Patent Publication Number: US-2006009924-A1

Title: Torque angle sensing system and method with angle indication

Description:
FIELD OF THE INVENTION  
      The present invention relates generally to a torque angle measuring device. More particularly, the present invention relates to a torque angle sensor that measures the current angle of rotation applied beyond a point of reference.  
     BACKGROUND OF THE INVENTION  
      The importance of accurately and consistently controlling tension or preload applied to threaded fasteners increases with precision or criticality of parameters and tolerances of the assembly as a whole. This is particularly true in mass production of precision-designed equipment which may later be subjected to maintenance or repair, following which load applied to the assembly fasteners must be substantially the same as that applied during original manufacture. For example, in the manufacture of internal combustion engines designed for high performance and fuel economy, the head is fastened to the engine block with a plurality of bolts prior to final machining of various block/cylinder critical surfaces. In the event that the head is later removed for repair or replacement, it is important that the same be precisely reassembled to the block so as to restore relationships of critical surfaces obtained during the original manufacturing machining operations.  
      Conventionally, preloading of threaded fasteners in engine and other assembly applications is controlled by monitoring torque applied to the assembly tool, such as with a mechanical or electrical torque wrench. Fastener preload control through monitoring of fastener torque alone, however, yields unpredictable and inconsistent results due in part to varying friction between the mating threads and beneath the fastener head. Where it has been attempted to obtain greater uniformity through use of lubricants or the like, results have continued to be unsatisfactory.  
      Another approach has been to monitor torque as a function of angle of rotation, determine rate of change of torque, and compare the resulting data during the manufacturing operation to empirically determine data prestored in a computer memory. Such arrangements still do not directly measure fastener tension, and in addition require expensive assembly and control hardware.  
      A third approach has been to tighten the fastener to a point at which the fastener material yields and the fastener head separates from the threaded body. Arrangements of this type suffer from the same inherent drawbacks as the torque wrench technique described above due to varying friction between the fastener and the assembly, and also increases the cost of both manufacture and repair due to requirement for special double-headed fasteners.  
      A further technique for controlling fastener preload has been found to yield particularly consistent results. This technique, termed “torque-turn” or “torque-angle,” involves initially tightening the fastener to a specified torque, and thereafter tightening the fastener through an additional prespecified angle. The initial tightening torque is empirically predetermined to be one at which the fastener is tightened in assembly but has not yet been substantially elastically stretched. By thereafter tightening the fastener through an additional angle or fraction of a turn, advantage is taken of the precision machining of the fastener threads so as to obtain predetermined elastic stretching of the fastener within the assembly. For example, a torque-turn or torque-angle fastening specification may call for initial tightening to a torque of twenty-five Newton-meters, followed by an additional one-half turn or a one hundred and eighty-degree rotation in three equal steps.  
      The following is an example of torque instructions that accompany a service manual and the need for torque angle measurements.  
      Tighten the cylinder head bolts. 
          a. Tighten the cylinder head bolts a first pass in sequence to 30 N•m (22 lb ft).     b. Tighten the cylinder head bolts a second pass in sequence to 70 degrees.     c. Tighten the cylinder head bolts ( 1 ,  2 ,  3 ,  4 ,  5 ,  6 ,  7 ,  8 ) to 70 degrees and the cylinder head bolts ( 9  and  10 ) to 60 degrees a final pass in sequence.        

      Computer-based equipment has been proposed for implementing such fastener preloading technique in mass production operations. However, as previously noted, control during maintenance and repair is as important as control during original assembly.  
      There remains a need in the art for inexpensive equipment which may be employed by maintenance and repair technicians in the field for obtaining the same precision control of fastener preloading as is done during the original manufacturing operation. Additionally, the products on the market that perform such a function are large and cumbersome. These products use torque angle detection techniques that inhibit their ability as well as for the operability in constrained spaces.  
      Accordingly, it is desirable to provide a device that is capable of determining the angle of rotation applied to a fastener as well as display the current angle of rotation.  
     SUMMARY OF THE INVENTION  
      It is therefore an object of the present invention to provide an apparatus that measures and displays the current angle of rotation at which a fastener is rotated.  
      It is another aspect of the present invention to provide an apparatus that measures the angle of rotation after a specified torque is applied to a fastener with an apparatus compactly sized to function in confining areas.  
