(19)
(11)EP 3 102 013 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
06.05.2020 Bulletin 2020/19

(21)Application number: 16172689.8

(22)Date of filing:  02.06.2016
(51)Int. Cl.: 
H05K 7/20  (2006.01)

(54)

SYSTEM AND METHOD OF ALTERNATE COOLING OF A LIQUID COOLED MOTOR CONTROLLER

SYSTEM UND VERFAHREN DER ABWECHSELNDEN KÜHLUNG EINER FLÜSSIGKEITSGEKÜHLTEN MOTORSTEUERUNG

SYSTÈME ET PROCÉDÉ DE REFROIDISSEMENT ALTERNÉS D'UN CONTRÔLEUR DE MOTEUR REFROIDI PAR LIQUIDE


(84)Designated Contracting States:
AL AT BE BG CH CY CZ DE DK EE ES FI FR GB GR HR HU IE IS IT LI LT LU LV MC MK MT NL NO PL PT RO RS SE SI SK SM TR

(30)Priority: 02.06.2015 US 201514728037

(43)Date of publication of application:
07.12.2016 Bulletin 2016/49

(73)Proprietor: Hamilton Sundstrand Corporation
Charlotte, NC 28217-4578 (US)

(72)Inventor:
  • PAL, Debabrata
    Hoffman Estates, Illinois 60195 (US)

(74)Representative: Dehns 
St. Bride's House 10 Salisbury Square
London EC4Y 8JD
London EC4Y 8JD (GB)


(56)References cited: : 
EP-A1- 2 819 279
US-A1- 2014 321 051
US-A- 5 283 715
  
      
    Note: Within nine months from the publication of the mention of the grant of the European patent, any person may give notice to the European Patent Office of opposition to the European patent granted. Notice of opposition shall be filed in a written reasoned statement. It shall not be deemed to have been filed until the opposition fee has been paid. (Art. 99(1) European Patent Convention).


    Description

    BACKGROUND



    [0001] The subject matter disclosed herein relates to a motor controller and, more particularly, to a system for cooling a motor controller of an aircraft engine.

    [0002] In modern aircraft engines, electrical power is generated by generators, which are driven by aircraft engines. Often, these generators are also used as electric starters to start engines. Motor controllers are used to control the starters and generator functions of these generators. Such motor controllers are often supportively disposed within the aircraft engine nacelle or other suitable locations such as electrical equipment bay (EE bay).

    [0003] Generally, the motor controller includes various electrical components and sub-assemblies used for controlling generators, which generate electrical energy from the mechanical energy of the aircraft engine. The components and sub-assemblies include, for example, printed wiring boards, inductors and inverter modules, each of which generates varying amounts of heat that needs to be dissipated in order for the motor controller to operate properly. This is normally accomplished by flowing fuel or another suitable coolant, such as a Propylene Glycol water mixture, through a heat exchanger associated with the motor controller during ground operations. However, for some applications where a liquid cooled motor controller is used, only air and not liquid is available for cooling. The present disclosure provides a method where the existing liquid cooled motor controller can also be efficiently cooled by combination of two-phase cooling provided by the liquid cooled cold plate and air cooling. US 5283715 A describes an integrated heat pipe and circuit board structure. EP 2 819 279 A1 discloses an electric cooling apparatus.

    BRIEF DESCRIPTION



    [0004] According to one embodiment of the present disclosure, a motor controller is provided according to claim 1.

    [0005] According to another embodiment of the present disclosure, a method of cooling a motor controller is provided according to claim 7.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0006] The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which:

    FIG. 1 is a cross-sectional view of a motor controller including a cooling system according to an embodiment of the present disclosure;

    FIG. 2 is a cross-sectional view of a portion of the motor controller taken along X-X of FIG. 1, according to an embodiment of the present disclosure;

    FIG. 3 is a perspective view of a fin core of a cold plate according to an embodiment of the present disclosure; and

    FIGS. 4a and 4b are front and back views of the motor controller absent the motor control housing according to an embodiment of the present disclosure.



    [0007] The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings.

