Abstract:
An electromotive furniture drive includes an electric motor, the rotational direction of which can be reversed, a motor controller, a manual control, a battery unit, and a mains power supply device. A speed-reducing transmission is connected downstream of the electric motor and a further transmission is connected downstream of each speed-reducing transmission and the battery unit has at least one battery. To enable simple, economical and easy installation, in particular in tight installation spaces, the furniture drive has a coupling device which includes a charging device for charging the at least one battery of the battery unit. The coupling device also has a reference device, which is connected to a charging device The furniture drive is especially suited for slatted bed frames and armchairs.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application is the U.S. National Stage of International Application No. PCT/EP2012/057779, filed Apr. 27, 2012, which designated the United States and has been published as International Publication No. WO 2012/146721 and which claims the priority of German Patent Application, Serial No. 20 2011 001 008.2, filed Apr. 29, 2011, pursuant to 35 U.S.C. 119(a)-(d). 
     BACKGROUND OF THE INVENTION 
     The invention relates to an electromotive furniture drive, especially for seating and reclining furniture. 
     Such electromotive furniture drives are known in various embodiments. They are implemented as linear drives having a linearly adjustable output element or as rotational drives having a rotating output element and have proven themselves extremely well in practice. The linear drives have one or a number of electric motors, wherein a speed reduction gear is connected downstream of each motor and a further gear in the form of a threaded spindle gear for example is connected downstream of the speed reduction gear, which further gear generates a linear movement of the output element from the rotational movement of the motor. The rotational drives have at least one speed reduction gear connected downstream of the respective electric motor, wherein the last gearing element forms the output element. The output element of the respective electromotive furniture drive is connected to a fixed furniture component and/or to a movable furniture component, so that the movable furniture components are adjusted relative to one another in the event of operation of the electric motor. The furniture can be implemented as a slatted frame, worktable, bed, reclining surface, treatment couch, hospital or healthcare bed, and also a lifting device for persons such as lifters or patient lifters. 
     It is common practice to provide such electromotive furniture drives with a so-called mains isolation circuit, which separates such drives from the electric supply network to a higher or lesser extent when not in use. 
     Furniture, especially seating/reclining furniture, is furniture which is mobile within an apartment, i.e. it can be positioned or placed in a living room at different locations. A TV chair is often repositioned and can change its position within a room depending on the time of day and the available daylight. It can be disadvantageous if fixed electrical connections to a socket outlet or long cables are connected to the furniture drive. One solution to this problem occurs by rechargeable battery units (accumulators) on the piece of furniture itself. A charger can be used for charging the battery units when this is required. The piece of furniture can be moved in the room without any disturbing cables. The adjusting drives can be supplied at any time and at any location by the battery unit with electrical power for adjustment. 
     If the battery unit is discharged, a certain period of time is required for recharging by the charger until sufficient electric power is available for drive adjustment. For this reason power supplies are known which are not arranged as a charger but as a mains power supply for the adjusting drives. Accordingly, the rechargeable battery is associated with a charging circuit which is ideally arranged in the housing of the rechargeable battery. This can lead to disadvantages however. 
     If the rechargeable battery changes its shape for any reason whatsoever, the housing and the charging circuit need to be adapted accordingly. A large number of electrically identical, but also similar rechargeable batteries are available on the market, but which show relevant geometrical differences among each other. If another rechargeable battery needs to be mounted or if a supplier substantially changes the geometrical dimensions, a new housing needs to be created. This also applies in the case that the specifications or the type of the rechargeable battery changes, and therefore a similar rechargeable battery or a different rechargeable battery is provided for mounting in the furniture drive, for which reason the charging circuit needs to be changed substantially. 
     SUMMARY OF THE INVENTION 
     The invention is therefore based on the object of providing an improved electromotive furniture drive. 
