closing” electronic shudder 70, thereby causing the current source to switch to the safe regime, opening door 24, delivering new workpiece 16 and finally closing door 24. Thus, during the safe regime of the source, electronic shudder 70 is in its “close” position providing the safe operation of cunent source 58 of FIG. 4 while the delivery is in progress.

[0029] As electronic shutter 70 is returned its open position, current source 58 returns to its normal, high-power regime. With door 24 of c-ell 14 previously closed, high power laser beam 18 is reliably confined within work cell 14. The manual start button 28 needs not to be depressed after the safe regime of current source 58 ends because laser beam 18 is always under the protection of cither shudder 70 or door 24 and. thus never interrupted. Referring specifically to FIG. 5, electronic shutter logic 55 is incorporated in laser 70. Functionally, logic 55 Operates in response to receiving multiple input signals from respective input devices disclosed detail below. The inputs; are pomplementary ; one of the inputs is an active high signai, whereas the other is an active low signal, Two safety channels 34 and 36 transmit the inputs into a logic block 30, Returning to the input devices, there are at least two door interlocks 38 and 40 each changing its state in response to the operation of door 24 of FIG. 1 Other laser input device are a keyswitch 42 changing its state when laser 72 is manually operated, and a fiber interlock 44 actuate the integrity of electrical wires, which traverse a protective shield with delivery fiber 22, is compromised, Also, a shutter control 82 is one of the input devices responding to the controller-generate commands and of course start button 28, Othcrinputs may be easily added, to the above disclosed devices.

[0030] All of the input deylces have respective contacts 39, 43, 41 and 83 receiving input signals the laser electronic controls that change the respective states of these devices. Just for the purposes of convenience, when 41 shown contacts arc normally open, a current source 58. which functions as the actuator in safety system 55, is in its safefe regime, i:e., shudder 70 is “closed and door 24 of work cell 14 is open. Obviously, one ordinary skill in thee elctronics readily realises that higmfkant structural changes itiay result in the contacts to be normally- dosed in lhe safe regime,

[0031] The logic block 30 ts conligured wiih multipl logic gates which are arranged in two groups with gases of one group being eoupled into active high signal safety channel 34 and the gates . of the other group mio active low signal.diatmel 36, The logic gates of one group are different frdm those df the other group and,along witb the dual channel structure of Iogic block 30, safety both theredundancy and diversification requirements.

[0032] The safety channel 34 transtnits high active signals (1), such as door A from first door interlock 38, key switch 42 and fiber interlock 44, respectivelyy. and deliveries these signals to an AND gate 46. For the latter to produce SAFE A. output signal, all three: active signals be all unitorm high (1), If any of the discussed input device were off, this gate would not performn its function. Formingg now to safety channel 36, its upstream gate 50 has functionality different from, , AND gafe 46 of channel 34- gate 50 is an OR gate. The. input signals into this gate are low active meaning that the OR gate's output is a cope of the input signals when the latter are all lew. Thus. OR gate 50 peiidrms its function only when all the three inputs from respective Interlocks 40, 42 and 44 are low. While Emotional diversity or corresponding gates 46 and 50 (and all subsequent matched gates of respective channels) improves the circuit's reliability, these have the same goal - to provide respective outputs only if all input devices are satisfied, i.e., open or, as fiber interlock 44, have respective outputs inverted, as sown in the exemplary schematic of FIG. 4. Accordingly, once the low active signals axe added In OR gate 50, the latter outputs an active low SAFE_B_ signall.

[0033] Any single fault does not lead to a loss of the safety .function due to the channel redundancy , but the htrdi must be detected. 'I he fault detection is achieved by the cress -monitoring operation luvolvim? two cates: an AND sate 48 of channel 34 and an OR ^ate 52 of channel 36. As exemplified by the operation of AND gate 48, one of its inputs receives active high SAFE A output carried in ehaimel 34 bom AND gain 46. The other input of gate 48 receives active low SAFE_B_ signal front OR. gate 50 of channel 36. The gate 48 is inverted which means that when the low SAFE_B_ signal is coupled mto the other inpi.it of gate 48 at channel 34, it becomes SAFE_B_ signal at the output of gate 48. The inverted OR gate 52 performs its functions When one of its inputs receives low SAFE B output from OR gate 50, and the other input gets high ALL_SAFE_A_ fr soigmna glate 46 of channel 34 which is mverted at the ompitt of gate 52. If the above conditions tor respective gates functions are met, gates 48 mid 50 output respective high ALL_SAFE_A and low ALL_SAFE_B_ signal indicating that there is no fault in either of two channels 34, 36, These two outputs then are then coupled into respective SET inputs of NAND and NOR latches 28 and 80 of safety channels 34 and 36 respectively .

[0034] Il is worth remembering that start button 28, which was previously depressed at the beginning of the process or at the restart of the system after detected emergencies, has its output sit on other SET inputs of respective latches 28. g(j which are memory devices. Accordingly, when the ALL_SAFE A and ALL SAFE_B_ signal are ooupfed into respective SET inputs of the hitches generating respective high ON and low ON signals again confinning that all input devices are satisfied.

[0035] Turning briefly to FIG. 1 and assuming, arguendo, that the above-discussed part of inventive electronic logic 55 could be utilized in system 10, if the operator intended to resume tiie high power operation, all he would need to do is to punch start button 28. Thereafter, the latches would output respective enabling signals coupled into the current source. But inventive electronic logic 55 is configured for a fully automated operation and thus should be completed to allow tins operation without human intervention.

