Pro-Dex v. Intelligent Automation
`U.S. Patent 7,091,683
`Pro-Dex Ex. 1039
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`U.S. Patent
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`Mar.2, 2004
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`Sheet 1 of 3
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`US 6,700,341 B2
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`U.S. Patent
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`Mar.2, 2004
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`Sheet 2 of 3
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`US 6,700,341 B2
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`U.S. Patent
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`Mar.2, 2004
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`US 6,700,341 B2
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`Sheet 3 of 3
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`US 6,700,341 B2
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`1
`MICROCONTROLLER FOR AND A
`METHOD OF CONTROLLING OPERATION
`OF THE SAFETY CLUTCH OF A HAND-
`HELD ELECTRIC POWER TOOL
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`BACKGROUND OF THE INVENTION
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`1. Ficld of the Invention
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`The present invention relates to a hand-held electrical
`power tool such as, e.g., a drilling tool or a chiseling tool,
`including a safety clutch for breaking the force transmitting
`chain from the electrical drive to the working tool sprindle
`in case of dangerous operational conditions such as jamming
`of the working tool, and relates in particular to a microcon-
`troller for controlling the safety clutch operation and a
`method of controlling the safety clutch operation.
`2. Description of the Prior Art
`With rotatable hand-held clectrical power tools, jamming
`of a workingtool, e.g., upon encountering a reinforcing iron
`during drilling bores in concrete, causes, as a result of high
`torque associated with jamming,rotation of the tool housing
`about the working tool axis, which can lead to an injury of
`the user. Such high torques are limited in the convention
`power tool with friction clutches which are arranged in the
`force transmitting chains of the powertools.
`German Publication DE 3707052 discloses a hand-held
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`electrical power tool with a microcontroller which in
`response to sensing of a rotational movementof the housing
`by acceleration sensor, actuates a safety clutch for breaking
`the force transmitting chain. A prerequisite for the use of the
`microcontroller is an availability of a free space for accom-
`modating a slight movement of the housing. E.g., if a bore
`is formed immediately adjacent to a wall, the use of this
`power tool is not possible as a hand of the user can be
`clamped between the housing and the wall. For drilling
`immediately adjacent to a wall, additionally, a conventional
`friction clutch should be used in the power tool. This
`method, in addition, requires a relatively high computing
`power and, therefore, a very expensive microprocessor.
`USS. Pat. No. 5,563,463 discloses a hand-held electrical
`power tool which measures, in real time, with speed and
`further sensors, respectively,
`the rotational speed of the
`motor and the input current. The microcontroller, via appro-
`priate hard- and software, controls and monitor the motor
`torque by using the measured rotational speed and input
`current of the motor. However, in the disclosed powertool,
`the interruption of the input current at an unpermissibly high
`torque leads, because of the inertia of the motor,
`to an
`unpermissibly large rotation of the housing.
`German Publication DE 43 34 933 discloses a hand-held
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`electrical power tool, in which a rotary vibration of the
`housingis sensed by acceleration sensors and, upon a missed
`zero crossing within a predetermined time period,the safety
`clutch is actuated and the force transmitting chain is broken.
`The drawback of the used solution consists in that at small
`
`torque increases can lead to
`vibrations, relatively small
`breaking of the force transmitting chain.
`invention is to
`Accordingly an object of the present
`provide a microcontroller for a hand-held electrical power
`tool with a safety clutch which would actuate the clutch only
`at high torque increases.
`SUMMARY OF THE INVENTION
`
`This and other object of the present invention, which will
`become apparent hereinafter, are achieved by providing a
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`microcontroller for controlling the operation of the salety
`clutch and including a unit for processing at
`least one
`parameter of the power tool and for outputting a resulting
`parameter in form of a calculated torque and a control unit
`for comparing an actually measured torque, which is input-
`ted into the control unit as a first input parameter, with the
`calculated torque, which is inputted into the control unit as
`a second input parameter, and for outputting a control signal
`when a difference between the actually measured and cal-
`culated torques exceeds a predetermined threshold.
`According to the first embodiment of the microcontroller
`according to the present
`invention,
`the processing unit
`includes a first calculation unit for transforming an input
`current of a powertool electromotor, whichis inputted in the
`first calculation unit as an input parameter, over a motor
`diagram, into the calculated torque output.
`Because of the dynamicsof the power transmitting chain,
`e.g., because of the inertia of the rotor and of the torsional
`resistance of the force transmitting chain, the motor current
`is time-delayed with a filter of a first or higher order and
`react to the change of the torque. This dynamic, however, is
`not transformed in a locally calculated torque. A measure of
`the torque increase is the difference between the actually
`measured and calculated torques.
`Advantageously,
`the processing unit further includes a
`second calculation unit for transforming a measured rota-
`tional speed of the power tool electromotor, which is input-
`ted in the second calculation unit as an input parameter, over
`a friction diagram, into a friction torque at a second calcu-
`lation unit output.
`The determination of the calculated torque based on the
`rotational speed and the input current of the motor increases
`the precision of the calculation of the calculated torque.
`In accordance with the second embodimentof the micro-
`controller according to the present invention, the processing
`unit includes a filter element in a form of a deep-passfilter
`which time-delays the locally calculated, by using the input
`current, torque and which outputs the calculated torque to
`the microcontroller.
`
`Advantageously, the control unite of the microcontroller
`includes further time-delay and filter elements which pre-
`vent short torque peaks, whichdo notlead to deviation of the
`housing dangeroustor the user, from causing the breaking of
`the force-transmitting chain.
`Advantageously, the microcontroller additionally controls
`the braking of electric motorrotor. The brakingis effected by
`feeding the remnant voltage of the rotor winding into the
`reversed polarized main winding by using an auxiliary
`winding.
`The method of controlling of the operation of the safety
`clutch of the hand-held electrical power tool includes trans-
`forming an input current of a tool electromotor, by using a
`motor diagram into a locally calculated torque or transform-
`ing an electrically filtered actually measure torque into a
`locally calculated torque comparing a difference between the
`actually measured torque and the calculated torque with a
`redetermined threshold value, and outputting a control sig-
`nal for actuating the safety clutch in response to the differ-
`ence between the actually measured and the calculated
`torque exceeding the predetermined value.
`The novel features of the present invention, which are
`considered as characteristic for the invention, are set forth in
`the appended claims. The inventionitself, however, both as
`to is construction and its mode of operation, together with
`additional advantages and objects thereof, will be best
`understood from the following detailed description of pre-
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`US 6,700,341 B2
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`3
`ferred embodiments, when read with reference to the accom-
`panying drawings.
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`BRIEF DESCRIPTION OF THE DRAWINGS:
`
`The drawings show:
`FIG. 1 a block-diagram of first embodimentof a micro-
`controller according to the present invention; and
`FIG. 2 a block-diagram of a second embodiment of a
`microcontroller according to the present invention; and
`FIG. 3 a side, partially cross-sectional view of an elec-
`trical hand-held power tool with a safety clutch and a
`microcontroller for controlling the operation of the safety
`clutch.
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`DETAILED PRESCRIPTION OF THE
`PREFERRED EMBODIMENTS
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`4
`outputs a control signal 6 that actuates the safety clutch and
`the brake which are operationally connected with the micro-
`controller.
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`Though the present invention was shown and described
`with references to the preferred embodiments, such are
`merely illustrative of the present invention and are not to be
`construed as a limitation thereof, and various modifications
`of the present invention will be apparent to those skilled in
`the art. It is, therefore, not intended that the present inven-
`tion be limited to the disclosed embodiments or details
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`thereof, and the present invention includes all variations
`and/or alternative embodiments within the spirit and scope
`of the present invention as defined by the appended claims.
