Patent Application
20060068696
The present invention generally relates to optoelectronic presence sensing devices, and particularly relates to the use of forced air systems to facilitate the maintenance and operation of such devices.
Optoelectronic presence sensing devices find wide use in a variety of industrial applications. For example, one prevalent use arises in the context of “machine guarding,” wherein the object detection functionality of such presence sensing systems provides a triggering mechanism for shutting down hazardous machines before personnel get too close. Because of the safety-critical nature of this type of application, the installation, testing, and ongoing maintenance of such presence sensing systems represent vital functions.
Other critical uses of such presence sensing systems include vehicle navigation and/or collision avoidance systems. For example, a shop floor forklift or other utility vehicle may be configured with one or more optical presence sensing systems that aid its operator in avoiding hazards or, in more sophisticated embodiments, provide for limited or full autonomous vehicle movement.
Regardless of their particular uses, optoelectronic presence sensing systems characteristically use some type of optical emitter, a corresponding optical receiver, and supporting power and control electronics. Optical energy emitted from a presence sensing device is directed into or through a field of view and objects within that field of view are detected based upon sensing return reflections from them. Object distance can be calculated by timing the round trip time of the outgoing and reflected light signals, and that distance can be compared to one or more pre-programmed thresholds to determine whether the encroachment merits a safety response.
Understandably, the operation of such devices can be compromised by the buildup of dust or other contamination on any device surfaces through which outgoing or reflected optical signals must pass. For example, a given device typically uses one or more optically transparent “viewing” windows through which its optical signals are passed and any contamination of these windows can reduce device sensitivity and/or trigger the detection of a device fault.
Device faults can be costly because one or more production machines typically are tied in with a given presence sensing system, and these machines typically are automatically taken offline for the duration of any presence sensing fault condition. As such, the buildup of contamination on the viewing windows of optoelectronic presence sensing devices raises a number of safety and efficiency issues in the typical manufacturing environment.
The present invention comprises a method and apparatus to reduce the surface contamination of a viewing window of an optoelectronic presence sensing device, such as the “scanning” window of a laser scanner as might be used in hazardous machine guarding applications or in object avoidance system applications. More particular, the present invention uses an air guard that is supplied with a source of pressurized air to vent air toward the viewing window to reduce the surface contamination thereof. The air guard may be configured such that it blows air across or in front of the window such that airborne contaminates generally are prevented from settling on the window. Additionally, or alternatively, the air guard may be configured such that it blows more focused and/or higher velocity air streams toward the viewing window toward the window surface to remove contaminants from the window's exterior surface. More generally, the air guard can be configured to direct air toward or across the window's surface in modulated (time varying) patterns and amplitudes as needed or desired.
Thus, according to an exemplary embodiment, an air guard for reducing surface contamination of a viewing window of an optoelectronic presence sensing device comprises a body section generally conforming to a contour of the viewing window, a first chamber formed within the body section and configured to receive pressurized air from an external source, and one or more first outlets in the body section configured to vent the pressurized air from the first chamber toward the viewing window to reduce surface contamination thereof. The body section may be integrated with the device housing of the presence sensing device, or may be affixed thereto, either permanently or removably. Indeed, air guards may be built as optional add-ons for particular models of presence sensing devices, or may be built into such devices.
In another exemplary embodiment, the present invention comprises an air guard for reducing surface contamination of a viewing window of an optoelectronic presence sensing device. The air guard comprises a body section generally conforming to a contour of the viewing window, first and second chambers formed within the body section, each configured to receive pressurized air from an external source, one or more slits formed in the body section and configured to vent pressurized air from the first chamber in a curtain like flow in front of the viewing window, and one or more nozzles formed in the body section and configured to vent pressurized air from the second chamber in one or more generally focused air streams directed toward the viewing window.
This exemplary air guard can be configured selectively to operate in a preventive mode wherein it vents air from the slits to create a curtain like air flow in front of the window, or in a cleaning mode wherein it vents air from the nozzles to create directed air flows that clean the window surface. The air guard may include or be associated with one or more control valves that provide operating mode control, and which may be configured to include the option of selectively blocking pressurized air from the air guard so that it can be operated in a standby mode. Mode control may be effected according to a timed schedule and/or may be controlled by the presence sensing device, an external controller, or by a control circuit included in the air guard itself.