    DETAILED DESCRIPTION OF THE INVENTION



    [0008] Referring now to FIG. 1-4, an example of a motor controller 20 including an air cooling system 30 is illustrated. In one embodiment, the motor controller 20 is located adjacent a turbofan within the nacelle of an aircraft engine (not shown). The motor controller 20 includes a generally hollow motor control housing 22 within which one or more heat generating components 24 are mounted. Examples of the heat generating components 24 include, but are not limited to, a printed wire board (PWB), capacitor, inverter module, an insulated gate bipolar transistor (IGBT), bus bar, and inductor for example.

    [0009] The air cooling system 30 of the motor controller 20 includes a cooling device 32 extending between a first end 26 and a second, opposite end 28 of the motor control housing 22. In one embodiment, the cooling device 32 is a cold plate. The cold plate 32 comprises a first and second substantially planar plate 34, 36 arranged generally parallel to one another and separated from each other by a distance. At least one fluid passage 38 (see FIG. 2) is defined within the gap formed between the first and second plates 34, 36 such that a fluid F may flow between the first and second ends 40, 42 of the cold plate 32. As shown in the FIGS. 1 and 2, a fluid inlet 44 is arranged in communication with the at least one fluid passage 38 for supplying a desired amount of fluid F to the interior of the cold plate 32. Once the desired amount of fluid is disposed therein, the fluid inlet 44 is sealed such that the total amount of fluid F within the cold plate 32 remains constant during operation of the motor controller 20. The fluid F sealed within the cold plate 32 may have a lowered boiling temperature compared to the fluid used in a conventional cold plate, such as 72°C for example. However, other fluids commonly used in sealed systems are within the scope of the disclosure.

    [0010] Due to the heat transfer that occurs within the motor controller housing 22, the fluid sealed within the cold plate 32 is configured to cycle between a liquid and a vapor to remove heat from the motor controller 20.

    [0011] With reference now to FIG. 2, a portion of the cold plate 32, such as adjacent the second end 42 of the cold plate 32 for example, is defined as an evaporator region. In the evaporator section, heat is transferred to a liquid portion of the fluid disposed therein, causing the liquid to vaporize. Similarly, another portion of the cold plate 32, for example adjacent the first end 40 of the cold plate 32, may be defined as a condenser region. In the condenser region, heat is released from the vaporized portion of the fluid, causing the vapor to condense to a liquid. In the condenser area, fins may be attached to the cold plate surfaces 34 and 36, disposed between the cold plate surfaces and the housing, to enhance heat transfer for a condenser (see FIG. 1).

    [0012] Referring now to FIG. 3, a plurality of fins may form a fin core 50 configured to enhance the heat transferability of the cold plate 32. More specifically, the fin core 50 may be interposed between at least a portion of the first and second plate 34, 36. In one embodiment, the portion of the fin core 50 arranged within the evaporator region of the cold plate 32 has a high fin density. A high fin density may be defined as a fin/distance ratio between about 7.1-9.8fins/cm (18-25 fins/inch) or greater.

    [0013] As shown in FIGS. 4a and 4b, the heat generating components 24 of the motor controller 20 are mounted at various positions to one or both of the first plate 34 and the second plate 36 of the cold plate 32. To optimize the efficiency of the cooling system 30, the components 24 configured to produce the greatest amount of heat are arranged within the evaporator region of the cold plate 32, near the second end 42 thereof, to maximize the amount of heat transferred to the liquid portion of the fluid F within the cold plate 32. As should be understood by a person having ordinary skill in the art, the positioning of the components 24 and the configuration of the cold plate 32 will vary based on a given application and the amount of heat to be dissipated.

    [0014] Referring again to FIG. 1, one or more openings (not shown) are formed in both the first end 26 and the second end 28 of the motor control housing 22 to define an air flow channel 60 between each of the first and second plates 34, 36 and an adjacent sidewall 52, 54 of the housing 22, respectively. During operation of the motor controller 20, cool inlet air A such as provided by a fan for example, is fed via an inlet duct or plenum 62 through the one or more openings (not shown) formed in the first end 26 of the housing 22. This air flow convectively cools the plurality of heat generating components 24 within the motor housing 22. Warmer air, as indicated by arrow B in FIG. 1, is similarly output from the motor control housing 22, such as to an outlet plenum or duct 64 coupled thereto, via the plurality of openings (not shown) formed in the second end 28 of the housing 22.