      The above and other aspects are achieved through the use of a novel combination of features as herein disclosed. In accordance with one embodiment of the present invention, an apparatus measures the angle of rotation beyond a specific reference point and an angle indicator linked to the apparatus indicates the current angle of rotation.  
      In a preferred embodiment, the apparatus comprises an angle selector that is adjustable to the desired angle of rotation, an angle rate sensor that measures the speed and direction of the rotation applied, a processor which calculates the current angle from the rate sensor measurements and a zero point indicator that serves as the basis point for the processor to calculate the selected angle of rotation.  
      In accordance with another embodiment of the present invention, a device for measuring the angle of rotation beyond a specific reference point is comprised of a means for measuring an angle of rotation of the fastener from a fixed reference point and a means for displaying the current angle of rotation. In this alternate embodiment, the means for measuring an angle of rotation is comprised of means for applying an angle of rotation to a fastener, and a means for measuring the angle of rotation as applied to the fastener from a fixed reference point. The means for measuring comprises a means for selecting the desired angle of rotation angle, a means for sensing data from the rate and speed of the rotation being applied to a fastener, a means for calculating the torque angle from the data and a means for indicating a zero point from which the means for calculating bases its angle of rotation measurement.  
      In accordance with another embodiment of the present invention, a method for determining the angle of rotation is comprised of measuring the angle of rotation as applied to a fastener and displaying the current angle of rotation. In this embodiment, the step of measuring the current angle of rotation is comprised of selecting the desired angle of rotation with an angle selector located on an apparatus. Further steps to the method are indicating the zero point to processor as to the basis point to determine the angle of rotation, applying torque to a fastener with a tool to which the apparatus is attached, measuring the rate and speed of the angle of rotation with the angle rate sensor starting from the zero point and calculating the area from the rate and speed to arrive at the torque angle, the area.  
      In accordance with another embodiment of the present invention, a system is used to determine the angle of rotation beyond a specific reference point. The system is comprised of an apparatus that measures the angle of rotation beyond a specific reference point and an angle indicator linked to the apparatus that indicates the current angle of rotation. In this preferred embodiment, the apparatus is comprised of an angle selector adjustable to the desired angle of rotation, an angle rate sensor that measures the speed and direction of the torque applied, a processor which calculates the current angle from the rate sensor measurements and a zero point indicator that instructs the processor as to the basis point to calculate the selected angle.  
      There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are, of course, additional features of the invention that will be described below and which will form the subject matter of the claims appended hereto.  
      In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein, as well as the abstract, is for the purpose of description and should not be regarded as limiting.  
      As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for the designing of other structures, methods and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       FIG. 1  provides an exploded perspective view of the preferred embodiment.  
       FIG. 2  provides a block diagram of the preferred embodiment.  
       FIG. 3  is a view of the preferred embodiment incorporated with a ratchet and socket.  
       FIG. 4  is a flowchart illustrating the steps that may be followed in accordance with one embodiment of the present inventive method or process.  
       FIG. 5  provides a view of an alternate embodiment.  
       FIG. 6  is a view of the alternate embodiment incorporated with a ratchet and socket. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION  
      A preferred embodiment of the present invention provides a device that measures an angle of rotation of a fastener after a specified torque has been applied to the fastener. As illustrated in  FIG. 1 , a preferred embodiment includes a shaft  10  is inserted between a socket and torque wrench. The wrench end  12  is connected to the torque wrench. The socket end  14  is connected to a socket that is chosen for the appropriate fastener. The shaft  10  is linked to an angular rate sensor  16  such as a gyroscope. Additionally, the apparatus contains an angle selector  18 . The angle selector  18  can be a potentiometer, which allows for angle selection in about five degree increments, or a resistance ladder, which allows for finer angle selection. The angle selector  18  varies the voltage and resistance. Any other suitable resistance adjuster can be used in place of either the ladder or the potentiometer.  
      The shaft  18  does not need to be a separate component between a socket and wrench. The shaft  18  itself can be incorporated either with the socket itself, the wrench itself, or be constructed as part of a combined socket and wrench.  