[0036] Returning to FIG. 5, the ON / ON outputs from respective latches 78, 80 are now received in respective inputs of AND gate 74 and inverted OR gate 76. The other inputs of respective gates 74 and 76 receive a single signal from shutter control 82 and perform the intended respective functions which result in two output enabling signals EN..A and EN„B_. The enabling signals are received in the circuitry of current source 58 which changes its current high-power regime to start operating in the safe regime characterized by the reduced cunent output to the regulated safe levels. Based on the foregoing, gates 74 and 76 function as an electronic shutter, hence the entire logic system 55 is referred to as the electronic shutter logic.

[0037] After new workpiece 16 is delivered into cell 14 of FIG. 4, the transition to the high-power regime of current source 58 includes first closing door 24 and then opening shutter 70. Thereafter, current source 58 operates in the high-power regime treating just delivered workpiece 16.

[0038] The electronic shutter logic 55 is further configured with a safety circuit including OR gate 68 and gates 69 coupled info respective channels 34 and 36. This circuit functions as a circuit breaker when signals DRB_DIS_A and DRV_DIS_B_ representing an internal failure of the current source, are feedbacked into respective inputs of gates 68 and 69. The other inputs of these gates receive respective outputs from the outs of respective cross-channel referencing gates 48 and 52. The outputs of respective gates 68 are fed into RESET inputs of respective latches 78 and 80 cancelling outputs EM A and EN B... if any of the input devices or source 58 malfunctions. As a result, the laser operation is interrupted. After the problem is solved, die restart of the laser requires the manual operation of start button 28.

[0039] The features disclosed herein in accordance with the present invention, arc not limited in their application to the details of construction and the arrangement of components set forth in tiie following description or illustrated in the accompanying drawings. These aspects are capable of assuming other embodiments and of being practiced or of being carried put in various ways. Examples of specific implementations are provided herein tor illustrative purposes only and are not intended to be limiting. In particular, acts, logic elements, components, elements, and features discussed in connection with the disclosed materia! are not intended to be excluded from a similar role in any other embodiments.

[0040] Having thus described several aspects of at least one example, it is to be appreciated that various alterations, modifications, and improvements will readily occur to those skilled in the art. For instance, examples disclosed herein may- also be used in other contexts. Such alterations, modifications, and improvements are intended to be part of tills disclosure, and are intended to be within the scope of the examples discussed herein. Accordingly, die foregoing description and drawings are by way of example only.

Claims

CLAIMS:1 , A fully automated safety system for monitoring the opsratfen of a hlgh-power laser which outputs a laser beam within a west cell having an openahle deer for mbotfealiy delivering workpieces to be beam treated inside the work oelb the automated safety system cornprismg: a plurality of input devices comprising a shutter control, which automatically outputs a shutter signal, and two door interlocks which output respective active high and few signals prior to opening the door of the work cell; a logic block receiving, active high, active low and shuter output signals, the logic block being configured to efeetromcahy process the received signals and output two enabling signals if the- shutter control and door Interlocks are satisfied; and a current source operable to output a low current output in a safe regime upon receiving the two enahhng signals and autuinaiiealiy switchable in a normal regime with a high currem output without human Intervention after a workpiece is delivered into the cell and the door is closed.

2. The automated safety system of claim 1, wherein the input devices further include a fiber interlock, keyswitch and start barton each in eieotrome commanioafion with the active high and low signal safely channels,3. The automated safety system ofvlaim fiywhereia the logic block is configured with two safety channels transmitting respective active high and low signals from the input devices, a plurality of logic elements arranged in two groups. the logic elements of each group being connected to one another in series and coupled into one or the other safety channel, fee logical elements of respective groups being costfigmed to provide diversification of the safety system.

4. The automated safety system of claim 3, wherein the logical elements of one of the groups include an upstream AND / gate receiving outputs of respective one door interlock, fiber interlock and keyswitch, art intermediary inverted AND gate, an electronic N AND latch and a downstream AND gate ail eoopled imo the active high safety channel.5, The automated safely system of claim -f wherein the logical demerits of fee other group include an upstream OR gate receiving the other of regular or inverted outputs of respective other door interlock, fiber interlock and the keyswitch, an intermediary inverted OR gate, a NOR electronic fetch and a downstream inverted OR gate all counted into the active low safety channel.6, The automated safety system of claim 4, wherein the intermediary inverted AND and OR logical elements each have two inputs, the inputs of the ifeermediary AND gate are coupled to the output of the upstream OR and the output of the upstream AND gate respectively, the inputs of the intermediary OR gate are coupled to the output of the upstream AND gate and the output of the upstream OR gate respectively, wherein the intermediary inverted AND and OR gates provide a cross-channd reference check.

7. The automated safety system of claim T wherein the NAND and NOR electronic latches each have two SET inputs receiving an input signal from the start button and respective otdpuis of fee intermediary AND and OR gates, the input signal from the start button being memorized by the NAND and NOR fetches, wherein ON and ON outputs of respective electronic latches indicate that the input devices of the active high and low signal safety channels are all satisfied.

8. The automated safely system of claim A wherein outputs of respective downatrwn ADD, OR gates in response to reeving respective oifiptris from the electronic fetches and shatter control output two enahdng signals rcdimdanily coopted into and prompting the current source to change the operation in the normal regime io the one in lite safe regime, wherein (he downstream AND and OR gates function as an eleetromc shutter,9. The automated safety system of claim 1 , wherein lite logic block is feather configured lo de- energize the current source if any of the input devices is not satisfied or the current source experiences an internal failure, the manual start button being manually •momentarily depressed hrfbre the current so uree i s energized .

10. The automated safety system of claim 9, whetoin the logic is configured with first and second feedback circuits imnstoitttog respective signals ffrom tite current sourcee :to one inputs of respective safety AND and inverted OR gates the other inputs of respective safety AND: and Inverted OR gates being coupled to high and low signal safely channels.11 The automated Safety System of claim 10, whereto outputs of respective safety -AND and

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