     This object is achieved by an electromotive furniture drive, especially a seating/reclining furniture drive, including a motor controller, a manual control, a rechargeable battery unit and a mains power supply device for adjusting movable furniture components relative to each other, wherein the electromotive furniture drive includes at least one electric motor with reversibility in the direction of rotation, wherein each electric motor is provided downstream with a speed reduction gear and wherein each speed reduction gear is provided downstream with a further gear, wherein the rechargeable battery unit has at least one rechargeable battery, and wherein the mains power supply device is arranged to be connectable to the mains and the input voltage on the mains side is transformed into at least one low voltage on the output side, and includes an isolating transformer or a transformer unit for electrical isolation between the mains-bound input side and the low-voltage-providing output side for the operation of the electromotive furniture drive and for charging the at least one rechargeable battery, wherein a coupling apparatus is provided which connects the rechargeable battery unit to the mains power supply device, wherein the coupling apparatus has a charging device for charging the at least one rechargeable battery of the rechargeable battery unit. 
     The electromotive furniture drive is simple, inexpensive and light, and is mounted especially in the constricted space of a seating furniture and can also be used universally. It comprises a rechargeable battery unit as the power supply unit and can be connected to a power supply device which supplies both the electric power for charging the rechargeable battery unit and also the necessary high electric power for operating the electromotive furniture drive when the rechargeable battery is discharged or partially discharged. 
     This leads to a high level of comfort for the user, because said user does not have to consider any relevant facts for recharging the rechargeable battery and, in addition, can use the power supply device at all times when the rechargeable battery is discharged in order to further operate the electromotive furniture drive. 
     The coupling apparatus can be attached at any location in the piece of furniture. The electromotive furniture drive is independent of the housing size of the rechargeable battery unit because it can also be fixed at another location. Furthermore, the charging device is arranged in the coupling apparatus, so that it is arranged independent of the motor controller and the rechargeable battery unit, thus leading to an advantageous modular and compact configuration. Furthermore, a charging device which is ideally adapted to the respective type of the adjustable battery can be provided in the mounting of the electromotive furniture drive in the piece of furniture. 
     It is provided that the coupling apparatus comprises a reference device which is connected to the charging device. As a result, different types of charging devices can be used, e.g. integrated charging circuits. 
     The reference device can be connected to at least one current detection device, a rechargeable battery voltage detection device and a charging supply voltage detection device. A connected mains power supply device and the rechargeable battery unit can be recognized with their voltage states. 
     The reference device can comprise a voltage divider, with which it is possible in a simple way, especially in the case of a discrete and therefore inexpensive configuration, to detect the parameters of voltage and current which are necessary for charging the rechargeable battery unit. 
     A simple discrete configuration can be realized for the voltage divider by at least three resistors switched in series. Of these three resistors, at least one thereof can be changed in a simple way by a transistor or any other switching element for example, e.g. it can be bridged. A temporary change, e.g. bridging for a preset period of time, can occur by means of a capacitor. 
     In accordance with a further embodiment, the charging device can be arranged in the manner of a switched-mode power supply. For this purpose, a respective integrated circuit can be used with a switching transistor and a storage coil. It is further also possible that the charging device can be provided with a function as a step-up converter. This may be necessary when the mains power supply device supplies a charging supply voltage which lies beneath an end-of-charge voltage of the rechargeable battery unit. 
     As a result, the charging device can be operated both as a step-down converter and also as a step-up converter. 
     In a further embodiment, the charging device can be operated as a step-down converter for reducing the charging voltage of the at least one rechargeable battery of the rechargeable battery unit while the charging current I is kept constant, and the charging device can be operated as a step-up converter with a constant charging current for the at least one rechargeable battery of the rechargeable battery unit until reaching an end-of-charge voltage of the at least one rechargeable battery of the rechargeable battery unit with constant charging current, whereas the charging device can be operated as a step-up converter with a constant charging voltage from reaching the end-of-charge voltage of the at least one rechargeable battery of the rechargeable battery unit. 
     In a further embodiment, the coupling apparatus may comprise plug-in connections at least for the rechargeable battery unit and the mains power supply device, thus providing a large level of design freedom. 
     In another embodiment, the mains power supply device can be provided with switched-mode power supply. 
     An arrangement of the mains power supply device with a mains isolation device can be possible, thus leading to power and energy savings. 
     In a further embodiment, the coupling apparatus can connect the motor controller to the rechargeable battery unit and the mains power supply device, thus providing a compact configuration. 