With these control aspects in mind, then, an exemplary embodiment of an air guard according to the present invention may comprise an air guard body section with one or more chambers and corresponding vents or outlets, and a control circuit configured to enable selective pressurization of the one or more vented chambers to effect a desired air flow pattern with respect to an optical window of the optoelectronic presence sensing device. The control circuit may be implemented in whole or in part within the air guard enclosure or implemented in whole or in part externally, such as in the optoelectronic presence sensing device or in a control system remote from the air guard. The particular implementation of the control circuit, which may include a microprocessor, Field Programmable Gate Array (FPGA), Application Specific Integrated Circuit (ASIC), Complex Programmable Logic Device (CPLD), or other such processing circuit, depends to some extent on the number and configuration of air chambers and control valves involved, and on the sophistication of any time-varying air flow control algorithms implemented.
Regardless, an exemplary optoelectronic presence sensing system comprises an optoelectronic presence sensing unit configured to detect objects by emitting optical signals through a viewing window and detecting return reflection signals therefrom, and an air guard unit configured to direct air generally toward the viewing window of the optoelectronic presence sensing unit to reduce exterior surface contamination thereof. The air guard may be configured according to the previously mentioned exemplary details, and may be integrated with a housing of the optoelectronic presence sensing unit, or affixed thereto.
Independent of any particular physical embodiments, the present invention further comprises a method of maintaining a viewing window of an optoelectronic presence sensing device with respect to window contamination. In an exemplary embodiment, that method comprises providing an air guard proximate to the viewing window of the presence sensing device, supplying the air guard with pressurized air, and selectively operating the air guard in a preventive mode wherein it vents the pressurized air in a generally laminar flow in front of the viewing window to prevent airborne contaminants from settling thereon, or in a cleaning mode wherein it vents the pressurized air in one or more directed air streams toward the viewing window to remove deposited surface contaminants thereon. Again, such operation may be controlled by the presence sensing device, by the air guard itself, or by an external controller.
Of course, the present invention is not limited to the above features and advantages. Those skilled in the art will recognize additional features and advantages of the present invention upon reading the following detailed description and upon viewing the accompanying figures, in which like elements are assigned like reference numbers.
In operation, the air guard 14 prevents the deposition of airborne contaminants (dust, oil, etc.) on an exterior surface of a viewing window 18 of the presence sensing device 12 by creating a laminar air flow in front of window 18 and/or cleans the exterior of window 18 by directing one or more streams of air at the window 18. By preventing contamination of window 18 and/or by at least partially removing surface contaminants from window 18, air guard 14 improves the operation of presence sensing device 10. That is, use of air guard 18 can reduce the frequency at which maintenance personal must clean window 18 and makes viable the use of presence sensing device 12 even in areas with substantial amounts of dust and/or mist.
With respect to such use, one typical application of presence sensing device 12 is as a “guarding” mechanism in and around hazardous machinery. In that role, presence sensing device 12 may be configured to remove power from a hazardous machine, or otherwise stop its hazardous moving parts, in response to detecting the encroachment of an object, e.g., a person, into a designated zone of danger. To that end, the typical presence sensing device uses some type of optoelectronic transmitter/detector arrangement that transmits optical signals outward through the viewing window 18. Objects within a defined detection range of the device 12 return reflected optical signals, which are received through the viewing window 18, and detected by the appropriate circuitry within device 12.
Such circuitry may include calculation units that translate detection signal transit times and angles into relative distances and directions, thus enabling the device 12 to determine whether any detected objects are within the zone of danger. Of course, device 12 may be used in other applications, such as in object detection and avoidance applications that, for example, include the use of presence sensing systems on factory floor vehicles to facilitate vehicle movement in potentially crowded industrial settings. Additional exemplary but non-limiting details for presence sensing device 12 may be found in U.S. application Ser. No. 09/934,352, filed on 21 Aug. 2001 and entitled “Presence Sensing System and Method.” That application is co-pending and commonly assigned with the instant application, and is incorporated herein by reference in its entirety.
