[go: up one dir, main page]

EP0157849B1 - Wärmetauscher - Google Patents

Wärmetauscher Download PDF

Info

Publication number
EP0157849B1
EP0157849B1 EP84903672A EP84903672A EP0157849B1 EP 0157849 B1 EP0157849 B1 EP 0157849B1 EP 84903672 A EP84903672 A EP 84903672A EP 84903672 A EP84903672 A EP 84903672A EP 0157849 B1 EP0157849 B1 EP 0157849B1
Authority
EP
European Patent Office
Prior art keywords
axis
heat exchanger
media
heat
elements
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
EP84903672A
Other languages
English (en)
French (fr)
Other versions
EP0157849A1 (de
Inventor
Folke Bengtsson
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.)
FOLBEX AB
Original Assignee
FOLBEX AB
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 FOLBEX AB filed Critical FOLBEX AB
Publication of EP0157849A1 publication Critical patent/EP0157849A1/de
Application granted granted Critical
Publication of EP0157849B1 publication Critical patent/EP0157849B1/de
Expired legal-status Critical Current

Links

Images

Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D7/00—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D7/16—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation
    • F28D7/163—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation with conduit assemblies having a particular shape, e.g. square or annular; with assemblies of conduits having different geometrical features; with multiple groups of conduits connected in series or parallel and arranged inside common casing
    • F28D7/1669—Heat-exchange apparatus having stationary tubular conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the conduits being arranged in parallel spaced relation with conduit assemblies having a particular shape, e.g. square or annular; with assemblies of conduits having different geometrical features; with multiple groups of conduits connected in series or parallel and arranged inside common casing the conduit assemblies having an annular shape; the conduits being assembled around a central distribution tube
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28D—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA DO NOT COME INTO DIRECT CONTACT
    • F28D9/00—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall
    • F28D9/0012—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the apparatus having an annular form
    • F28D9/0018—Heat-exchange apparatus having stationary plate-like or laminated conduit assemblies for both heat-exchange media, the media being in contact with different sides of a conduit wall the apparatus having an annular form without any annular circulation of the heat exchange media
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F3/00—Plate-like or laminated elements; Assemblies of plate-like or laminated elements
    • F28F3/02—Elements or assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with recesses, with corrugations
    • F28F3/04—Elements or assemblies thereof with means for increasing heat-transfer area, e.g. with fins, with recesses, with corrugations the means being integral with the element
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2225/00—Reinforcing means
    • F28F2225/04—Reinforcing means for conduits
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F28—HEAT EXCHANGE IN GENERAL
    • F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
    • F28F2250/00—Arrangements for modifying the flow of the heat exchange media, e.g. flow guiding means; Particular flow patterns
    • F28F2250/10—Particular pattern of flow of the heat exchange media
    • F28F2250/102—Particular pattern of flow of the heat exchange media with change of flow direction

Definitions

  • This invention relates to a heat exchanger intended to be flown through by two media and to exchange heat via heat exchanging surfaces in such a way that the media do not directly contact each other, and at which heat exchanger the heating surfaces are located rotary symmetrically in relation to an axis, and in an annular area about said axis and the main flow direction of the media is in parallel with said axis.
  • This art is known from e.g. CH-A-460 830.
  • the capacity of the structure to withstand higher internal pressure is achieved without having to increase the material thickness. Furthermore, the invention improves the maintaining of the liqud film along the heat exchanging surfaces, in that the running liquid during its downward flow continuously is subjected to changes in direction, whereby jets and droplets are formed which by impact on the underlying surfaces wet the same.
  • a structure is obtained, which without the arrangement of special devices, such as bellows or the like, is capable to withstand high tensile and compressive forces, which can arise due to high temperature differences.
  • Fig. 1 is a basic longitudinal section of a heat exchanger according to the invention
  • Fig. 2 is a basic cross-section
  • Fig. 3 is a longitudinal section of a plate assembled of two metal sheets
  • Fig. 4 shows the upper end of a plate seen in the direction of the sheet surface
  • Fig. 5 is a view in the direction of the arrow c-c in Fig. 4
  • Fig. 6 is a view in the direction of the arrow d-d in Fig. 4
  • Fig. 7 is a view from above in the direction of the arrow a-a in Fig. 4
  • Fig. 8 is a section along the line b-b in Fig. 4
  • Fig. 9 is a longitudinal section through the invention applied as an evaporator.
  • Fig. 1 illustrates a heat exchanger 1, at which both media are liquids.
  • the apparatus is all- welded but can, of course, be provided with suitable flange connections when a simple disassembly of the apparatus for inspection and cleaning is required.
  • the heating surface is annular (see Fig. 2) and consists of a plurality of radially positioned plate elements 2, each of which consists of two embossed metal sheets 3, 4 welded together along their long sides.
  • the heat exchanger is rotary symmetrically formed and consists of an outer shell 5, an inner shell 6 covered by a top end-wall, plate elements 2 placed between the inner shell 6 and outer shell 5, an inlet pipe 7 going to the center of the outer shell 5 at the bottom end, an outlet pipe 8 going from the center of the outer shell 5 at the top end, an inlet piece 9 going to the space between the inner shell 6 and the outer shell 5 at the upper end thereof and an outlet piece 10 going from said space at the lower end thereof.
  • the inlet piece 9 is connected to a distributing box 13, which passes one of the media to the interior of the plate elements 2 and a collecting box 15 which collects the said one medium coming out of the plate elements 2 and passes it to the outlet piece 10.
  • Each one of the plate elements consists of two parallelly corrugated sheets 3 and 4, which are welded together along the sides 11, 12 being parallel with the corrugations. A passage parallel with said sides (channel) is thus formed between the two sheets.
  • the pitch h1, h2, h3 of the corrugations are increasing from the center to the outside of the heat exchanger so that opposite plate elements 2 are abutting each other at the top of the corrugations whereby the plate elements support each other.
  • the plates can be embossed in a press in optional widths and lengths.
  • Figs. 7 and 8 show one type of plate embossing and the forming of the end connecting rings.
  • Fig. 1 shows, that the plates are cut obliquely at the ends at 18 and 19, whereby so-called dead corners are avoided due to an improved flow pattern. Furthermore, the risk of crevice corrosion is reduced, because of the better run-off and exchange of flowing liquid.
  • the design of the heating surface according to Figs. 7 and 8 and the embossing offer the great advantage, that the thickness of the sheet material can be reduced, compared to spot- welded structures, without thereby causing any loss of mechanical strength. This is of special importance when the structure is manufactured of titanium or a corresponding very expensive material.
  • the external collecting box 15 is so connected to the heating surface, that the medium flows internally through the elements 2.
  • the material for the collecting boxes, externally as well as internally, and also for the heating surfaces with inner and outer connecting rings, thus, must be selected considering the corrosion attacks to be expected. As regards the mechanical strength, the normal calculation standards apply.
  • the inner shell 6 shown in Fig. 1 forces the medium flowing in from below in the centre to flow on the heating surface externally of the elements 2, whereafter the medium continues to flow upward countercurrent to the medium flowing downward internally in the elements 2. At the upper end of the heating surface the medium is directed inwards to the centre and then flows out of the apparatus through the upper central outlet channel 8.
  • the length of the internal shell 6 is so adjusted as to provide for the necessary inflow and outflow openings.
  • the inner shell 6 can be manufactured of a very thin material, as the shell is subjected only to internal overpressure corresponding to the maximum pressure drop for the medium flow through the heat exchanger.
  • the outer shell 5 in Fig. 1 is seal-welded to the external connecting ring 20. From a strength aspect, the outer shell shall be dimensioned for an internal overpressure corresponding to the pressure and temperature prevailing in the medium flowing externally of the elements.
  • the outer shell normally also should be dimensioned for full internal vacuum. In such cases the shell mostly is reinforced by so-called vacuum reinforcing rings suitably spaced along the length of the shell.
  • annular, radially positioned plate heating surface serves as a part of said reinforcement due to the vacuum.
  • the extent, to which the plates 2 contribute to the reinforcement depends on the width of the sheets 3, 4 and length of the shell to be vacuum reinforced. Vacuum reinforcing rings can be a relatively expensive part of an apparatus and, therefore, the possibility of, entirely or partially, taking the plates into account can be of a reasonable value.
  • the mechanically weakest point in a plate heat exchanger is the connection to the collecting boxes where the strength of the weld connection between the sheets and the connecting portion is entirely decisive for the pressure and temperature, at which the apparatus can be permitted to operate.
  • the connecting method shown in Figs. 4-6 has proved very efficient and withstands bursting pressures of more than 300 kp/cm 2 . It is also known, that the heat load at welding is of great importance for the service life of the apparatus, due to the stresses induced at welding into the structure.
  • the longitudinal welds of the plate elements as well as the connecting welds to the external and internal connecting rings (20 and 21 in Fig. 1) are caried out by fusion welding without filler metal. This implies welding with moderate heat load and with substantially reduced risk of crack formation adjacent the welds.
  • the softest possible design is chosen, for example by pre-stressing the plate elements, a structure substantially free of stresses can be obtained.
  • annular heating surface with circular cross-section can be produced which is entirely self-bearing or self- supporting, irrespective of the pressure conditions internally and externally of the plate elements.
  • Spot welding or seam welding internally on the sheets for holding together the elements at internal overpressures in the passageways is superfluous. This implies, that the necessary pressing forces for the forming of passageways with transverse grooves and supporting points are substantially (probably 70-90%) lower than those required for the production of perfect contact surfaces for spot or seam welding.
  • the low pressing forces required also imply, that the stresses in the sheets are relatively insignificant, and the risks of crack formation in the depressing points are eliminated.
  • the plate surface according to Figs. 7 and 8 can be manufactured of very thin sheet metal by using a suitable embossing pattern with supporting points. As the supporting points have a small area and are well rounded, the risk of crevice corrosion is eliminated, compared to the spot weld surfaces according to above. The risk that deposits of solid particles may accumulate at the supporting points is also reduced considerably.
  • the pre-stressing of the plates yields a structure substantially free of stresses, which is an essential advantage.
  • Fig. 1 and Fig. 9 the plate elements are cut obliquely both upwardly and downwardly whereby the flow conditions for inflowing and outflowing media externally of the elements are improved.
  • the evaporator according to Fig. 9 operates with the driving steam internally of the elements 2.
  • the steam is received in a distribution chamber at the top of the apparatus, from where it flows into the upper portion of the elements.
  • the distribution chamber is somewhat enlarged so that it can be entered for inspections.
  • the driving steam, together with the formed condensate flows downward through the elements. Due to the heating surface being formed with grooves, ridges and supporting points, the condensate film on the wall is continuously broken and thinned, thereby improving the heat transfer to the wall (5-10%).
  • the condensate flows down into a condensate space 23 beneath the heating surface, from where it is discharged. Non-condensable gases are removed from said space via a separate connecting piece 24, which is provided with a "fender" 25, which also may have annular configuration.
  • the outer and inner shells 5, join substantially sealingly the annular heating surface along sub- stantiallythe entire length.
  • an upwardly located distribution chamber 26 the outer shell 5 has been cut down a distance so as to provide an annular gap 27 around the upper portion of the heating surface for the intake and uniform distribution of solution circulating outside the plate elements.
  • an opening gap 28 is provided for discharge, in that the inner shell has been given a smaller diameter.
  • the inner shell forms by means of its top end wall 29 a large separation chamber 30, which corresponds to the expansion vessel or steam separator, which normally is comprised in conventional evaporators.
  • an inner cylinder 31 is located, which is tight-welded to the lower inner connecting ring 22 and is also tight-welded to the apparatus bottom at 33, which can be a head as shown in the sketch, or a curved end wall.
  • a droplet separator can be built-in in the central separation chamber.
  • the solution to be evaporated is circulated by a pump from the buffer space 34 at the bottom of the apparatus to the distribution chamber 26 about the upper portion of the heating surface.
  • the annular gap 27 for ingoing circulated solution is dimensioned for a certain moderate pressure drop, thereby ensuring uniform distribution.
  • the entire free cross-section outside the plate elements 2 is filled completely with inflowing circulation solution, which thereafter flows downward in the form of a film on the heating surfaces.
  • the temperature of the circulated solution is very close to the boiling point, so that boiling/steam emission starts practically immediately.
  • the free space thus, is filled with heavily oversaturated/soaked steam, which contains water droplets of all sizes from mist and upward.
  • turbulence rapidly is caused in the steam, whereby moist and droplets are thrown outward towards the walls.
  • the turbulence grows in violence as the steam amount increases on the downward flow.
  • the design of the heating surface ensures that all parts of the heating surface are thoroughly wetted, which is a prerequisite for satisfactory operation and one hundred percent utilization of the heating surface installed.
  • the conditions on the falling film side, as described above, also renders it possible to operate the apparatus with a minimum of excess liquid, which implies lower power consumption in the circulation pump.
  • the gap 28 is located between the heating surface and the inner shell, so that steam formed and excess circulation liquid can leave the heating package.
  • the mixture of steam and liquid flows past a series of baffle plates 35 where a first coarse separation takes place.
  • the main part of the liquid is thrown outwards towards the cylinder, which is an extension of the lower inner connecting ring of the heat exchanger, and thereafter flows down into the buffer space 34 for circulating solution.
  • the steam performs a U-turn, whereby liquid droplets additionally are separated, and thereafter flows upward through the main separation chamber 30.

