Abstract:
The smart lid for smart bolts and probes is an electronic sensor for use with a smart bolt or probe having a color indicator for indicating tension. The smart lid includes a color sensor that provides electrical data corresponding to light received from the color indicator of the smart bolt or probe, a microcontroller that receives electrical data from the color sensor and converts that data to a digital form and compares the data against at least one limit, and provides a digital indication wirelessly to a remote monitor if the at least one limit has been exceeded. In this fashion a warning or emergency condition can be indicated when the tension experienced by the smart bolt is too low or too high. The smart lid may include an electrical power source that scavenges electrical power from ambient electromagnetic fields (EMF) and stores the electrical power in a battery.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to mechanical fasteners and to electronic sensors for detecting failure of mechanical components, and particularly to a smart lid for smart bolts and probes that automatically detects failure of a smart bolt in a structure or machine and generates an alert for maintenance or emergency repair. 
         [0003]    2. Description of the Related Art 
         [0004]    Such structures as buildings, bridges, pipelines, petroleum plants, ships and aircraft must be robustly designed, carefully built and regularly inspected to prevent ‘wear and tear’ damage to components, such as bolts, from causing catastrophic failures. Even well designed and built structures will not last forever, so periodic inspection of bolts is often required to ensure structural integrity. As used herein, the terms “bolt” or “bolts” shall be taken to include any kind of bolt, including all tension-based bolts, screws, studs and fasteners. 
         [0005]    Machines often have bolts with similar maintenance and inspection issues as structures. For example, failure of a bolt in a machine can cause delays and loss of productivity in both public and commercial enterprises. The maintenance of machinery constitutes a huge cost to industry. Some studies in Europe have shown the direct cost of maintenance often ranges between 4% to 8% of the total sales price. The indirect cost of maintenance issues, such as reduced quality and lost productivity, is likely to be at least that much. Unfortunately, bolts play a role in that in those maintenance issues and costs. 
         [0006]    One aspect of dealing with the problem of bolt-related failure has been to ensure that the bolts were properly installed in the first place. When using bolted joints in industrial plants and mechanical systems, there often is some uncertainty regarding the desired amount of torque that should be applied, and how much corresponding preload is actually applied depends on the method of tightening selected, in part due to varying friction conditions. Insufficient preload, often caused by an inaccurate tightening method, is a frequent cause of bolted joint failure. While some design engineers appreciate the features and characteristics of the main methods employed to tighten bolts, whatever method is used to tighten a bolt, a degree of bolt preload scatter is to be expected, and hence a technique for failure monitoring of each bolt is desired. Furthermore, other applications include other types of failure criteria that also suggest local bolt monitoring. 
         [0007]    One approach to dealing with preload variation and scatter has been the “smart bolt.” For example, smart bolts, such as those manufactured by Stress Indicators Inc. of Gaithersburg, Md. 20877 (accessible by Internet at www.smartbolts.com, marketed under the name SmartBolts, provide a visual indication (a dot on the bolt head that changes color according to the condition of the bolt) of the tension that a bolt is under in a central portion of the bolt (“smart bolts”). 
         [0008]    Some existing smart bolts are used in structures and industrial plants that have red dot, yellow dot, yellow dot then green dot, or other color combinations that turn black (or a different designated color) as the bolt is tightened. For example, the two-color (red/black) smart bolt from Stress Indicators Inc. will change from red to black as the bolt is sufficiently tightened. The three-color smart bolt from Stress Indicators Inc. will change from yellow to green as the bolt is optimally tightened, and then from green to black if the bolt is over-torqued. The color indicator in a smart bolt is also reversible, meaning that an optimally tightened bolt that becomes loose over time will change back to a color that indicates that it has not been sufficiently tightened. 
         [0009]    Smart bolts provide an easily discernable visible indication that the smart bolt is properly tightened or not. This is even more important with some modem materials because internal damage in such materials can be very serious, but still leave little to no surface evidence, other than a smart bolt color indication. In all these cases, smart bolts provide a needed quick and accurate visual indication that something is wrong. 