     Further characterizing parts and features of a preferred embodiment are provided in the description below and are the subject matter of further sub-claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The invention will be explained below in closer detail by reference to the drawings, wherein: 
         FIG. 1  shows an exemplary and schematic illustration of a furniture drive arranged as a linear drive in accordance with the invention; 
         FIG. 2  shows a schematic block diagram of an embodiment the furniture drive according to  FIG. 1 ; 
         FIGS. 3 to 3   a  show diagrams for explaining a section of a charging process, and 
         FIG. 4  shows a schematic circuit diagram of a reference device of  FIG. 2 . 
     
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       FIG. 1  shows an electromotive furniture drive  1  with a rechargeable battery unit  8 , a mains power supply device  9  and a coupling apparatus  10 . 
     The electromotive furniture drive  1  is arranged in this embodiment as a so-called linear drive  2 , and the mains power supply device  9  is implemented for example as a switched-mode power supply or with an isolating transformer, rectifier, and filter circuit. The linear drive  2  has a lifting pipe  3  which is extendable and retractable depending on the rotational direction of an electric motor (not shown in greater detail), on whose free end a connecting part in the form of a clevis  4  is attached. A further connecting part in the form of a further clevis  4  is fastened on the housing of the linear drive  2 . The respective connecting part is connected in a way not shown in greater detail to a respective furniture component, so that during operation of the electric motor  5  the furniture components connected to the linear drive  2  move relative to one another. 
     As a result, the electromotive furniture drive  1  is installed in a seating furniture such as a recliner which is locally movable within an apartment. The installation space is limited in such a seating furniture, so that the drive and the power supply, i.e. the rechargeable battery unit  8  and the mains power supply device  9 , need to be arranged at different locations. The rechargeable battery unit  8  is arranged within or on the seating furniture, and the mains power supply device  9  is arranged as a plug-in power unit or ground unit outside of the seating furniture. Since the seating furniture is movable, a plug-in connection is provided between the mains power supply device  9  and the electromotive furniture drive  1 . 
     The electric motor  5  is connected to a motor controller  6 , which is connected to a manual control  7  in wired form using an operating line  16 . The manual control  7  comprises two pushbuttons here. According to another embodiment (not shown in greater detail), the manual control  7  is coupled via a wireless transmission link to the motor controller  6  and transmits radio waves or infrared light waves to the control unit of the at least one electric motor  5 , i.e. the linear drive  2  to the motor controller  6 . 
     According to the illustration in  FIG. 1 , the manual control  7  is connected to the motor controller  6  in a first embodiment, wherein the motor controller  6  is implemented as a relay controller having relay switches and/or as a semiconductor circuit having semiconductor switches. The manually operable button switches of the manual control  7  switch the control current of the relay switches or the semiconductor switches, wherein the power switches of the relay switches or the semiconductor switches switch the high motor current of the linear drive  2 . 
     According to the illustration in  FIG. 1 , the manual control  7  is connected to the motor controller  6  in a second embodiment, which connects the supply line  13  and a motor line  28  of the electric motor  5  of the linear drive  2  and the electrical lines of the manually operable button switches of the manual control  7  to one another. According to this embodiment, the contacts of the manually operable button switches of the manual control  7  are implemented as power switches and switch the high motor current of the electric motor  5  of the linear drive  2  in the event of a button press. Such an embodiment of a motor controller  6  can also be understood as power distribution and/or power branching, which according to other embodiments (not shown in closer detail) is also arranged as a fixedly enclosed or cast-in distributor. 
     In a further developed embodiment, which is not shown in closer detail, the motor controller  6  is inserted into the housing of the linear drive  2  or is placed thereon. In another further developed embodiment, which is also not shown in closer detail, the motor controller  6  is arranged on or in the coupling apparatus  10 . The linear drive  2  can be arranged in a manner of a double drive not shown in closer detail, which accommodates at least one motor, but preferably two motors, in a common housing. According to a further embodiment (not shown in closer detail), the electromotive furniture drive  1  comprises a plurality of motors, wherein a plurality of linear drives  2  and/or double drives can be used. 
     The supply line  13  connects the motor controller  6  to the coupling apparatus  10 , either via a fixed line connection or via a plug-in connection. 
