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GB1490923A - Sound-absorbing structures - Google Patents

Sound-absorbing structures

Info

Publication number
GB1490923A
GB1490923A GB26606/75A GB2660675A GB1490923A GB 1490923 A GB1490923 A GB 1490923A GB 26606/75 A GB26606/75 A GB 26606/75A GB 2660675 A GB2660675 A GB 2660675A GB 1490923 A GB1490923 A GB 1490923A
Authority
GB
United Kingdom
Prior art keywords
sheet
facing
porous
members
sheets
Prior art date
Legal status (The legal status 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 status listed.)
Expired
Application number
GB26606/75A
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Short Brothers PLC
Original Assignee
Short Brothers and Harland Ltd
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 Short Brothers and Harland Ltd filed Critical Short Brothers and Harland Ltd
Priority to GB26606/75A priority Critical patent/GB1490923A/en
Priority to DE19762627801 priority patent/DE2627801A1/en
Priority to FR7619134A priority patent/FR2317504A1/en
Publication of GB1490923A publication Critical patent/GB1490923A/en
Expired legal-status Critical Current

Links

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F02—COMBUSTION ENGINES; HOT-GAS OR COMBUSTION-PRODUCT ENGINE PLANTS
    • F02C—GAS-TURBINE PLANTS; AIR INTAKES FOR JET-PROPULSION PLANTS; CONTROLLING FUEL SUPPLY IN AIR-BREATHING JET-PROPULSION PLANTS
    • F02C7/00—Features, components parts, details or accessories, not provided for in, or of interest apart form groups F02C1/00 - F02C6/00; Air intakes for jet-propulsion plants
    • F02C7/24—Heat or noise insulation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/10—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material
    • B32B3/12—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a discontinuous layer, i.e. formed of separate pieces of material characterised by a layer of regularly- arranged cells, e.g. a honeycomb structure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B15/00—Layered products comprising a layer of metal
    • B32B15/14—Layered products comprising a layer of metal next to a fibrous or filamentary layer
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B3/00—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form
    • B32B3/26—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer
    • B32B3/266—Layered products comprising a layer with external or internal discontinuities or unevennesses, or a layer of non-planar shape; Layered products comprising a layer having particular features of form characterised by a particular shape of the outline of the cross-section of a continuous layer; characterised by a layer with cavities or internal voids ; characterised by an apertured layer characterised by an apertured layer, the apertures going through the whole thickness of the layer, e.g. expanded metal, perforated layer, slit layer regular cells B32B3/12
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B5/00—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts
    • B32B5/02—Layered products characterised by the non- homogeneity or physical structure, i.e. comprising a fibrous, filamentary, particulate or foam layer; Layered products characterised by having a layer differing constitutionally or physically in different parts characterised by structural features of a fibrous or filamentary layer
    • B32B5/022—Non-woven fabric
    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10K—SOUND-PRODUCING DEVICES; METHODS OR DEVICES FOR PROTECTING AGAINST, OR FOR DAMPING, NOISE OR OTHER ACOUSTIC WAVES IN GENERAL; ACOUSTICS NOT OTHERWISE PROVIDED FOR
    • G10K11/00—Methods or devices for transmitting, conducting or directing sound in general; Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/16—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general
    • G10K11/172—Methods or devices for protecting against, or for damping, noise or other acoustic waves in general using resonance effects
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B32—LAYERED PRODUCTS
    • B32B—LAYERED PRODUCTS, i.e. PRODUCTS BUILT-UP OF STRATA OF FLAT OR NON-FLAT, e.g. CELLULAR OR HONEYCOMB, FORM
    • B32B2307/00—Properties of the layers or laminate
    • B32B2307/50—Properties of the layers or laminate having particular mechanical properties
    • B32B2307/56—Damping, energy absorption

Landscapes

  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Textile Engineering (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Multimedia (AREA)
  • Soundproofing, Sound Blocking, And Sound Damping (AREA)