         [0010]    While smart bolts are a significant improvement over simple prior art bolts, structural and mechanical inspection by trained individuals, while necessary, is still both expensive and time-consuming. Even well-funded inspection programs can run into difficulties trying to inspect large numbers of widely scattered structures or machines because of the sheer magnitude of the task. For example, it is has been reported that there are roughly 600,000 bridges in the U.S. alone, and some tens of thousands are in need of repair or replacement. The sheer magnitude of the inspection task suggests mistakes in inspection have and will continue to occur. 
         [0011]    Because the bolt inspection task is expensive, time-consuming, and subject to human error, it would be desirable to address these shortcomings. Thus, a smart lid for smart bolts and probes mitigating or solving the aforementioned problems is desired. 
       SUMMARY OF THE INVENTION 
       [0012]    The smart lid for smart bolts and probes is an electronic sensor for use with a smart bolt or probe having a color indicator for indicating tension. The smart lid includes a color sensor that provides electrical data corresponding to light received from the color indicator of the smart bolt or probe, a microcontroller that receives electrical data from the color sensor and converts that data to a digital form and compares the electrical data against at least one limit, and provides a digital indication wirelessly through an antenna to a remote monitor if the at least one limit has been exceeded. In this fashion a warning or emergency condition can be indicated when the tension experienced by the smart bolt is too low, or in some embodiments, too low or too high. The smart lid may include an electrical power source that scavenges electrical power from ambient electromagnetic fields (EMF) and stores the electrical power in a battery. Alternatively, the smart lid may be powered by a previously charged battery. The smart lid uses a housing that is removably coupled to the smart bolt with a flexible, resilient retainer. 
         [0013]    These and other features of the present invention will become readily apparent upon further review of the following specification and drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is an environmental side view of a smart lid for smart bolts and probes according to the present invention, the lid being shown in section to show details thereof. 
           [0015]      FIG. 2  is an environmental side view of a smart lid for smart bolts and probes according to the present invention, the lid being uncapped from the bolt head and tethered to the bolt by a retainer spring. 
           [0016]      FIG. 3  is a top view of a flexible retainer spring for removably mounting the smart lid for smart bolts and probes of  FIG. 1  to a bolt. 
           [0017]      FIG. 4  is a block diagram of an electronic circuit for a smart lid for smart bolts and probes according to the present invention. 
       
    
    
       [0018]    Similar reference characters denote corresponding features consistently throughout the attached drawings. 
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0019]    The smart lid for smart bolts and probes uses a novel smart lid that can be removably attached to a smart bolt (or a probe). The smart lid uses a color sensor to perform automatic color detection of the central portion of the smart bolt that provides a color-coded tension indication and wireless transmission of the detected color-coded tension indication directly or indirectly through other smart lids to a computer for storage and analysis. The smart lid provides an automatic electronic process that eliminates the need for a manual inspection process, and uses electronic detection of color changes, eliminating subjective human judgments and producing greater uniformity in maintenance, inspection, and emergency detection procedures. 
         [0020]      FIG. 1  shows a side view of a smart lid  100  for smart bolts  105  and probes mounted on top of a smart bolt. The smart lid  100  may also be used with smart probes, which are functionally similar to smart bolts in that they provide a visual indication of tension, even though the probe itself provides little or no binding effect between structural or mechanical elements, as a bolt would. In this fashion, the smart lid can be used for probes measuring displacement between any two points in a structure, such as the Opti-mechanical indication of displacement described in U.S. Pat. No. 4,904,132, which is hereby incorporated by reference in its entirety. 
         [0021]    The smart lid  100  is physically coupled and tethered to the smart bolt  105  by a flexible retainer spring  110 , as can be seen more clearly in  FIG. 3 . One end of the flexible retainer  110  contains an aperture through which the smart bolt  105  can be positioned so that the aperture is positioned between the head  115  of the smart bolt  105  and a washer  120 . The opposite end of the retainer  110  is fixed to the lid  100 . The retainer  110  may be made from spring steel, and may be biased to hold the lid  100  away from the head  115  of the bolt  105  when the lid  100  is uncapped from the bolt  105  to permit access with a tool for tightening or untightening the bolt  105 . 
