IT1189187B - Dispositivo con due masse volaniche ruotanti l'una rispetto all'altra - Google Patents

Dispositivo con due masse volaniche ruotanti l'una rispetto all'altra

Info

Publication number
IT1189187B
IT1189187B IT19962/86A IT1996286A IT1189187B IT 1189187 B IT1189187 B IT 1189187B IT 19962/86 A IT19962/86 A IT 19962/86A IT 1996286 A IT1996286 A IT 1996286A IT 1189187 B IT1189187 B IT 1189187B
Authority
IT
Italy
Prior art keywords
weights rotating
flywheel weights
flywheel
rotating
weights
Prior art date
Application number
IT19962/86A
Other languages
English (en)
Other versions
IT8619962A0 (it
Inventor
Paul Maucher
Oswald Friedmann
Original Assignee
Luk Lamellen & Kupplungsbau
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Luk Lamellen & Kupplungsbau filed Critical Luk Lamellen & Kupplungsbau
Publication of IT8619962A0 publication Critical patent/IT8619962A0/it
Application granted granted Critical
Publication of IT1189187B publication Critical patent/IT1189187B/it

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/10—Suppression of vibrations in rotating systems by making use of members moving with the system
    • F16F15/12—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon
    • F16F15/131—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon the rotating system comprising two or more gyratory masses
    • F16F15/139—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon the rotating system comprising two or more gyratory masses characterised by friction-damping means
    • F16F15/1397—Overload protection, i.e. means for limiting torque
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/10—Suppression of vibrations in rotating systems by making use of members moving with the system
    • F16F15/12—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon
    • F16F15/131—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon the rotating system comprising two or more gyratory masses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16F—SPRINGS; SHOCK-ABSORBERS; MEANS FOR DAMPING VIBRATION
    • F16F15/00—Suppression of vibrations in systems; Means or arrangements for avoiding or reducing out-of-balance forces, e.g. due to motion
    • F16F15/10—Suppression of vibrations in rotating systems by making use of members moving with the system
    • F16F15/12—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon
    • F16F15/131—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon the rotating system comprising two or more gyratory masses
    • F16F15/13128—Suppression of vibrations in rotating systems by making use of members moving with the system using elastic members or friction-damping members, e.g. between a rotating shaft and a gyratory mass mounted thereon the rotating system comprising two or more gyratory masses the damping action being at least partially controlled by centrifugal masses
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16D—COUPLINGS FOR TRANSMITTING ROTATION; CLUTCHES; BRAKES
    • F16D13/00—Friction clutches
    • F16D13/58—Details
    • F16D13/70—Pressure members, e.g. pressure plates, for clutch-plates or lamellae; Guiding arrangements for pressure members
    • F16D2013/703—Pressure members, e.g. pressure plates, for clutch-plates or lamellae; Guiding arrangements for pressure members the pressure plate on the flywheel side is combined with a damper

Landscapes

  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Aviation & Aerospace Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Mechanical Operated Clutches (AREA)
  • One-Way And Automatic Clutches, And Combinations Of Different Clutches (AREA)
  • Gyroscopes (AREA)
  • Coloring (AREA)
  • Seats For Vehicles (AREA)
IT19962/86A 1985-04-04 1986-04-03 Dispositivo con due masse volaniche ruotanti l'una rispetto all'altra IT1189187B (it)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
DE3512372 1985-04-04
DE3516907 1985-05-10
DE3532005 1985-09-07

Publications (2)

Publication Number Publication Date
IT8619962A0 IT8619962A0 (it) 1986-04-03
IT1189187B true IT1189187B (it) 1988-01-28

Family

ID=27192975

Family Applications (1)

Application Number Title Priority Date Filing Date
IT19962/86A IT1189187B (it) 1985-04-04 1986-04-03 Dispositivo con due masse volaniche ruotanti l'una rispetto all'altra

Country Status (6)

Country Link
US (2) US4751992A (it)
JP (6) JP2795320B2 (it)
DE (1) DE3610735A1 (it)
ES (1) ES8706237A1 (it)
FR (3) FR2580050B1 (it)
IT (1) IT1189187B (it)

