United States Patent [191
`Zarniko et al.
`
`[11] Patent Number:
`[ 45] Date of Patent:
`
`4,943,119
`Jul. 24, 1990
`
`[75]
`
`[54] HEIGHT CONTROL DEVICE AND METHOD
`FOR A FIXTURE FOR MACHINING AN
`OBJECT ESSENTIALLY DEFINED BY A
`SINGLE PLANE
`Inventors: Martin Zarniko, Diez; Willibald
`Sehr, Waldbrunn-Ellar, both of Fed.
`Rep. of Germany
`[73] Assignee: MOBA - Electronic, Fed. Rep. of
`Germany
`[21] Appl. No.: 274,831
`Nov. 22, 1988
`[22] Filed:
`Foreign Application Priority Data
`[30]
`Aug. 24, 1988 [DE] Fed. Rep. of Germany ... 8810670[U]
`Int. CI.5 ...................... E0lC 23/08; G0lS 15/08;
`[51]
`G0lS 15/88
`[52] U.S. CI . ........................................ 299/1; 181/123;
`299/39; 404/84; 404/90
`[58] Field of Search ................. 299/1, 36, 39; 404/72,
`404/75, 84, 90; 73/105, 146, 628, 629, 597;
`181/123, 124; 367/87, 140
`
`[56]
`
`References Cited
`U.S. PATENT DOCUMENTS
`3,158,945 12/1964 Curlett et al. .................... 404/84 X
`3,414,327 12/1968 Austin ..................................... 299/1
`3,720,818 3/1973 Spragg et al. .................... 73/105 X
`4,213,719 7/1980 Swisher, Jr. et al .................. 404/84
`4,750,584 6/1988 Tanaka et al ....................... 181/123
`Primary Examiner-Jerome W. Massie, IV
`Assistant Examiner-David J. Bagnell
`Attorney, Agent, or Firm-Harry M. Weiss
`ABSTRACT
`[57]
`A height control device for a fixture which comprises at
`least a pair of gauging devices each having an ultrasonic
`transceiver for gauging a certain distance. A signal
`generator is connected to both gauging devices for
`generating a signal representative of the change in the
`level height due to machining. A control device is also
`provided for elevating or lowering the machining fix(cid:173)
`ture.
`
`10 Claims, 2 Drawing Sheets
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`4
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`7
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`5
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`2
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`6 ---------
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`3
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`CATERPILLAR EXHIBIT 1005
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`Page 1 of 6
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`

`

`U.S. Patent
`
`Jul. 24, 1990
`
`Sheet 1 of2
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`4,943,119
`
`4
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`7
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`5
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`2
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`FIG.1
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`3
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`9
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`7'
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`10
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`4
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`7
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`5 711
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`FIG.2
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`Page 2 of 6
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`

`

`U.S. Patent
`
`Jul. 24, 1990
`
`Sheet 2 of2
`
`4,943,119
`
`11
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`12
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`13
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`14
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`19
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`25
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`23
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`28
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`27
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`15
`22
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`16
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`17
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`,
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`20
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`21
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`FIG.3
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`11 I
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`26
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`.__ _ _ _ _ _ -,lt-_29 _ _ 3_0 _ _ 3, __ FIG. 4
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`24
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`Page 3 of 6
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`

`

`1
`
`4,943,119
`
`HEIGHT CONTROL DEVICE AND METHOD FOR
`A FIXTURE FOR MACHINING AN OBJECT
`ESSENTIALLY DEFINED BY A SINGLE PLANE
`
`This invention relates to a height control device for a
`fixture for machining an object essentially defined by a
`single plane by means of a machining tool for changing
`the level height of the plane, in particularly for a milling
`fixture for stripping road surfacing.
`
`10
`
`15
`
`2
`SUMMARY
`Viewed from one aspect, the present invention pro(cid:173)
`vides a height control device of the aforementioned
`5 type in such an embodiment that it compensates for the
`wear of the machining tool, provides highly accurate
`height control of the machining tool and eliminates the
`sensitivity to damage or maladjustments prevalent in
`mechanical sensors.
`This aspect is achieved by the present invention pro(cid:173)
`viding a height control device for a fixture for machin(cid:173)
`ing an object essentially defined by a single plane by
`means of a machining tool for changing the level height
`of the plane, in particularly for a milling fixture for
`stripping road surfacing,comprising:
`a first gauging device featuring a first ultrasonic
`transceiver for gauging the distance from the ultrasonic
`transceiver to the unmachined plane of the object,
`a second gauging device featuring a second ultrasonic
`transceiver for gauging the distance from the second
`ultrasonic transceiver to the machined plane,
`a signal generator connected to both gauging devices
`for generating a first signal representing the change in
`the level height due to machining from the quotient or
`difference of the distances measured by said first and
`second gauging devices, and
`a control device for elevating or lowering the ma-
`chining fixture so that the signal representing the
`change in the level height due to machining essentially
`corresponds to a setpoint value for changing the level
`height due to machining.
`The invention provides for two gauging devices, one
`of which measures the distance to the unmachined
`plane, the other, the distance to the machined plane. A
`signal generator establishes a variable from the quotient
`or difference of the distances which represents the
`change in the height level as a result of machining and
`which can be considered as the cutting depth in the
`applicational case of the milling fixture. A control de(cid:173)
`vice provides for elevating or lowering the machining
`fixture in such a way that said variable representing the
`change in the height level due to machining is brought
`into agreement with a setpoint variable. This arrange(cid:173)
`ment as provided for by the invention automatically
`compensates wear of the machining tool. Furthermore,
`obtaining the quotient fully compensates the ambient
`conditions as regards their effect on the accuracy of the
`ultrasonic gauging device whilst obtaining the differ(cid:173)
`ence also achieves adequate compensation of the ambi(cid:173)
`ent conditions affecting ultrasonic gauging in practical
`applications. More precisely, obtaining the quotient, for
`example, compensates any effect of changing air tem(cid:173)
`perature, pressure, flow and humidity and fluctuating
`operating voltages on the travel time of the ultrasonic
`signal. Due to the difference between the distance to the
`unmachined plane and the distance to the machined
`plane being very slight, as compared to the gauging
`distance, obtaining the difference is sufficient to com(cid:173)
`pensate said influences.
`Highly accurate height control can thus be achieved
`by a simple arrangement of at least two ultrasonic gaug(cid:173)
`ing devices which is insensitive to said disturbing fac(cid:173)
`tors and capable of compensating any tool wear.
`Viewed from another aspect the invention provides
`for a third gauging device featuring a third ultrasonic
`transceiver for gauging the distance from said third
`ultrasonic transceiver to the unmachined plane of the
`object. This third gauging device is spaced from the
`
`BACKGROUND OF THE INVENTION
`One such milling fixture for stripping road surfacing
`has a roller-type milling cutter provided with a rotary
`drive. Said roller-type milling cutter is mounted on a
`road surface-handling machine by means of a height
`control device. Said roller-type milling cutter is held in
`a bearing frame. Said bearing frame can be elevated and
`lowered with respect to the road surface-handling ma- 20
`chine by means of a hydraulic actuator, said height
`control device signalling the hydraulic actuator such
`that the roller-type milling cutter strips a defined thick(cid:173)
`ness layer from the road surfacing. Said height control
`device has a mechanical sensor for sensing the level 25
`height of the bearing frame with respect to the unma(cid:173)
`chined road surfacing. This mechanical sensor in prior
`art height control devices constitutes, for example, a
`sensing wheel with height adjustment. Although mill(cid:173)
`ing cutters when "as new", i.e. when the roller-type 30
`milling cutter is unworn , permit achieving good accu(cid:173)
`racies when using such a prior art height control device
`for guiding the roller-type milling cutter with respect to
`the unmachined road surfacing so that the layer thick(cid:173)
`ness stripped from the road surfacing remains essen- 35
`tially constant, the resulting wear of the roller-type
`milling cutter in the course of operation causes a reduc(cid:173)
`tion in the actual cutting diameter of the milling cutter.
`Said prior art height control device can only be made to
`compensate for such wear by readjusting the mechani- 40
`cal sensor manually. A further problem of said prior art
`height control device is that the mechanical sensor for
`sensing the road surfacing can easily be damaged under
`the rough conditions which normally exist in road re-
`pair work.
`It is generally known that gauging can also be done
`with non-mechanical proximity-type sensors. Ultra(cid:173)
`sonic sensors have also been in use in the construction
`equipment sector for some time. However, the applica-
`tion of ultrasonic gauging devices in the construction
`equipment sector is limited to instances in which highly
`accurate control is not a mandatory requirement. The
`reason for this limitation in the scope of application is
`that the sensing accuracy of an ultrasonic gauging de- 55
`vice is greatly influenced by the temperature, flow and
`humidity of the ambient air, by the operating voltage,
`by the momentary atmospheric pressure and by similar
`influencing factors, at least when not provided with
`relatively complicated means of compensation. Since 60
`the percentual overall error accumulated under worst(cid:173)
`case conditions from these influencing factors is of a
`magnitude similar to that of the cutting depth to be
`maintained relative to the distance of an ultrasonic
`gauging device away from a road surface, a height 65
`control device for milling fixtures used in stripping a
`road surfacing exists only in mechanical form, not in(cid:173)
`corporating ultrasonic gauging.
`
`45
`
`50
`
`Page 4 of 6
`
`

`

`4,943,119
`
`3
`first gauging device in a direction perpendicular to the
`direction of machining. This arrangement permits
`height control of the machining tool with which adapta(cid:173)
`tion to a plane of the object for machining is possible
`when deviating from the horizontal.
`Viewed from a further aspect a signal is also gener(cid:173)
`ated for said third gauging device by obtaining the
`quotient or difference with the signal of the second
`gauging device to indicate the change in the level
`height as a result of machining.
`Viewed from yet a further aspect of the invention
`these two signals representing the change in the level
`height due to machining can each be compared sepa(cid:173)
`rately to a setpoint value for the change in the level
`height, thus producing a first and a second reference 15
`signal.
`Viewed from yet a further aspect of the invention
`said reference signals are used to signal a prior art elec(cid:173)
`trohydraulic actuator in which an electrically operated
`first and second hydraulic valve is placed in circuit to 20
`move the left-hand and right-hand hydraulic actuators
`for adjusting the height of the tool on both sides accord(cid:173)
`ingly.
`Some embodiments of the invention will now be
`described by way of example and with reference to the 25
`accompanying drawings in which:
`FIG. 1 is a schematic front view of a milling fixture
`for stripping road surfacing and featuring a height con(cid:173)
`trol device in accordance with the present invention;
`FIG. 2 is a plan view of the milling fixture shown in 30
`FIG.1;
`FIG. 3 is a circuit diagram of the height control de(cid:173)
`vice; and
`FIG. 4 is a circuit diagram of a transceiver circuit as
`contained in the circuit diagram as depicted in FIG. 3. 35
`As can be seen from FIG. 1, a milling fixture identi(cid:173)
`fied in its entirety by the reference number 1 has a bear(cid:173)
`ing frame 2 mounting a roller-type milling cutter 3. Said
`rollertype milling cutter 3 is a rotary axis located essen(cid:173)
`tially horizontal mounted in bearing frame 2 free to turn 40
`and driven in the required direction of rotation. Bearing
`frame 2 is mounted on a ( not shown ) road surface-han(cid:173)
`dling machine for adjustment by two hydraulic cylin(cid:173)
`ders 4, 5 to permit both raising and lowering of bearing
`frame 2 and a specific angular inclination of the bearing 45
`frame 2 by corresponding actuation of said hydraulic
`cylinders 4, 5 so that the turning axis of the roller-type
`milling cutter 3 can be angularly inclined with respect
`to the horizontal. The aforementioned milling cutter 1
`having bearing frame 2, milling cutter 3 and hydraulic 50
`cylinders 4,5 is prior art and, therefore, there is no need
`to go into detail in describing the mechanical configura(cid:173)
`tion. Actuating the hydraulic cylinders 4, 5 by means of
`( not shown) valves to adjust the working height is also
`prior art.
`As can be seen from FIG. 1 particularly in conjunc(cid:173)
`tion with FIG. 2 the height control device,as the object
`of the invention for the milling fixture l,features a first
`ultrasonic transceiver 6, a second ultrasonic transceiver
`7 and preferably also a third ultrasonic transceiver 8 60
`secured to the bearing frame 2 of said milling fixture 1
`in such a way, that the first and third ultrasonic trans(cid:173)
`ceivers 6,8 are located outside of the working range of
`the milling cutter 3 so that they can gauge the distance
`to the unmachined plane of the road surfacing by sens- 65
`ing the ultrasonic propagation time. By contrast, the
`second ultrasonic transceiver 7 is arranged in such a
`way that it is capable of gauging the distance to the
`
`4
`machined road surfacing by sensing the ultrasonic prop(cid:173)
`agation time.
`In FIG. 2 the unmachined area of the road surfacing
`is characterized by identification with reference number
`5 9 and cross-hatched diagonally, whilst the milled area
`of the road surfacing is identified by reference number
`10 and is cross-hatched vertically.
`Instead of arranging the first and third ultrasonic
`transceivers 6, 8 to the right and left of the working area
`10 of the roller-type milling cutter 3 it is also possible to
`place said ultrasonic transceivers 6,8 ahead of the mill(cid:173)
`ing area of said roller-type milling cutter 3 as indicated
`by the reference numbers 6' and 8'. It is also possible to
`replace the second ultrasonic transceiver 7 arranged in
`the center in FIG. 2 by two separate ultrasonic trans(cid:173)
`ceivers 7', 7" each arranged near to the edge of the
`milled surface 10 of the road surfacing. This kind of
`arrangement permits sensing unsymmetrical wear of
`said roller-type milling cutter 3.
`Turning now to FIG. 3 a circuit diagram of the
`height control device as the object of the invention will
`be explained. Ultrasonic transceivers 6, 7', 7",8 are con(cid:173)
`nected via trasceiver circuits 11, 12, 13, 14 and an ana(cid:173)
`log/ digital converter 15 to a microcomputer 16,17 com(cid:173)
`prising a commercially available microprocessor type
`8031 and a storage of the EPROM type. Each of the
`transceiver circuits 11 thru 14 is connected to a power
`oscillator 19.
`For setting a setpoint value for the milling depth
`corresponding to the change in the level height as a
`result of machining, a setting control 20 is used which in
`conjunction with a further setting control 21 for setting
`the gauging sensitivity is connected via a further ana(cid:173)
`log/ digital converter 22 to the microcomputer 16.
`Turning now to FIG. 4 the design of the transceiver
`circuit 11 will be explained which is identical to that of
`receiver circuits 12 thru 14. Said transceiver circuit has
`a port 23 connecting the ultrasonic transceiver, a port
`24 connecting the power oscillator, a port 25 serving as
`the control input from the microcomputer 16 and an
`output port 26 connected to the input of the analog/-
`digital converter 15. The transceiver circuit has a
`monostable multivibrator 27, a gate 28, an amplifier 29,
`a rectifier stage 30 and a sensing circuit 31 which may
`be designed as an integration circuit. When the mi(cid:173)
`crocomputer 16 applies a control pulse to port 25, this
`will trigger the monostable multivibrator 27. For the
`duration of the signal as established by the monostable
`multivibrator amplifier 29 is deactivated and gate 28
`opened. In this condition power oscillator 19 is con(cid:173)
`nected to the corresponding ultrasonic transceiver caus-
`ing it to emit an ultrasonic pulse. On time-out of the
`pulse duration as dictated by the monostable multivibra(cid:173)
`tor 27, gate 28 is closed and amplifier 29 activated. The
`55 pulses which are then received are amplified by ampli(cid:173)
`fier 29, rectified by the rectifier stage 30 and sensed in
`the sensing circuit 31 preferably by integration for ana(cid:173)
`log measurement.
`As an alternative to the foregoing circuits other prior
`art circuits may be used to determine the ultrasonic
`propagation times of each ultrasonic transceiver 6, 7', 7"
`and 8. Since such techniques and circuits are nothing
`new to the expert in the field of ultrasonic measure(cid:173)
`ments, there is no need to detail these alternative cir-
`cuits.
`After establishing the difference or the quotient of the
`ultrasonic propagation time of the signals sensed by the
`ultrasonic receivers 6,7' and by the ultrasonic receivers
`
`Page 5 of 6
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`

`

`4,943,119
`
`5
`7", 8 respectively the microprocessor determines the
`milling depth from said quotient. As an alternative, the
`milling depth may also be determined from the differ(cid:173)
`ence of the signals. The right-hand and left-hand milling
`depth is each compared to a setpoint value, whereby 5
`any milling depth not equivalent to the setpoint value
`produces a reference signal with which the microcom(cid:173)
`puter 16 signals the corresponding hydraulic valve to
`adjust the hydraulic cylinders 4, 5 concerned accord(cid:173)
`ingly. The electrohydraulic height control of the bear- 10
`ing fixture 2 is nothing new and thus requires no further
`explanation.
`As an alternative to the example of the foregoing
`embodiment the height control may also feature a single
`ultrasonic sensor for gauging the height of the unma- 15
`chined road surfacing and a further, single ultrasonic
`transceiver for gauging the height of the machined,
`stripped road surfacing.
`It is clearly understood that the height control device
`as the object of the present invention may be used just 20
`as well in other machines for machining the level height
`of a plane of an object. Height difference control de(cid:173)
`vices are feasible, for instance, in machines for applying
`coatings with a specific coating thickness, as well as in
`grinding and planing machines for removing surfaces to 25
`a specific thickness. The range of application of the
`present invention is dictated solely by the difference
`between the distances sensed by the ultrasonic sensing
`device adjacent to the working area and in the working
`area itself being small as compared to the distances 30
`themselves.
`We claim:
`1. A height control device for a fixture for machining
`an object essentially defined by a single plane by means
`of a machining tool for changing the level height of the 35
`plane, in particularly for a milling fixture for stripping
`road surfacing comprising:
`a first gauging device featuring a first ultrasonic
`transceiver for gauging the distance from the ultra(cid:173)
`sonic transceiver to the unmachined plane of the 40
`object,
`a second gauging device featuring a second ultrasonic
`transceiver for gauging the distance from the sec(cid:173)
`ond ultrasonic transceiver to the machined plane,
`a signal generator connected to both gauging devices 45
`for generating a first signal representing the change
`in the level height due to machining from the quo(cid:173)
`tient or difference of the distances measured by
`said first and second gauging devices, and
`a control device for elevating or lowering the ma- 50
`chining fixture so that the signal representing the
`change in the level height due to machining essen(cid:173)
`tially corresponds to a setpoint value for changing
`the level height due to machining.
`2. A height control device as claimed in claim 1, 55
`wherein a third gauging device featuring a third ultra(cid:173)
`sonic transceiver for gauging the distance from the
`third ultransonic transceiver to the unmachined plane of
`the object is provided, and in which said first and third
`gauging devices are spaced from each other in a direc- 60
`tion perpendicular to the machining direction of the
`machining device.
`3. A height control device as claimed in claim 2,
`wherein said signal generator is also connected to said
`third gauging device to generate a second signal repre- 65
`senting the change in the level height from the quotient
`
`6
`or difference of the distances measured by said second
`and third gauging devices.
`4. A height control device as claimed in claim 3,
`wherein said control device compares both the first and
`second signal representing the change in the level
`height due to machining to a setpoint value for the
`change in the level height and generates a first and a
`second reference signal.
`5. A height control device as claimed in claim 4,
`wherein said control device signals separate, electri(cid:173)
`cally operated first and second hydraulic valves by
`means of said first and second reference signals and in
`which hydraulic actuators are height-adjusted by means
`of said hydraulic valves.
`6. A method for providing a height control device for
`a fixture for machining an object essentially defired by
`a single plane by means of a machining tool for chang(cid:173)
`ing the level height of the plane, in particularly for a
`milling fixture for stripping road surfacing comprising
`the steps of:
`providing a first gauging device featuring a first ultra(cid:173)
`sonic transceiver for gauging the distance from the
`ultrasonic transceiver to the unmachined plane of
`the object;
`providing a second gauging device featuring a second
`ultrasonic transceiver for gauging the distance
`from the second ultrasonic transceiver to the ma(cid:173)
`chined plane;
`providing a signal generator connected to both gaug(cid:173)
`ing devices for generating a first signal represent(cid:173)
`ing the change in the level height due to machining
`from the quotient or difference of the distances
`measured by said first and second gauging devices;
`and
`providing a control device for elevating or lowering
`the machining fixture so that the signal represent(cid:173)
`ing the change in the level height due to machining
`essentially corresponds to a setpoint value for
`changing the level height due to machining.
`7. The method as claimed in claim 6 including provid(cid:173)
`ing a third gauging device featuring a third ultrasonic
`transceiver for gauging the distance from the third ul(cid:173)
`trasonic transceiver to the unmachined plane of the
`object, said first and third gauging devices are spaced
`from each other in a direction perpendicular to the
`machining direction of the machining device.
`8. The method as claimed in claim 7 wherein said
`signal generator is also connected to said third gauging
`device to generate a second signal representing the
`change in the level height from the quotient or differ(cid:173)
`ence of the distances measured by said second and third
`gauging devices.
`9. The method as claimed in claim 8 including the
`step of using said control device to compare both the
`first and second signal representing the change in the
`level height due to machining to a setpoint value for the
`change in the level height and to generate a first and
`second reference signal.
`10. The method as claimed in claim 9 wherein said
`control device signals separate, electrically operated
`first and second hydraulic valves by means of said first
`and second reference signals and in which hydraulic
`actuators are height-adjusted by means of said hydraulic
`valves.
`
`* * * * *
`
`Page 6 of 6
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