Abstract:
A drive-over tire tread depth measurement system is configured with environmental protection components for preventing or impeding environmental contaminates from falling through openings in a vehicle support surface or cover plate onto underlying components such as sensor optical windows and adjacent surfaces. The environmental protection components may include air discharge assemblies, movable shields, guards, wipers or deflectors such as drip edges, water-accumulating textured surfaces, flow diverters, and selectively placed flanges or fixed guards which operate cooperatively to displace accumulated contaminates, debris, or liquids from the optical windows and adjacent sensor surfaces. A portion of the vehicle support surface or cover plate is removable to permit access to underlying components.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of, and claims priority from, co-pending U.S. patent application Ser. No. 14/185,181 filed on Feb. 20, 2014, and which in turn is related to, and claims priority from, U.S. Provisional Patent Application Ser. No. 61/768,194 filed on Feb. 22, 2013. Each of the aforementioned applications are incorporated herein by reference. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH 
     Not Applicable. 
     BACKGROUND OF THE INVENTION 
     The present invention is related to optical sensors disposed within a surface over which vehicles are driven, which are exposed to environmental conditions, and in particular, to methods and apparatus for protecting optical surfaces from environmental debris and for the automatic clearing of accumulated environmental debris from the optical surfaces. 
     The use of optical sensors for the acquisition of data associated with motor vehicle are becoming prevalent in the automotive service industry and for use in monitoring vehicular traffic. For some applications, such as the acquisition of data associated with vehicle wheels, and in particular, tire conditions, the optical sensors are disposed in, or below, a supporting surface over which the vehicle wheels roll, such as a roadway surface, vehicle service bay floor, or vehicle service/inspection support structure. Embedded or drive-over optical sensors may include components for projecting illuminating energy towards and onto the surfaces of a passing vehicle, as well as receiving components for capturing reflected energy from the passing vehicle. For example, some tire tread depth measurement systems consist of a laser emitter configured to project a laser light onto or across the surface of a tire passing over the optical sensor, and a cooperatively configured imaging sensor disposed in proximity for acquiring images of the projected laser light reflected from the passing tire. 
     Optical sensors disposed in a drive-over configuration, where a vehicle is driven or rolled over the sensor, are typically contained within a sealed housing having one or more panels of optically transparent material such as glass or plastic through with illuminating light is projected and/or reflected light is observed. While such sealed housings function well to provide protection against water or debris intrusion and damage to the sensors, performance of the sensors can be degraded to the point of inoperability by the accumulation of environmental contaminants, such as dust, dirt, rocks, salt, and water on the optically transparent panels. Such accumulations of environmental contaminates can occlude the optical lines of sight for both emitter components and imaging components. 
     Accordingly, it would be advantageous to provide optical sensors, disposed in a drive-over configuration, with components for preventing or impeding environmental contaminates from falling onto the panels of optically transparent material and adjacent sensor surfaces. The mechanisms may be either active mechanisms, in the form of movable shields, guards, or deflectors, or passive components such as drip edges, water-accumulating textured surfaces, flow diverters, or selectively placed flanges or fixed guards. 
     It would be further advantageous to provide optical sensors, disposed in a drive-over configuration, with a mechanism for selectively shielding the panels of optically transparent material during periods of inactivity. In one embodiment, the shielding mechanism is recessed below the surface over which a vehicle is driven in order to isolate the shielding mechanism from direct contact with the vehicle wheels. 
     It would be further advantageous to provide optical sensors, disposed in a drive-over configuration, with a mechanism for cleaning and/or clearing of environmental contaminates from the exposed surface of the panels of optically transparent material and adjacent surfaces. 
     BRIEF SUMMARY OF THE INVENTION 
     Briefly stated, the present disclosure sets forth a mechanism for selectively shuttering openings in a vehicle supporting surface through which underlying optical sensors emit or receive light energy during acquisition of data associated with vehicle. The mechanism includes at least one shutter panel which is selectively movable between an open position, in which the opening is unobstructed, and a closed position in which the opening is at least partially blocked by the shutter panel to prevent or deflect environmental contaminates such as dust, dirt, rocks, salt, or water from passing downward through the openings and onto the surface of the underlying optical sensors. When in the closed position, the shutter panel remains recessed below the vehicle supporting surface. 
     In an alternate embodiment, optical sensors disposed below a vehicle supporting surface in a drive-over configuration are protected against environmental contaminates by passive components such as drip edges, water-accumulating textured surfaces, flow diverters, selectively placed flanges and/or fixed guards which are disposed on various surfaces below the vehicle supporting surface, in proximity to openings there in through which the optical sensors transmit or receive light. 