Abstract

1490923 Sand insulation SHORT BROS & HARLAND Ltd 21 June 1976 [23 June 1975] 26606/75 Heading F2X [Also in Divisions B5 and F1] A sand absorbing structure comprises a porous facing sheet 20 and a non-porous backing sheet 21 with a core structure 22 connecting the facing and backing sheets and forming with the facing and backing sheets a plurality of side-byside resonating chambers, and intermediate porous members 25 each dividing an associated one of the chambers into two cells 23, 24, the intermediate porous members being so constructed and arranged that adjacent intermediate members or adjacent groups of intermediate members have differing porosities to cause adjacent associated chambers or groups of chambers to absorb sounds of differing ranges of frequencies. The porosity of the intermediate members may be constant in one direction parallel to the facing sheet but vary in a second direction parallel to the facing sheet but normal to the one direction. Facing and backing sheets 20 and 21 may be of metallic material. Intermediate porous member 25 may be a perforate sheet, the porosity being varied by variation of the size of the perforations and/or by variation of the number of perforations per unit area of the sheet. A porous sheet of woven or non- woven organic or inorganic fibres may overlie and be bonded or welded to facing sheet 20 or intermediate sheet 25. The facing and intermediate sheets may also be sheets of woven or non-woven organic or inorganic fibres with the fibres providing variable porosity. The porosity of facing sheet 20 whether of metal or fibres may be varied to accommodate variations in ambient conditions. The sound absorbing structure may be used to line at least one of the ducts of a gas turbine engine and may be of annular configuration. In alternative arrangements the backing sheet is conical and is inclined to the facing sheet and intermediate sheet so that the intermediate sheet divides the chamber in different proportions.
GB26606/75A 1975-06-23 1975-06-23 Sound-absorbing structures Expired GB1490923A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
GB26606/75A GB1490923A (en) 1975-06-23 1975-06-23 Sound-absorbing structures
DE19762627801 DE2627801A1 (en) 1975-06-23 1976-06-22 SOUND ATTENUATION DEVICE
FR7619134A FR2317504A1 (en) 1975-06-23 1976-06-23 SOUND ABSORBING STRUCTURE AND GAS TURBINE ENGINE INCLUDING SUCH A STRUCTURE

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB26606/75A GB1490923A (en) 1975-06-23 1975-06-23 Sound-absorbing structures

Publications (1)

Publication Number Publication Date
GB1490923A true GB1490923A (en) 1977-11-02

Family

ID=10246278

Family Applications (1)

Application Number Title Priority Date Filing Date
GB26606/75A Expired GB1490923A (en) 1975-06-23 1975-06-23 Sound-absorbing structures

Country Status (3)

Country Link
DE (1) DE2627801A1 (en)
FR (1) FR2317504A1 (en)
GB (1) GB1490923A (en)