Families Citing this family (61)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US5269725A (en) * 1984-06-12 1993-12-14 Luk Lamellen Und Kupplingbau Gmbh Torsion damping apparatus for use with friction clutches in the power trains of motor vehicles
DE8511027U1 (de) * 1985-04-15 1988-02-04 LuK Lamellen und Kupplungsbau GmbH, 7580 Bühl Drehmomentübertragungseinrichtung
BR8502761A (pt) * 1984-06-12 1986-02-18 Luk Lamellen & Kupplungsbau Conjunto para a compensacao de choque de rotacao
US5139124A (en) * 1985-09-07 1992-08-18 Luk Lamellen Und Kupplungsbau Gmbh Apparatus for compensating for fluctuations of torque between the engine and the transmission of a motor vehicle
DE8525579U1 (de) * 1985-09-07 1993-06-03 LuK Lamellen und Kupplungsbau GmbH, 7580 Bühl Einrichtung zum Kompensieren von Drehstößen
DE8535705U1 (de) * 1985-12-19 1993-05-13 LuK Lamellen und Kupplungsbau GmbH, 7580 Bühl Einrichtung zum Kompensieren von Drehstößen
JP2718413B2 (ja) * 1986-07-05 1998-02-25 ルーク・ラメレン・ウント・クツプルングスバウ・ゲゼルシヤフト・ミツト・ベシユレンクテル・ハフツング 振動緩衝装置
FR2602560B1 (fr) * 1986-08-06 1990-11-02 Valeo Unite d'embrayage, et applications notamment friction d'embrayage, embrayage et organe d'accouplement hydraulique comportant une telle unite, en particulier pour vehicule automobile
JPH076545B2 (ja) * 1986-09-30 1995-01-30 アイシン精機株式会社 トルク変動吸収装置
JPH079252B2 (ja) * 1986-09-30 1995-02-01 アイシン精機株式会社 トルク変動吸収装置
DE3704643A1 (de) * 1987-02-14 1988-08-25 Daimler Benz Ag Geteiltes schwungrad
JPH0623789Y2 (ja) * 1987-09-19 1994-06-22 アイシン精機株式会社 トルク変動吸収装置
DE3743075A1 (de) * 1987-12-18 1989-06-29 Fichtel & Sachs Ag Torsionsschwingungsdaempfer mit waelzlagerung
US5194046A (en) * 1988-01-29 1993-03-16 Luk Lamellen Und Kupplungsbau Gmbh Damper type flywheel assembly with at least one substantially segment-shaped member
DE3806013A1 (de) * 1988-02-26 1989-09-07 Voith Gmbh J M Kupplung fuer wechselnde betriebszustaende, insbesondere zweimassenschwungrad
US5122134A (en) * 1990-02-02 1992-06-16 Pfizer Hospital Products Group, Inc. Surgical reamer
JP2650787B2 (ja) 1993-05-27 1997-09-03 ハウメディカ インク フレキシブル骨髄リーマシステム
DE4420934B4 (de) * 1993-06-19 2004-11-04 Luk Lamellen Und Kupplungsbau Beteiligungs Kg Drehmomentübertragungseinrichtung
US5437356A (en) * 1993-10-18 1995-08-01 Hoffco, Inc. Centrifugal clutch
FR2721984B1 (fr) * 1994-06-30 1996-09-06 Valeo Volant amortisseur, et embrayage notamment pour vehicule automobile equipe d'un tel volant
ES2130884B1 (es) * 1994-07-15 2000-02-16 Fichtel & Sachs Ag Dispositivo partido de volante
US5722788A (en) 1996-01-24 1998-03-03 Bent Manfacturing Company Traffic delineator with wheels
US6014941A (en) 1996-02-29 2000-01-18 Bent Manufacturing Company Traffic delineator
IT1291497B1 (it) * 1997-02-04 1999-01-11 Magneti Marelli Spa Metodo e dispositivo di controllo di una frizione di un veicolo
US5935007A (en) * 1997-05-29 1999-08-10 Meritor Heavy Vehicle Systems, Llc Torsional vibration damper
US6019542A (en) 1998-01-23 2000-02-01 Bent Manufacturing Company Drop-over base for traffic delineation device
DE19817907A1 (de) * 1998-04-22 1999-10-28 Rohs Voigt Patentverwertungsge Reibscheibendämpfer
US6305312B1 (en) 1999-06-09 2001-10-23 Bent Manufacturing Company Stackable vertical panel traffic channelizing device