     The coupling apparatus  10  is connected on its part by a rechargeable battery line  14  to the rechargeable battery unit  8  and via a feed line  15  to the mains power supply device  9 . These connections can also be arranged in a fixed or pluggable manner. The coupling apparatus  10  will be described below in closer detail. 
     The rechargeable battery unit  8  comprises a rechargeable battery which is provided for supplying the linear drive  5  when no mains power supply device  9  is connected for example. 
     The mains power supply device  9  is connected according to the illustration of  FIG. 1  via a mains cable  12  to a mains plug  11 , wherein the mains plug  11  can be arranged on the mains power supply device  9  in another embodiment not shown in closer detail. In another embodiment, a mains isolation device can be integrated in the mains power supply device  9 . It needs to be mentioned that in this case the mains power supply device  9  according to the illustration of  FIG. 1  is provided with an enclosing housing, so that the mains plug  11  is placed on the housing or can be integrally formed thereon. 
     The mains plug  11  conducts the input-side mains voltage to the mains power supply device  9  via the mains cable  12  at first, which mains power supply device  9  supplies on the secondary side a low voltage in form of a DC voltage as the operating voltage and conducts the same at first to the coupling apparatus  10 . The operating voltage lies in the range of approximately 29 V for example, wherein it corresponds to specific safety regulations, and it is used on the one hand for operating the motor controller  6  and therefore the linear drive  2  and on the other hand for charging the rechargeable battery of the rechargeable battery unit  8 . 
     The charging of the rechargeable battery unit  8  occurs by the coupling apparatus  10 , which comprises the charging circuit for this purpose which will be described below in closer detail. Furthermore, the coupling apparatus  10  provides electric power to the motor controller  6  for adjusting the linear drive  2 . For this purpose, it either supplies the electrical power of the mains power supply device  9  or the rechargeable battery unit  8  via the supply line  13  to the motor controller  6 . If the linear drive  2  is not operated, the coupling apparatus  10  charges the rechargeable battery of the rechargeable battery unit  8  by means of the electrical power of the mains power supply device  9  when it is connected. 
     If only the rechargeable battery unit  8  is connected to the coupling apparatus  10 , the coupling apparatus  10  supplies the motor controller with electrical power of the rechargeable battery unit  8 . If the rechargeable battery unit  8  is discharged and the mains power supply device  9  is connected, the linear drive  2  is supplied with electrical power of the mains power supply device  9  during the operation of said linear drive, otherwise the rechargeable battery unit  8  is recharged with the electrical power of the mains power supply device  9 . 
       FIG. 2  shows a schematic block diagram of an embodiment of a furniture drive  1  according to  FIG. 1 . 
     The coupling apparatus  10  is arranged in this embodiment in a separate housing and comprises terminal connections V 1  to V 3  for connecting the motor controller  6  by means of a supply line  13  to the terminal connection V 1 , the rechargeable battery unit  8  via the rechargeable battery line  14  to the terminal connection V 2 , and the mains power supply device  9  via a feed line  15  to the terminal connection V 3 .  FIG. 2  shows the state in which the rechargeable battery unit  8  and the mains power supply device  9  are also connected to these connections of the coupling apparatus  10  apart from the motor controller  6 . These connections can be arranged in one embodiment as plug-in connections. 
     Furthermore, the coupling apparatus  10  comprises a positive line  18  with a diode D 1  and a rechargeable battery positive line  19  with a diode D 2 . 
     The negative lines (−) of the motor controller  6 , the rechargeable battery unit  8 , the mains supply line  9  and the coupling apparatus  10  are connected among each other and to ground. 
     The positive line  18  is connected to the positive line (+) of the mains power supply device  9  by the terminal connection V 3 , wherein its other end is connected to the anode of the diode D 1 , which on its part is connected with its cathode via the terminal connection V 1  to the positive line (+) of the motor controller  6 . The cathode of the diode D 2  is also connected to this connection, whose anode is connected with the positive rechargeable battery line  19  of the rechargeable battery unit  8  via the terminal connection V 2  to the positive line (+) of the rechargeable battery unit  8 . The diodes D 1  and D 2  are used for electrical decoupling of the positive line  18  and the positive rechargeable battery line  19 . 
     The terminal connection  13  can also comprise a limiter diode D 3  for protection against voltage peaks. In  FIG. 2  the limiter diode D 3  is a hot-carrier diode for example. 
