Abstract:
An electronic torque-angle instrument including a generally tubular body having a gripping section and a pivoting head for engaging a workpiece, such as a nut or bolt, and a housing associated with the body and containing electronics, including a microprocessor, which permit individual or simultaneous measurement of torque and angle applied to the workpiece. The microprocessor includes stored programs which interpret a signal from an input, such as a gyroscopic sensor, and sends the interpreted signal to an output means. The signal is finally displayed as an accurate torque measure and/or angle measure from the output means

Description:
RELATED APPLICATION  
       [0001]     This application is related to and claims the filing priority of U.S. Provisional Application No. 60/740,085, filed on Nov. 28, 2005 and entitled “Torque-Angle Instrument”. The &#39;085 application is hereby incorporated by reference. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     This application relates to wrenching tools and, specifically, to torque-angle measuring and recording wrenches.  
         [0004]     2. Description of the Prior Art  
         [0005]     The object of a wrenching tool is to rotate or hold against rotation an item, such as a threaded fastener (e.g. a bolt) joining two objects together. As the fastener is tightened it is stretched until it exerts the appropriate amount of compression force (called “bolt load”) to the objects being held together or in place by the bolt. There is a relationship between the amount of torque that is applied to the head of a fastener and the amount of load applied to the joined objects. However, torque measurement is a poor method of determining ‘bolt load,’ because variations in frictional components vary the ‘bolt load’ achieved for a given torque applied.  
         [0006]     Torque is considerably influenced by friction forces, the condition of the head, the amount, if any, of lubrication, as well as by other factors. The reliability of a torque measurement as an indication of desired load is, therefore, significantly variable. The solution is to rotate the bolt a specified number of degrees. This removes the friction-based error factor. Accordingly, a torque-angle fastener installation process, rather than torque measurement alone, is recommended in situations where tightening to recommended specifications is critical.  
         [0007]     In a torque-angle fastener installation, a fastener is first tightened to a desired torque using a torque wrench; then the fastener is rotated through a predetermined additional angle of rotation. Because angle-based torquing is a more accurate way to ensure even tightening, more and more manufacturers are using the torque-angle procedure for tightening fasteners.  
         [0008]     Another advantage of torque-angle installation is that like fasteners exert the same clamp forces without deviation from one fastener to the next due to variable conditions of lubrication, surface finish and the like previously mentioned.  
         [0009]     At present, there are various wrenching tools available which meter angular rotation. Early angle measurement wrenching tools relied on some type of mechanical reference, usually a flexible strap connected to a “ground” clamp, for measurement of the angular rotation of a fastener.  
         [0010]     More modern tools now use gyroscopes to meter angular rotation. One such device is disclosed in U.S. Pat. No. 4,262,528 to Holting et al. A gyroscope operates by offering opposition to a swiveling motion around an axis located transversely to its axis of rotation. Other torque-angle measuring tools on the market include KD Tools #3336 Torque Angle Gauge, Lisle Corp. #28100 Torque Angle Meter, SPX Corp. #4554 Stinger Torque Angle Gauge, Fel-Pro TRQ-1 Torque-to-Angle Indicator, and Kent-Moore J36660A Torque/Angle Meter. The disadvantages of these devices is that they require mechanical reference to a stationary point. This requires repositioning the reference arm for every fastener to be tightened, and a poorly positioned arm could cause gross errors in measurement, perhaps leading to component failure.  
         [0011]     Still other similar devices come at a very high price (&gt;US$1,200) and include complex menu-driven operation, which in some markets, such as automotive, may be prohibitive.  
         [0012]     The present instrument in its various embodiments provides a solution to these and other problems in the relevant field.  
       SUMMARY OF THE INVENTION  
       [0013]     There is disclosed herein a torque-angle instrument, such as a wrench, including a method of operation, for measuring applied torque and applied angle to a work-piece which avoids the disadvantages of prior devices while affording additional structural and operating advantages.  
