(19)
(11)EP 2 195 491 B1

(12)EUROPEAN PATENT SPECIFICATION

(45)Mention of the grant of the patent:
17.06.2020 Bulletin 2020/25

(21)Application number: 08795393.1

(22)Date of filing:  15.08.2008
(51)International Patent Classification (IPC): 
E02F 9/26(2006.01)
G05B 19/042(2006.01)
E02F 9/20(2006.01)
(86)International application number:
PCT/US2008/009812
(87)International publication number:
WO 2009/025772 (26.02.2009 Gazette  2009/09)

(54)

AN AUTOMATED CONTROL MODULE FOR A POWER MACHINE

AUTOMATISCHES STEUERMODUL FÜR EINE KRAFTMASCHINE

MODULE DE CONTRÔLE AUTOMATISÉ POUR UNE MACHINE MOTRICE


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

(30)Priority: 21.08.2007 US 842421

(43)Date of publication of application:
16.06.2010 Bulletin 2010/24

(73)Proprietor: Clark Equipment Company
West Fargo, ND 58078-6000 (US)

(72)Inventor:
  • OSBORN, Jason, A.
    Oakes, ND 58474 (US)

(74)Representative: Vossius & Partner Patentanwälte Rechtsanwälte mbB 
Siebertstrasse 3
81675 München
81675 München (DE)


(56)References cited: : 
EP-A- 0 824 860
US-A- 4 263 979
US-A- 6 112 839
US-A1- 2004 133 327
WO-A-00/20989
US-A- 6 067 782
US-A1- 2003 147 727
  
      
    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] Power machines, such as skid steer loaders or diggers include one or more lift arms or other devices that support or actuate an implement or tool. The lift arms or other devices are typically operated or actuated hydraulically via input from operator controls. The operator input is used to generate a control signal to energize hydraulic circuitry to actuate the lift arms or other devices. Different models or manufacturers utilize different circuit configurations for hydraulically operating the lift arms or other devices of the power machine. The different circuit configurations make it difficult to adapt the power machine for automated control. The present invention addresses these and other issues and provides advantages over prior control systems.

    [0002] WO 00/20989 A1 discloses a reconfigurable control unit that stores a plurality of application programs in a memory and selects only the application program as needed depending on the work vehicle type that the reconfigurable control unit is coupled to. The type of work vehicle to which the reconfigurable control unit is coupled to is determined based upon a unique configuration message received from a controller on the work vehicle. The work vehicle type may also be determined by scanning a data bus connector that couples the reconfigurable control unit to the work vehicle, or by soliciting operator input to determine which type of work vehicle the reconfigurable unit is coupled to.

    [0003] US 2003/0147727 A1 discloses an hydraulic excavator having an area limiting excavation control function for controlling operation of a front working device so as to form a target work plane. A remote control terminal for wirelessly maneuvering the hydraulic excavator is provided in a management office so that entry of setting information of a target excavation plane and remote maneuvering can be performed from the side of the remote control terminal.

    [0004] EP 0 824 860 A1 discloses a universal modular control system for controlling a mobile material distribution apparatus. The universal modular control system is adaptable for use with any of a plurality of distribution apparatus. It includes a control module for controlling the distribution apparatus and a user console for communicating with a user. The control module and user console are coupled via a data link.

    [0005] US 6 112 839 A discloses an auxiliary hydraulic system for a work vehicle which can be coupled to an auxiliary implement. The implement includes a hydraulic actuator and a sensor for generating a feedback signal to an implement controller, which in turn generates an automatic command signal. The system includes a fluid source, a coupler for fluidly coupling to the actuator, a control valve fluidly coupled to the source and the coupler to regulate the fluid flow between the source and the actuator in response to a valve command signal, an input device for generating a manual command signal, and a mode device for generating a mode signal. The system also includes an auxiliary control unit operable in first and second modes in response to the mode signal, which generates the valve command signal based on the manual command signal and the automatic control signal when operating in the first and second modes, respectively.

    [0006] US 6 067 782 A discloses an electrohydraulic steering system for machines including manual and automatic steering modes which can be activated by a switch. The system has a hydraulic steering cylinder for displacement of the steerable wheels.