         [0022]    The smart lid  100  is shown in  FIG. 1  in a closed position, fitted around and capping the head  115  of the smart bolt  105 , being retained by a friction fit. The smart lid  100  is not limited to any particular orientation, and can be physically and removably coupled to the smart bolt  105  when the smart bolt  105  extends upwards, downwards, sideways or in any other orientation. 
         [0023]    The smart lid  100  contains a color sensor  125  for sensing the color indication provided by the smart bolt  105  corresponding to the amount of tension experienced by the smart bolt  105 . The color sensor  125  converts the sensed color indication into a digital electronic format corresponding to the color of the smart bolt  105  indicator. The sensed color indication can be of single color, such as red, yellow, or green, or multiple colors, and can include a grayscale indication. The color sensor  125  can either include a small light source or work with ambient light passing through or around the smart lid  100  depending on the application environment the smart lid  100  is to be used in. The color sensor  125  is mounted on a printed circuit board (PCB)  130  in the smart lid housing  135 . The smart lid housing  135  forms the primary exterior structure of the smart lid  100 . However, different portions of the flexible retainer  110  extend both inside and outside of the housing  135 , as shown in  FIG. 1 . Furthermore, an antenna  140  may extend outside the housing  135 , or may remain entirely inside the housing  135 , depending on the application environment. The housing  135  is preferably formed out of polyvinyl chloride (PVC) or another comparable plastic material, but is not limited to any particular material. 
         [0024]    The PCB  130  physically and electrically supports the color sensor  125  that is mounted thereon, and supports the antenna  140  and a microcontroller  455  (shown in  FIG. 4 ). The microcontroller  455  receives and processes signals from the color sensor  125 , and converts those signals into an appropriate digital electronic format. The microcontroller  455  wirelessly transmits tension information in the appropriate digital electronic format, which may be encoded or encrypted for secure communications, corresponding to the sensed color indication from the color sensor through the antenna  140 . While monitoring of the smart bolt  105  color indicator by the smart lid  100  is continuous, transmission of tension information can be continuous, periodic or event-driven, such as when the tension enters into a warning or emergency level. Typically the indicated tension enters a warning level, then an emergency level as tension drops below the optimal range, but corresponding warning and emergency levels above the optimal range can also be used if supported by the smart bolt  105  color indicator. The microcontroller  455  is programmed with the appropriate warning and emergency levels, as well as internal damage diagnostics and self-recovery features. 
         [0025]    The tension information can take any form, including specifying a color mix (red-blue-green) and/or gray scale indications, or a simple warning/emergency indication that the tension is approaching or exceeding tension specifications, respectively. While under-tension is known to be the primary cause of structural or mechanical problems associated with bolts, over-tension can also be a problem and can also be reported by the smart lid  100 . 
         [0026]    The color sensor  125 , antenna  140 , and microcontroller  455  are powered by and suitable power source, which may optionally include an electromagnetic field (EMF) scavenging device  145 , such as those known in the art, that convert ambient EMF (such as that emitted by radio station broadcasts) into small amounts of electrical power. The EMF scavenging device  145  includes a battery  445  to buffer and store energy for the microcontroller  455 , color sensor  125  and wireless communications. 
         [0027]      FIG. 2  shows the smart lid  100  uncapped from the head  115  of the smart bolt  105 . As was the case in  FIG. 1 , in  FIG. 2  the smart bolt  105  has its narrower, threaded portion positioned through the aperture of the flexible retainer  110  and the washer  120 . The color indicator  107  on the smart bolt  105  is shown in phantom. When the smart lid  100  is in the closed position, as shown in  FIG. 1 , the color sensor  125  is correspondingly positioned directly above or adjacent to the color indicator  107 . The arrangement in  FIG. 2  is the same as shown in  FIG. 1 , other than the open position of the smart lid  100  and corresponding change (decrease) in deflection of the flexible retainer  110 . 