         [0014]     In a first embodiment of the disclosed method, the invention includes the steps of providing a wrench having a gripping section, a drive head, and internal circuitry coupled to the drive head, wherein the circuitry comprises a microprocessor having stored programming, input means, output means, and a power supply for powering the microprocessor, the input means and the output means, and then engaging the drive head of the wrench to a workpiece. The method then further comprise the steps of applying torque to the workpiece around the drive head, operating the input means to create a first signal related to the torque and angle being applied to the workpiece, receiving the first signal into the microprocessor from the input means, interpreting the signal by the stored programming, sending the interpreted signal to the output means, and then displaying the interpreted signal as an accurate torque measure and/or angle measure from the output means.  
         [0015]     It is an aspect of the invention to include circuitry input means which comprise a gyroscopic sensor for measuring the rate of rotation around the drive head.  
         [0016]     In an embodiment of the electronic torque-angle instrument, the device comprises a generally tubular body including a gripping section and a pivoting head for engaging a workpiece, such as a nut or bolt, and a housing associated with the body and containing electronics, including a microprocessor, which permit individual or simultaneous measurement of torque and angle applied to the workpiece.  
         [0017]     It is an aspect of the electronic torque-angle instrument to include a microprocessor having stored programs for controlling the operation of the device. The device also includes input means, such as a gyroscopic sensor for measuring a rate of rotation around the pivoting head.  
         [0018]     It is another aspect of the torque-angle instrument to include stored programs providing at least one of the features selected from the group consisting of bending beam deflection compensation; simultaneous torque and angle measurement; preset scroll stop at full-scale torque only; scroll through (past) angle mode without waiting for sensor initialization; angle mode torque units from last changed units; ignoring angle measure in reverse direction; sensor output offset monitoring; alternating display of peak torque and angle values; use of pre-torque direction to select allowable angle sensing direction; use of integer math to yield accuracy comparable to floating-point math; motion indicator at angle sensor initialization; temperature drift compensation; direct connection of the torque and angle sensors to the microprocessors; angle zero set function; signal level monitoring for over-speed indication; and sample data interrupt technique used to convert instantaneous angular velocity signal to filtered angle position.  
         [0019]     These and other aspects of the invention may be understood more readily from the following description and the appended drawings.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]     For the purpose of facilitating an understanding of the subject matter sought to be protected, there is illustrated in the accompanying drawings and flowcharts an embodiment thereof, from an inspection of which, when considered in connection with the following description, the subject matter sought to be protected, its construction and operation, and many of its advantages should be readily understood and appreciated.  
         [0021]      FIG. 1  is a side view illustrating one possible embodiment for the instrument of the present invention;  
         [0022]      FIG. 1A  is a close-up view of the user interface section of the embodiment of the present invention shown in  FIG. 1 ;  
         [0023]      FIG. 2  is a side view illustrating another possible embodiment for the instrument of the present invention;  
         [0024]      FIG. 3  is a schematic illustrating an embodiment of the electronics of the present instrument;  
         [0025]      FIG. 4  is a level ( 1 ) operation flowchart, labeled “OP MODE Angle Cal,” showing the available paths for the program to leave the angle calibration state;  
         [0026]      FIG. 5  is a level ( 1 ) operation flowchart, labeled “OP MODE Error,” showing the paths available for the program to leave the error state;  
         [0027]      FIG. 6  is a level ( 1 ) operation flowchart, labeled “OP MODE Setup,” showing the paths available for the program to leave the setup state;  
         [0028]      FIG. 7  is a level ( 1 ) operation flowchart, labeled “OP MODE Sleep,” showing the paths available for the program to leave the sleep state;  
         [0029]      FIG. 8  is a level ( 1 ) operation flowchart, labeled “OP MODE TA Measure,” showing the paths available for the program to leave the torque and angle (TA) measure state;  
         [0030]      FIG. 9  is a level ( 1 ) operation flowchart, labeled “OP MODE Torque Cal,” showing the paths available for the program to leave the torque calibration state;  
         [0031]      FIG. 10  is a level ( 1 ) operation flowchart, labeled “OP MODE Torque Measure,” showing the paths available for the program to leave the torque measure state;  
         [0032]      FIG. 11  is a level ( 1 ) operation flowchart, labeled “OP MODE Wake Up,” showing the paths available for the program to leave the wake up state;  
         [0033]      FIG. 12  is a level ( 2 ) operation flowchart showing the different states within the Torque and Angle Measure Mode;  
         [0034]      FIG. 13  is a level ( 2 ) operation flowchart showing the different states within the Torque Measure Mode;  
         [0035]      FIG. 14  is a level ( 3 ) operation flowchart showing the logic within the TRACK state of the Torque and Angle Measure Mode of  FIG. 12 ; and  
         [0036]      FIG. 15  is a level ( 3 ) operation flowchart showing the logic within the TRACK state of the Torque Measure Mode of  FIG. 13 . 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0037]     While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in sufficient detail a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiment illustrated.  