    SUMMARY



    [0007] An assembly for a power machine as recited in the independent claim is provided. The dependent claims define embodiments.

    [0008] In illustrated embodiments, the automated control module is configured to receive a signal from a sensor and generate a universal control signal that can be processed by different machine controllers having different control configurations to generate a device-specific control signal for one or more components of the power machine. In one embodiment, the universal control signal is transmitted to a machine controller on the power machine through a connector assembly including a connector plug and socket. In another embodiment, the universal control signal is transmitted through a wireless interface. The machine controller processes the universal control signal and outputs a device-specific control signal to operate different devices on board the power machine.

    BRIEF DESCRIPTION OF THE DRAWINGS



    [0009] 

    FIG. 1 is an illustration of a power machine including operator controls that interface with a machine controller.

    FIG. 2 is a schematic illustration of a control assembly for a power machine including automated machine control.

    FIG. 3 is a schematic illustration of a lift arm of a power machine including an automated control module and sensors coupled to the lift arm.

    FIG. 4 is a schematic illustration of a wireless interface for an automated control module for automated machine control.

    FIG. 5 is a flow chart illustrating an embodiment for implementing automated machine control.

    FIG. 6 is a schematic illustration of an automated machine control module or assembly connected to a machine controller or component through a controller area network (CAN).


    DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS



    [0010] The application discloses embodiments of a control application or assembly implementable on a power machine 100 of the type illustrated in FIG. 1. The power machine 100 illustrated in FIG. 1 is a skid steer loader including a bucket attachment, however, application of the control system described herein is not limited to a skid steer loader or the particular skid steer loader illustrated in FIG. 1. For example, other implements or tools can be coupled to different power machines or vehicles and controlled via embodiments of the control system described herein.

    [0011] As shown in FIG. 1, the illustrated power machine 100 includes a lift arm assembly 102, which in the illustrated embodiment supports a bucket 104. The lift arm assembly 102 includes a plurality of lift arms 105 (only one lift arm visible in FIG 1) to raise and lower the bucket 104 or other attachment. Lift arms 105 of the lift arm assembly 102 are raised and lowered hydraulically via a lift cylinder 106 or other actuator device. The bucket 104 or other attachment is pivotally coupled to the lift arms 105 to adjust an orientation or tilt of the bucket or attachment relative to the lift arms 105. The orientation or tilt is adjusted via operation of one or more tilt cylinders 108 or other actuator device. Operation of the lift and tilt cylinders 106, 108 is controlled via lift arm control circuitry 110 as schematically illustrated in FIG. 1. The lift arm circuitry 110 controls hydraulic flow to the hydraulic cylinders 106, 108 through various valves or other hydraulic circuitry as will be appreciated by those skilled in the art.

    [0012] As shown in FIG. 1, the illustrated power machine or vehicle 100 includes an operator cab 112 supported relative to a body or frame 114 of the vehicle. The cab 112 includes via various operating controls 116 (illustrated schematically) to drive or operate the vehicle. The operating controls 116 include lift/tilt operating controls 120 to raise, lower and/or orient the bucket or other attachment as well as drive controls 122 to impart forward, reverse or steer motion to the power machine or vehicle through wheels 124. Illustratively the operator controls 116 include various levers, buttons or joystick devices to input commands to control lift, drive or other functions of the power machine or vehicle.

    [0013] As shown in FIG. 1, input from the operator controls 116 is provided to a machine controller 126. The machine controller 126 processes the input from the operator controls 116 to operate the lift arm assembly and drive functions of the power machine. In particular, the machine controller 126 provides input to drive control circuitry 130 to impart forward, reverse and steer motion to the power machine or vehicle and input to the lift arm control circuitry 110 to raise/ lower or orient the bucket 104 or other attachment.

    [0014] FIG. 2 illustrates an embodiment of a control assembly for the vehicle of the type illustrated in FIG. 1. Although the power machine illustrated in FIG. 1 is a wheeled vehicle, application is not limited to wheeled vehicles and embodiments disclosed herein can be adapted for a track vehicle or other vehicles as will be appreciated by those skilled in the art.

