US3850015A - Roll gap detection - Google Patents

Roll gap detection Download PDF

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Publication number
US3850015A
US3850015A US00361473A US36147373A US3850015A US 3850015 A US3850015 A US 3850015A US 00361473 A US00361473 A US 00361473A US 36147373 A US36147373 A US 36147373A US 3850015 A US3850015 A US 3850015A
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US
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Prior art keywords
transducer
pick
annulus
roll
disposition
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Expired - Lifetime
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US00361473A
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English (en)
Inventor
K Andresen
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Fried Krupp AG
Vereinigte Flugtechnische Werke Fokker GmbH
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Vereinigte Flugtechnische Werke Fokker GmbH
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Assigned to FRIED, KRUPP GMBH, 4300 ESSEN, FED. REP. OF GERMANY reassignment FRIED, KRUPP GMBH, 4300 ESSEN, FED. REP. OF GERMANY ASSIGNMENT OF ASSIGNORS INTEREST. Assignors: MESSERSCHMITT-BOELKOW-BLOHM GMBH
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B7/00—Measuring arrangements characterised by the use of electric or magnetic techniques
    • G01B7/14—Measuring arrangements characterised by the use of electric or magnetic techniques for measuring distance or clearance between spaced objects or spaced apertures
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21B—ROLLING OF METAL
    • B21B38/00—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product
    • B21B38/10—Methods or devices for measuring, detecting or monitoring specially adapted for metal-rolling mills, e.g. position detection, inspection of the product for measuring roll-gap, e.g. pass indicators
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S425/00—Plastic article or earthenware shaping or treating: apparatus
    • Y10S425/235—Calendar