         [0038]     The present application discloses a wrench that measures both torque and angle of rotation. It allows the tool user to perform bolt-tightening jobs requiring angle specifications with a single tool. A vibrating handle and audible tone alert the user when the measured torque or angle reaches a user-selected preset value.  
         [0039]     With reference to U.S. Pat. No. 5,589,644 entitled “Torque-Angle Wrench,” the instrument described herein implements a number of software features that utilize and facilitate the measurement of torque and angle, individually and simultaneously, to provide accurate fastener installation control. The present instrument may include the same methods of user operation as the wrench disclosed in the &#39;644 patent. The application relates in particular to an improvement of the electronic torque wrench disclosed in the &#39;644 patent, the disclosure of which is hereby incorporated herein by reference.  
         [0040]     The present instrument is an electronic torque wrench with the addition of a gyroscopic sensor for measuring the rate of rotation of the wrench around the drive-head. A circuit board containing the sensor may be fit into a similar pre-existing wrench housing, such as, for example, that of the TECH WRENCH™ manufactured and sold by the assignee of the present application, Snap-on Incorporated of Wisconsin.  
         [0041]     The present instrument incorporates a number of software-based innovations to produce an easy to use and accurate wrench, capable of measuring both applied torque and applied angle simultaneously. Such innovations include:  
         [0042]     Bending beam deflection compensation;  
         [0043]     Simultaneous torque and angle measurement;  
         [0044]     Preset scroll stop at full-scale torque only;  
         [0045]     Scroll through (past) angle mode without waiting for sensor initialization;  
         [0046]     Angle mode torque units from last changed units;  
         [0047]     Ignoring angle measure in reverse direction;  
         [0048]     Sensor output offset monitoring;  
         [0049]     Alternating display of peak torque and angle values;  
         [0050]     Use of pre-torque direction to select allowable angle sensing direction;  
         [0051]     Use of integer math to yield accuracy comparable to floating-point math;  
         [0052]     Motion indicator at angle sensor initialization;  
         [0053]     Temperature drift compensation;  
         [0054]     Direct connection of the torque and angle sensors to the microprocessors;  
         [0055]     Angle zero set function;  
         [0056]     Signal level monitoring for over-speed indication; and  
         [0057]     Sample data interrupt technique used to convert instantaneous angular velocity signal to filtered angle position.  
         [0000]     A. Instrument Housing  
         [0058]     Referring to  FIGS. 1, 1A  and  2 , a few possible embodiments of the torque-angle instrument are shown. There is illustrated an electronic torque-angle instrument, generally designated by the numeral  10 . The instrument  10  is defined by an elongated housing  11 , including a tubular gripping portion  12  at one end, made of steel, aluminum, or other suitable rigid material, a forward extending portion  13  containing a wrench head  14  pivotally supported at the working end of housing  11 , and an electronic housing unit  15  which contains the electronics and display components to be described below. Wrench head  14  is shaped to slidably engage a socket (not shown) which is to be used to tighten the head of a bolt or a nut.  