    [0015] The heat generated by the plurality of components 24 mounted to the cold plate 32 also conducts through the first and second plates 34, 36, respectively, to the fluid F trapped within the interior of the cold plate 32. In the configuration of the illustrated, nonlimiting embodiment, a portion of the fluid F in a liquid phase is arranged near the second end 42 of the cold plate 32. As heat from the plates 34, 36 conducts to the fluid, the liquid within the evaporator region vaporizes and travels through the one or more fluid passages 38 to the condensing region, near the first end 52 of the cold plate 32. In addition to convectively cooling the heat generating components 24, a portion of the cool air A provided at the first end 26 of the motor housing 22 is configured to conductively cool the vaporized fluid within the condenser region via the first and second plates 34, 36. The heat transfer that occurs between the vaporized fluid and the cool air A causes the vaporized fluid to cool and condense into a liquid which then moves through the fluid passage 38, such as due to gravity for example, back to the second end 42 of the cold plate 32.

    [0016] An air cooled motor controller 20 as described herein enables the use of a liquid-cooled motor controller in additional applications where a power electronics cooling system is not available on an aircraft. Only thermal modifications need be completed to adapt the motor controller from a liquid cooled application to an air cooled application. In addition, the air cooled motor controller 20 disclosed herein results in an improved heat transfer such that other components previously configured to enhance the heat transfer of the system, for example an inductor housing, may be eliminated resulting in both a weight and cost reduction.

    [0017] While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified within the scope of the invention defined by the appended claims.


    Claims

    1. A motor controller (20), comprising

    a motor control housing (22) having an air inlet at a first end (26) and an air outlet at a second end (28);

    a plurality of heat generating elements (24) disposed within the motor control housing; and

    a cooling system including a cooling device (32) arranged within the motor control housing, wherein the cooling device is a cold plate comprising a first planar plate (34) and a second planar plate (36) separated by a gap (38) having a fluid (F) sealed therein and including:

    an evaporator region wherein the fluid absorbs heat via vaporization; and

    a condenser region wherein the vaporized fluid releases heat via condensation;

    wherein the plurality of heat generating elements (24) is cooled by conduction to the cooling device (32) and by convection from an airflow between the air inlet and the air outlet; and

    wherein the airflow cools the vaporized fluid at the condenser region; and characterized by the cooling device extending from the first housing end (26) of the motor control housing to the second housing end (28) of the motor control housing opposite the first housing end (26), the cooling device and the motor control housing thus defining two airflow channels (60) therebetween; and wherein

    at least one heat generating element of the plurality of heat generating elements (24) is mounted at each of the first planar plate (34) and the second planar plate (36); and

    at least one heat generating element of the plurality of heat generating elements (24) is disposed in each of the evaporator region and the condenser region, wherein the heat generating elements that produce that produce the greatest amounts of heat are arranged in the evaporator region of the cold plate (32).


     
    2. The motor controller according to claim 1, wherein a first portion of the cooling device (32) includes a high density fin core (50).
     
    3. The motor controller according to claim 2, wherein the high density fin core comprises at least 7.1 fins per cm (18 fins per inch).
     
    4. The motor controller according to claim 1, wherein a second portion of the cooling device (32) is configured as the condenser region such that the fluid disposed therein is configured to release heat.
     
    5. The motor controller according to claim 4, wherein the condenser region of the cooling device (32) is disposed vertically above the evaporator region of the cooling device (32).
     
    6. The motor controller according to any preceding claim, wherein the fluid (F) sealed within the cooling device (32) is configured to cycle between a liquid and a vapor.
     
    7. A method of cooling a motor controller (20), comprising:

    providing a cooling device (32) disposed within a motor control housing (22), wherein the cooling device is a cold plate comprising a first planar plate (34) and a second planar plate (36) separated by a gap (38) having a fluid (F) sealed therein and including:

    an evaporator region wherein the fluid absorbs heat via vaporization; and

    a condenser region wherein the vaporized fluid releases heat via condensation;

    the cooling device (32) and the motor control housing (22) defining two airflow channels (60) therebetween;

    introducing an air flow into a first end (26) of the motor control housing (22), the air flow travelling along the two airflow channels (60); cooling a vaporized portion of the fluid at the condenser region such that the fluid condenses; and

    extracting the air flow from a second end (28) of the motor control housing, and characterized by the cooling device (32) extending from the first housing end of the motor control housing to the second housing end of the motor control housing opposite the first housing end, the method characterized by

    mounting at least one heat generating element (24) at each of the first planar plate (34) and the second planar plate; plate (36); and

    disposing at least one heat generating element (24) in each of the evaporator region and the condenser region, wherein the heat generating elements that produce that produce the greatest amounts of heat are arranged in the evaporator region of the cold plate.