Definitions

  • the present invention relates to a device for measuring the gap between the working rolls of a rolling mill, so that the result of measuring may serve as input for a controller for maintaining the gap constant by means of automatic feedback control.
  • Rolling mills generally require control of the roll gap because the thickness of the rolled sheet stock or the like is usually to be kept within very close tolerances.
  • the feedback control must meet significant dynamic requirements which include a fast operating actuator for adjusting the gap and which further include a pick up device detecting the thickness of the rolled stock as controlled variable in one way or another. This pick up device should operate without or with only insignificant delay so that the stock width will not vary beyond per missible limits.
  • measuring strip or sheet stock thickness right at the roll gap is not accurate enough due to the deformation of the rolls during working and further due to some resilient reaction of the stock after emerging from the gap. Therefore, the strip or rolled sheet stock thickness is usually measured indirectly by detecting the roll gap in one way or another.
  • the different controllers for the roll gap differ primarily in the set up and design of the gap detection.
  • a rather simple but relatively inaccurate method uses the displacement of the roll positioning plunger as representation of the gap.
  • the inaccuracy here stems from the fact that the gap is only indirectly ascertained and roll flattening, mill stand expansion, and eccentricities in the support rolls render the relationship between the true gap and measured input rather unreliable.
  • the measured value supposedly representing the roll gap must be subjected to numerous corrections as to all these disturbing influences.
  • Another method uses a spindle between the inserts of the support rolls, and the changes in spindle force are used as an (indirect) representation ofthe roll gap.
  • the controller operates here to maintain the spindle force at a constant level, and hopefully the roll gap is maintained constant therewith.
  • This method works actually as a first order approximation, but this system uses as command input a supplemental spindle device which does not consider roll flattening, and eccentricities of the support are entered into this pick up system with the wrong sign. Thus, it is quite impossible here to provide for an optimized controller on that basis.
  • each roll has a particular transducing surface rotating in datum plane which extends transverse to the axis of. the respective roll. Upon rotation thereof, no changes occur in the pick up transducer as facing that datum plane at a particular distance. Changes in the disposition of the roll axis causes change of the rotating annulus in the datum plane, and that lateral-radial change is picked up.
  • Such a reference annulus cooperates with the respective head on thebasis of one several possible physical principles.
  • the reference annulus may influence the respective pick up head magnetically, optically, capacitively electromechanically or otherwise.
  • the principle of the invention is to be seen in that the annulus has a particularly surface of rotational symmetry providing constant activation of the respective head during rotation, and any shift of the annulus in the datum plane changes the effective head-annulus interaction and the resulting head output.
  • Each such head includes preferably a pair of pick ups responding, e.g., to concentric edges of the respective annulus and providing balanced. outputs when the edges have similar disposition to the pick ups. This then establishes a zero position separately on each head.
  • the heads are preferably motorically adjusted in radial direction as far as the respective associated annulus is concerned, so that the signals derived from the heads and combined may have characteristics of an error signal.
  • the relative position of the transducer heads establish representation of the desired gap, and the head signals together form representation of the controlled variable (actual gap width) minus the desired gap representation.
  • FIGS. 1a and lb are respectively generalized, somewhat schematic side and front views of a roll with reference ring and pick up head;
  • FIG. 2 illustrates in detail the pick up head constructed as electromagnetic transducer
  • FIG. 3 is a schematic front view of the components as they detect and monitor a roll gap
  • FIGS. 4a and 4b are respectively a front view par tially in section and a top view of the transducer and pick up head for particularly adjusting its disposition;
  • FIG. 5 is a circuit diagram used in conjunction with the device of FIG. 3 for generating a signal representing the difference of desired and actual disposition of a roll;
  • FIG. 6 shows two circuits of the type of FIG. 5 combined for generating a gap error signal.
  • FIG. 1 shows representatively one of the working rolls 10, which may be the upper or the lower one in a two-high rolling mill and having a reference ring or annulus 11 provided at one of its axial end faces from which a shaft end projects for journalling the roll.
  • the annulus 11 is concentrically disposed in relation to the working surface of the roll. Therefore, the relative disposition of annulus l1 depends on the relative disposition of roll in the mill stand so that, in turn, the disposition of the annulus represents the disposition of the roll and of its working surface.
  • the annulus 11 has a particular, axially facing surface 1 la of rotational symmetry with two edges of different radii and correspondingly different distances from the cylindrical rolling surface of these edges.
  • This surface lla defines a datum plane which extends transverse to the axis of rotation of the roll. Any displacement of the rolling surface of roll 10 in direction transverse to the rolling surface shifts the annulus so that particularly the axially facing surface lla shifts in the datum plane transverse to the axis of rotation.
  • the reference annulus 11 is associated with a stationary transducer head 13, having a particular axial disposition to the datum plane as well as to the axis of rotation of roll 10.
  • the transducer head faces the annulus and is particularly responsive to the relative disposition of the said axially facing surface 11a in the datum plane.
  • the transducer head 13 responds particularly to any shift of the annulus in its plane of rotation, but the interaction between transducer and annulus is constant as long as such a shift does not occur, due to the rotational symmetry of annular surface 11a.
  • the transducer head generally has a pair of pick ups such as magnetic coils, capacitive probes or optical detectors responding particularly to the disposition of the axial facing surface Ila of annulus 11 and adjacent the edges thereof. These edges provide a discontinuity and any shift of the annulus in the datum plane changes the respective input of at least one of the pick ups. Induction, capacitance, or reflection as effective at and in the respective pick up changes when the respective closest edge passes across the respective pick up.
  • pick ups such as magnetic coils, capacitive probes or optical detectors responding particularly to the disposition of the axial facing surface Ila of annulus 11 and adjacent the edges thereof. These edges provide a discontinuity and any shift of the annulus in the datum plane changes the respective input of at least one of the pick ups. Induction, capacitance, or reflection as effective at and in the respective pick up changes when the respective closest edge passes across the respective pick up.
  • the transducer head 13 is provided as two inductive pick ups and includes an E-shaped core, whose three legs face the annulus but in different radial levels. Each one of the three outer legs carries a coil having inductance L, and L respectively; these are the two pick ups.
  • the reference annulus 11 has (radial) width in the datum plane, closest to the head, corresponding to the inner distance of the outer legs from each other. The annulus as such interacts magnetically with each of the pick up coils (L and (L As annulus 11 and head 13 have relative disposition corresponding to the illustrated position of FIG. 2, the inductances are L L 1. This then defines a normal or zero position.
  • these inductances are connected across the center tapped secondary of a transformer 21 which is energized by an oscillator 20 of constant frequency.
  • the junction between the two inductances L and L will have zero voltage relative to the grounded center tap if the inductances indeed are equal. If the inductances are not equal a non zero voltage develops as between the said junction and ground. The phase and amplitude of that voltage is indicative of a difference in the inductances.
  • This output voltage is amplified in an amplifier 24 and rectified at 25 to provide a dc. output A whose polarity and magnitude represents the imbalance in the inductances.
  • the rectifier 25 is controlled by the oscillator 20 to establish phase dependent rectification.
  • the position of the roll 10 relative to head 13 is ascertained by this device and particularly the output A of rectifier 25 is a representation of the rolls position relative to the stationary position of head 13. Neither temperature deviations, nor axial distance variations between the head and the annulus enter into the output A, because these disturbances cancel in the formation of L L Having described the subsystem as provided for the detection of the relative disposition of an individual roll in the stand, I proceed to the detection of the roll gap, which requires the detection of the disposition of upper and lower rolls in the stand. Turning, therefore, to FIG. 3, the roll 10 is shown here as the lower one, there being a second roll 10' member above roll 10 and defining a rolling gap G therewith. I
  • Roll 10 is provided with an annulus 11 which coopcrates with a transducer head 13.
  • Elements 11 and 11, and 13 and 13' correspond to other and are similar in construction and dimension.
  • the two heads each have a pair of magnetic pick up coils and the arrangement on the upper roll will be just as was explained with reference to FIG. 2.
  • the two transducer heads 13 and 13 are not individually mounted to the rolling stand. Rather, a frame 131 is used for mounting both transducers in particular position to each other, and the frame 131 is secured to the stand within one and the same horizontal plane. Thus, forces acting on the stand during rolling do not act on the frame. This way dimensional changes which the stand may undergo during rolling are not transmitted upon the transducer mount.
  • the frame 131 provides, so to speak, for a coarse or approximate relative disposition of the transducer heads 13 and 13. The fine and accurate position will be adjusted and predetermined in a manner explained later with reference to FIG. 4.
  • FIG. 6 shows the circuit for the gap detection which is basically a duplication of the circuit of FIG. 5 except that FIG. 6 shows a common oscillator 20 and a transformer with a single primary winding.
  • the circuit therefore, shows two pairs of inductances, identified by indices -A and -B, and there is a second signal path including an amplifier 24' and a phase dependent rectifier 25 for providing a do signal B that represents the imbalance of the two inductances LIB L2B of transducer l3.
  • Rectifiers 25 and 25 are synchronously controlled from oscillator 20.
  • the four inductances LIA, L2A, LlB, L2B establish inherently a bridge circuit, but the bridge voltage is not used directly (though it could). Rather, each of the two junctions between the coils of each pair is respectively referenced to ground.
  • a signal representation of the difference A B is generated by a dc.
  • differential amplifier 26 receiving signal A and B at oppositely poled inputs.
  • the two signals A and B represent individually the deviation of the respective roll from arbitrarily selected positions, wherein the respective annuli face the transducers 13 and 13 symmetrically.
  • the signal A B represents the relative deviation of the two rolls from those individually predetermined radial levels.
  • the radial levels for the two transducers may now be selected, so that the rolls -10 establish a particular gap if the annuli ll, 11 have disposition relative to the transducers 13, 13' so that A B (e.g., 0).
  • a B e.g., 0
  • the output of amplifier 26 as providing a signal A B can be used as representation of the error signal between controlled variable and desired value for automatic feedback control of the thickness of the rolled stock.
  • the transducer system as such does not necessarily provide a signal representation of the rolling gap as such. Assuming the transducers had disposition that A B 0 for gap zero, then A B 0 will in fact develop for non zero gap and that signal will represent the actual gap width. If however, the transducers 13, 13' have disposition that A B O the desired gap width, then A B 0 represents an error signal, but neither A nor B is directly the desired variable or the command signal in this representation. Nevertheless, A B could be interpreted as representation ofthe actual gap width with the desired gap width serving as zero point setting for that particular scale of representing gap width, but permitting positive or negative values in that kind of representation.
  • FIG. 4 shows by way of example how the transducers can be adjustably mounted.
  • the head such as 13 projects from a casing 12 containing a stepping motor 19.
  • the drive shaft of the motor has a gear 18 meshing with a biased gear 17.
  • Gear 17 in turn is mounted on a spindle or worm gear 16 for providing for elevation adjustment of head 13.
  • the motor 19 is separately and, e.g., step-wise controlled for accurately adjusting the level of transducer action.
  • the motor 19 may be controlled by pulses for step action. This way the head disposition can be determined on the basis of accurately metered pulse trains.
  • the calibration of the device as described following for example a replacement of worn rolls by new or refinished ones, is carried out as follows.
  • the rolls (in running condition) are at first moved towards each other by the roll position actuator.
  • Usually only one roll is adjustable as to relative height above (or below) the other one.
  • each of the transducers l3 and 13 is adjusted and trimmed in its disposition until the signals A and B have separately zero value. This then establishes a zero condition as far as calibration is concerned.
  • the processing of the signals may include filtering to remove any modulation at the roll-rotation frequency. No problem will arise here if the frequency of the oscillator 20 is sufficiently higher than the roll rotation frequency.
  • desired gap width is, therefore, determined by adjustment of the disposition of one of the transducer heads.
  • the adjustment is carried out by control of motor 19 for example by means of an encoding switch, a process controller or any analog signal fed to the motor. This way, it is possible to change the command and reference value for the rolling gap and strip thickness, for example for purposes of correction.
  • the accuracy of the initial adjustment and of the command input depends primarily upon the accuracy of the pitch of the worn gear. This way, even large gaps can readily be adjusted as the accuracy of worm gear pitch is significant and usually constant throughout the extension.
  • the transducer system as detecting the dispositions of the rolls separately has a number of advantages.
  • the signals are developed in stationary transducer heads, operating without making contact with any rotating part of the rolls.
  • no slip rings or other device for transmitting signals from a moving to a stationary part are needed. This way the system can be used in slowly as well as in fact running mills.
  • the inventive transducer system operates with a high resolution that is quite independent from the size of the gap to be controlled. Accuracy, sensitivity and resolution are not influenced by any cooling process (or lack of it).
  • recalibration is not difficult, so that the overall operation of replacing worn rolls is facilitated.
  • the recalibration and zero adjustment does not require additional mounting operation; only the level adjustment of one or both of the transducers must be repeated.
  • the motors 19 are preferably step motors and one can use digital means for the position adjustment as well as digital indication during and for the calibration.
  • the transducers and casings are mounted in the level of the support rolls 15 which provide adequate protection for these instrument packages.
  • Apparatus for detecting the width of the gap between two rolls in a rolling mill comprising:
  • each said annulus having a planar, ring-shaped surface with concentric edges;
  • each transducer having a pair of pick ups of particular respective disposition to the edges, for being responsive to radial dimensions of the respective adjacent annulus and to a shift of the said surface transverse to the axis of rotation of the respective roll, and providing a constant output for constant disposition of the axis of the respective roll in relation to the respective transducer;
  • first circuit means respectively connected to the pick ups and providing a balanced output when the pick ups ofa transducer have the desired disposition relative to the said edges, the first circuit means providing two outputs respectively for the two transducers;
  • transducers each have magnetic pick up heads, the inductance of each head being changed when the respective adjacent edge shifts in one direction transverse to said axes.
  • the pick-ups of each pair of pick ups are electrically connected in circuit; the first circuit means including an oscillator connected for energizing the pick ups, so that the pick ups provide similar outputs when the pick ups have locally symmetric disposition to the respective portion of the annulus as facing directly the head; and wherein the first circuit means further includes a means for deriving a signal from the pick ups including an amplifier and a phase dependent rectifier.
  • Apparatus as in claim 4 there being one amplifier and one rectifier for each pair of pick ups and transducer and wherein the oscillator energizes the pairs of pick ups, said second circuit means for combining ineluding a differential amplifier connected to the respective rectifiers.
  • At least one of the transducers including a pair of pick up coils on an E-shaped core facing the respective annulus, the spacing between the outer legs of the E being equal to the width of the ring-shaped surface.
  • each transducer having a pair of pick up coils, an amplifier and a rectifier, the coils energized by the said oscillator, the second circuit means further including a differential amplifier connected to the rectifier.
  • each transducer being mounted for individual adjustment in radial direction relative to the respective annulus.
  • Apparatus as in claim 9 including a stepping motor and a worm gear geared to the stepping motor, for at least one transducer head, the head being geared to the worm gear for adjustment of the radial disposition of the one transducer.
US00361473A 1972-05-20 1973-05-18 Roll gap detection Expired - Lifetime US3850015A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE2224833A DE2224833C3 (de) 1972-05-20 1972-05-20 Vorrichtung zur Messung des Spaltes eines Arbeitswalzenpaares für ein Walzgerüst

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US00361473A Expired - Lifetime US3850015A (en) 1972-05-20 1973-05-18 Roll gap detection

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US (1) US3850015A (fr)
JP (1) JPS5423819B2 (fr)
DE (1) DE2224833C3 (fr)
FR (1) FR2185452B3 (fr)
GB (1) GB1391029A (fr)
IT (1) IT987665B (fr)
SE (1) SE413634B (fr)

Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3916661A (en) * 1974-02-22 1975-11-04 Davy Loewy Ltd Rolling mills
US3936258A (en) * 1974-01-30 1976-02-03 Intercole Automation, Inc. Calender
US3961509A (en) * 1974-05-21 1976-06-08 Vereinigte Flugtechnische Werke-Fokker Gesellschaft Mit Beschrankter Haftung Roll gap control
US4044580A (en) * 1975-07-02 1977-08-30 Marotta Scientific Controls, Inc. Rolling mill gap sensor
US4059794A (en) * 1974-07-15 1977-11-22 British Steel Corporation Method and apparatus for monitoring pass alignment in rolling mills
US4833931A (en) * 1987-08-14 1989-05-30 Westinghouse Electric Corp. Thermally self-adjusting mount for proximity sensor
US5160886A (en) * 1991-02-14 1992-11-03 Carlen Controls, Inc. Permanent magnet resolver for producing a resolver-to-digital converter compatible output
US6677749B2 (en) * 2002-04-10 2004-01-13 Hewlett-Packard Development Company, L.P. Using variable inductance to indicate roller wear
US9764368B2 (en) 2011-09-23 2017-09-19 Sms Group Gmbh Rolling mill and rolling method

Families Citing this family (12)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2439580C3 (de) * 1974-08-17 1982-09-23 Achenbach Buschhütten GmbH, 5910 Kreuztal Meßeinrichtung zur Ermittlung des Abstandes der Stützwalzeneinbaustücke eines Quarto-Walzgerüstes
DE2530593C2 (de) * 1975-07-09 1983-08-18 Vereinigte Flugtechnische Werke Gmbh, 2800 Bremen Meßvorrichtung zur Erfassung des Spaltes eines Arbeitswalzenpaares
JPS5252660A (en) * 1975-10-27 1977-04-27 Fuji Electric Co Ltd Measuring method gap in electric machine having glass-bind-rotor
JPS53149077A (en) * 1977-05-30 1978-12-26 Do Poritefunichiesuki I Device for measuring power volume using in continuous rolling process
AT388453B (de) * 1985-10-24 1989-06-26 Voest Alpine Ag Vorrichtung zur welligkeitsmessung eines bleches
DE3628733A1 (de) * 1986-08-23 1988-02-25 Schloemann Siemag Ag Vorrichtung zum axialen anstellen der walzen von walzgeruesten zur herstellung von profilstahl
JPH0686883B2 (ja) * 1990-02-20 1994-11-02 日機装株式会社 軸受監視装置
DE4141260A1 (de) * 1991-12-14 1993-06-17 Ibn Gmbh Dresden Einrichtung zum messen des achsabstandes von walzen zueinander
DE4203469C2 (de) * 1992-02-04 1994-03-10 Mannesmann Ag Meßverfahren und Meßsystem zur Erfassung eines Spaltes eines Walzenpaares
JP5081699B2 (ja) * 2008-04-02 2012-11-28 新日鉄エンジニアリング株式会社 圧延ロールギャップ調整方法
WO2013041083A2 (fr) * 2011-09-23 2013-03-28 Sms Meer Gmbh Installation et procédé de laminage
CN108080439A (zh) * 2016-11-21 2018-05-29 刘青 齿轮箱感应装置

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2684001A (en) * 1952-02-23 1954-07-20 Olin Ind Inc Automatic screw-down control
US3570288A (en) * 1967-10-21 1971-03-16 Krupp Gmbh Rolling-mill assembly with improved control system
US3662576A (en) * 1969-06-21 1972-05-16 Ver Flugtechnische Werke Control for roll gap of a rolling mill

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2684001A (en) * 1952-02-23 1954-07-20 Olin Ind Inc Automatic screw-down control
US3570288A (en) * 1967-10-21 1971-03-16 Krupp Gmbh Rolling-mill assembly with improved control system
US3662576A (en) * 1969-06-21 1972-05-16 Ver Flugtechnische Werke Control for roll gap of a rolling mill

Cited By (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3936258A (en) * 1974-01-30 1976-02-03 Intercole Automation, Inc. Calender
US3916661A (en) * 1974-02-22 1975-11-04 Davy Loewy Ltd Rolling mills
US3961509A (en) * 1974-05-21 1976-06-08 Vereinigte Flugtechnische Werke-Fokker Gesellschaft Mit Beschrankter Haftung Roll gap control
US4059794A (en) * 1974-07-15 1977-11-22 British Steel Corporation Method and apparatus for monitoring pass alignment in rolling mills
US4044580A (en) * 1975-07-02 1977-08-30 Marotta Scientific Controls, Inc. Rolling mill gap sensor
US4833931A (en) * 1987-08-14 1989-05-30 Westinghouse Electric Corp. Thermally self-adjusting mount for proximity sensor
US5160886A (en) * 1991-02-14 1992-11-03 Carlen Controls, Inc. Permanent magnet resolver for producing a resolver-to-digital converter compatible output
US6677749B2 (en) * 2002-04-10 2004-01-13 Hewlett-Packard Development Company, L.P. Using variable inductance to indicate roller wear
US9764368B2 (en) 2011-09-23 2017-09-19 Sms Group Gmbh Rolling mill and rolling method
US10654084B2 (en) 2011-09-23 2020-05-19 Sms Group Gmbh Rolling mill and rolling method

Also Published As

Publication number Publication date
JPS4956658A (fr) 1974-06-01
IT987665B (it) 1975-03-20
DE2224833C3 (de) 1981-05-21
GB1391029A (en) 1975-04-16
DE2224833A1 (de) 1973-11-29
FR2185452B3 (fr) 1976-05-07
JPS5423819B2 (fr) 1979-08-16
DE2224833B2 (de) 1980-08-21
FR2185452A1 (fr) 1974-01-04
SE413634B (sv) 1980-06-16

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AS Assignment

Owner name: FRIED, KRUPP GMBH, 4300 ESSEN, FED. REP. OF GERMAN

Free format text: ASSIGNMENT OF ASSIGNORS INTEREST.;ASSIGNOR:MESSERSCHMITT-BOELKOW-BLOHM GMBH;REEL/FRAME:005108/0470

Effective date: 19860423