Cited By (28)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0020016A1 (en) * 1979-05-23 1980-12-10 Coal Industry (Patents) Limited Acoustic liner for attenuating noise
EP0020015B1 (en) * 1979-05-23 1984-03-28 Coal Industry (Patents) Limited Acoustic liner for attenuating noise
US4540335A (en) * 1980-12-02 1985-09-10 Mitsubishi Jukogyo Kabushiki Kaisha Controllable-pitch moving blade type axial fan
EP0413987A2 (en) * 1989-08-23 1991-02-27 GEBHARDT VENTILATOREN GMBH & CO. Axial fan
GB2252076A (en) * 1991-01-22 1992-07-29 Short Brothers Plc Noise attenuation panel
AU634310B2 (en) * 1989-11-08 1993-02-18 Royal Ordnance Plc Composite materials useful in the protection of aircraft structures
EP1148470A2 (en) * 2000-04-21 2001-10-24 Mitsubishi Heavy Industries, Ltd. Active sound reduction aparatus and active noise insulation wall having same
GB2364366A (en) * 2000-06-30 2002-01-23 Short Brothers Plc A noise attenuation panel
EP1217605A1 (en) * 2000-12-21 2002-06-26 AIRBUS FRANCE (Société par Actions Simplifiée) Method of manufacturing a panel with a protected acoustic sound damping layer and acoustic panel thereby created
EP1239454A1 (en) * 2001-03-09 2002-09-11 Airbus France Method of manufacturing a panel with an adapted, acoustically resistive layer and resulting panel
GB2391059A (en) * 2000-06-30 2004-01-28 Short Brothers Plc A noise attenuation panel
US7311175B2 (en) 2005-08-10 2007-12-25 United Technologies Corporation Acoustic liner with bypass cooling
US7401682B2 (en) 2005-08-10 2008-07-22 United Technologies Corporation Architecture for an acoustic liner
EP1548229A3 (en) * 2003-12-22 2009-08-05 United Technologies Corporation Airfoil surface impedance modification for noise reduction in turbofan engines
GB2459844A (en) * 2008-05-06 2009-11-11 Rolls Royce Plc Turbofan engine casing liner panel
JP2010526231A (en) * 2007-04-30 2010-07-29 エアバス フランス Acoustic panel with variable acoustic characteristics
WO2011086273A1 (en) * 2009-12-22 2011-07-21 Airbus Operations Sas Acoustic treatment panel having scalable thickness
ITTO20111124A1 (en) * 2011-12-09 2013-06-10 Alenia Aermacchi Spa ELEMENT FOR SOUND ABSORPTION, IN PARTICULAR INTENDED TO BE MOUNTED ON AIRCRAFT COMPONENTS, SUCH AS GONDOLAS ENGINES.
GB2527644A (en) * 2014-04-30 2015-12-30 Boeing Co Methods and apparatus for noise attenuation in an engine nacelle
CN105719634A (en) * 2014-12-04 2016-06-29 北京市劳动保护科学研究所 Broadband composite sound absorption structure
US9656761B2 (en) 2014-04-30 2017-05-23 The Boeing Company Lipskin for a nacelle and methods of making the same
US9708072B2 (en) 2014-04-30 2017-07-18 The Boeing Company Aircraft engine nacelle bulkheads and methods of assembling the same
US9938852B2 (en) 2014-04-30 2018-04-10 The Boeing Company Noise attenuating lipskin assembly and methods of assembling the same
US10279548B2 (en) 2014-11-03 2019-05-07 Short Brothers Plc Methods and precursors for manufacturing a perforated composite part
EP3678128A1 (en) * 2019-01-04 2020-07-08 Rohr, Inc. Acoustic liner and method of forming an acoustic liner
US10793282B2 (en) 2016-07-28 2020-10-06 The Boeing Company Liner assembly, engine housing, and methods of assembling the same
CN113347539A (en) * 2021-05-18 2021-09-03 深圳市大分子科技有限公司 Sound absorbing material and loudspeaker
EP4253031A1 (en) * 2022-04-01 2023-10-04 Airbus Operations (S.A.S.) Acoustic panel comprising at least two honeycomb structures nested in one another, aircraft comprising at least one such acoustic panel

Families Citing this family (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE2710383C3 (en) * 1977-03-10 1984-03-22 Zink Gmbh & Co Kg, 7121 Cleebronn Method for producing a pyrotechnic sound signal
US4265955A (en) * 1978-05-01 1981-05-05 The Boeing Company Honeycomb core with internal septum and method of making same
GB2038410B (en) * 1978-12-27 1982-11-17 Rolls Royce Acoustic lining utilising resonance
GB2076049B (en) * 1980-05-17 1983-10-26 Rolls Royce Variable acoustic impedance lining
US4645032A (en) * 1985-09-05 1987-02-24 The Garrett Corporation Compact muffler apparatus and associated methods
US5160248A (en) * 1991-02-25 1992-11-03 General Electric Company Fan case liner for a gas turbine engine with improved foreign body impact resistance
DE4404502C2 (en) * 1994-02-12 2002-02-28 Bosch Gmbh Robert Sound absorbing cover
US7984787B2 (en) * 2009-01-23 2011-07-26 Dresser-Rand Company Fluid-carrying conduit and method with noise attenuation
FR3028886B1 (en) 2014-11-24 2019-09-13 Safran Aircraft Engines TURBOREACTOR BLOWER NOISE REDUCTION BODY
DE202015004064U1 (en) 2015-06-10 2015-09-18 Akustikbüro Krämer + Stegmaier GmbH Device for reducing sound pressure levels
CN106098050A (en) * 2016-06-07 2016-11-09 西安交通大学 A kind of continuous gradient sound absorption structure

Family Cites Families (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
BE554083A (en) * 1956-02-18
GB899685A (en) * 1959-12-29 1962-06-27 Bolt Beranek & Newman Sound-absorbing member, e.g., for ducts
US3734234A (en) * 1971-11-08 1973-05-22 Lockheed Aircraft Corp Sound absorption structure
FR2300384A1 (en) * 1975-02-07 1976-09-03 Lockheed Aircraft Corp Sound absorbing panel effective in two frequency domains - combines action of Helm holtz resonator with that of laminar honeycomb absorber