`Whatis claimedis:
`1. An electrical hand-held power tool, comprising an
`electromotor(11) for driving the power tool (9); a brake (12)
`for braking the electromotor; a safety clutch (10) arrangedin
`a force transmitting chain of the power tool; and a micro-
`FIG. 1 shows a block-diagram of a microcontroller
`controller for controlling operation of the safety clutch(10),
`accordingto the present invention foran electrical hand-held
`the microcontroller comprising means (2,5,4;8) for process-
`powertool (9) (shownin FIG. 3) that includesanelectrically
`ing at least one parameter of the power tool and for output-
`controlled safety clutch (10), which is provided in the force
`ting a resulting parameterin formof a calculated torque M';
`transmission chain of the powertool, an electric motor (11),
`and a control unit (7) for comparing an actually measured
`and a controllable brake (12). The microcontroller 1 controls
`torque M which is inputted in the control unit (7) as a first
`operation of the safety clutch in accordance with the fol-
`input parameter, with the calculated torque M* which is
`lowing input parameters:
`torque M;
`input current I, and
`inputted into the control unit (7) as a second input parameter,
`rotational speed of the clectromotor n. In the first compu-
`and for outputting a control signal @ when a difference
`tation unit 2 of the microcontroller 1, the input current I of
`between the actually measured and calculated torques
`the electric motoris transformed, over the motor diagram 3,
`exceeds a predetermined threshold.
`locally in an electrical torque at the output to which at a
`2. A power tool according to claim 1, wherein the pro-
`summation point 4, a calculated friction torque, which is
`cessing means comprises a first calculation unit (2) for
`obtained in a second calculation unit 5 by transformation of
`transforming an input current I of a powertool electromotor,
`the input rotational speed overthe friction diagram 6 in the
`whichis imputted in the first calculation unit (2) as an input
`calculated friction torque, is added. The sum ofthe electrical
`parameter, over a motor diagram (3), into the calculated
`and friction torques is outputted as a stationary calculated
`torque M* and a control unit (7) for comparing anactually
`torque M? which is inputted in a control unit 7 of the
`measured torque, which is inputted into the control unit (7)
`microcontroller 1 as an input parameter. In the control unit
`as a first input parameter, with the calculated torque M; at an
`7, the calculated torques M' is compared with the actually
`output thereof.
`measured torque M,and the torque difference A is compared
`3. A powertool according to claim 2, wherein the pro-
`with a threshold parameter.
`If the torque difference A
`cessing means comprises a second calculation unit (5) for
`exceeds a predetermined threshold, the control unit 7 out-
`transforming a measuredrotational speed n of the powertool
`puts a control signal @ which actuates the safety clutch (10)
`electromotor, which is imputted in the second calculation
`and the brake (12).
`unit as an input parameter, over a friction diagram, into a
`In the embodimentof the microcontroller shown in FIG.
`friction torque at a sccond calculation unit output.
`2, the microcontroller 1 includesa filter unit 8 to which the
`4. A microcontroller according to claim 3, wherein the
`torque M is also communicated, in addition to being com-
`processing means further comprises a summation point (4)
`municated to the control unit 7. In the filter unit 8, the torque
`having input means connected with the outputs of the first
`M istime-delayed and is communicated to the control unit
`and second calculation units (2,5) and output means for
`7 of the microprocessor 1 in form of a calculated torque M’*
`outputting a calculated torque M’ obtained by summation of
`as a first input parameter. In the control unit 7, the calculated,
`input torques inputted from the first and second calculation
`in the filter unit 8, torque M’ is compared with the actually
`units (2,5).
`measured torque M that is inputted into the control unit 7 as
`5. A power tool according to claim 1, wherein the pro-
`a second input parameter. As in the first embodimentof the
`cessing means comprisesafilter unit (8) for converting the
`microcontroller 1, the difference A between the calculated
`actually measured torque M which is imputted therein,into
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`and the measured torque is compared with a predetermined
`the calculated torque M’*.
`threshold parameter. In case, the torque difference A exceeds
`%
`the predetermined threshold parameter, the control unit 7
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