Pro-Dex v. Intelligent Automation
`U.S. Patent 7,091,683
`Pro-Dex Ex. 1048
`
`- 1 -
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`

`

`U.S. Patent May 29, 1984
`
`Sheet 1 of 14
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`4,450,727
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`- 2 -
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`

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`U.S. Patent May 29, 1984
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`Sheet 2 of 14
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`4,450,727
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`U.S. Patent May 29, 1984
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`Sheet 3 of 14
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`4,450,727
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`- 4 -
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`

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`U.S. Patent May 29, 1984
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`Sheet 4 of 14
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`4,450,727
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`- 5 -
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`

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`U.S. Patent May 29, 1984
`
`Sheet 5 of 14
`
`4,450,727
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`100
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`CLEAR PEAK, POINTER
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`CNT 1, AND CNT’ 2 REGISTERS
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`- 6 -
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`

`

`U.S. Patent May 29, 1984
`
`Sheet 6 of 14
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`4,450,727
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`STORE TORQUE_IN
`SEQUENTIAL MEMORY
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`- 7 -
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`

`

`U.S. Patent May 29, 1984
`
`Sheet 7 of14
`
`4,450,727
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`BREAK
`AWAY
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`- 8 -
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`

`

`U.S. Patent May 29, 1984
`
`Sheet 8 of 14
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`4,450,727
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`FROM THE X-COORDINATE OF THE INTERSECTION POINT, GET THE
`TORQUE VALUE IN TORQUE MEMORY POINTED TO BUY IT
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`- 9 -
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`

`

`U.S. Patent May 29, 1984
`
`Sheet 9 of 14
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`4,450,727
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`U.S. Patent May 29, 1984
`
`Sheet 10 of 14
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`4,450,727
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`£50
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`- 11 -
`-11-
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`

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`U.S. Patent May 29, 1984
`
`Sheet 11 of 14
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`4,450,727
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`- 12 -
`-12-
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`

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`U.S. Patent May 29, 1984
`
`Sheet 12 of 14
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`4,450,727
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`- 13 -
`-13 -
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`

`U.S. Patent May 29, 1984
`
`Sheet 13 of 14
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`4,450,727
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`SUCCESS]
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`- 14 -
`-14-
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`

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`U.S. Patent May 29, 1984
`
`Sheet 14 of 14
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`4,450,727
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`
`
`fgWINDOW
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`X COORDINATE.——o-
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`- 15 -
`-15-
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`