     
    8. The method according to claim 7, wherein upon cooling of the vaporized portion of the fluid, the fluid is configured to travel to an opposite end of the cooling device (32).
     
    9. The method according to claim 8, wherein a fan is configured to move the air flow through the motor control housing (22).
     


    Ansprüche

    1. Motorsteuerung (20), umfassend
    ein Motorsteuergehäuse (22), das einen Lufteinlass an einem ersten Ende (26) und einen Luftauslass an einem zweiten Ende (28) aufweist;
    eine Vielzahl von wärmeerzeugenden Elementen (24), die innerhalb des Motorsteuergehäuses angeordnet sind; und
    ein Kühlsystem, das eine Kühlvorrichtung (32) beinhaltet, die innerhalb des Motorsteuergehäuses angeordnet ist, wobei die Kühlvorrichtung eine Kälteplatte ist, die eine erste flache Platte (34) und eine zweite flache Platte (36) umfasst, die durch eine Lücke (38) getrennt sind, in der ein Fluid (F) eingeschlossen ist, und Folgendes beinhaltet:

    einen Verdampferbereich, in dem das Fluid Wärme über Verdampfung aufnimmt; und

    einen Kondensatorbereich, in dem das verdampfte Fluid Wärme über Kondensation freisetzt;

    wobei die Vielzahl von wärmeerzeugenden Elementen (24) durch Leitung zur Kühlvorrichtung (32) und durch Konvektion von einem Luftstrom zwischen dem Lufteinlass und dem Luftauslass gekühlt wird;
    und

    wobei der Luftstrom das verdampfte Fluid im Kondensatorbereich kühlt; und

    dadurch gekennzeichnet, dass sich die Kühlvorrichtung vom ersten Gehäuseende (26) des Motorsteuergehäuses zum zweiten Gehäuseende (28) des Motorsteuergehäuses gegenüber dem ersten Gehäuseende (26) erstreckt,

    wobei die Kühlvorrichtung und das Motorsteuergehäuse dadurch zwei Luftstromkanäle (60) dazwischen definieren; und wobei mindestens ein wärmeerzeugendes Element aus der Vielzahl von wärmeerzeugenden Elementen (24) an jeder aus der ersten flachen Platte (34) und der zweiten flachen Platte (36) montiert ist; und

    wobei mindestens ein wärmeerzeugendes Element aus der Vielzahl von wärmeerzeugenden Elementen (24) in jedem aus dem Verdampferbreich und dem Kondensatorbereich angeordnet ist, wobei die wärmeerzeugenden Elemente, die die größten Wärmemengen erzeugen, in dem Verdampferbereich der Kälteplatte (32) angeordnet sind.


     
    2. Motorsteuerung nach Anspruch 1, wobei ein erster Abschnitt der Kühlvorrichtung (32) einen hochdichten Rippenkern (50) beinhaltet.
     
    3. Motorsteuerung nach Anspruch 2, wobei der hochdichte Rippenkern mindestens 7,1 Rippen pro cm (18 Rippen pro Zoll) umfasst.
     
    4. Motorsteuerung nach Anspruch 1, wobei ein zweiter Abschnitt der Kühlvorrichtung (32) als der Kondensatorbereich so konfiguriert ist, dass das Fluid, das darin angeordnet ist, dazu konfiguriert ist, Wärme freizusetzen.
     
    5. Motorsteuerung nach Anspruch 4, wobei der Kondensatorbereich der Kühlvorrichtung (32) vertikal über dem Verdampferbereich der Kühlvorrichtung (32) angeordnet ist.
     