    [0015] As shown in FIG. 2, the control assembly 140 includes operator and automated control components to provide automated and user operator control of the power machine or vehicle. In the illustrated embodiment, control assembly 140 includes a drive control component 142 and a lift arm control component 144. The drive control component 142 operates left drive motor 145 and right drive motor 146 through the drive control circuitry 130. In the illustrated embodiment, the left and right drive motors 145, 146 are hydrostatic motors and the drive control circuitry 130 includes various valves and components that provide hydraulic fluid flow to the left and right drive motors 145, 146 to drive and steer the power machine in response to drive signals 148 generated by the drive control component 142.

    [0016] The lift arm control component 144 operates the lift and tilt cylinders 106, 108 through the lift arm control circuitry 110. Illustratively, the control circuitry 110 includes various valves and components that provide hydraulic fluid flow to lift and tilt cylinders 106, 108 to raise, lower or tilt an implement or tool coupled to the lift arm assembly 102. The hydraulic fluid flow is controlled in response to the arm control signal 150 generated by the lift arm control component 144.

    [0017] As previously described, the machine controller 126 receives input from operator controls 116. In the illustrated embodiment, drive control input 122 is processed by the drive control component 142 to generate the drive signals 148 to energize the left and right drive motors 145, 146 to impart forward, reverse or steer motion. Lift/tilt control input 120 is processed by the lift arm control component 144 to generate the arm control signal 150 to operate the lift and tilt functions. The lift arm control component 144 is programmed to include device specific control parameters, such as how much current is needed to move the hydraulic cylinder 106, 108 a specified distance. The lift arm control component 144 utilizes these device specific parameters to generate the arm control signal 150.

    [0018] As shown, in the illustrated embodiment, machine controller 126 also utilizes input from an automated control assembly 160 to operate the power machine. In the illustrated embodiment, the automated control assembly 160 includes an automated control module 162, which as shown is configured to receive input from one or more sensors 164 as shown. In the illustrated embodiment, the automated control module 162 generates a universal signal 166 based upon the input from the one or more sensors 164. The universal control signal 166 is transmitted to the machine controller 126 to generate a device-specific control signal.

    [0019] Illustratively, sensors 164 include laser receivers or other sensor devices, which provide an electrical signal to locate a position of the power machine or components on the power machine relative to a reference position. To provide automated control of the lift arm assembly 102, the universal signal 166 is transmitted to the lift arm control component 144. The lift arm control component 144 uses the programmed device parameters to generate the device specific control signal.

    [0020] Thus as described, the universal signal 166 is adapted for use for different control components and circuitry and thus can be adapted for use on machines having different control configurations. In the illustrated embodiment, the universal signal 166 generated by the automated control module 162 includes a position signal, which is utilized to generate the device specific control signal to actuate or energize on-board devices (e.g. hydraulic cylinders 106, 108) in response to location input from the sensors 164.

    [0021] As shown, in FIG. 2, the machine can be operated based upon user input through the operator controls 116 and/or based upon sensor input through the automated control module 162. In the illustrated embodiment, the operator controls 116 include a control selector 168 to allow the operator to choose user based control or automated control. Illustratively, the control selector 168 can be a toggle switch or other device that allows the user to switch between user control and automated control.

    [0022] FIG. 3 illustrates an embodiment of an automated control assembly. In the illustrated embodiment, the automated control module 162 is attached to the lift arm 105 of the power machine and receives input from one or more sensors 164 coupled to the lift arm 105 or attachment (e.g. bucket 104).

    [0023] The one or more sensors 164 are coupled to the lift arm 105 or attachment to provide position information for the lift arm 105 or attachment.

    [0024] As previously described, input from the one or more sensors 164 is processed by the automated control module 162 to generate the universal control signal 166. The universal control signal 166 is transmitted to the machine controller 126 to control functions of the power machine, for example lift and tilt functions, as previously described. In the embodiment shown, the automated control module 162 is removably attached to the lift arm. Sensors are mounted remote from the automated control module 162 and are electrically connected to the automated control module 162 via wires.