Cited By (58)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0020016A1 (en) * 1979-05-23 1980-12-10 Coal Industry (Patents) Limited Acoustic liner for attenuating noise
EP0020015B1 (en) * 1979-05-23 1984-03-28 Coal Industry (Patents) Limited Acoustic liner for attenuating noise
US4540335A (en) * 1980-12-02 1985-09-10 Mitsubishi Jukogyo Kabushiki Kaisha Controllable-pitch moving blade type axial fan
EP0413987A2 (en) * 1989-08-23 1991-02-27 GEBHARDT VENTILATOREN GMBH & CO. Axial fan
EP0413987A3 (en) * 1989-08-23 1991-09-25 Gebhardt Ventilatoren Gmbh & Co. Axial fan
AU634310B2 (en) * 1989-11-08 1993-02-18 Royal Ordnance Plc Composite materials useful in the protection of aircraft structures
GB2252076A (en) * 1991-01-22 1992-07-29 Short Brothers Plc Noise attenuation panel
GB2252076B (en) * 1991-01-22 1994-11-09 Short Brothers Plc Noise attenuation panel
EP1148470A2 (en) * 2000-04-21 2001-10-24 Mitsubishi Heavy Industries, Ltd. Active sound reduction aparatus and active noise insulation wall having same
US6609592B2 (en) 2000-06-30 2003-08-26 Short Brothers Plc Noise attenuation panel
US6827180B2 (en) 2000-06-30 2004-12-07 Short Brothers Plc Noise attenuation panel
GB2391059B (en) * 2000-06-30 2005-02-16 Short Brothers Plc A noise attenuation panel
GB2391059A (en) * 2000-06-30 2004-01-28 Short Brothers Plc A noise attenuation panel
GB2364366B (en) * 2000-06-30 2003-12-03 Short Brothers Plc A noise attenuation panel
GB2364366A (en) * 2000-06-30 2002-01-23 Short Brothers Plc A noise attenuation panel
US6820337B2 (en) 2000-12-21 2004-11-23 Airbus France Process for making a panel with a protected acoustic damping layer and acoustic panel as made
FR2818581A1 (en) * 2000-12-21 2002-06-28 Eads Airbus Sa PROCESS FOR MANUFACTURING A PANEL WITH A PROTECTED ACOUSTIC CUSHIONING LAYER AND ACOUSTIC PANEL THUS OBTAINED
US7257894B2 (en) 2000-12-21 2007-08-21 Airbus France Process for making a panel with a protected acoustic damping layer
EP1217605A1 (en) * 2000-12-21 2002-06-26 AIRBUS FRANCE (Société par Actions Simplifiée) Method of manufacturing a panel with a protected acoustic sound damping layer and acoustic panel thereby created
FR2821788A1 (en) * 2001-03-09 2002-09-13 Eads Airbus Sa METHOD FOR MANUFACTURING A PANEL WITH AN ADAPTED ACOUSTIC RESISTIVE LAYER AND ACOUSTIC PANEL THUS OBTAINED
EP1239454A1 (en) * 2001-03-09 2002-09-11 Airbus France Method of manufacturing a panel with an adapted, acoustically resistive layer and resulting panel
US6755280B2 (en) 2001-03-09 2004-06-29 Airbus France Method for producing a panel comprising an adapted acoustically resistive layer and panel so obtained
EP1548229A3 (en) * 2003-12-22 2009-08-05 United Technologies Corporation Airfoil surface impedance modification for noise reduction in turbofan engines
US7311175B2 (en) 2005-08-10 2007-12-25 United Technologies Corporation Acoustic liner with bypass cooling
US7401682B2 (en) 2005-08-10 2008-07-22 United Technologies Corporation Architecture for an acoustic liner
RU2467191C2 (en) * 2007-04-30 2012-11-20 Эрбюс Франс Aircraft gondola with acoustical board having variable acoustic property
JP2010526231A (en) * 2007-04-30 2010-07-29 エアバス フランス Acoustic panel with variable acoustic characteristics
US7963362B2 (en) 2007-04-30 2011-06-21 Airbus Operations Sas Acoustic panel having a variable acoustic characteristic
GB2459844B (en) * 2008-05-06 2011-01-19 Rolls Royce Plc Fan section
GB2459844A (en) * 2008-05-06 2009-11-11 Rolls Royce Plc Turbofan engine casing liner panel
US8578697B2 (en) 2008-05-06 2013-11-12 Rolls-Royce Plc Fan section