      Both the angular rate sensor  16  and the potentiometer  18  are linked to a microcontroller or processor  20 . The angular rate sensor  16  measures the output steady state voltage that deviates depending on the speed and direction of the torque, using the Corolis effect. The processor then takes these measurements and calculates the area underneath the measured voltage curve to arrive at the torque angle.  
      A housing  22 ,  24 ,  26  encases the shaft  10  and all the other components of the apparatus. The housing  22 ,  24 ,  26  contains a door  28  for insertion of a power source, which in the preferred embodiment includes batteries  30 .  
      The following is an example of how the device is used. After inserting the apparatus between the ratchet and socket, the user adjusts the angle selector  18  to the desired angle. At the time of selection of the angle, the processor  20  notes the voltage. Torque is then applied to the fastener until the desired torque is reached. At this time, the zero point is set. After setting the zero point, the wrench is rotated further. The angular rate sensor  16  measures the output steady state voltage and its deviation based upon the speed and direction of the torque. From these measurements, the processor  20  calculates the torque angle.  
      At some point, the apparatus indicates to the user when the currently calculated torque angle approaches and/or equals the desired angle. The alert can include a constant display of the angle through the use of a display such as a light emitting diode display or can include a single emitting diode to indicate when the angle has been reached. In the preferred embodiment, the invention contains light emitting diodes  32 ,  34  that provide indication to the user. The first diode  32  alerts the user that the fastener is within ten degrees of the specified angle. The second diode  34  alerts the user that the fastener is within one degree of the specified angle. Additionally, a sounding indicator  36  or a sound device activates concurrently with light emitting diode  34 . The sound device  36  in the preferred embodiment is a buzzer. The sound indicator  36  is not limited to the use of a buzzer. It will be readily apparent to one skilled in the art the available replacements for this device.  
       FIG. 2  is a block diagram of the preferred embodiment. At the center of the diagram is a microcontroller  20 . Feeding into the micorcontroller  20  is a potentiometer or other angle selector  18 . The user of the apparatus uses the angle selector  18  to select the desired torque angle. The selection is fed into the microcontroller  20 . From this point, the microcontroller  20  monitors the voltage. The point of selection is used as a reference to calculate the measured torque angle. The output of the gyroscope or angular rate sensor  16  is inputted into the microcontroller or processor  20 . The angular rate sensor  16  measures the output steady state voltage. The output deviates depending on the speed and direction of the torque. These measurements are fed into the microcontroller  20  to where a calculation takes place. The calculation is the area underneath the curve of all the measurements obtained from the angular rate sensor  16 . With this calculation, the torque angle can be detected.  
      The processor  20  controls the light emitting diodes  32 ,  34 ,  40 . The first diode  40  is activated when the zero point is selected subsequent to the depression of button  42 . The button instructs the processor  20  that the current location is the zero-point or reference point from which to calculate the torque angle. When the processor  20  acknowledges the zero point, the light emitting diode  40  is activated.  
      The other diodes are used to alert the user of the currently calculated torque angle. This ranges from a constant display of the angle through the use of a display such as a light emitting diode display or a liquid crystal display to a single emitting diode that alerts as to when the angle is reached. In the preferred embodiment, the invention contains the light emitting diodes,  32 ,  34 , which warn the user. The first diode  32  alerts the user that they are within ten degrees of the specified angle. The second diode  34  alerts the user that they are within one degree of the specified angle. Additionally, a sounding indicator  36  or a sound device activates concurrently with light emitting diode  34 .  
      A switch  44  is also incorporated on the apparatus. The switch  44  controls the power used by the gyroscope  16 , the angle selector  18  and the light emitting diodes  32 ,  34 ,  40 . The switch  44  serves as a power conservation device when the device is not being used to determine the torque angle.  
       FIG. 3  shows the preferred embodiment of the torque angle sensor  46  with a ratchet handle and socket. The sensor  46  is placed between the ratchet  48  and the socket  50 . The ratchet  48  is used to generate the torque to turn a fastener. The torque is transferred to the sensor  46  and then onto the socket  50 . The sensor  46  measures the speed and directions of the torque and uses these calculations to arrive at the angle of rotation.  
       FIG. 4  is a flowchart illustrating the steps that may be followed in accordance with one embodiment of the present inventive method or process. The first step  52  in the process is selecting the desired angle of torque with an angle selector  18 . The preferred embodiment uses a resistance ladder to achieve this method. However a potentiometer as well as other devices are interchangeable with that used in the preferred embodiment. The resistance ladder has a finer angle selection than the potentiometer.  