`

`1
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`4,450,727
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`DIGITAL RETORQUE MEASURING APPARATUS
`
`DESCRIPTION
`
`2
`signals. Since their detection schemes look for changes
`in relative torque values these spikes could trigger false
`readings.
`The present invention is directed to solving one or
`moreof these problems.
`DISCLOSURE OF THE INVENTION
`
`1. Technical Field
`This invention relates to torque measuring systems
`and, more particularly, it involves techniques for sens-
`Thepresent invention is broadly directed toa digital
`ing the amount of previously applied torque to a fas-_
`tener.
`torque detection scheme centering around the use of a
`microprocessor to convert an analog torque signal into
`2. Background Art
`discrete digital sample values which are stored and then
`In a variety of manufacturing applications it is often
`examined in more detail for given characteristics. Dur-
`imperative that a predetermined amount of torque be
`ing the retorque or retightening process, the micro-
`applied to a fastener to form a proper joint. For exam-
`processor is devoted almost exclusively to. the task of
`ple, in automotive applications bolts must be tightened
`converting the analog input signal into discrete samples.
`within a certain prescribed range of torque to properly
`join two parts together thereby assuring good reliability
`It is not burdened with the chore of makingrelatively
`of the joint during expected use. A relatively simpletest
`sophisticated calculations during the time that the input
`has been used in the past to measure fastener torque
`data is being received. Instead, it performs only rela-
`levels. An operator uses a hand torque wrench to en-
`tively simple calculations necessary to define.a “win-
`‘gage the fastenerto be tested. He then uses the wrench
`dow” subset of the samples where the breakaway or
`to apply more torque to the fastener until it finally be-
`negative valley torque values are expected to be found.
`gins to rotate in the tightening direction. Early tech-
`In the preferred embodiment,
`the microprocessor
`niques called for the operator to merely view the read-
`operates generally to detect a change in. slope in the
`ing of the wrench torque indicator just prior to the
`torque curve by subtracting two endpoints of relatively
`“sive” or “breakaway” of the fastener as this torque
`wide segments and comparing the difference with the
`level was thought to be generally associated with the
`contents of a peak slope storage register. If the slope
`amountof torque originally applied to the fastener dur-
`values of a given number of consecutive segments are
`ing the normal assembly process. Later improvements
`substantially less than the peak slope value then the
`of suchatest included the use of a wrench which would
`microprocessor “knows” that breakaway has occurred.
`30
`maintain the position of the indicator at the maximum
`The microprocessor continues to generate and store
`torque level experienced.
`digital samples for a brief but sufficient period oftime to
`Unfortunately, the prior art methods of sensing the
`encompass the negative valley region if a valley did, in
`applied torque were not very precise and the results
`fact, occur during the test. After the window has been
`were not capable of being accurately reproduced from
`defined, the microprocessor stops generating any fur-
`operator to operator. The breakaway torque level was
`ther samples and,
`instead, enters a search mode for
`hard to accurately measure because it wasdifficult for
`examining. the data contained in the window in much
`‘the operator to instantaneously stop applying any more
`more detail. In the disclosed example, the valley torque
`torque as soon ashe noticed fastener motion. Hence, the
`value is found by identifying a data sample followed by
`torque reading was often too high dueto this overshoot-
`a relatively long number of decreasing data-sample
`ing problem.
`values. This effectively identifies the beginning of a
`U.S. Pat. No. 4,244,213 and U.S. Pat. No. 4,319,494 to
`valley and causes the microcomputerto store the most
`Marcinkiewicz (hereby incorporated by reference) dis-
`negative (i.e. least positive) sample value in a negative
`close dramatic improvements in retorque measuring
`peak register. The value in the negative peak register is
`techniques. These patents broadly disclose the concept
`displayed when a certain number of morepositive read-
`of electronically and automatically detecting the
`ings are encountered thus identifying the following
`amount of previously applied torque to a fastener. In
`“hill” of the valley. If there is no discernible valley
`general, electrical circuitry is used to automatically
`torque level, the microprocessor branches to a routine
`detect a changein slopeof the torque signal. The torque
`for detecting the breakaway torque. According ‘to the
`value associated with the occurrence of the slope.
`teachings of the preferred embodiment,