DE10117745A1 (de) * 2000-04-20 2001-11-22 Luk Lamellen & Kupplungsbau Kupplungsscheibe
US6536369B1 (en) 2000-08-18 2003-03-25 Bent Manufacturing Company Handle for traffic delineator
JP4277501B2 (ja) * 2001-10-17 2009-06-10 アイシン精機株式会社 トルク変動吸収装置
US7195111B2 (en) 2002-09-02 2007-03-27 Exedy Corporation Clutch device having a clutch damper and dual-mass flywheel assembly
US7358226B2 (en) * 2003-08-27 2008-04-15 The Regents Of The University Of California Ultrasonic concentration of drug delivery capsules
DE112004001721T5 (de) * 2003-09-16 2006-10-19 Exedy Corp., Neyagawa Flexibles Schwungrad
JP2005114158A (ja) * 2003-09-16 2005-04-28 Exedy Corp ２マスフライホイール
WO2005028914A1 (ja) * 2003-09-16 2005-03-31 Exedy Corporation 2マスフライホイール
DE102005004993B4 (de) * 2004-02-18 2015-09-24 Schaeffler Technologies AG & Co. KG Torsionsschwingungsdämpfer
FR2871204B1 (fr) * 2004-06-08 2007-09-28 Valeo Embrayages Double volant amortisseur, en particulier pour vehicule automobile
US7335107B2 (en) * 2004-08-27 2008-02-26 Caterpillar Inc. Torsional coupling
DE102005012861A1 (de) * 2005-01-26 2006-08-03 Rohs, Ulrich, Dr.-Ing. Dämpfungseinrichtung, insbesondere für ein Zweimassenschwungrad
DE102005062267A1 (de) * 2005-12-24 2007-06-28 Zf Friedrichshafen Ag Torsionsschwingungsdämpfer
US7547981B2 (en) * 2007-02-09 2009-06-16 Caterpillar Inc. Machine having electrical power system and method
JP5082725B2 (ja) * 2007-09-28 2012-11-28 アイシン精機株式会社 トルク変動吸収装置
DE102009004719B4 (de) * 2008-01-28 2020-10-01 Schaeffler Technologies AG & Co. KG Drehschwingungsdämpfer
JP5169656B2 (ja) * 2008-09-10 2013-03-27 アイシン精機株式会社 ダンパ装置
JP5267224B2 (ja) * 2009-03-06 2013-08-21 トヨタ自動車株式会社 トルクリミッタおよび動力伝達装置
JP4999898B2 (ja) 2009-08-27 2012-08-15 株式会社エクセディ トルクリミッタ装置
JP5120386B2 (ja) * 2010-01-20 2013-01-16 アイシン精機株式会社 トルク変動吸収装置
JP5690576B2 (ja) * 2010-12-20 2015-03-25 トックベアリング株式会社 速度依存型回転ダンパ
JP5131369B2 (ja) * 2011-08-03 2013-01-30 アイシン精機株式会社 トルク変動吸収装置
JP5304875B2 (ja) * 2011-11-21 2013-10-02 アイシン精機株式会社 トルク変動吸収装置
FR2989753B1 (fr) * 2012-04-20 2014-04-18 Valeo Embrayages Dispositif d'amortissement pendulaire, en particulier pour une transmission de vehicule automobile
WO2014059987A2 (de) * 2012-10-18 2014-04-24 Schaeffler Technologies AG & Co. KG Zweimassenschwungrad und drehmomentübertragungseinrichtung mit zweimassenschwungrad
US9683627B2 (en) 2013-10-31 2017-06-20 Valeo Embrayages Mechanism for filtering torque fluctuations of secondary member
DE112016002822A5 (de) * 2015-06-24 2018-03-08 Schaeffler Technologies AG & Co. KG Antriebsstrang für ein Kraftfahrzeug mit einer Reibungskupplung und Reibungskupplung für einen Antriebsstrang eines Kraftfahrzeugs
FR3039871B1 (fr) * 2015-08-05 2018-03-02 Valeo Embrayages Dispositif d'amortissement d'oscillations de torsion
CN107304794B (zh) * 2016-04-18 2020-07-24 北汽福田汽车股份有限公司 车辆及其扭转减振器
FR3051868B1 (fr) * 2016-05-30 2019-01-25 Valeo Embrayages Dispositif d'amortissement pour embrayage de vehicule automobile et embrayage comprenant un tel dispositif
US10816046B2 (en) 2016-08-15 2020-10-27 Cnh Industrial America Llc Clutch control for shared power dissipation
JP7161625B2 (ja) 2020-09-25 2022-10-26 有限会社T.P.P. 摩擦クラッチのプレッシャープレート装置
DE102021123117B3 (de) 2021-09-07 2022-12-22 Schaeffler Technologies AG & Co. KG Einstellbarer Drehmomentbegrenzer