     In a further embodiment, optical sensors disposed in a drive-over configuration are provided with a mechanism for cleaning and/or clearing of environmental contaminates from surfaces disposed below the openings in the vehicle supporting surface. The mechanism may be operated periodically on a selected cycle, upon each use by activation of a drive-over trigger, or on an as-needed basis, controlled either by the operator or a feedback system evaluating the integrity of emitted and/or reflected light at the optical sensor. To clean and/or clear the environmental contaminates from the surfaces, the mechanism selectively discharges a flow of high-pressure air or an air/fluid mixture across the surfaces to be cleared or cleaned, to transport accumulated debris off the surfaces and into an adjacent discharge region. 
     The foregoing features, and advantages set forth in the present disclosure as well as presently preferred embodiments will become more apparent from the reading of the following description in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       In the accompanying drawings which form part of the specification: 
         FIG. 1  is a perspective illustration of an embodiment of a drive-over tire tread depth optical sensor system; 
         FIG. 2  is a perspective illustration of the vehicle support surface/cover plate of an embodiment of the drive-over tire tread depth optical sensor system; 
         FIG. 3  is a perspective illustration of an embodiment of the drive-over tire tread depth optical sensor system, with the vehicle support surface/cover plate removed, showing the sensor housing with environmental protection features installed adjacent one pair of optical windows only for comparison; 
         FIG. 4  is a perspective illustration of another embodiment of the drive-over tire tread depth optical sensor system, showing a sensor housing with a complete set of environmental protection features installed; 
         FIG. 5  is a side sectional view of an embodiment of the drive-over tire tread depth optical sensor system, illustrating the optical field of view and laser projection pathway through the openings in the vehicle support surface/cover plate; 
         FIG. 6  is a close-up view of a portion of  FIG. 5 , illustrating placement of drip guards, gutters, and a mechanical shutter in the open position; 
         FIG. 7  is a close-up section view similar to  FIG. 6 , illustrating the placement of drip guards, gutters, and a mechanical shutter in the closed position; 
         FIG. 8  is a close-up side section view of an embodiment of the drive-over tire tread depth optical sensor system, illustrating cover plate features, gutters, deflecting lips and baffles; and 
         FIG. 9  is a representation of the angular relationships between a surface of an approaching vehicle wheel, a vehicle air dam, the laser projection pathway, and the optical field of view from the drive-over tread depth optical sensor system of the present disclosure. 
     
    
    
     Corresponding reference numerals indicate corresponding parts throughout the several figures of the drawings. It is to be understood that the drawings are for illustrating the concepts set forth in the present disclosure and are not to scale. 
     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. 
     DETAILED DESCRIPTION 
     The following detailed description illustrates the invention by way of example and not by way of limitation. The description enables one skilled in the art to make and use the present disclosure, and describes several embodiments, adaptations, variations, alternatives, and uses of the present disclosure, including what is presently believed to be the best mode of carrying out the present disclosure. 
     Turning to the Figures, and to  FIGS. 1 and 2  initially, an exemplary drive-over tire tread depth optical sensor system is shown generally at  100 . The sensor system consists of a vehicle support surface  102  for supporting the wheels of a vehicle being driven over the sensor system. A cover plate or deflector  103  may be disposed on a portion of the vehicle support surface  102 , and configured to divert water accumulating on the vehicle support surface  102  from entering the sensor system  100 . Suitable ramps  102   a ,  102   b  may be provided if the sensor system  100  is disposed on a floor surface. Alternatively, the sensor system  100  may be disposed in a recessed portion of a floor or roadway surface, with the vehicle support surface  102  substantially coplanar with the adjacent floor or roadway surfaces. Suitable trigger mechanisms  104   a ,  104   b  for activating the sensor system  100  may be incorporated into the vehicle support surface  102 , ramps  102   a ,  102   b , or adjacent floor or roadway surfaces. The entire vehicle support surface  102 , or at least a portion thereof, may be configured to be opened or removed, allowing access to the underlying components of the sensor system for manual cleaning, repair, or replacement as necessary from time to time. 
     As seen in  FIGS. 3 and 4 , the various electronic and optical components which comprise the sensor system  100  are disposed within an environmentally sealed sensor housing  106 , positioned below the vehicle support surface  102  and/or cover plate  103 . The sensor housing  106  may be mounted directly on the underlying base structure, or may be mounted in a configuration which is biased against an underside surface of the vehicle support surface  102  and/or cover plate  103  to maintain a predetermined position and orientation relative to the vehicle support surface  102  and/or cover plate  103  which may undergo deflection under load from a passing vehicle. 
     Optical components (not shown) disposed within the sealed sensor housing  106  are positioned and oriented to transmit and/or receive light along associated fields of view through one or more optical windows  108  which are disposed in the upper surface of the sealed housing  106 . In the embodiment shown in the Figures, a total of four optical windows  108   a - 108   d  are shown in the sensor housing  106 , arranged in 2×2 grid configuration. With a longitudinal axis aligned in the normal direction of vehicle travel over the sensor system  100 , the longitudinally forward optical windows  108   a ,  108   b  (those over which the vehicle will pass first in the normal direction of travel) in each longitudinally aligned pair of optical windows is associated with an optical imaging sensor (not shown) for acquiring images from an associated field of view oriented towards the approaching vehicle. The longitudinally rearward optical windows  108   c ,  108   d  in each longitudinally aligned pair of optical windows is associated with a laser emitter system (not shown) for projecting laser illumination along an optical axis towards the tire tread surface of a vehicle passing over the vehicle support surface  102  and/or cover plate  103 . The laser emitter system is aligned to illuminate the tire tread surface of an approaching vehicle within the field of view of the associated optical imaging sensor. 
     As best seen in  FIGS. 5 and 9 , the fields of view and optical axis associated with each pair of longitudinally aligned optical windows  108  are aligned at acute angles relative to the vehicle support surface  102  or cover plate  103 , and pass through suitably sized openings  110  in the vehicle support surface  102  or cover plate  103 . The acute angles are selected to enable the laser optical axis to intersect the surface of an approaching vehicle tire within a region on the tire surface which falls within the optical imaging sensor field of view, before the vehicle tire is directly over the optical windows  108   a - d , and which is at a sufficient angle to avoid obstruction from adjacent vehicle body components, such as an air dam or mud flaps. Those of ordinary skill will recognized that the number and arrangement of the optical windows  108  may vary depending upon the particular configuration of the sensor system  100 . 
     In the embodiment illustrated in  FIGS. 1 and 2 , it will be noted that a driver-over trigger mechanism  104   a  or  104   b  is disposed to activate the sensor assembly  100  as a vehicle wheel approaches the openings  110 , and that the laser optical axis and the optical imaging sensor field of view are oriented to intersect a leading edge of the tire tread surface as the tire rotates towards the openings  110  when the vehicle is driven in the forward direction. With this configuration, an increasingly larger portion of the optical sensor field of view is occupied by the tire tread surface as the vehicle moves forward, increasing the shielding of the optical imaging sensor from external light sources, such as the sun, which could result in glare or noise in images acquired by the optical imaging sensor. An additional benefit of acquiring images from the tire tread surface as the vehicle travels in the forward direction towards the sensor windows  108   a ,  108   b  is that there is a reduced chance for either the laser optical axis and/or the imaging sensor field of view to be obstructed by a vehicle body component. Typically, lower body panels and/or mud flaps disposed on the rearward side of vehicle wheels will reduce the amount of the tire surface visible to the optical imaging sensor field of view if a vehicle approaches the sensor windows  108   a ,  108   b  in a reverse direction. 
     The acute angles of the laser optical axis and the optical imaging sensor field of view relative to the vehicle support surface  102  or cover plate  103  permit the optical windows  108  in the sensor housing  106  to be longitudinally displaced relative to the corresponding openings  110  in the vehicle support surface  102  or cover plate  103 , as best seen in  FIG. 5 . As such, environmental contaminates or debris falling directly downward into the unobstructed openings  110  in the vehicle support surface  102  or cover plate  103  generally will not land on the optical windows  108 , but will accumulate on the upper surface of the sensor housing  106  in adjacent proximity there to. Absent any preventative measures, the accumulated environmental contaminates may flow or migrate onto the exposed upper surfaces of the optical windows  108 , degrading system performance and/or occluding either the laser optical axis or optical imaging sensor field of view. 
     Turning to  FIGS. 3 and 4 , a variety of features and preventive measures are employed in association with the sensor housing  106 , vehicle support surface  102 , and the cover plate  103  for protection of the optical surfaces from an accumulation of environmental contaminates and debris. It will be understood that while the present disclosure illustrates specific protective features, sensors systems  100  may incorporate different protective features described herein, as well as different numbers and combinations of the described protective features as necessitated by the sensor system configuration and operating conditions without departing from the scope of the present disclosure. 