         [0028]      FIG. 3  shows a top view of the flexible retainer spring  110  for removably mounting the smart lid  100  for smart bolts and probes to the smart bolt  105 . The flexible retainer spring  110  has an annular portion  311  defining an aperture adapted to receive the narrow (threaded) portion or shaft of the smart bolt  105 , and an attached elongated tether portion  313  having an end adapted to be inserted partially into and fixed to the smart lid  100 , thereby physically coupling the smart lid  100  to the smart bolt  105  and tethering the lid  100  to the bolt  105  in both the closed and open positions, or in any position in between. The flexible retainer spring  110  can be deflected between the closed and open positions without permanent deformation, as shown in  FIG. 1  and  FIG. 2 , respectively. 
         [0029]      FIG. 4  shows a block diagram of an electronic circuit  400  for implementing the smart lid for smart bolts and probes. The circuit  400  contains an analog front-end (“AFE”) transducer  450  for interfacing signals from the color sensor  125  to the microcontroller  455 . The AFE  450  electrically conditions the signals coming from the color sensor  125  prior to their conversion by the microcontroller  455  so that the signals are electrically compatible with the specified input ranges of the microcontroller  455 . The microcontroller  455  supervises all the different operations of the circuit  400  for the smart lid  100 . The microcontroller  455  is a standard, currently-available microcontroller, comprising a CPU, memory and peripheral circuitry. The microcontroller  455  is electrically coupled to a wireless communication module  460  using either a standard or proprietary communication standard. Alternatively, the microcontroller  455  can include internally any or all circuitry of the smart lid  100 , including the wireless communication module  460 . The microcontroller  455  preferably includes power savings or power management circuitry  445  and modes to reduce power consumption significantly when the microcontroller  455  is not active or is less active. The microcontroller  455  may contain at least one Analog-to-Digital Converter (ADC) channel for interfacing to the AFE  450 . 
         [0030]    The battery/power management module  445  preferably includes the electromagnetic field (EMF) scavenging device  145 , but can alternatively run off of previously stored electrical power from the battery alone. The battery/power management module  445  powers all the circuitry in the smart lid  100 , including the color sensor  125 , AFE  450 , microcontroller  455 , wireless communication module  460 , and antenna  140 . Even though the smart bolt  100  is preferably powered by continuously harvesting RF energy, it is beneficial to minimize power consumption. To minimize power consumption, the various tasks performed by the circuit  400  should be repeated no more often than necessary under the circumstances. 
         [0031]    Color information from the smart bolt  105  and other information from the microcontroller  455  is preferably transmitted wirelessly through a wireless communication module  460  and antenna  140 . As stated above, the wireless communication component can use standard or proprietary communication protocols. Smart lids  100  can also communicate with each other to relay information about the current status of the structure or machine and the smart lids  100  themselves. In each smart lid  100 , the transmission of this information may be scheduled to be transmitted periodically. The smart lid  100  has a data storage medium (memory) to store color indication and internal status information, such as power levels, while the communication component is in an OFF state between transmission periods. On the other hand, once the communication commences in the ON state, the microcontroller  455  can execute the following tasks: 
         [0032]    1. Neighbor discovery: in this task each smart bolt  100  sends a beacon identifying its location, capabilities (e.g. residual energy), status. 2. Cluster formation: cluster head will be elected based on the findings in (1). The cluster children communicate directly with their cluster head (CH). 3. Route discovery: this task interconnects the elected cluster heads together and finds the route towards the sink smart lid (node) so that minimum energy is consumed. 4. Data transmission: the microcontroller processes the collected color data and based on the adopted data dissemination approach, the smart lid  100  will do one of the following. (a) Transmit the data as is without considering the previous status; or (b) transmit the data considering the previous status. Here we can have several scenarios, which include: (i) transmitting the data if the change in reported tension exceeds the warning or emergency levels; and (ii) otherwise, do not transmit. 
         [0033]    It is to be understood that the present invention is not limited to the embodiments described above, but encompasses any and all embodiments within the scope of the following claims.