         [0059]     The present invention is easily adaptable to operate with most any similar wrench or instrument regardless of most operation parameters, such as torque capacity, and many physical dimensions, such as length, weight, etc. The electronic housing unit  15  is shown provided on the outside thereof with a display window  16 , but may comprise instead light emitting diodes or other type of character indicating display, adapted to respond to the signals presented thereto by the underlying display circuitry to be discussed below. Also included on the instrument  10  are selection keys or buttons  17 , each performing a unique function in cooperation with the electronic circuit and display components in electronic housing unit  15 .  
         [0000]     B. Circuitry  
         [0060]     The circuitry can be split into four major functions. These are:  
         [0061]     Microprocessor (the logic and control center, plus support hardware);  
         [0062]     Power Supply (for the microprocessor and the sensors);  
         [0063]     Inputs (sensors, keypad and programming port); and  
         [0064]     Outputs (LCD, buzzer and vibrating motor).  
         [0065]     With reference to  FIG. 3 , each function of the wrench is explained in detail below.  
         [0066]     1. Microprocessor U 2 :  
         [0067]     The microprocessor circuitry receives the torque and angle (gyroscope) sensor outputs, along with the keypad and battery voltage monitor outputs. These are interpreted by the software program, yielding accurate torque and/or angular rotation information, which is sent to the LCD for display. The microprocessor also controls audio (buzzer) and tactile (vibrating motor) alerts.  
         [0068]     The preferred microprocessor U 2  is a Texas Instruments MSP430F427 Microcontroller. Capacitors C 3  and C 4  filter noise from the power supply traces as they connect to the DVCC and AVCC (digital and analog supply voltage) inputs, respectively. Crystal X 1 , operating at 32.768 kHz, provides the clock signal for U 2 . Capacitor C 9  filters noise from U 2  pin  10  (VREF), which is not used. Resistor R 1  and Capacitor C 6  form an RC network. When connected to U 2  pin  58  (RST), they assure that when the AA batteries are replaced, U 2  is not allowed to function until the supply voltage has stabilized. Diode D 1  allows the voltage at pin  58  to fall immediately upon battery removal, thus protecting U 2  from damage. Resistors R 8 , R 9  and R 13  establish the multiple analog voltages for the LCD display.  
         [0069]     2. Power Supply:  
         [0070]     The power supply provides regulated power to the microprocessors, the sensors, the buzzer and the vibrating motor.  
         [0071]     Connector J 2  connects the battery holder, containing preferably three AA batteries, to the circuit board. Capacitors C 15  and C 16  filter noise that may be picked up by the battery holder leads before it reaches the voltage regulators. Voltage Regulators U 4 -U 6  are preferably Micrel MIC5235-3.0YM5 regulators with enable inputs. Capacitors C 17 -C 20  and C 21 -C 22  quench oscillations and noise from the regulators to which they are attached. Regulator U 4  supplies power to the micro U 2 , and is always active, as the enable pin (U 4  pin  3 ) is tied to the battery (+). Regulator U 5  supplies power to the torque sensor SG 1 , and is only active when the micro is active, and sends a H 1  output to the enable pin (U 5  pin  3 ), thus saving battery life when not in use. Regulator U 6  supplies power to the vibrating motor through connector J 3 , and is only active when U 2  pin  53  sends a H 1  output to U 6  pin  3 .  
         [0072]     3. Inputs:  
         [0073]     The inputs provide the signals that the microprocessor interprets, so that it can determine what work the wrench is imparting on the effected fastener.  
         [0074]     Torque Sensor SG 1  is a four-element full-bridge strain gage attached to a bending beam. Two elements are active (measuring tension and compression), while the other two provide temperature compensation. When voltage is supplied to point ( 1 ) on SG 1  from U 5  pin  5 , the sensor acts as a wheatstone bridge. When no torque is applied to the bending beam, all four elements have equal resistance, therefore the voltage at points  2  and  4  are equal, at [+3V-A]/2. However, if torque is applied, the active elements change resistance (one element increases while the other decreases, depending on the direction of the torque applied), and the bridge becomes unbalanced, creating a voltage differential between points  2  and  4  on SG 1 . The value of the differential voltage is linearly representative of the torque being applied to the bending beam. Torque Sensor SG 1  is connected to the PCB at the Edge Tab Connector. It receives power through its connection to the regulator U 5  (pin  3 ). The differential outputs (points  2  and  4 ) are fed to the micro U 2  pins  4  and  5 . Capacitor Cl filters noise that might be picked up at SG 1 , while Capacitor C 2  filters noise from the power supply trace.  