     Environmental contaminates and debris falling directly through the openings  110  in the vehicle support surface  102  or cover plate  103  may be captured within one or more gutters  112  disposed on the upper surface of the sensor housing  106  between the optical window pairs ( 108   a ,  108   d ) and ( 108   b ,  108   c ), in vertical alignment with the openings  110 . Preferably, each gutter  112  extends parallel to the optical windows  108 , and includes raised sidewalls  113  which are continuous along each longitudinal edge. As best seen in  FIGS. 5 and 8 , one or more of the raised sidewalls  113  of each gutter  112  have a maximum height and/or optional contoured upper edge  113   a  formed into a baffle or deflecting lip, which is limited by the laser optical axis and/or optical imaging sensor field of view, ensuring an unobstructed line of sight for the laser emitters or optical imaging sensors between the optical windows  108  and the associated vehicle support surface or cover plate openings  110 . Environmental contaminates or debris deposited into the gutters  112  are prevented from migrating or flowing onto the optical windows  108  by the sidewalls  113 , and are directed in a generally lateral direction for discharge off the side edges of the sensor housing  106 . 
     When the sensor system  100  is not acquiring images or in use, some or all of the openings  110  in the vehicle support surface  102  or cover plate  103  may be fully or partially closed by actuated shutters  114 . As best seen in  FIGS. 3, 4, 6, and 7 , an actuated shutter  114  associated with at least one of the openings  110  may be mounted to the sensor housing  106 , together with an associated actuation mechanism. The actuation mechanism may include a shutter actuator  116  linked by a mechanical coupling  117  to a shutter actuation cam  118  for articulating movement of the actuated shutter  114  between an open position (shown in  FIGS. 3, 5, 6, 8 ) and a closed position (shown in  FIGS. 4, 7 ) which at least partially closes an opening  110  in the vehicle support surface  102  or cover plate  103 . The actuation mechanism as shown in  FIGS. 3 and 4  is pneumatically operated, suitably coupled to a remote source of pressurized air. Those of ordinary skill in the art will recognize that a wide variety of actuation mechanisms may be utilized, including mechanical, electrical, and hydraulic systems. Similarly, while  FIGS. 3-7  illustrate the use of the shutter actuating cam  118  coupled to the mechanical coupling for articulating the movement of each shutter  114  between an open position and a closed position, any of a variety of suitable mechanical mechanisms may be utilized, including, but not limited to, hinges, levers, and pivots. 
     As best seen in  FIGS. 6 and 7 , it is preferable that the shutter  114  be disposed below the upper surface of the vehicle support surface  102  or cover plate  103  in both the open and closed positions, for protection against damage in both positions, and to avoid interference with an laser optical axis or the optical imaging sensor field of view when in the open position. The shutter  114  may be composed of a lighter gauge material than the vehicle support surface  102  or cover plate  103 , having sufficient durability for exposure to environmental debris and contaminates. As shown in  FIG. 7 , when in a closed configuration, the shutter  114  need not fully seal or close an associated opening  110 , but rather, may act as a deflecting surface with appropriate lips  114   a , edges  114   b , and recessed regions  114   c  (as shown in  FIGS. 4 and 8 ) to direct incoming environmental contaminates and debris which fall through the opening  110  away from sensitive regions on the underlying surfaces of the sensor housing  106 . Preferably, the shutter  114  has dimensions which are larger than the opening  110  with which it is associated, such that environmental contaminates or debris passing through the opening  110  may not fall past the lips  114   a  of the shutter  114  when the shutter is in the closed position. 
     For some applications, the cover plate  103  may optionally be mounted to the vehicle support surface  102  in proximity to one or more openings  110 , in such a manner as to extend partially over, and into, the openings without interference with an optical axis or field of view passing there through. The cover plate  103  functions in cooperation with the shutter  114  (if present) to divert incoming environmental contaminates or debris onto the surface of the shutter. As seen in  FIGS. 2 and 8 , a rolled or rounded edge or lip  103   a  of the cover plate  103  may extend inward towards the sensor housing, and serve to collect, control, or divert liquid contaminates (i.e., water, oil, salt solutions, etc.) to thereby form droplets or fluid flows at controlled locations relative to the sensor housing  106  below by taking advantage of liquid surface tension, adhesion characteristics, and air flow. Similarly, raised edges  103   b  of the cover plate  103  above the surface of the vehicle support surface  102  further serve to divert fluid flow of liquids accumulating on the vehicle support surface  102  away from the openings  110 . 
     Incoming liquid contaminates may be further controlled by application of suitable surface coatings on the sensor housing  106  and optical windows  110 , as well as surface textures, grooves, lips and drip edges formed on the various surfaces, such as the underside surface of the cover plate  103  to encourage droplet formation over the gutters  112 , and to divert liquid flows away from the optical windows  108 . Exemplary coatings which may be applied to any of the exposed surfaces on the sensor housing, such as the optical windows  108  or gutters  112 , include optically transparent nano-coatings, hydrophobic coatings, and other surface coatings which resist adhesion and/or encourage beading of liquid contaminates. 