    [0025] In the embodiment shown in FIG. 3, the automated control module 162 is electrically coupled to one or more machine controllers 126 through a connector assembly 170. The connector assembly 170 includes an electrical cable 172 and connector plug 174 that is insertable into an electrical socket or port 176 to removably connect the automated control module 162 to the machine controller 126. In the illustrated embodiment, the cable 172 and connector plug 174 are connected to the automated control module 162 and the connector plug 174 is inserted into socket 176 connected to the power machine via a bracket or support 178. The socket 176 is electrically coupled to the machine controller 126 to provide the electrical interface between the automated control module 162 and the machine controller 126 when the connector plug 174 is inserted into the socket 176.

    [0026] Alternatively, the automated control module 162 includes socket 176 and the automated control module 162 is electrically connected to the machine controller 126 via a cable (not shown) "on-board" the power machine to provide the electrical interface to the machine controller 126 as previously described.

    [0027] In another embodiment illustrated in FIG. 4, the automated control module 162 is electrically coupled to the machine controller 126 via a wireless interface. In the embodiment shown, the automated control module 162 includes a wireless communication device 180 that is configured to interface or talk to a wireless communication device 182 "on-board" the power machine.

    [0028] The wireless communication devices 180, 182 wirelessly transmit and receive data or information through known communication protocols. In the embodiment shown, the wireless communication device 180 coupled to the automated control module 162 transmits the universal control signal 166 to the wireless communication device 182 coupled to the machine controller 126. The machine controller 126 receives the universal control signal 166 and generates a device control signal to operate devices or motors "on-board" the power machine.

    [0029] In an alternate embodiment, the wireless communication component 180 is separate from the automated control module 162 and is electrically connected to the automated control module 162 for use. Similarly, the wireless communication device 182 can be an integral component of the machine controller 126 or separately attached.

    [0030] FIG. 5 is a flow chart of an illustrated embodiment of an automated control assembly. As shown in step 184, the automated control module 162 is attached to the power machine to provide automated control. The automated control module 162 can be attached to the one or more lift arms as illustrated in FIG. 3 via a mounting bracket (not shown in FIG. 5). Sensors 164 are connected to the automated control module 162 to provide position input as described. Sensors 164 can be connected prior to or following attachment of the automated control module 162 to the power machine.

    [0031] In step 186 in FIG. 5, the automated control module 162 is enabled to implement automated control. In the illustrated embodiment, the automated control module is electrically coupled to the machine controller 126 to transmit and/or receive data as described. In the embodiments illustrated, the automated control module 162 is electrically coupled to the machine controller 12 by plugging connector plug 174 into socket 176 or via a wireless interface.

    [0032] Thereafter automated control is enabled via control selector 168 as previously illustrated in FIG. 2.

    [0033] FIG. 6 schematically illustrates an embodiment of an automated control assembly including an automated control module 162 that is implemented through a controller area network. (CAN). In the illustrated embodiment, the automated control module 162 is connected to a controller area network bus 190 to communicate with machine controller 126 on the CAN bus 190. As shown, input from the operator controls 116 is also transmitted to the machine controller 126 through the CAN bus 190 via an operator controls component 192. The illustrated machine controller 126 receives input from the operator controls 116 or automated control module 162 and outputs a control signal to operate actuator devices 106, 108, 145, 146 or other devices of the power machine.

    [0034] Although a particular machine controller is shown, application is not limited to interface with the particular machine controller 126 shown and other embodiment can be utilized to implement embodiments of the present invention.

    [0035] Although the present invention has been described with reference to preferred embodiments, workers skilled in the art will recognize that changes may be made in form and detail without departing from the scope of the invention as defined by the claims.


    Claims

    1. An assembly adapted for a power machine (100) having a hydraulic drive assembly including one or more hydraulic motors (145, 146), the assembly comprising a machine control assembly (126) operably coupled to the power machine (100) to control movement of the power machine (100), a control selection component configured to receive a control selection input from a control selector (168) providing one of an automated control mode selection and an operator control mode selection,

    an automated control module (162) configured to receive an input signal indicative of a position of the power machine (100) relative to a reference point from at least one sensor (164) and generate an automated control command (166) responsive to the input signal from the at least one sensor; and

    wherein the machine control assembly (126) is configured to receive the control selection input from the control selector (168) and if the input control selection is the automated control mode selection, the machine control assembly (126) is configured to utilize the automated control command (166) from the automated control module (162) to provide a device control signal to energize the one or more hydraulic motors to provide forward, reverse and steer motion to drive and steer the power machine (100) and if the input control selection is the operator control mode selection, the machine control assembly (126) is configured to utilize an operator control command from an operator input device to provide the device control signal to energize the one or more hydraulic motors to provide forward, reverse and steer motion to drive and steer the power machine (100); and a c

    ommunication interface (170) configured to transmit the automated control command (166) to the machine control assembly (126) to generate the device control signal utilizing the automated control command (166).


     
    2. The assembly of claim 1 wherein the communication interface comprises:
    a connector assembly (170) including an electrical cable (172) and a connector plug (174) configured to provide an electrical connection between the automated control module (162) and the machine control assembly (126) to transmit the automated control command (166) to the machine control assembly (126).
     
    3. The assembly of claim 2 wherein the automated control module (162) is removably connectable to the power machine (100).
     
    4. The assembly of claim 1 wherein the at least one sensor is a laser receiver and the automated control command (166) is generated based upon a position signal provided from the laser receiver with respect to a reference position.
     
    5. The assembly of claim 1 wherein the automated control module (162) is coupled to the machine control assembly (126) through a controller area network bus.
     


    Ansprüche

    1. Anordnung, die für eine Kraftmaschine (100) mit einer hydraulischen Antriebsanordnung mit einem oder mehreren Hydraulikmotoren (145, 146) eingerichtet ist, wobei die Anordnung eine Maschinensteuerungsanordnung (126), die mit der Kraftmaschine (100) wirkverbunden ist, um eine Bewegung der Kraftmaschine (100) zu steuern, ein Steuerungsauswahlbauteil, das eingerichtet ist, eine Steuerungsauswahleingabe von einer Steuerungsauswahleinrichtung (168) zu empfangen, die eine Automatiksteuerungsmodus-Auswahl oder eine Bedienersteuerungsmodus-Auswahl bereitstellt,

    ein Automatiksteuerungsmodul (162), das eingerichtet ist, ein Eingangssignal von zumindest einem Sensor (164) zu empfangen, das eine Position der Kraftmaschine (100) in Bezug auf einen Referenzpunkt angibt, und einen Automatiksteuerungsbefehl (166) als Reaktion auf das Eingangssignal von dem zumindest einen Sensor zu erzeugen; und

    wobei die Maschinensteuerungsanordnung (126) eingerichtet ist, die Steuerungsauswahleingabe von der Steuerungsauswahleinrichtung (168) zu empfangen, und falls die eingegebene Steuerungsauswahl die Automatiksteuerungsmodus-Auswahl ist, ist die Maschinensteuerungsanordnung (126) eingerichtet, den Automatiksteuerungsbefehl (166) von dem Automatiksteuerungsmodul (162) zu verwenden, um ein Vorrichtungssteuerungssignal bereitzustellen, um den einen oder die mehreren Hydraulikmotor(en) mit Energie zu versorgen, um eine Vorwärts-, Rückwärts- und Lenkbewegung bereitzustellen und die Kraftmaschine (100) anzutreiben und zu lenken, und falls die eingegebene Steuerungsauswahl die Bedienersteuerungsmodus-Auswahl ist, ist die Maschinensteuerungsanordnung (126) eingerichtet, einen Bedienersteuerungsbefehl von einer Bedienereingabevorrichtung zu verwenden, um das Vorrichtungssteuerungssignal bereitzustellen, um den einen oder die mehreren Hydraulikmotor(en) mit Energie zu versorgen, um eine Vorwärts-, Rückwärts- und Lenkbewegung bereitzustellen, um die Kraftmaschine (100) anzutreiben und zu lenken; und

    eine Kommunikationsschnittstelle (170), die eingerichtet ist, den Automatiksteuerungsbefehl (166) an die Maschinensteuerungsanordnung (126) zu senden, um das Vorrichtungssteuerungssignal unter Verwendung des Automatiksteuerungsbefehls (166) zu erzeugen.