However, it should be understood that exemplary details regarding the optoelectronics implemented in device 12 are not limiting with respect to the present invention. Thus, as used herein, the term “optoelectronic presence sensing device” encompasses diffuse sensing systems, such as those based Charge-Coupled Detectors (CCDs), and scanning systems, such as those using rotating mirror-based laser scanner assemblies.
In any case, turning to the exemplary details as illustrated in
In operation, pressurized air is supplied to the air guard 14 from an external source (not illustrated), which may be provided to air guard 14 through air supply hoses coupled to one or more air inlet ports—two such inlet ports, ports 28 and 30, are illustrated. Note that ports 28 and 30 may include body ferrules for more secure coupling of the air supply lines.
As is seen in the partial cut-away view of
When pressurized air is supplied to chamber 32 via inlet port 28, that pressurized air is vented through the one or more slits 24, which are configured to create a generally laminar flow in front of viewing window 18—illustrated as the roughly vertical air currents in the drawing. That laminar vertical flow in front of window 18 acts like an “air curtain” that at least partially prevents airborne contaminants from settling onto the exterior surface of window 18. Thus, the air guard 14 may be understood as operating in a “prevent” mode when it is venting pressurized air from the one or more slits 24, in that the curtain-like air flow created in front of window 18 prevents at least some contaminants from settling onto the exterior surface of the window. Note that, preferably, the one or more slits 24 comprise one or more long slits generally running the length of the viewing window's bottom edge, or at least spanning the perimeter length of the viewing window 18 that corresponds to the field of view being monitored by device 12.
When pressurized air is supplied to chamber 34 via inlet port 30, that pressurized air is vented through the one or more nozzles 26, which may be configured as a plurality of spaced apart holes generally arrayed along the bottom perimeter of window 18. As seen in
Preferably, the nozzles are configured such that there is some overlap between the directed air streams emitted therefrom, to ensure that a contiguous cleaning pattern is formed by the combination of air streams. That is, the nozzles preferably are arranged to prevent gaps between the areas cleaned by each particular nozzle 26. As with the one or more slits 24, the number and positioning of nozzles 26 may be set up to span the bottom edge of window 18, or at least to span the length of window 18 corresponding to the desired field of view for device 12.
While the above configuration illustrates an exemplary air guard body system defining two chambers 32 and 34, with corresponding air inlets 28 and 30, it should be understood that air guard 14 may be implemented with one chamber, two chambers, or more than two chambers, and that each chamber can be vented through differently positioned and/or differently configured outlets, such that variable air flow patterns and velocities can be achieved by pressurizing different ones of the chambers individually or in desired combinations. Each chamber can be configured with its own inlet, in which case control valves can be omitted if desired, and wherein supplying air through the appropriate air hose pressurizes the corresponding chamber. However, whether each chamber has its own air inlet, or two or more chambers share an air inlet, the use of control valves within the air guard 14 still may be desirable as it allows the hose or hoses to remain pressurized while air is shut off from the chambers.
In any case,
Thus, during times when the preventive air flow across window 18 is not needed, control valve 36 may be closed to block pressurized air from flowing into chamber 32. Similarly, cross section 6-6 shown in
Continuing with a discussion of the cross section views,
In considering the above details, it should be understood that the control valves 36 and 38 can be omitted if flow control is not needed or desired. Further, in at least one embodiment, the control valves 36 and 38 may be configured such that chambers 32 and 34 are operated in mutually exclusive fashion. Thus, if the air flow into chamber 32 is on, then the air flow into chamber 34 is off, and vice versa. With that configuration, the air guard 14 operates in either the prevent mode (i.e., the air curtain mode), or in the cleaning mode (i.e., the contaminant blow-off mode), responsive to one or more valve control signals.
Further, as shown in
In such an embodiment, a cable 48 may be connected to the input terminal 46 of air guard 14, such that an external controller (not shown) and/or device 12, may provide one or more valve control signals to air guard 14 to control air flow into one or both chambers 32 and 34 as needed or desired. In an exemplary embodiment, input terminal 46 may include power, ground, and control connections, but such details are implementation specific and can be varied as needed.
If an external controller is used to control air guard 14, it may be convenient to configure terminal 46 for easy field access. However, it should be understood that terminal 46 still may be recessed and/or covered for reliability reasons and for the option of operating in a wet or damp environment. Further, if device 12 is used to control operation of air guard 14, then any electrical interconnections between air guard 14 and device 12 may be made through one or more internal wiring connections, such that external wiring connections are not required. Such an arrangement may be particularly convenient where air guard 14 is formed integrally with housing 16 of device 12. Even if air guard 14 is not integrally formed with housing 16, the inside face of body section 20 of air guard 14, and a corresponding mating surface of housing 16, each may be configured with complementary electrical mating connectors, such that mounting or fastening air guard 14 to housing 16 provides for any desired signal interconnection between the two items.
In general, the number of signal interconnections implemented can be varied according to the configuration of the air guard. For example, in one or more of the above embodiments, air guard 14 included two air chambers 32 and 34, with one used for blowing an air curtain to reduce dust accumulation on the window, and one used for blowing more focused, cleaning air streams toward the window. Air guard 14 can provide separate signal control inputs to actuate these different modes and, extending that concept further, it should be understood that air guard 14 can include multiple chambers, possibly with each chamber having a different arrangement or configuration of air outlets. In such configurations, then, air guard 14 can be configured with additional signal lines, or possibly with an intelligent control interface (e.g., a command/data bus interface) that permits external actuation of the different chamber/nozzle combinations to effect a desired, possibly time-varying, air flow pattern for cleaning and/or guarding the window.
Regardless of such details,
In either case, control circuit 50 may be configured to assert one or more valve control signals for controlling air flow from air guard 14 as a function of window contamination. In an exemplary embodiment, control circuit 50 is configured to switch air guard 14 from a standby mode (no air flow), or from the prevention mode (air flow from slits 24), to a cleaning mode (air flow from nozzles 26), in response to detecting a given level of window contamination. Thus, the cleaning operation of nozzles 26 could be temporarily enabled responsive to sensing a buildup of contamination on window 18. In a similar variation of this embodiment, the control circuit 44 of air guard 14 can be configured to have at least limited control decision logic and thus can be configured to provide selective activation responsive to receiving dust detection information from device 12, or from an external controller that has access to data or signals from device 12.
It should be understood that the term “control circuit” as used in the above paragraphs in the context of device 12 and/or air guard 14 broadly connotes hardware, software, or some combination thereof. Thus, it should be understood that control circuit 44 of air guard 14 and/or control circuit 50 of device 12, each may be implemented using discrete logic circuits, integrated logic circuits, or other hardware circuits, or may be implemented functionally based on stored program instructions as executed by one or more microprocessors or other digital processing circuits. Such details are implementation dependent, based on cost considerations and the desired level of control functionality, and thus should not be considered as limiting the present invention.
Indeed, as shown in an exemplary embodiment of the present invention illustrated in
As a further illustration of the range of control methods contemplated by the present invention,
In any case, exemplary processing begins with default operation in the prevention mode (air flow from slit(s) 24 enabled) (Step 100). Of course, standby (no air flow) could be the default starting mode. In any case, a timer, denoted as TIMER1, is initialized to time the interval at which it is desired to temporarily switch air guard 14 from operating in the prevention mode, to operating in the cleaning mode (air flow from nozzles 26) (Step 102).
Control logic then checks for expiration of TIMER1 (Step 104). Upon such expiration, control logic actuates one or more control valves in air guard 14—alternatively, the control valves can be located in or associated with the air supply lines feeding air guard 14 for convenient external control—to switch air flow from slits 24 to nozzles 26 (Step 106). That is, upon expiration of TIMER1, air guard 14 temporarily is switched from prevention mode to cleaning mode and a second timer, denoted as TIMER2, is initialized/started (Step 108).
The cleaning mode of operation is maintained until expiration of TIMER2 (Step 110), at which point operation reverts back to the prevention mode (Step 112). That is, TIMER1 may be reinitialized/re-started and the above operations repeated. Of course, standby periods where no air flows from air guard 14 may be incorporated into the above logic as needed or as desired, and, as noted earlier herein, air guard 14 may be operated non-modally, such that air flows continuously from slits 24 and nozzles 26 so long as pressurized air is supplied.