Family Cites Families (34)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE678363C (de) 1936-07-17 1939-07-14 Siemens Schuckertwerke Akt Ges Kupplung mit Kraftspeichern bei dieselelektrischen Fahrzeugen zwischen Dieselmotor und elektrischen Generator, der beim Anlassen des Dieselmotors als Antriebsmotor dient
US2203117A (en) * 1937-03-23 1940-06-04 Whatmough Wilfred Ambrose Centrifugal clutch
FR876921A (fr) * 1940-09-24 1942-11-23 Kloeckner Humboldt Deutz Ag Amortisseur d'oscillations
US2368299A (en) * 1942-04-25 1945-01-30 Hayter Gordon Willis Centrifugal clutch
FR53833E (fr) * 1944-07-31 1946-09-09 Deutsche Schiff & Maschb Ag Amortisseur des oscillations de masses rotatives
DE802976C (de) * 1948-10-07 1951-02-26 Richard Binder Reibscheibenkupplung mit Drehschwingungsdaempfer, insbesondere fuer Kraftfahrzeuge
DE1090103B (de) * 1955-01-17 1960-09-29 Klaue Hermann Fliehkraftkupplung, insbesondere fuer Kraftwagenschaltgetriebe
JPS4527929Y1 (it) * 1966-07-20 1970-10-28
US4063623A (en) * 1976-06-29 1977-12-20 Borg-Warner Corporation Fluid coupling with centrifugal and torque responsive lock up clutch
FR2365728A1 (fr) * 1976-09-23 1978-04-21 Ferodo Sa Dispositif amortisseur de torsion, en particulier friction d'embrayage, notamment pour vehicule automobile
JPS5361554U (it) * 1976-10-22 1978-05-25
DE2743595C2 (de) * 1977-09-28 1985-04-25 Deutsche Automobilgesellschaft Mbh, 3000 Hannover Fliehkraftkupplung
JPS592335Y2 (ja) * 1978-04-05 1984-01-23 株式会社大金製作所 ダンパ−機構
JPS601497B2 (ja) * 1978-08-03 1985-01-16 アイシン精機株式会社 回転トルク伝達装置
US4305493A (en) * 1979-12-26 1981-12-15 Borg-Warner Corporation Friction shoe assembly for a speed responsive centrifugal clutch assembly
US4431100A (en) * 1980-07-16 1984-02-14 Kabushiki Kaisha Komatsu Seisakusho Torque fluctuation damper
FR2499183B1 (fr) * 1981-02-04 1986-03-07 Valeo Dispositif amortisseur de torsion, notamment friction d'embrayage pour vehicule automobile
FR2499181B1 (fr) 1981-02-04 1986-03-28 Valeo Dispositif amortisseur de torsion, en particulier friction d'embrayage, notamment pour vehicule automobile
DE3107371C2 (de) * 1981-02-27 1986-01-30 Bayerische Motoren Werke AG, 8000 München Drehschwingungsgedämpfte Kupplungsscheibe für Kraftfahrzeuge
US4425991A (en) * 1981-05-18 1984-01-17 Hays Bill J Automotive clutch improvements
US4471863A (en) * 1981-08-28 1984-09-18 Borg-Warner Corporation Multi-stage torsional damping device
FR2518203A1 (fr) * 1981-12-11 1983-06-17 Peugeot Volant amortisseur de vibrations, notamment pour vehicule automobile
DE3227809A1 (de) * 1982-07-24 1984-01-26 LuK Lamellen und Kupplungsbau GmbH, 7580 Bühl Drehschwingungsdaempfer, insbesondere fuer mit drehmomentenwandlern ausgeruestete kraftfahrzeugantriebe
JPS59151624A (ja) * 1983-02-19 1984-08-30 Honda Motor Co Ltd 車両の動力伝達系における捩り振動吸収装置
FR2551814B1 (fr) * 1983-09-14 1986-02-07 Valeo Disque de friction d'embrayage
DE3418671C2 (de) 1983-10-24 1996-05-23 Luk Lamellen & Kupplungsbau Dämpfungseinrichtung zum Aufnehmen bzw. Ausgleichen von Drehstößen
DE3447926C2 (de) * 1983-11-15 1995-07-06 Luk Lamellen & Kupplungsbau Einrichtung zum Kompensieren von Drehstößen
DE3411239C2 (de) * 1983-11-15 1996-05-23 Luk Lamellen & Kupplungsbau Einrichtung zum Kompensieren von Drehstößen
DE3345409A1 (de) * 1983-12-15 1985-06-27 Fichtel & Sachs Ag, 8720 Schweinfurt Torsions-schwingungsdaempfer mit integriertem vordaempfer
DE3400183A1 (de) 1984-01-04 1985-07-11 Fichtel & Sachs Ag, 8720 Schweinfurt Torsions-schwingungsdaempfer mit einer feder fuer beide reibeinrichtungen
DE3405949A1 (de) 1984-02-18 1985-08-22 Fichtel & Sachs Ag, 8720 Schweinfurt Torsionsschwingungsdaempfer mit mehrfunktionen-bauteil
US4611701A (en) * 1984-03-05 1986-09-16 Luk Lamellen Und Kupplungsbau Gmbh Torsion damping assembly for use in motor vehicles
JPS60192124A (ja) * 1984-03-09 1985-09-30 Daikin Mfg Co Ltd ダンパ−デイスクの摩擦装置
DE3412961A1 (de) * 1984-04-06 1985-10-24 Fichtel & Sachs Ag, 8720 Schweinfurt Geteiltes schwungrad

Also Published As

Publication number Publication date
JPS61282641A (ja) 1986-12-12
FR2580047B1 (it) 1992-12-04
US4751992A (en) 1988-06-21
JPS61282640A (ja) 1986-12-12
FR2580050A1 (it) 1986-10-10
JPH10238592A (ja) 1998-09-08
JP3347956B2 (ja) 2002-11-20
FR2580047A1 (it) 1986-10-10
JP3020913B2 (ja) 2000-03-15
JPH10238591A (ja) 1998-09-08
FR2676102A1 (fr) 1992-11-06
IT8619962A0 (it) 1986-04-03
ES8706237A1 (es) 1987-06-01
FR2676102B1 (it) 1994-12-16
ES553717A0 (es) 1987-06-01
JP2795320B2 (ja) 1998-09-10
DE3610735A1 (de) 1986-10-09
JPH09217788A (ja) 1997-08-19
JP2776421B2 (ja) 1998-07-16
US4681199A (en) 1987-07-21
FR2580050B1 (it) 1993-11-19
JPH10238590A (ja) 1998-09-08

Similar Documents

Publication Publication Date Title
IT1189187B (it) Dispositivo con due masse volaniche ruotanti l'una rispetto all'altra
IT8867632A0 (it) Smorzatore ruotante
DE68912033D1 (de) Rotierende Plattenvorrichtung.
DE3381840D1 (de) Polarisationsoptischer drehkompensator und optischer isolator mit einem solchen kompensator.
FR2538481B1 (fr) Disque d'embrayage
IT8967006A0 (it) Smorzatore ruotante
FI892479A0 (fi) Siirtolaite
FR2583839B1 (fr) Disque d'embrayage
DE69025488D1 (de) Plattengerät mit Plattenstapelanordnung
IT8049306A0 (it) Dispositivo d'innesto elettromagne tico
FR2536481B1 (fr) Disque d'embrayage
AT389575B (de) Einstellbare reibungskupplung
DK31285D0 (da) Koblingsanordning
DE3676435D1 (de) Schwungradvorrichtung.
ATA76889A (de) Viskosekupplung
FR2532019B1 (fr) Disque d'embrayage
FR2343163A1 (fr) Disques d'embrayages
DE3575664D1 (de) Selbstschliessende verabreichungsvorrichtung.
FR2601734B1 (fr) Disque d'embrayage
FI882767A0 (fi) Poistolaite
FR2531163B1 (fr) Disque d'embrayage
IT8621007A0 (it) Dispositivo per smorzar vibrazioni rotazionali.
AU9162582A (en) Damper with friction lag device
DE3610871B4 (de) Einrichtung mit zwei relativ zueinander verdrehbaren Schwungmassen
FR2570452B1 (fr) Disque d'embrayage avec masse d'equilibrage

Legal Events

Date Code Title Description
TA Fee payment date (situation as of event date), data collected since 19931001

Effective date: 19970428