         [0075]     Gyro Sensor U 1  is preferably a Murata ENC-03M Piezoelectric Gyroscopic Sensor. Its output (pin  4 ) varies in relation to its rate of rotation in one sensitive axis, while the reference (pin  1 ) is static at the approximate value of the output at 0%/sec. rotation. Sensor U 1  is connected to the main PCB at slot H 2 . Supply voltage is fed to U 1  pin  3  directly from the micro (U 2  pin  46 ), thus powering the sensor U 1  only as necessary to save battery life. The output (U 1  pin  4 ) is fed to the micro U 2  pin  6 , while the reference (U 1  pin  1 ) is fed to the micro U 2  pin  7 . Capacitor C 5  filters noise that might be picked up at U 1 . Capacitors C 7  and C 8  provide improved noise performance out of the sensor U 1 . The keypad serves as the user interface with the tool. It allows the user to change preset values and engineering units, store and print data, etc. The keypad consists of contact pads on the PCB, plus rubberized overlays containing either four or six conductive-backed buttons. The contact pads feed directly to the micro at pins  47 - 52 . Resistors R 2 -R 7  serve as pull-up resistors.  
         [0076]     The battery monitor circuit is a switched voltage divider that is used to measure the voltage of the AA batteries. Resistors R 12  and R 14  served as the voltage divider. The junction of these provides a voltage that is a fraction of the battery voltage, which is within the range of the micro input (U 2  pin  2 ). Transistor Q 2  serves as an inverter, converting the active-H 1  output from the micro (pin  44 ) to an active-LO signal that is fed to Transistor Q 1 . Transistor Q 1  connects the voltage divider to the battery, only as necessary to take battery voltage readings, thus saving battery life.  
         [0077]     4. Outputs  
         [0078]     The outputs provide information to the user for appropriately operating the wrench.  
         [0079]     The Liquid Crystal Display (LCD) module L 1  provides alphanumeric information regarding the operating modes, preset value, measurement results, etc. of the wrench. It is connected to the micro (U 2 ) through conductive strips that connect to U 2  pins  12 - 24  and  36 - 39 .  
         [0080]     The Vibrating motor creates a tactile alert for the user, that torque should be released on the wrench. This motor is connected to the PCB though connector J 3  to the output of Regulator U 6  (pins  5  and  2 ) and is enabled by a logic H 1  at U 6  pin  3 .  
         [0081]     The Buzzer BZ 1  provides an audio alert to the user, indicating preset coincidence or warning of over-torque conditions. Buzzer BZ 1  is connected to Transistor Q 3 , which serves as a driver. When a square-wave signal from the micro U 2  (pin  45 ) is fed through current limiting resister R 16 , it causes Q 3  to switch ON and OFF, driving BZ 1  at its fundamental (resonant) frequency. Resister R 17  properly biases Q 3 , while Diode D 2  quenches any voltage spikes that might be generated by BZ 1  when Q 3  switches open.  
         [0082]     The J-TAG Interference H 1 A provides a means for reprogramming the microprocessor without removing it from the PCB. Port H 1 A is connected to the micro U 2  at pin  9  and pins  54 - 58 . When H 1 A is connected to a suitable computer through an MSP430 Flash Emulation Tool (Texas Instruments P/N MSP-FETP4301F 1.1 or similar), a new programming code can be set into the memory of micro U 2 .  
         [0083]     The outputs also include an RS-232 data output to support the optional memory functions of the wrench. The circuitry for this function is not described in detail, as it is common architecture and not related to the invention.  
         [0000]     C. Operation Flowcharts:  
         [0084]     Referring now generally to  FIGS. 4-15 , the operational modes and states of the invention can be more readily understood. The software runs a variety of state machines. They are described below.  