    6. Motorsteuerung nach einem der vorstehenden Ansprüche, wobei das Fluid (F), das innerhalb der Kühlvorrichtung (32) eingeschlossen ist, dazu konfiguriert ist, periodisch zwischen einer Flüssigkeit und einem Dampf zu wechseln.
     
    7. Verfahren zum Kühlen einer Motorsteuerung (20), umfassend:

    Bereitstellen einer Kühlvorrichtung (32), die innerhalb eines Motorsteuergehäuses (22) angeordnet ist, wobei die Kühlvorrichtung eine Kälteplatte ist, die eine erste flache Platte (34) und eine zweite flache Platte (36) umfasst, die durch eine Lücke (38) getrennt sind, wobei ein Fluid (F) darin eingeschlossen ist, und Folgendes beinhaltet:

    einen Verdampferbereich, in dem das Fluid Wärme über Verdampfung aufnimmt; und

    einen Kondensatorbereich, in dem das verdampfte Fluid Wärme über Kondensation freisetzt;

    wobei die Kühlvorrichtung (32) und das Motorsteuergehäuse (22) zwei Luftstromkanäle (60) dazwischen definieren;

    Einleiten eines Luftstroms in ein erstes Ende (26) des Motorsteuergehäuses (22), wobei sich der Luftstrom entlang der zwei Luftstromkanäle (60) bewegt;

    Kühlen eines verdampften Teils des Fluids in dem Kondensatorbereich, so dass das Fluid kondensiert; und Abziehen des Luftstroms aus einem zweiten Ende (28) des Motorsteuergehäuses, und

    dadurch gekennzeichnet, dass sich die Kühlvorrichtung (32) von dem ersten Gehäuseende des Motorsteuergehäuses zum zweiten Gehäuseende gegenüber dem ersten Gehäuseende erstreckt, wobei das Verfahren gekennzeichnet ist durch

    Montieren mindestens eines wärmeerzeugenden Elements (24) an jeder aus der ersten flachen Platte (34) und der zweiten flachen Platte (36); und

    Anordnen mindestens eines wärmeerzeugenden Elements (24) in jedem aus dem Verdampferbereich und dem Kondensatorbereich, wobei die wärmeerzeugenden Elemente, die die größten Wärmemengen erzeugen, in dem Verdampferbereich der Kälteplatte angeordnet sind.


     
    8. Verfahren nach Anspruch 7, wobei nach dem Kühlen des verdampften Teils des Fluids, das Fluid dazu konfiguriert ist, sich zu einem entgegengesetzten Ende der Kühlvorrichtung (32) zu bewegen.
     
    9. Verfahren nach Anspruch 8, wobei ein Gebläse dazu konfiguriert ist, den Luftstrom durch das Motorsteuergehäuse (22) zu bewegen.
     


    Revendications

    1. Contrôleur de moteur (20), comprenant

    un boîtier de contrôle de moteur (22) ayant une entrée d'air à une première extrémité (26) et une sortie d'air à une deuxième extrémité (28) ;

    une pluralité d'éléments de génération de chaleur (24) disposés à l'intérieur du boîtier de contrôle de moteur ; et
    un système de refroidissement incluant un dispositif de refroidissement (32) agencé à l'intérieur du boîtier de contrôle de moteur, dans lequel le dispositif de refroidissement est une plaque froide comprenant une première plaque plane (34) et une deuxième plaque plane (36) séparées par un espace (38) ayant un fluide (F) scellé à l'intérieur et incluant :

    une région d'évaporateur dans lequel le fluide absorbe la chaleur via vaporisation ; et

    une région de condenseur dans lequel le fluide vaporisé libère la chaleur via condensation ;

    dans lequel la pluralité d'éléments de génération de chaleur (24) est refroidie par conduction au dispositif de refroidissement (32) et par convection d'un flux d'air entre l'entrée d'air et la sortie d'air ; et

    dans lequel le flux d'air refroidit le fluide vaporisé au niveau de la région de condenseur ; et

    caractérisé par le dispositif de refroidissement s'étendant de la première extrémité de boîtier (26) du boîtier de contrôle de moteur à la deuxième extrémité de boîtier (28) du boîtier de contrôle de moteur opposée à la première extrémité de boîtier (26),

    le dispositif de refroidissement et le boîtier de contrôle de moteur définissant donc deux canaux de flux d'air (60) entre eux ; et dans lequel

    au moins un élément de génération de chaleur de la pluralité d'éléments de génération de chaleur (24) est monté au niveau de chacune de la première plaque plane (34) et de la deuxième plaque plane (36) ; et

    au moins un élément de génération de chaleur de la pluralité d'éléments de génération de chaleur (24) est disposé dans chacune de la région d'évaporateur et de la région de condenseur, dans lequel les éléments de génération de chaleur qui produisent les plus grandes quantités de chaleur sont agencés dans la région d'évaporateur de la plaque froide (32).


     
    2. Contrôleur de moteur selon la revendication 1, dans lequel une première portion du dispositif de refroidissement (32) inclut un noyau d'ailette haute densité (50).
     
    3. Contrôleur de moteur selon la revendication 2, dans lequel le noyau d'ailette haute densité comprend au moins 7,1 ailettes par cm (18 ailettes par pouce).
     
    4. Contrôleur de moteur selon la revendication 1, dans lequel une deuxième portion du dispositif de refroidissement (32) est configurée en tant que région de
    condenseur de sorte que le fluide disposé à l'intérieur est configuré pour libérer la chaleur.
     
    5. Contrôleur de moteur selon la revendication 4, dans lequel la région de condenseur du dispositif de refroidissement (32) est disposée verticalement au-dessus de la région d'évaporateur du dispositif de refroidissement (32).
     
    6. Contrôleur de moteur selon une quelconque revendication précédente, dans lequel le fluide (F) scellé
    à l'intérieur du dispositif de refroidissement (32) est configuré pour effectuer un cycle entre un liquide et une vapeur.
     
    7. Procédé de refroidissement d'un contrôleur de moteur (20), comprenant :

    la fourniture d'un dispositif de refroidissement (32) disposé à l'intérieur d'un boîtier de contrôle de moteur (22), dans lequel le dispositif de refroidissement est une plaque froide comprenant une première plaque plane (34) et une deuxième plaque plane (36) séparées par un espace (38) ayant un fluide (F) scellé à l'intérieur et incluant :

    une région d'évaporateur dans lequel le fluide absorbe la chaleur via vaporisation ; et

    une région de condenseur dans lequel le fluide vaporisé libère la chaleur via condensation ;

    le dispositif de refroidissement (32) et le boîtier de contrôle de moteur(22) définissant deux canaux de flux d'air (60) entre eux ;

    l'introduction d'un flux d'air dans une première extrémité (26) du boîtier de contrôle de moteur (22), le flux d'air circulant le long des deux canaux de flux d'air (60) ;
    le refroidissement d'une portion vaporisée du fluide au niveau de la région de condenseur de sorte que le fluide se condense ; et

    l'extraction du flux d'air d'une deuxième extrémité (28) du boîtier de contrôle de moteur, et

    caractérisé par le dispositif de refroidissement (32) s'étendant de la première extrémité de boîtier du boîtier de contrôle de moteur à la deuxième extrémité de boîtier du boîtier de contrôle de moteur opposée à la première extrémité de boîtier,

    le procédé étant caractérisé par

    le montage d'au moins un élément de génération de chaleur (24) au niveau de chacune de la première plaque plane (34) et de la deuxième plaque plane (36) ; et

    la disposition d'au moins un élément de génération de chaleur (24) dans chacune de la région d'évaporateur et de la région de condenseur, dans lequel les éléments de génération de chaleur qui produisent les plus grandes quantités de chaleur sont agencés dans la région d'évaporateur de la plaque froide.


     
    8. Procédé selon la revendication 7, dans lequel lors du refroidissement de la portion vaporisée du fluide, le fluide est configuré pour circuler vers une extrémité opposée du dispositif de refroidissement (32).
     
    9. Procédé selon la revendication 8, dans lequel un ventilateur est configuré pour déplacer le flux d'air à travers le boîtier de contrôle de moteur (22).
     




    Drawing















    REFERENCES CITED IN THE DESCRIPTION



    This list of references cited by the applicant is for the reader's convenience only. It does not form part of the European patent document. Even though great care has been taken in compiling the references, errors or omissions cannot be excluded and the EPO disclaims all liability in this regard.

    Patent documents cited in the description