     
    2. Anordnung nach Anspruch 1, wobei die Kommunikationsschnittstelle aufweist:
    eine Verbinderanordnung (170) mit einem elektrischen Kabel (172) und einem Verbindungsstecker (174), die eingerichtet sind, eine elektrische Verbindung zwischen dem Automatiksteuerungsmodul (162) und der Maschinensteuerungsanordnung (126) bereitzustellen, um den Automatiksteuerungsbefehl (166) an die Maschinensteuerungsanordnung (126) zu senden.
     
    3. Anordnung nach Anspruch 2, wobei das Automatiksteuerungsmodul (162) lösbar mit der Kraftmaschine (100) verbindbar ist.
     
    4. Anordnung nach Anspruch 1, wobei der zumindest eine Sensor ein Laserempfänger ist und der Automatiksteuerungsbefehl (166) basierend auf einem von dem Laserempfänger bereitgestellten Positionssignal in Bezug auf eine Referenzposition erzeugt wird.
     
    5. Anordnung nach Anspruch 1, wobei das Automatiksteuerungsmodul (162) mit der Maschinensteuerungsanordnung (126) durch einen Bus eines Controller Area Networks gekoppelt ist.
     


    Revendications

    1. Ensemble adapté pour une machine motrice (100) ayant un ensemble d'entraînement hydraulique incluant un ou plusieurs moteurs hydrauliques (145, 146), l'ensemble comprenant un ensemble de contrôle de machine (126) couplé fonctionnellement à la machine motrice (100) pour contrôler le mouvement de la machine motrice (100), un composant de sélection de contrôle configuré pour recevoir une entrée de sélection de contrôle d'un sélecteur de contrôle (168) fournissant une sélection parmi une sélection de mode de contrôle automatisé et une sélection de mode de contrôle par un opérateur,

    un module de contrôle automatisé (162) étant configuré pour recevoir un signal d'entrée indiquant une position de la machine motrice (100) par rapport à un point de référence provenant d'au moins un capteur (164) et générer une commande de contrôle automatisé (166) en réponse au signal d'entrée provenant de l'au moins un capteur ; et

    dans lequel l'ensemble de contrôle de machine (126) est configuré pour recevoir l'entrée de sélection de contrôle du sélecteur de contrôle (168) et si la sélection de contrôle d'entrée est la sélection de mode de contrôle automatisé, l'ensemble de contrôle de machine (126) est configuré pour utiliser la commande de contrôle automatisé (166) du module de contrôle automatisé (162) pour fournir un signal de contrôle de dispositif pour alimenter le ou les moteurs hydrauliques pour fournir un mouvement de marche avant, de marche arrière et de direction pour entraîner et diriger la machine motrice (100) et si la sélection de contrôle d'entrée est la sélection de mode de contrôle par un opérateur, l'ensemble de contrôle de machine (126) est configuré pour utiliser une commande de contrôle par un opérateur provenant d'un dispositif d'entrée par un opérateur pour fournir le signal de contrôle de dispositif pour alimenter le ou les moteurs hydrauliques pour fournir un mouvement de marche avant, de marche arrière et de direction pour entraîner et diriger la machine motrice (100) ; et

    une interface de communication (170) configurée pour transmettre la commande de contrôle automatisé (166) à l'ensemble de contrôle de machine (126) pour générer le signal de contrôle de dispositif en utilisant la commande de contrôle automatisé (166).


     
    2. Ensemble selon la revendication 1, dans lequel l'interface de communication comprend :
    un ensemble de connexion (170) incluant un câble électrique (172) et une fiche de connexion (174) configurés pour fournir une connexion électrique entre le module de contrôle automatisé (162) et l'ensemble de contrôle de machine (126) pour transmettre la commande de contrôle automatisé (166) à l'ensemble de contrôle de machine (126).
     
    3. Ensemble selon la revendication 2, dans lequel le module de contrôle automatisé (162) peut être connecté de manière amovible à la machine motrice (100).
     
    4. Ensemble selon la revendication 1, dans lequel l'au moins un capteur est un récepteur laser et la commande de contrôle automatisé (166) est générée sur la base d'un signal de position fourni par le récepteur laser par rapport à une position de référence.
     
    5. Ensemble selon la revendication 1, dans lequel le module de contrôle automatisé (162) est couplé à l'ensemble de contrôle de machine (126) par un bus de réseau local de contrôleur.
     




    Drawing























    Cited references

    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