         [0085]     (1) The OP_MODE state machine defines how the wrench should behave. For example, if the OP MODE (i.e., operation mode) is SLEEP, the wrench should be sleeping. If the OP MODE is TORQUE_MEASURE, the wrench should be measuring torque.  
         [0086]     (2) Each OP MODE state has its own state machine. For example, OP MODE TORQUE_MEASURE has many states. It can show and update a preset value, it can show how much torque is currently being measured, and it can display the maximum torque reading.  
         [0087]     (3) Each state within each OP MODE state has a variety of logic operations that can define what to display, check if an error has occurred, or change hardware parameters (e.g. sound the horn or turn on the vibrating motor).  
         [0088]     The flowcharts starting with the phrase “OP MODE” shows a high-level view of the actions required to leave a given state. For example, with reference to  FIG. 10 , “OP MODE: Torque Measure” shows all possible operational paths for the program to leave the “Torque Measure” operation mode. A description of each flowchart is given below.  
         [0089]      FIG. 4  illustrates seven available paths for the program to leave the “calibrate angle” state. The user may enter the “measure torque” state (two paths), the “measure torque &amp; angle” state (two paths), the “sleep” state (one path), and the “error” state (four paths) along the noted paths by the listed functions. For example, to enter the “measure torque” state, the two available paths include pressing the power button—path labeled “Power PB Press (TU)”—or a successful calibration—path labeled “Successful, NTA (TU)”.  
         [0090]      FIG. 5  illustrates four paths available for the program to leave the “error” state. The program includes a single path to enter the “measure torque” state and the “measure torque &amp; angle” state, and two available paths to enter the “sleep” state.  FIG. 6  illustrates the seven paths available for the program to leave the “setup” state. The program may enter the “measure torque” state (three paths), the “measure torque &amp; angle” state (two paths), and a single path to enter both the “sleep” state and the “error” state.  FIG. 7  illustrates a single path available into the “wake up” state for the program to leave the “sleep” state, accomplished by pressing the power button.  
         [0091]     The program may leave the “measure torque &amp; angle” operation state along nine paths, as shown in  FIG. 8 . Only the “setup” state and “wake up” state are unavailable from this state. From the “calibrate torque” state, as shown in  FIG. 9 , seven paths are available for the program to leave, including the “measure torque” state (two paths), the “measure torque &amp; angle” state (two paths), the “sleep” state (single path), and the “error” state (two paths). Similar to the “measure torque &amp; angle” state of  FIG. 8 , the “measure torque” state may be left to all but the “setup” state and the “wake up” state along its eight available paths shown in  FIG. 10 .  
         [0092]      FIG. 11  illustrates the five paths available for the program to leave the “wake up” state. The program may enter the “setup” state (two paths), and the “measure torque” state, the “measure torque &amp; angle” state, and the “sleep” state along a single path each.  
         [0093]     Regarding the Level ( 2 ) Flowcharts,  FIG. 12  illustrates the steps of operation through the different modes (e.g., Zero_Init_Mode, Zero_Angle_Mode, Track_Mode, Preset_Init_Mode, etc.) within the “Measure Torque &amp; Angle” state of  FIG. 8 , while  FIG. 13  illustrates operational steps through the different modes (e.g., Zero_Torque_Mode, Preset_Init_Mode, Track_Mode, Peak_Init_Mode, etc.) within the “Measure Torque” state of  FIG. 10 .  
         [0094]     As for the Level ( 3 ) Flowcharts,  FIG. 14  illustrates the logic steps of the software within the “TRACK” state of the “Measure Torque &amp; Angle” mode shown in  FIG. 12 .  FIG. 15  shows the logic steps of the software within the “TRACK” state of the “Torque Measure” mode of  FIG. 13 . Those skilled in the art would be able to prepare the necessary software programming from these many flowcharts without additional experimentation.  
         [0095]     The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. While particular embodiments have been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made without departing from the broader aspects of applicants&#39; contribution. The actual scope of the protection sought is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.