`the torque
`change was displayed as being representative of the
`value associated with the intersection of projections
`amount of torque previously applied to the fastener.
`from two specially defined segments in the window is
`Preferably,
`the circuitry was adapted to detect the
`displayed as the breakaway torque. One ofthe segments
`torque signal value associated with a negative valley
`is associated with the minimum slope within the win-
`occuring after the breakaway point. This negative val-
`dow whereas the other segmentis the first one to devi-
`ley torque, when it occurs, provides an even better
`ate substantially from the contents of the peak slope
`indication of the amount of torque applied to the fas-
`register loaded during the “window definition” se-
`tener duringits original tightening process.
`quence. This technique will serve to consistently iden-
`While the above commonly assigned patents cer-
`tify the breakaway torque value even though the torque
`tainly advanced the state of the art, the particular em-
`curve may vary from that to be normally expected.
`bodiments disclosed therein for carrying out their broad
`The techniqueofthe present inventionis particularly
`teachings can be even further improved. Spurious peaks
`advantageous because it allows the microprocessor to
`or spikes in the torque signal are often encountered
`generate many closely spaced samples. since time con-
`under true operating conditions. These spikes can be
`suming calculations are minimized during the fastener
`generated by things like electrical noise but generally
`tightening process. Soon after breakawayis sensed, the
`they are due to the operator “jerking” the wrench dur-
`microprocessor stops sampling the analog torque signal
`ing the test instead of smoothly applying the torque to
`and now hasplenty of time to go back into memory to
`the fastener. Unfortunately, the analog circuit approach
`calculate the breakaway or valley torque levels with
`of the previous patents cannot readily filter out those
`
`10
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`15
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`20
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`25
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`35
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`40
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`50
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`65
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`4,450,727
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`3
`great precision. Chancesof error are minimized because
`the computer has time to look at many samples and may
`employ techniquesto filter out invalid data signals from
`true trends in the torque curve.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Those skilled in the art will come to appreciate the
`full range of advantages of various features of this in-
`vention by reading the following specification and by
`reference to the drawings in which:
`FIG..1 is a perspective view illustrating a hand torque
`wrench which may embody the present invention;
`FIG. 2 is a typical torque curve that may be gener-
`ated during the testing procedure according to the
`teachings of the present invention;
`FIG.3 is a block diagram ofthe electrical circuitry of
`the preferred embodiment; FIGS. 4 (A-C) comprise a
`schematic diagram showing the details of the electrical
`circuitry of the preferred embodiment;
`FIGS. 5 (A-J) comprise a flow chart illustrating
`sequential steps to be performed in carrying out various
`aspects of the preferred embodiment of the present
`invention; and
`FIG. 6 is a curve illustrating the breakaway value
`detection of the preferred embodiment.
`DESCRIPTION OF THE PREFERRED
`EMBODIMENT
`
`10
`
`15
`
`20
`
`25
`
`FIG.1 illustrates one example of a torque wrench
`testing device suitable for incorporating and using the
`teachings of the present invention. Torque wrench 10
`includes a handle 12 on which housing 14 is mounted on
`intermediate portions thereof. The interior portion of
`housing 14 includes the components making up the
`electronic circuitry which will be described in detail
`later on in this specification. An LCD display 16, key-
`board 18, rotation switch 20 and on/off switch 22 are
`provided on the top panel of housing 14. A shaft 24
`attached to an opposite end of handle 12 includes a
`cylindrical head 26 at its end. Head 26 includessuitable
`strain gauges or other transducers therein for sensing
`the amount of torque applied to a fastener by wrench
`10. A more detailed description of torque wrench 10
`may be obtained by reference to U.S. Pat. No. 4,125,016
`to Lehoczkyet al issued Nov. 14, 1978, which is hereby
`incorporated by reference.
`Torque wrench 10is typically used to test the amount
`of previously applied torque to a fastener such as bolts
`28. Head 26 of torque wrench 10 includes a suitable
`socket in its lower end for receiving the head of one of
`the bolts 28. The wrenchis then rotated by the operator