WO2011086273A1 (en) * 2009-12-22 2011-07-21 Airbus Operations Sas Acoustic treatment panel having scalable thickness
CN102686481A (en) * 2009-12-22 2012-09-19 空中客车运营简化股份公司 Acoustic treatment panel having scalable thickness
US8505679B2 (en) 2009-12-22 2013-08-13 Airbus Operations Sas Panel for the acoustic treatment with a progressive thickness
CN102686481B (en) * 2009-12-22 2016-01-13 空中客车运营简化股份公司 A kind of aircraft nacelle comprising air intake
ITTO20111124A1 (en) * 2011-12-09 2013-06-10 Alenia Aermacchi Spa ELEMENT FOR SOUND ABSORPTION, IN PARTICULAR INTENDED TO BE MOUNTED ON AIRCRAFT COMPONENTS, SUCH AS GONDOLAS ENGINES.
WO2013084135A1 (en) * 2011-12-09 2013-06-13 Alenia Aermacchi S.Pa. Element for sound absorption mounted on aircraft components
US9994302B2 (en) 2011-12-09 2018-06-12 Alenia Aermacchi S.P.A. Element for sound absorption mounted on aircraft components
US9708072B2 (en) 2014-04-30 2017-07-18 The Boeing Company Aircraft engine nacelle bulkheads and methods of assembling the same
US10294867B2 (en) 2014-04-30 2019-05-21 The Boeing Company Methods and apparatus for noise attenuation in an engine nacelle
GB2537063A (en) * 2014-04-30 2016-10-05 Boeing Co Methods and apparatus for noise attenuation in an engine nacelle
US9604438B2 (en) 2014-04-30 2017-03-28 The Boeing Company Methods and apparatus for noise attenuation in an engine nacelle
US9656761B2 (en) 2014-04-30 2017-05-23 The Boeing Company Lipskin for a nacelle and methods of making the same
GB2527644B (en) * 2014-04-30 2016-08-31 Boeing Co Methods and apparatus for noise attenuation in an engine nacelle
GB2537063B (en) * 2014-04-30 2018-03-28 Boeing Co Methods and apparatus for noise attenuation in an engine nacelle
US9938852B2 (en) 2014-04-30 2018-04-10 The Boeing Company Noise attenuating lipskin assembly and methods of assembling the same
GB2527644A (en) * 2014-04-30 2015-12-30 Boeing Co Methods and apparatus for noise attenuation in an engine nacelle
US10946596B2 (en) 2014-11-03 2021-03-16 Short Brothers Plc Methods and precursors for manufacturing a perforated composite part
US10279548B2 (en) 2014-11-03 2019-05-07 Short Brothers Plc Methods and precursors for manufacturing a perforated composite part
CN105719634A (en) * 2014-12-04 2016-06-29 北京市劳动保护科学研究所 Broadband composite sound absorption structure
US10793282B2 (en) 2016-07-28 2020-10-06 The Boeing Company Liner assembly, engine housing, and methods of assembling the same
EP3678128A1 (en) * 2019-01-04 2020-07-08 Rohr, Inc. Acoustic liner and method of forming an acoustic liner
US11391244B2 (en) 2019-01-04 2022-07-19 Rohr, Inc. Acoustic liner and method of forming an acoustic liner
US11808235B2 (en) 2019-01-04 2023-11-07 Rohr, Inc. Acoustic liner and method of forming an acoustic liner
CN113347539A (en) * 2021-05-18 2021-09-03 深圳市大分子科技有限公司 Sound absorbing material and loudspeaker
CN113347539B (en) * 2021-05-18 2022-09-13 深圳市大分子科技有限公司 Sound absorbing material and loudspeaker
EP4253031A1 (en) * 2022-04-01 2023-10-04 Airbus Operations (S.A.S.) Acoustic panel comprising at least two honeycomb structures nested in one another, aircraft comprising at least one such acoustic panel
FR3134220A1 (en) * 2022-04-01 2023-10-06 Airbus Operations (S.A.S.) Acoustic panel comprising at least two cellular structures nested one inside the other, aircraft comprising at least one such acoustic panel

Also Published As

Publication number Publication date
DE2627801A1 (en) 1977-01-13
FR2317504A1 (en) 1977-02-04

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Legal Events

Date Code Title Description
PS Patent sealed [section 19, patents act 1949]
PCNP Patent ceased through non-payment of renewal fee