     Environmental contaminates, debris, and liquids which pass through the openings  110  in the vehicle support surface  102  and/or cover plate  103 , and which accumulate or collect on the upper surfaces of the sensor housing  106 , including the optical windows  108  and within the gutters  112  must be periodically removed. Manual removal of accumulated material requires removal of the vehicle support surface  102  to access the underlying surface of the sensor housing  106 , and is not always convenient or practical. In an embodiment of the present invention, an automated system for the clearing of accumulated debris from the sensor housing surfaces is provided. The cleaning system, best seen in  FIGS. 3 and 4 , consists of one or more air knife or air blade assemblies  122 , each of which are configured with one or more air nozzles  124  to direct a flow or blast of pressurized air across the surfaces of the sensor housing. As best seen in  FIG. 3 , a pair of air knife assemblies  122  may be disposed along the longitudinal midline of the sensor housing  106 , laterally between adjacent optical windows  108  and gutters  112 . Each air knife assembly  122  includes air nozzles or discharge openings  124  which are oriented to direct a flow or blast of pressurized air laterally outward towards the lateral edges of the sensor housing  106 . For example, as seen in  FIG. 4 , at least one air nozzle  124  is associated with each optical window  108  and each gutter  112 . 
     During operation, pressurized air is periodically delivered to the air knife assemblies  122  and discharged through the air nozzles  124 . The discharged flow or blast of pressurized air displaces accumulated contaminates, debris, or liquids from the surface of the sensor housing  106 , optical windows  108 , and/or gutters  112  in a laterally outward direction, off the lateral edges of the sensor housing  106  and into a surrounding discharge area. While shown in  FIGS. 3 and 4  in a configuration which enables the lateral discharge of accumulated contaminates, debris, and liquids, those of ordinary skill will recognize that the air knife assemblies  122  and air nozzles  124  may be configured to direct the flow or blasts of pressurize air in other directions relative to the surface of the sensor housing  106  as necessitated by the configuration of the optical windows  108 , gutters  112 , and other components located in proximity thereto, without departing from the scope of the present invention. 
     In an alternate embodiment, the air knife assemblies  122  are either replaced by, or supplemented with, wiper mechanisms (not shown) configured to sweep one or more wiper blades across the various surfaces to displace any accumulated contaminates, debris or liquids from the surface of the sensor housing  106 , optical windows  108 , and/or gutters  112 . Preferably, the wiper mechanisms are configured to sweep the material in a laterally outward direction, off the lateral edges of the sensor housing  106  and into a surrounding discharge area. 
     For some applications it may be beneficial to apply a spray of cleaning solution to the optical windows  108  prior to, or in conjunction with, the discharge of pressurized air from the associated air nozzles  124  or the sweeping action of a wiper mechanism. A suitable cleaning solution delivery system (not shown) may be disposed in operative proximity to the optical windows  108 , or may be incorporated into the air knife assemblies  122 . Alternatively, a cleaning solution may be supplied directly to the air knife assemblies and delivered to the optical windows  108  directly through the air nozzles  124  with the flow or blasts of pressurized air. 
     Control of the active mechanisms for protection against environmental contaminate and debris ingress, as well as the periodic clearing of accumulated material may be manual or automatic. Preferably, operation of the shutters  114  is controlled automatically by a suitably configured processing system (not shown), such that the shutters  114  remain in a closed position as a default, and are opened only when necessary to enable the acquisition of tire tread images by the optical imaging sensors, such as when a drive-over trigger mechanism  104  is activated by a vehicle approaching the sensor assembly  100 . 
     Operation of the air knife assemblies  122  is similarly handled by a suitably configured processing system (not shown). The processing system may be programmed with software instructions to activate the air knife assemblies  122  upon each activation of the drive-over trigger mechanism  104 , on a fixed cyclical basis such as after set number of tire tread images are acquired, on a fixed time schedule such as after every hour of operation, or on a variable basis by monitoring the quality of acquired images to identify the presence of accumulating debris or contaminates on the optical windows  108 . 
     While the present disclosure and accompanying figures are seen to illustrate a drive-over tire tread depth sensor system  100  which incorporates multiple environmental protection features, including mechanical shutters  114 , gutters  112 , and air knife assemblies  122 , those of ordinary skill in the art will recognize that other combinations of environmental protection features may be utilized without departing from the scope of the present disclosure, depending upon the particular configuration and/or operating environment in which a drive-over optical sensor system is to be utilized. 
     As various changes could be made in the above constructions without departing from the scope of the disclosure, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.