      The next step  54  is indicating the zero point to the processor in order to determine the angle of torque. The preferred embodiment accomplishes this function with the use of a button or switch  42 . The button or switch  42  instructs the processor to mark this as the origination point from where to measure the torque angle. The processor responds with illuminating a light emitting diode. The illumination is a signal that the processor has indeed received the instruction and has marked it as a reference point.  
      The next step  56  is applying torque to rotate a fastener with a tool. The tool can be a ratchet or socket or any other device that is capable of applying torque. The tool can actually be the device incorporated or built into a torque-generating device. The tool can be manual-driven or power driven.  
      The next step  58  is measuring the rate and speed of the applied torque rotation with the angle rate sensor  16  starting from the zero point. The angle sensor  16  or gyroscope does this by measuring the Corolis effect of the torque.  
      From these measurements, the next step  60  of calculating the area is arrived at to determine the torque angle. The mathematical computations are completed by the processor. The output steady state voltage deviates depending on the speed and direction of the torque. This deviation enables the processor to calculate the torque angle.  
      The next step  62  is indicating the rotation angle of torque applied beyond the zero point using the angle indicator  32 ,  34 . The preferred embodiment uses two angle indicators. The first indicator, a light emitting diode  32 , is illuminated when the torque angle is within ten degrees of the pre-selected desired torque angle. The second indicator, a light emitting diode  34 , is illuminated when the torque angle is within one degree of the specified angle. Concurrently with the second indicator, the apparatus uses a sound indicator  36 . When the emitting diode  34  is activated, the sound indicator is triggered. In the preferred embodiment, the apparatus is a buzzer.  
      The indicating step  62  can use any number of devices. For example, the indicator  34 ,  36  can range from a graduated display that can be used to indicate the current angle calculated to a plurality of diodes as in the preferred embodiment. Additional indicating devices will be readily apparent to those of ordinary skill in the art.  
       FIG. 5  provides a view of an alternate embodiment. In this embodiment, the indicator of torque angle is a display  64  of a digital multimeter  66 . In this embodiment, the current angle of rotation is constantly displayed throughout the angle of rotation. A shaft  70  is placed between a fastener and a torque-generating device such as a ratchet  48 . The speed and direction of rotation of the shaft  70  is monitored by an adapter  72 , which uses these measurements to arrive at the angle of rotation. The angle of rotation is transferred to the digital multimeter  64 . The angle of rotation is shown on the display  66 , which is based from the zero point and continues to show the current angle of rotation.  
      The speed and direction of the angle of rotation applied to the shaft  70  is transmitted to the adapter  72  via the hard wire  74 . The shaft  70  need not be hard wired to the adapter  72 . The transmission can be accomplished by an infrared transmission or over a radio frequency, so that the data from the shaft  70  is transmitted in a non-hard wired configuration. The data is transmitted to a receiver on the adapter  72 . The receiver captures the data to calculate the current angle and transmits this a signal to the multimeter  66 .  
      In addition to a visual display, the preferred embodiment contains a sound generating device  78  on the adapter  72 . When the desired angle of rotation has been reached, the sound device  78  is activated. In the preferred embodiment, the sound device  78  is audible to the human ear with an adequate distance from operation of the invention.  
       FIG. 6  shows an alternate preferred embodiment of the torque angle adapter with a ratchet  48  handle and socket  50 . The shaft  70  is placed between the ratchet  48  and the socket  50 . The ratchet  48  is used to generate the torque to turn a fastener. The torque is transferred to the shaft  70  and then onto the socket  50 . The shaft  70  is monitored by the angular rate sensor  16  to measure the speed and directions of the angle of rotation and uses these calculations to arrive at the angle of rotation. The angle of rotation is calculated by the microcontroller  20 . The result of this calculation is transformed into a signal by the microcontroller  20  and transmitted to the digital multimeter  66  where is seen on the display  76 .  
      The many features and advantages of the invention are apparent from the detailed specification, and thus, it is intended by the appended claims to cover all such features and advantages of the invention which fall within the true spirits and scope of the invention. Further, since numerous modifications and variations will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation illustrated and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention.