Pro-Dex v. Intelligent Automation
`U.S. Patent 7,091,683
`Pro-Dex Ex. 1024
`
`- 1 -
`
`

`

`U.S. Patent
`
`Oct. 29, 1991
`
`Sheet 1 of 6
`
`5,061,885
`
`QAddlHO
`lig=ON
`
`
`
`WNOISQaddlH9Le
`
`WNODISON
`
`801
`
`WNOIS10x|{c
`
`YOLVTIDSO
`
`eeeeeeee3Lt14g
`
`
`
`nanaonwew(M77
`
`JTONY
`
`YINIWHSALSG
`
`- 2 -
`
`
`
`

`

`Sheet 2 of 6
`
`5,061,885
`
`FIG. 2A
`
`FIG. 2B
`
`U.S. Patent
`
`Oct. 29, 1991
`
`- 3 -
`
`

`

`U.S. Patent
`
`Oct. 29, 1991
`
`Sheet 3 of 6
`
`5,061,885
`
`
`
`FIG. 3
`
`- 4 -
`
`

`

`Oct. 29, 1991
`
`SWITCH 9
`
`
`
`
`
`MOTORPOWERSOURCE
`
`
`
`
`
`CIRCUITPOWERSOURCE
`
`FROM
`
`- 5 -
`
`USS. Patent |
`
`Sheet 4 of6
`
`5,061,885
`
`ccWw
`
`e=2O
`
`Q
`oO
`
`

`

`U.S. Patent
`
`Oct. 29, 1991
`
`Sheet 5 of 6
`
`5,061,885
`
`
`
`QNOOAS20HA14VSdOLSHAMOdSHL
`
`
`
`
`
`1NOG3ldYVO$1DNINSLHOLLWNidSHL
`
`
`
`TLNSYkNDKHOLOW
`
`
`
`
`
`NOILVLOYSHL
`
`
`
`SdOLSATIYVHOdWSL
`
`
`
`INIOdLYVLS
`
`ONIM3AYOS40
`
`- 6 -
`
`
`

`

`U.S. Patent
`
`Oct. 29, 1991
`
`Sheet 6 of 6
`
`5,061,885
`
`
`
`
`
`GQNOOSS¢'0H3LdVSdOLSYSMOdSHL
`
`LNOQ3IdYVDSIONINSLHOILWNidSHL
`
`
`
`]LNSYYNDHOLOW
`
`NOWVLOYSHL
`
`
`
`SdOLSAllYVYOdW3L
`
`
`
`LNIOdLYVLS
`
`ONIM3SYOS4O
`
`- 7 -
`
`
`

`

`1
`
`_ POWER SCREWDRIVER
`
`5,061,885
`
`2
`suck up a screw through the top cover C. The suction
`pipe D is connected to a vacuum pump (not shown).
`The top coverC is slidably supported by a spring E.
`The top cover C is withdrawn into the body of the
`screwdriver by pressing the screwdriver as a screw is
`screwed into the object.
`The motor M is connected to a rotation detector 1,
`which has a rotation sensor 10 mechanically mounted
`on the motor M. Therotation sensor 10 includes a re-
`flection photointerrupter 101 and a rotating slit disk 102
`having a predetermined numberofslits. The reflection
`photointerrupter 101 illuminates to the rotating slit disk
`102 and detects the reflecting light from the non-slit
`area of the rotating slit disk 102, which represents the
`rotation of the motor M. Thusthe reflection photointer-
`rupter 101 provides the output pulses representing the
`rotation of the motor M. The output signal from the
`rotation sensor 10 is delivered to a stop discriminator 12
`through a waveform arrangement circuit 11 (signal
`conditioner) where the signal is arranged in a certain
`waveform.
`Thestop discriminator 12 determines when the motor
`M stops by detecting the absence of rotation pulse sig-
`nals from the waveform arrangementcircuit 11 (signal
`conditioner) for a predetermined period. As shownin
`FIG. 3, the stop discriminator 12 comprises a flip-flop
`120 and timers 121 and 122. When the motor M stops,it
`is unknown whetherornotthe rotating slit disk 102 will
`stop at the exact position whereoneoftheslits is below
`the reflection photointerrupter 101. Therefore, theflip-
`flop 120 detects both the up and downpulses and timers
`121 and 122, respectively, are used to determine if the
`pulses have stopped the pulses for the predetermined
`time regardless of where the rotating slit disk comes to
`rest.
`The stop signal from the stop discriminator 12 is fed
`to a voltage controller 2 and a power controller 4
`through a delay circuit 5. The delay circuit 5 provides a
`predetermined delay after stopping of the motor M
`during which torqueisstill applied by the motor to the
`bit, to improvethestability of “MASHIJIME”.
`The voltage controller 2 includes an oscillator 20, a
`counter 21 and a voltage converter 22. The oscillator 20
`receives the instruction signal from a time determiner 3
`and generates pulses whose frequency corresponds to
`the instruction signal. The time determiner3 is operated
`to set the frequency ofthe oscillator 20 by the operator,
`and the determiner 3 adjusts
`the time of “MA-
`SHIJIME”. The pulses from the oscillator 20 are
`counted at the counter 21, the output of which is con-
`verted to a voltage by the voltage converter 22. The
`voltage converter 22 has a predetermined minimum
`voltage and a predetermined maximum voltage. The
`voltage converter 22 outputs voltage signals corre-
`sponding to the counter output and in the range from
`the maximum to the minimum voltage. The counter 21
`counts the predetermined number of pulses from the
`oscillator 20. Therefore counting the predetermined
`numberof pulses takes a longer time when the pulse
`frequency from the oscillator 20 is low than when the
`pulse frequency is high. Thus the count time is defined
`by the frequency set by the time determiner 3. The
`counter 21 supplies an end signal to a timer 6 whenit
`finishes counting.
`The voltage converter 22 in the embodiment shown
`in FIG. 4 has resistors R1-R8 connected in series and
`photocoupiers PC1-PC8 which are in parallel and by-
`
`5
`
`25
`
`40
`
`BACKGROUNDOF THE INVENTION
`Thepresent invention relates to a screwdriver by an
`electric motor.
`Powerscrewdrivers are utilized in a field of precision
`machinery such as assembly of watches.
`In screwing with power screwdrivers, the poweris
`increased to strengthen the rotation torque when the
`driver screw tightens to the point that it cannot rotate
`anymore. By increasing the power,
`the screwdriver
`tries to rotate, and sometimesit rotates a little bit and
`tightens the screw. The operation is called “MA-
`SHIJIME”, which meansfinal increased tightening. In
`“MASHIJIME” the power
`is gradually increased,
`which may makethe rotation torque of the motorstable
`and provide a reliable attachment.
`Though longer “MASHIJIME” provides more sta-
`ble torque, in some jobs, shorter assembly time may be
`needed more than stable torque. Furthermore, “MA-
`SHIJIME”time varies depending on the type of screw
`to be screwed or the production system where the
`powerscrewdriveris applied.
`The screwdriver occasionally rotates a half revolu-
`tion or morein the final tightening “MASHIJIME”for
`several reasons. One reasonis that the bit of the driver
`rotates in the screw head because the bit does not match
`the head of the screw or because thebit is broken. Such
`false rotation of the screwdriver causes weak and unre-
`liable fastenings because ofthe lack offinal tightening
`so that the device so assembled become substandard.
`In manual operation,
`the operator may detect the
`false rotation of the power screwdriver bit. But today
`screwdrivers are mostly operated by automatic ma-
`chines like robots, which makes it difficult to detect
`false rotation of the screwdriver bit and causes many
`substandard devices.
`An object of the invention is to provide a power
`screwdriver which can change the final
`tightening
`“MASHIJIME”time.
`A further object of the invention is to provide a
`power screwdriver which can detect repetitive occur-
`rence of false rotation of a bit of a screwdriver.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`FIG. 1 is a block diagram showing one embodiment
`of the invention.
`FIGS. 2A and 2B are explanatory drawing showing
`the mechanical construction of the embodiment;
`FIG. 3 is a block diagram showing a detail of a stop
`discriminator;
`FIG. 4 is a circuit diagram showing a detail of a
`voltage converter;
`FIG. 5 is a circuit diagram showing a detail of a
`powercontroller;
`FIG. 6 and 7 are graphs showingtherelation between
`motor current and time illustrating the operation of a
`power screwdriver according to the teachings of the
`invention;
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENT
`
`In the embodiment shown in FIGS. 1 and 2, a power
`screwdriver comprises a motor M and a bit B. The
`motor M is controlled by a power controller 4. As
`shownin FIG. 2, the bit B is covered by a top coverC.
`A suction pipe D is provided at the base of the bit B to
`
`65
`
`- 8 -
`
`

`

`5,061,885
`
`— 5
`
`25
`
`30
`
`45
`
`50
`
`55
`
`3
`4
`pass the resistors, respectively. The resistors R1-R8 are
`The operatorstarts turning the screw and,as the screw
`coupled to the corresponding bits of the output of the
`is tightened, the torque increases gradually. The current
`counter 21. Eachresistor is bypassed by a photocoupler
`5 flowing in the motor M increases depending on the
`PC coupled to the output of the counter 21. This forms
`torque increase during interval c. When the screw is
`a composite, segmented resistor having a resistance
`almost tightened to a face of the work, the motor M is
`forced to temporarily stop rotating during interval d.
`corresponding to the digital value of the output of the
`In the a, b, c and d intervals, the rotation sensor 10 in
`counter 21. Thus, at an output terminal OUT,an output
`voltage corresponding to the output of the counter 21
`FIG. 1 delivers the rotation pulses to the stop discrimi-
`may be developed.
`nator 12 through the waveform arrangement circuit 11
`Transistor Tri-Tr8 are connected between the
`for signal conditioning. When the motorMstops, and
`no pulses are fed to the stop discrimination circuit 12,
`counter 21 and photocouplers PC1-PC8. The transis-
`tors Tr are individually switched by the individual out-
`the circuit 12 sense the stopping of rotation of the motor
`puts of the counter 21. Whenatransistor Tris “ton” the
`M and issues the stop signal on line 116 to the delay
`circuit 5. At the time, the current in the motor M in-
`photodiode of the corresponding photocoupler PC
`emits light thereby shunting the correspondingresistor
`creases and it is held for the rest time defined by the
`segment.
`delay circuit 5, i.e., interval d. The screw is firmly tight-
`The outputofthe digital-to-analog voltage converter
`ened to the face of the work in this interval d, which
`22 is sent to a power controller 4 via line 106 which
`prevents substandardtightening.
`gradually increases the voltage supply online 108 to the
`The stop signal on line 116 makes the oscillator 20
`M in accordance with the output of the voltage con-
`Start generating pulses. The counter 21 counts the
`verter 22. The powercontroller 4 alters the voltage to
`pulses and delivers a count value to thedigital to analog
`the motor M between a predetermined minimum volt-
`voltage converter 22. The voltage converter 22 outputs
`age at which the motor M stops to a predetermined
`a voltage signal on line 106 which increasesin stepwise
`maximum voltage.
`fashion corresponding to the count number. Thesignal
`Whenthe counter 21 reaches the maximum count, the
`on line 106 is applied to the power controller 4. The
`increase of voltage from the voltage converter 22 and
`powercontroller 4 supplies the motor M with a voltage-
`from the powercontroller 4 stop. Simultaneously, the
`increasing drive signal thereby increasing the torque of
`timer6 starts via a signal on line 112 from the counter
`the motor M in stepwise fashion during interval e. The
`21, and, after predetermined interval, the timer 6 sends
`increase of the driving voltage stops when the counter
`a signal via line 114 to a power source open/close
`21 stops counting and the voltage then reachesthe pre-
`switch 9 which delivers a disable signal on line 110 to
`determined maximum value. The counter 21 providesat
`the powercontroller4.
`this time the count end signal on line 112 to the timer6,
`The powercontroller 4 respondsto the stop signal by
`whichthenstarts to count for a certain time (0.2 second
`cutting off the power to the motor M. In this embodi-
`in the illustrated embodiment). During the interval f,
`ment, the power source open/close switch 9 provides a
`the maximum voltageis held level. After timeout bythe
`enable/disable signal on line 110 to the power control-
`timer6, the power source open/close switch 9 issues the
`ler 4 after the predetermined interval from the time
`stop signal on line 110 to the powercontroller 4, and the
`whenthe motor M stops and then re-enables the power
`motor M stops. At this point, the screwing job is done.
`controller 4 for turning the next screw.
`At a predetermined time after the motor M stops, 0.6
`The details of the power controller 4 are shown in
`seconds in the illustrated embodiment,
`the power
`FIG. 5.
`source open/close switch 9 provides the return signal
`The rotation speed of the motor M is controlled by
`on line 110, by which the motor M generates again and
`controlling a current between the emitter and the col-
`repeats the operation described above.
`lector of a Transistor T2. The Transistor T2 forms a
`FIG. 7 shows the wave form of the motor current
`current amplifier with a transistor T1, which is con-
`whentheoscillator 20 generates a lower frequency than
`illustrated in FIG. 6. In FIG. 7 the interval e of “MA-
`trolled by the output of an operational amplifier 40.
`Before starting “MASHIJIME”, the initial rotation
`SHIJIME” is longer than in FIG. 6. A longer “MA-
`velocity of the motor M is controlled so as to be a stan-
`SHIJIME”provides a more securely fastened screw.
`dard value determined by determiner 42 and aninitial
`Contrary to this, the interval e may be shortened from
`rotation variable register 43. At the starting of “MA-
`the interval shown in FIG. 6. For example, an almost
`zero timeinterval and vertical increase of motor current
`SHIJIME”, a changeover switch 45 is changed by the
`signal from the delay circuit 5 and the motor M is con-
`may be provided. Many other times for interval e may
`also be used.
`trolled by said voltage converter 22 and by a secondary
`power source standard value determiner 44 to increase
`A false rotation detector 7 and a false rotation analy-
`stepwise the revolution velocity of the motor M.
`zer 8 will be explained with reference to FIG. 1.
`An open/close switch 46 in FIG. 5 ts switched by the
`Thestop signal of the motor M from thestop discrim-
`ination circuit 12 is fed to the false rotation detector 7
`signal from the power source open/close switch 9 in
`FIG. 1 to switch the outputof the operational amplifier
`via line 120. Thefalse rotation detector 7 includes a gate
`40 on or off. The output of the operational amplifier 40
`circuit 70 which is opened by the stop signal on line 120
`switches the transistor Tr2 on or off which stops or
`and transmits the rotation pulses of the motor M on a
`Starts the motor M.
`line 122 to a rotation pulse counter 71. The rotation
`The operation of the rotation detector 1, the voltage
`pulse counter 71 counts the rotation pulses and outputs
`controller 2, the time determiner 3, the power control-
`the count value signal
`to a coincidence detector 72,
`ler 4, the delay circuit 5 and the timer 6 will be de-
`which compares the rotation pulses representing the
`65
`scribed with reference to FIGS. 6 and 7. As shownin
`actual rotation angle with the predetermined standard
`FIG. 6, excess current flows in the motorMatstarting,
`rotation angle indicated by an angle determiner 73 by a
`as shownin interval a, and the current soon decreases
`signal on line 124. The angle determiner 73 mayset any
`1/n rotation as standard value. The coincidence detector
`downto a Stationary state, as shown during intervalb.
`
`40
`
`60
`
`- 9 -
`
`

`

`5,061,885
`
`6
`output, a counter having an output for counting the
`output of the oscillator and a controller which
`supplies the power corresponding to the output of
`the counter; and
`meansforsetting a time of increase of a power supply
`at an arbitrary value, wherein said meansforset-
`ting includes a means for changing a frequency of
`the output of the oscillator.
`2. A power screwdriver as claimed in claim 1
`wherein
`said controller has resistors connected in series, each
`of which may be respectively bypassed by the
`output of the counter, said resistors forming a com-
`posite resistance corresponding to the output of the
`counter.
`
`3. A power screwdriver comprising:
`a motor;
`means for detecting stoppage of the motor due to
`load in excess of a predetermined value;
`meansfor gradually increasing power to the motorto
`a predeterminedvalueafter detecting said stoppage
`of the motor;
`meansforsetting a time of increase of a power supply
`at an arbitrary value;
`meansfor detecting rotation of a driven bit in excess
`of a standard rotation when said means for gradu-
`ally increasing power to said motor increases the
`powersupply;
`means for counting a number of detected rotations;
`and
`meansfor delivering an alarm signal if a count from
`said means for counting reaches a standard value.
`4. A power screwdriver as claimed in claim 3 com-
`prising:
`means for determining said standard value of the
`countat an arbitrary value.
`5. A power screwdriver as claimed in claim 3 com-
`prising:
`means for determining said standard rotation at an
`arbitrary value.
`6. A power screwdriver as claimed in claim 3 com-
`prising:
`meansfor indicating said rotation when said means
`for gradually increasing power to said motor in-
`creases the power supply.
`*
`*
`*
`*
`*
`
`5
`72 provides a decision of the false rotation occurrence
`of the bit B whenit receives rotation pulses indicating a
`rotation angle of more than the standard value and
`delivers an NGsignal. Since the motor M rotates only
`slightly in the final tightening, namely “MASHNIME”,
`the coincidence detector 72 may decide that a false
`rotation has occurred if it detects more thana half rota-
`tion. In the embodiment shown, a half rotation is se-
`lected by the angle determiner 73 as a standard value.
`An angle indicator 74 is connected to the rotation
`pulse counter 71 and coincidence detector 72. The angle
`indicator 74 indicates the actual rotation angle from the
`count from rotation pulse counter 71 and thesettled
`rotation angle from the angle determiner 73.
`The output from the coincidence detector 72 online
`126is inverted at an invertor INV andis provided as an
`OKsignal which indicates, when active, that there is no
`false rotation.
`Thefalse rotation output signal from the coincidence
`detector 72 is also fed to a false rotation analyzer 8. The
`false rotation analyzer 8 includes a false rotation
`counter 80, a coincidence detector 81 and a false rota-
`tion determiner 82. Thefalse rotation counter 80 counts
`the numberof occurrenceofthe false rotation which is
`compared at the coincidence detector 81 with the oc-
`currence numberdeterminedbythe false rotation deter-
`miner 82. The coincidence detector 81 decides that the
`bit B is chipped if the number counted by the false
`rotation counter 80 reaches the standard numberindi-
`cated by the false rotation determiner 82. In such a case
`the coincidence detector 81 provides a Bit-Chipped
`signal.
`The signals OK, NG and Bit-Chipped may be dis-
`played by an appropriate indicator, and the signals may
`be utilized as control signals to other equipment. The
`NGsignal and the Bit-Chipped signals can also be sup-
`plied to the power controller 4 to stop the motor M.
`Whatis claimed is:
`1. A power screwdriver comprising:
`a motor;
`means for detecting stoppage of the motor due to
`load in excess of a predetermined value;
`meansfor gradually increasing power to the motor to
`a predetermined valueafter detecting said stoppage
`of the motor, wherein said means for gradually
`increasing powerincludes an oscillator having an
`
`5
`
`10
`
`20
`
`25
`
`30
`
`35
`
`45
`
`30
`
`35
`
`65
`
`- 10 -
`-10 -
`
`

`

`UNITED STATES PATENT AND TRADEMARKOFFICE
`CERTIFICATE OF CORRECTION
`
`5,061,885
`:
`PATENTNO.
`> October 29, 1991
`DATED
`INVENTOR(S): Kenji Fukuhara
`
`It is certified that error appears in the above-indentitied patent and thatsaid Letters Patentis hereby
`corrected as shownbelow:
`
`On title page,
`
`item [73] Assignee: delete "Kayashi" and insert --Hayashi--
`
`Signed and Sealed this
`
`Sixteenth Day of November, 1993
`
`Artest:USnee lehmm—
`
`Attesting Officer
`
`Commissioner of Patents and Trademarks
`
`BRUCE LEHMAN
`
`
`
`- 11 -
`
`

`

`
`
`UNITED STATES PATENT AND TRADEMARKOFFICE
`CERTIFICATE OF CORRECTION
`
`PATENTNO.
`
`: 5,061,885
`
`> October 29, 1991
`DATED
`INVENTOR(S): Kenji Fukuhara
`
`It is certified that error appears in the above-indentified patent and that said Letters Patent is hereby
`corrected as shown below:
`
`On the title page:
`"Hayashi",
`
`Item [73] "Assignee" , delete "Kayashi" and insert
`
`Signed and Sealed this
`
`First Day of March, 1994
`
`Aates:Weance bhma~
`
`Attesting Officer
`
`Commissioner of Patents and Trademarks
`
`BRUCE LEHMAN
`
`- 12 -
`
`
`