`in the fastening or clamping direction until further rota-
`tional movement of bolt 28 is noted. This is commonly
`referred to in the industry as the “breakaway” of the
`fastener undertest.
`FIG. 2 showsa typical torque level signal curve that
`may be encountered in this type of retorqueing opera-
`tion. The torque level increases linearly with applied
`force until such time as the fastener begins further rota-
`tional movement. This point shall be referred to as the
`breakaway torque level and is noted by the reference
`numeral 30. In many fasteners the torque level actually
`decreases for a short period of time even though the
`operatoris still applying force to the fastener. This point
`is labeled with the reference numeral 32 and shall be
`referred to as the valley torque. As set forth in the
`above referenced patents to Marcinkiewicz, valley
`torque 32 provides a very close approximation of the
`
`35
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`40
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`45
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`50
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`55
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`60
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`65
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`4
`amount of torque previously applied to the fastener. In
`some instances, however, the particular fastener under
`test does not develop a torque curve with a well defined
`valley. Instead, the slope of the torque curve merely
`changes to some minimum level at the breakawaypoint
`and then increases with further applied force. This is
`represented by the dotted line in FIG. 2. The torque
`level will then increase to a point labeled 34 until the
`operator ceases to apply further force to the wrench.
`According to the teachings of the present invention,
`the valley torque value 32 is automatically and precisely
`identified or, if no valley occurs, the breakaway torque
`level is identified and displayed. The latter, while not
`being quite as accurate as the valley torque level,still
`does provide a close approximation of the amount of
`torque previously applied to the fastener undertest.
`Unfortunately, the input torque curve often encoun-
`ters short-lived but highly fluctuating torque readings.
`These spikes often occur during the early phase of the
`retorqueing process and thus are shownin FIG.2 in an
`exaggerated mannerby reference numerals 36. As noted
`above,the spikes can be causedbyelectrical noise or by
`operator error in not smoothly applying force to the
`fastener undertest. As will appear later herein the pres-
`ent invention provides the capability of precisely de-
`tecting the valley or breakaway torquelevels in spite of
`the occurrence of such spikes.
`Turning then to FIG. 3 there is disclosed a block
`diagram of the major functional components of the
`hardwarefor carrying out the objectives of the present
`invention. The analog input torque signal is supplied
`over line 40 to one input of a comparator network 42.
`The analog torquesignal is representative of the amount
`of torque applied to the fastener. Typically, strain
`gauges in torque wrench head 26 are configured in a
`Wheatstone Bridge circuit whose output forms the ana-
`log torque signal.
`The system employs a microprocessor 44 which
`forms the heart of a microcomputer system. Micro-
`processor 44 has an output which is connected to a
`digital to analog converter 46 whose output is coupled
`to another input of comparator 42. Under the control of
`a program within program storage memory 48 the mi-
`croprocessor 44 uses a reiterative process to generate
`discrete digital samples from the analog input signal.
`The microprocessor 44 converts the output signal from
`comparator 42 into a binary number whichis, in turn,
`converted back to an analog signal by way of D/A
`converter 46. The analog output of converter 46 is
`compared to the torque signal and fed back to the input
`of microprocessor 44. This interactive process is re-
`peated until a binary number is found which matches
`the torque signal. The binary numbers or samples are
`stored in a random access memory 50 on a sequential
`first in/first out (FIFO) basis. Memory 50 serves as a
`window sample storage device for storing a subset of
`the digital samples associated with portions of the
`torque curve shown in FIG.2.
`According to the teachings of this invention, two
`broad functional steps are employed to ascertain the
`breakaway or valley torque values. Thefirst step is to
`define the window of samples in memory 50. The win-
`dow should be wide enough to encompass the break-
`awaytorque value 30 and valley torque value 32. How-
`ever, the size of the window should not be any larger
`than necessary. The next broad step is for the micro-
`processor 44 to examine orsearchall of the data values
`in the window for the precise breakaway or valley
`
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`-17-
`
`