Rather than the above timed operation,
In any case, once cleaning mode operation ends or times out (Step 118) operation reverts back prevention and/or standby mode operation (Step 120), and the process repeats responsive to detecting and subsequent build-up of window contamination. Note that the detection-based processing of
Thus, in relatively clean environments, system 10 could save pressurized air resources by remaining in standby mode for longer periods. Conversely, in relatively dirty environments, system 10 may run in prevent mode more or less continuously, with frequent cleaning mode switchovers. Of course, system 10 can be configured so that such timer settings are manually settable, so that installation personal can “tune” the operation of system 10 for the needs of a particular installation location.
Further, it should be understood that control circuit 44 of air guard 14 and/or control circuit 50 of device 12 can be configured to implement guarding/cleaning modes of essentially any desired degree of sophistication, particularly when air guard 14 is implemented with multiple chambers/nozzles that provide a number of different cleaning and/or guarding patterns, or with nozzle/outlet configurations that enable time-varying flow types and directions. Thus, it should be understood that control circuits 44 or 50 can be configured with various timing algorithms, time-varying air flow pattern algorithms, and time-varying air flow amplitudes, as needed or desired.
Along these lines, the present invention also contemplates the use of a controllable air source, such that flow rate and/or pressure can be varied to effect different modes of air guard operation. For example, a low flow rate can be used for general contamination protection, and a high flow rate can be periodically provided for brief cleaning intervals.
In general, then, air guard 14 can be configured with one or more chambers that vent through multiple outlets (nozzles) that provide multiple cleaning “channels” at multiple angles with respect to the device window. With the ability to direct different streams at different angles, air guard 14 may be operated according to sophisticated cleaning algorithms that vary the time, direction, and/or intensity of cleaning air directed toward the device window.
From the variations described immediately above, and from the various embodiments described throughout this document, those skilled in the art should appreciate that the present invention contemplates a variety of physical and functional embodiments for system 10. As noted, air guard 14 may be separate from device 12, and may be permanently or removably attachable thereto, or may be integrated into the housing 16 of device 12. It may, by way of non-limiting examples, be operated in a continuous air flow mode, or may be operated in one or more of standby, prevention, and cleaning modes. Such variations may be based on timed schedules and/or based on sensing contamination.
Additionally, it should be understood that air guard 14 can be configured for use with a variety of optoelectronic presence sensing devices. While the illustrated device 12 is, by way of non-limiting example, configured as a laser scanner, device 12 may comprise another type of device. For example, device 12 may comprise a “light curtain,” which in an exemplary embodiment comprises one or more linear transmitter segments (“sticks”) and one or more corresponding receiver segments. The transmitter segments generally include an optical face through which an array of optical transmitters transmit individual beams, and the corresponding receiver segments generally include an optical face through which an array of optical receivers detect the beams from respective ones in the transmitter array.
Air guard 14 could be configured for attachment to light curtain segments such that guarding/cleaning air is directed across the optical faces of such segments. Also, if desired, the light curtain control electronics can be used to control or otherwise trigger operation of the air guard 14 in such configurations.
Finally, it should be understood that air guard 14 can be configured to include its own control/timing logic, e.g., control circuit 44, such that it operates wholly, or at least partly, autonomously with respect to alternating between preventive modes and cleaning modes, and with respect to varying the cleaning patterns and flow velocities as needed or desired. Alternatively, air guard 14 may be simplified in favor of implementing control logic for its operation in external logic. If the control logic is implemented apart from air guard 14, its signal interface can be configured to provide for externally controlled actuation of its various chambers and nozzles in desired combinations.
Such external logic may be implemented in the device to which air guard 14 is attached, which may be a particularly suitable arrangement where that device triggers air guard cleaning operations responsive to detecting contamination of its viewing window. However, it should be understood that such logic can be implemented remotely, such as in a remote controller of a factory floor control system. To that end, air guard 14 may be configured with a direct control interface (e.g., discrete signal lines, dry contacts, signaling current loops, or other suitably robust signal interface), or with an intelligent bus or network interface (e.g., CAN Bus, Safety Bus, IIC Bus, RS-422, etc.) through which air guard mode control signals or commands are sent. In such embodiments, the earlier illustrated air guard control circuit 44 can be configured with the appropriate bus interface/isolation circuits and bus control/command logic as needed.
Thus, it should be understood that the present invention is not limited by the foregoing description or by the accompanying drawings. Instead, the present invention is limited only by the following claims, and the reasonable equivalents thereof.