Landscapes

  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Geometry (AREA)
  • Heat-Exchange Devices With Radiators And Conduit Assemblies (AREA)

Claims (3)

1. Von zwei Medien durchströmter Wärmetauscher zum Wärmetausch über Wärmetauschflächen in der Weise, daß die Medien sich nicht direkt kontaktieren bzw. berühren, wobei die Heizflächen rotationssymmetrisch bezüglich zu einer Achse herum angeordnet sind, so daß ein zentraler Hohlraum ohne Wärmetauschflächen um die zentrale Achse herum gebildet ist, und wobei die Hauptströmungsrichtung der Medien zur Achse parallel verläuft, dadurch gekennzeichnet, daß die Wärmetauschflächen aus Metallblechen (3, 4) bestehen, die paarweise zu Plattenelementen (2) zusammengebaut sind und die parallel zu der besagten Achse gewellt bzw. abgekantet sind, und daß die Teilung (h1, h2 ...) der Wellen bzw. Abkantungen mit dem Abstand von der Achse sich nach außen hin vergrößert, so daß die Wellen bzw. Abkantungen von gegenüberliegend angeordneten Elementen (2) aneinanderstößen und stützende Punkte für die Elemente bilden.
2. Wärmetauscher gemäß Anspruch 1, dadurch gekennzeichnet, daß die Metallbleche (3, 4) aus ihrer Fläche um eine zur Achse rechtwinklig verlaufende Linie der Fläche herum gebogen oder leicht gekrümmt sind.
3. Wärmetauscher gemäß Anspruch 1, bei dem die Metallbleche Seite an Seite entlang ihrer zwei Endkanten (18, 19) durch Schweißen miteinander verbunden sind, dadurch gekennzeichnet, daß die verbindende Kante (18, 19) nach unten hin geneigt geformt ist, um das Auslaufen zu erleichtern.
EP84903672A 1983-09-28 1984-09-28 Wärmetauscher Expired EP0157849B1 (de)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
SE8305270 1983-09-28
SE8305270A SE455229B (sv) 1983-09-28 1983-09-28 Vermevexlare med i ring placerade veckade lameller

Publications (2)

Publication Number Publication Date
EP0157849A1 EP0157849A1 (de) 1985-10-16
EP0157849B1 true EP0157849B1 (de) 1988-01-07

Family

ID=20352677

Family Applications (1)

Application Number Title Priority Date Filing Date
EP84903672A Expired EP0157849B1 (de) 1983-09-28 1984-09-28 Wärmetauscher

Country Status (7)

Country Link
EP (1) EP0157849B1 (de)
JP (1) JPS61500178A (de)
BR (1) BR8407092A (de)
DE (1) DE3468520D1 (de)
FI (1) FI78981C (de)
SE (1) SE455229B (de)
WO (1) WO1985001570A1 (de)

Families Citing this family (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DK615289D0 (da) * 1989-12-06 1989-12-06 Turbovent As Varmegenvindende ventilator
WO2010069602A2 (de) * 2008-12-19 2010-06-24 Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V. Apparat zur verteilung von fluiden und deren wärme- und/oder stofftausch
FR3009073A1 (fr) * 2013-07-29 2015-01-30 Didier Costes Reacteur surgenerateur a sodium et azote
IT201600114405A1 (it) * 2016-11-14 2018-05-14 Calini Donatella Una camera di combustione e assorbitore di calore per motori stirling in configurazione alfa

Family Cites Families (8)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
SE183544C1 (de) * 1963-01-01
DE957949C (de) * 1957-01-24 Waagner-Birö Aktiengesellschaft, Wien Wärmetauscheinrichtung in Verbindung mit einer Fliehkrafttrenneinrichtung
SE121818C1 (de) * 1948-01-01
US881523A (en) * 1904-10-31 1908-03-10 Winter Kunststoff Heinr J Apparatus for continuous evaporation.
US2941787A (en) * 1956-04-13 1960-06-21 Pedar Ltd Apparatus for heat exchange
FR1330305A (fr) * 1962-05-11 1963-06-21 échangeur de chaleur
ES349259A1 (es) * 1967-01-04 1969-04-01 Hourwitz Perfeccionamientos en los intercambiadores termicos de gas-liquido.
DE2029783C3 (de) * 1970-06-16 1974-03-07 Linde Ag, 6200 Wiesbaden Wärmetauscher

Also Published As

Publication number Publication date
DE3468520D1 (en) 1988-02-11
BR8407092A (pt) 1985-08-13
WO1985001570A1 (en) 1985-04-11
EP0157849A1 (de) 1985-10-16
SE8305270D0 (sv) 1983-09-28
FI78981B (fi) 1989-06-30
SE455229B (sv) 1988-06-27
FI852047L (fi) 1985-05-22
JPS61500178A (ja) 1986-01-30
SE8305270L (sv) 1985-03-29
FI78981C (fi) 1989-10-10
FI852047A0 (fi) 1985-05-22

Similar Documents

Publication Publication Date Title
US3995689A (en) Air cooled atmospheric heat exchanger
JP4202928B2 (ja) 一体式熱交換器を有する浸水式蒸発器
CN101256043B (zh) 板壳式非饱和蒸发冷凝设备
CN101780341A (zh) 一种管式降膜蒸发器
US6340052B1 (en) Heat exchanger
EP0157849B1 (de) Wärmetauscher
EP1038147B1 (de) Plattenwärmetauscher
EP1058069B1 (de) Absorber
CN113048816A (zh) 一种立式蒸发器
CN201775968U (zh) 一种管式降膜蒸发器
US6296049B1 (en) Condenser
CA1274820A (en) Heat exchanger
JPS6242701A (ja) 自由流型蒸発器及び液体を蒸発させる方法
CN216456937U (zh) 一种立式蒸发器
CN221505736U (zh) 一种立式蒸发器
US20150176908A1 (en) Cooling tower with geodesic shell
CN201643753U (zh) 带回流升膜式蒸发器
CN109386827A (zh) 一种锅炉盘管冷凝式省煤器
GB1559329A (en) Air cooled atmospheric heat exchanger
GB1559330A (en) Water cooling apparatus
US20240053103A1 (en) Evaporative wet surface air cooler
CN212006844U (zh) 一种外导流折流杆水水换热器
US11761707B2 (en) Evaporative wet surface air cooler
CN217424101U (zh) 一种水箱及换热器装置
GB2039022A (en) An assembly of tubular heat- exchanger elements

Legal Events

Date Code Title Description
PUAI Public reference made under article 153(3) epc to a published international application that has entered the european phase

Free format text: ORIGINAL CODE: 0009012

17P Request for examination filed

Effective date: 19850520

AK Designated contracting states

Designated state(s): CH DE FR GB LI

GRAA (expected) grant

Free format text: ORIGINAL CODE: 0009210

AK Designated contracting states

Kind code of ref document: B1

Designated state(s): CH DE FR GB LI

REF Corresponds to:

Ref document number: 3468520

Country of ref document: DE

Date of ref document: 19880211

ET Fr: translation filed
PLBE No opposition filed within time limit

Free format text: ORIGINAL CODE: 0009261

STAA Information on the status of an ep patent application or granted ep patent

Free format text: STATUS: NO OPPOSITION FILED WITHIN TIME LIMIT

26N No opposition filed
PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: CH

Payment date: 19910925

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: GB

Payment date: 19910927

Year of fee payment: 8

Ref country code: FR

Payment date: 19910927

Year of fee payment: 8

PGFP Annual fee paid to national office [announced via postgrant information from national office to epo]

Ref country code: DE

Payment date: 19911029

Year of fee payment: 8

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: GB

Effective date: 19920928

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: LI

Effective date: 19920930

Ref country code: CH

Effective date: 19920930

GBPC Gb: european patent ceased through non-payment of renewal fee

Effective date: 19920928

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: FR

Effective date: 19930528

REG Reference to a national code

Ref country code: CH

Ref legal event code: PL

PG25 Lapsed in a contracting state [announced via postgrant information from national office to epo]

Ref country code: DE

Effective date: 19930602

REG Reference to a national code

Ref country code: FR

Ref legal event code: ST