`

`4,450,727
`
`=0
`
`20
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`25
`
`35
`
`6
`5
`analog torque signal on the noninverting inputis greater
`torque values. Memory 50 contains 128 samples in the
`thanthat supplied by D/A converter46 to the inverting
`preferred embodiment. During these steps registers
`input, microprocessor 44 will see a logical1at its input.
`52-58areutilized in the performanceofcertain calcula-
`Aswill be described in connection with the conversion
`tions as will later be described. The detected breakaway
`routine the microprocessor generates a binary number
`or valley torque is then displayed on display 16. Alter-
`and sendsthis numberto the input of D/A converter 46.
`natively, or in addition to display 16 there may be pro-
`D/A converter 46 isa CMOSbinary multiplying digital
`vided a printer for generating a hard copy ofthe test
`to analog converter using conventional ladder switch-
`results. The system utilizes a buzzer or beeper 60 which
`ing techniques to effect the conversion process. In this
`will beep once if the value displayed is the breakaway
`particular embodiment D/A converter 46 utilizes a
`torque and will beep twiceif the value displayed is the
`DAC1232 component 64 made by National Semicon- |
`valley torque.
`FIGS. 4 (A-C) comprise an electrical schematic of
`ductor. The output of component64 is coupled to an op
`amp 66 in the manner suggested by the component
`the components making up the system of the preferred
`manufacturer. Op amp 66 serves as an inverting ampli-
`embodiment. Microprocessor 44 is an eight bit micro-
`fier whose output has an absolute magnitude propor-
`processor such as the Motorola MC146805. As known
`tional to the digital value at the input to D/A converter
`in the art, microprocessor 44 includes various input-
`46.
`/output ports for. receiving and sending information.
`Other inputs to microprocessor 44 may include cir-
`Among the inputs to microprocessor 44 are the
`cuitry generally designated by the numerals 68 and 70
`switches associated with keyboard 18. Keyboard 18
`for communicating with an optional printer. The cir-
`allows the user to select various modes of operation and
`cuitry 68 provides outputs to the printer whereas cir-
`to enter control data values. For example, one mode
`cuitry 70 accepts acknowledgement signals from the
`that can be selected will cause the system to detect the
`absolute peak torque (peak mode) that is applied to the
`printer.
`Circuitry 74 operates as a calibration circuit. When
`fastener under test. Another mode of operation adapts
`the system enters the calibration mode the relay in the
`the system to track or display the instantaneous torque
`circuit activates the switch which, in turn, couples the
`value. Of particular concern to the present inventionis
`precision calibration resistor to amplifier 62 so that its
`the retorque modes. The system can be programmed by
`output is equivalent to a full scale reading. Suitable
`the user in a first retorque mode to detect breakaway
`calibration techniques may be then used to calibrate the
`torque only or in a second retorque mode where the
`system. Theoscillator circuitry 76 generates the master
`valley torque is displayed if one occurred during the
`clock signal for driving microprocessor 44 in the man-
`test and, if not, then breakawayis displayed. The detec-
`ner known in the art. Suitable circuitry for driving
`tion of the breakaway torque only follows the same
`buzzer 60 is also connected to microprocessor44.
`operational steps as in the second mode of operation
`The output of microprocessor 44 is connected to
`(except for the additional valley detection routine) and
`external memory devices and display 16 as well as to the
`thus, the present invention will be described in connec-
`D/A converter 46. The memory devices include a pro-
`tion with this second retorque mode of operation.
`grammable read only memory 78 which contains the
`The operator can program in a threshold torque
`operating program for the microprocessor 44 and two
`value andasensitivity reference value that are designed
`random access memories (RAMs)80 and 82.Display 16
`to be used for the particular fastener checking test. As
`includes a display driver component 84 for controlling
`will become apparent later herein the threshold torque
`the operation of a multidigit
`liquid crystal display
`value is the value above which the microprocessor
`(LCD) 86. The transfer of data within the system in-
`begins to save digital samples in memory. Normally, the
`cluding the reading and writing of the memories are
`threshold is set at a sufficiently high level that extrane-
`carried out in a manner known in the art and mayin-
`ous input signals generated during set up are effectively
`clude such devices as address buffer 88 and a binary to
`ignored. Thesensitivity reference value is a fraction or
`BCD decoder 96 serving as a chip selector.
`percentage of the peak slope value below which will be
`Selected sections of RAM memories 80 and 82 are
`used to trigger the window definition step ofthe system
`used as the window sample memory 50, peak slope
`operational sequence. The importance ofthis sensitivity
`register 52, peak x fraction register 53, initial peak regis-
`reference value will become apparent later herein. Suf-
`ter 54, negative peak register 56 and minimum slope
`fice it to say that the user has a considerable degree of
`register 58. Those skilled in the art will appreciate that
`flexibility in defining the particular parameters of the
`the purpose of registers 52-58 is to temporarily store
`test to be performed. Thisflexibility is especially advan-
`data and thus, the registers may be made upofindivid-
`tageousdueto the fact that the same torque wrench and
`ual storage devicesor, as in the preferred embodiment,
`detection system may be used for a wide variety of
`dedicated locations within a larger RAM memory.In
`different fasteners, each having their own particular
`fact, the internal memory (not shown) in microproces-
`tightening characteristics.
`sor 44 may be used in someinstances.
`The output from the strain gauge bridge or analog
`With additional reference to the flow chart of FIGS.
`input signal
`is sensed by a differential amplifier 62
`5 (A-J), the operation of the system of this invention
`whose inputs are coupled to the two outputs of the
`will be described. When the user chooseseither of the
`bridge. The output of differential amplifier 62 thus is a
`retorque modes of operation the microprocessoris in-
`voltage whose absolute magnitudeis proportional to the
`structed by the program shown in FIGS. 5 (A-J). Ini-
`amountof torque applied to the fastener. The output of
`tially, all of the counters, registers and flags pertinent to
`differential amplifier 62 is connected to the noninvert-
`this routine are cleared as illustrated in steps 100-112
`ing input of comparator 42. Theinverting input of com-
`(FIG. 5(A)). As the operator uses wrench 10 to apply
`parator 42 is coupledto the outputof digital to analog
`torque to the fastener under test the analog torquesig-
`converter 46. The output of comparator 42 will either
`nal is converted into digital values by way of the con-
`be a logical one or zero depending uponthe relationship
`version routine shown in FIGS. 5G-J.
`between the voltage valuesat its inputs. As long as the
`
`40
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`'
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`_
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`45
`
`50
`
`60
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`65
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`4,450,727
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`7
`The A/D conversion routine is entered by way of a
`software interrupt (SWI) which occurs about once
`every one millisecond to generate a digital sample with
`a value corresponding to the analog torque signal value
`occurring at the time the sample is taken. The micro-
`processoris designed to convert the analog signal into a
`precision twelve bit data value, even though the mi-
`crocomputer system employs conventional eight bit
`processing techniques. FIG. 5G showsthe steps used to
`generate thefirst eight bits of the digital sample value.
`Briefly, the most significant eight bits of the previous
`value which wasstored in memoryis fetched and fed to
`the input of D/A converter 46. After waiting about 2
`usec for the output of the D/A to be generated, the
`microprocessor determines whether
`that
`signal
`is
`greater or less than the analog torque signal. Depending
`on the outcome of those tests the microprocessor in-
`creases or decreases the value of the most significant
`eight bits of the sample value until approximate match-
`ing occurs. Then in FIG. 53 the microprocessor uses a
`successive approximation technique to set the lower
`four bits to the precise value. The upper eight bits are
`saved for the next conversion routine.
`Returning to FIG. 5(A) each new torque reading is
`tested in step 152 to determine whetherit is greater than
`the user programmed threshold value. As soon as this
`happensthe microprocessor 44 will start storing succes-
`sive samples in sequential locations in memory 50 as
`represented by step 160 and the address pointeris decre-
`mented to the next memory location (step 162). It
`should be realized that during a typical test over about
`a thousand numberof samples will be taken. It would be
`wasteful of memoryto haveto store all of these samples
`since very few of them are really very pertinent. There-
`fore, a memory segment which is sufficiently large to
`store 128 samples is used as a recirculating buffer where
`the newest sample value takes the place of the oldest
`sample value. Of course, if economy is not of a great
`concern then a memorylarge enough to storeall of the
`samples could be employed.
`Test 166 (FIG. 5(B)) determines if at least 50 torque
`samples have been stored. If so, the microprocessor
`calculates the slope of a 50 sample wide segment. As
`reflected by step 172 this is accomplished by subtracting
`the value of the N-50 sample reading from the current
`or N sample value. In other words, the torque of the
`current data sample has subtracted from it the value of
`the 50th preceding sample. Since all of the samples are
`taken at equally spaced time intervals this simple sub-
`traction process calculates the slope over a relatively
`wide segment of the torque/time curve represented in
`FIG.2. If the current slope is greater than the maximum
`or peak slope that has been generated so far, the slope
`value is stored in a memory location corresponding to
`peak slope register 52. Additionally, the new peak slope
`value is multiplied by the user programmablesensitivity
`factor and loaded in the peak x fraction register 53.
`After registers 52 and 53 are loaded, a software counter
`referred to as counter No. 1 is cleared by operation 181.
`Software counters are well knownin the art and gener-
`ally consist of a given memorylocation whose contents
`are either incremented or decremented by controlsig-
`nals.
`It should be appreciated that during the portion of the
`curve of FIG. 2 between the threshold level (Th) and
`breakaway 30 that the slopes of each of the segments
`will be substantially constant. Thus, the system gener-
`ally passes through the preceding sequence of steps
`
`until the current slope is less than the contents of the
`peak x fraction register 53 as represented by the test
`block 184. When eight successive segments have slopes
`less than or equal to the contents of the peak x fraction
`register (test 186) operation 188 sets the breakaway 1
`flag and buzzer 60 is beeped once.
`It might be best to reflect on what has happened at
`this point. The object of this portion of the sequenceis
`to start the definition of the window (labeled “W”in
`FIG. 2) which will be examined by the microprocessor
`in more detail later on. The window must be relatively
`small so as to minimize the examination time butit has
`to be sufficiently large so as to encompass breakaway
`point 30 and valley torque 32 if one does occur. So far
`in the program the microprocessor has determined that
`the conditions are right for breakaway to have oc-
`curred. When eight successive segments have slopes
`less than the peak x fraction register 53 the chances are
`very good that the breakaway point 30 has occurred in
`one of the previously generated 64 samples. The point
`lableled B1 on the curve of FIG.2 represents where the
`breakaway 1 flag may have occurred in a typicaltest.
`Note particularly that this flag and thus the beginning of
`the window “w”could not have been set by short lived
`spikes in the torque signal.
`After the breakaway 1 flag (B1) is set, the micro-
`processor 42 will continue to convert the analog torque
`signal into digital samples until 64 more samples are
`taken after the B1 flag has been set. In FIG. 5B this test
`164 is made by looking for a true state for the break-
`away 1 flag. A second software counter referred to as
`counter No. 2 is incremented by 1 every time a new
`sample is taken (block 190). In test 191 when the con-
`tents of counter No. 2 is greater than or equal to 64 the
`breakaway 2 flag (block 192) is set defining the end of
`the window as reflected by B2 in FIG. 2. The micro-
`processor 44 then stops generating any further samples
`because the end of the window has now been defined.
`Referring to FIG. 5A the test 158 will be true and test
`194 negative so that the microprocessor will now jump
`to the “Search”routine beginning at block 200 in FIG.
`SE and encompassing FIGS. 5C through 5F as well.
`Turning then to FIG. 5E, preliminary steps 200-208
`are taken to ensure that all of the sample values within
`the windowaresignificantly larger than the threshold
`value as would be expected in a normaltest. If for some
`reason the torque values are below the threshold an
`error is detected. As noted before, the system may be
`used in two retorque modes(test 210); one in which
`only the breakaway torque is detected and the otherin
`which the valley torque is displayed if one occurs and
`otherwise, just breakaway torque is displayed. The
`breakaway torque is detected in the same manner in
`both modes. Therefore, description of the second mode
`wiil suffice. In the second mode of operation the micro-
`processor searches the window for a valley torque level
`32 if one, in fact, occurred during the test of the particu-
`lar fastener. In operational step 214 the microprocessor
`begins with the first sample in the window andstores
`that valuein initial peak register 54 and negative peak
`register 56 (FIG. 3). A software counter referred to as
`counter No. 1 is loaded with the number8 as reflected
`by step 216. A software pointer referred to as a torque
`memorypointer is incremented to fetch or point to the
`next sample in the wi