     This allows that when the rechargeable battery unit  8  (even when it has a discharged rechargeable battery) and power supply device  9  are connected the mains power supply device  9  forms the power supply via the diode D 1  for the motor controller  6 . If the mains power supply device  9  is not connected (not shown), the rechargeable battery unit  8  will supply the motor controller  6  via the diode D 2 . 
     The coupling apparatus  10  further comprises a charging device  22 , a reference device  23 , at least one current detection device  24 , a rechargeable battery voltage detection device  25  and a charging supply voltage detection device  26 . 
     The charging device  22  is used for charging the rechargeable battery of the connected rechargeable battery unit  8 . For the purpose of obtaining electrical power for charging the rechargeable battery, the charging device  22  is connected via a charging supply line  20  via the terminal connection V 3  to the positive line (+) of the mains power supply device  9 . One output of the charging device  22  is connected via the at least one current detection device  24  to a charging line  21  which is connected to the positive line (+) of the connected rechargeable battery unit  8 , i.e. to the terminal connection V 2 . 
     A charging process occurs on the basis of reference values which are provided to the charging device  22  by the reference device  23  depending on a rechargeable battery voltage and a charging current via a connection a 5 . The respective charging current is determined by the at least one current detection device  24  and supplied to the reference device  23  by the connection a 3 . The rechargeable battery detection device  25  detects the rechargeable battery voltage of the rechargeable battery of the connected rechargeable battery unit  8  at a connection a 1  on the positive line (+) of the rechargeable battery unit  8  and transfers it to the reference device  23  via a connection a 2 . Furthermore, the reference device  23  is connected via a connection a 4  to the charging supply voltage detection device  26 , which detects a voltage value of the mains power supply device  9 . 
     The reference device  23  recognizes via the rechargeable battery voltage detection device  25 , at least one current detection device  24  and the charging supply voltage detection device  26  whether only one of the rechargeable battery unit  8  and the mains power supply device  9  is connected or both thereof. Furthermore, it can determine whether the electromotive furniture drive  1 , i.e. its motor controller  6 , is in operation. A charging process of the rechargeable battery will only occur when the motor controller  6  is not in operation or if all motors  5  are not in operation. 
     The charging device  22  comprises an integrated control circuit in one embodiment, which produces the respective charging voltage and the respective charging current for the rechargeable battery unit  8  from the mains power supply device  9 . For this purpose, the charging device  22  is equipped with a type of switched-mode power supply unit which is controlled by the control circuit on the basis of the values supplied by the reference device  23 . 
     In an embodiment not shown in closer detail, the switched-mode power supply unit of the charging device is arranged as a secondary switching controller with a switching transistor, e.g. a MOS-FET, and an inductor. Said secondary switching controller is operated on the basis of a reference value as a so-called step-down converter in a specific range. It can also be operated as a so-called step-up converter. In its capacity as a step-down converter, it generates a charging voltage for the rechargeable battery which lies beneath the output voltage of the mains power supply device  9 , and in its capacity as a step-up converter it generates a charging voltage for the rechargeable battery which lies over the output voltage of the mains power supply device  9 . 
     This will be explained below in closer detail by reference to examples in connection with  FIGS. 3 and 3   a , which show diagrams of sections of a charging process. 
       FIG. 3  shows the charging voltage U and a charging current I (dashed line) over time t. The dot-dashed lines are used for characterizing specific voltages and points of time. 
     The rechargeable battery unit  8  is a lithium-ion battery with a nominal voltage U 2  of 25.2 V DC. Its start-of-charge voltage U 1  lies at approximately 22 V and its end-of-charge voltage U 3  is at 29.4 V. The mains supply device  9  is provided, according to respective standards, with an output voltage of 29 V and is a switched-mode power supply unit for example. 
     The rechargeable battery voltage of the rechargeable battery unit  8  is now determined by the rechargeable battery voltage detection device  25 . When the main supply device  9  is connected, then this will be recognized by means of the charging supply voltage detection device  26 . If the rechargeable battery voltage lies beneath a specific safety value, e.g. a minimal voltage U 0  of 14 V, no charging process will be started. This can also be displayed or reported (not shown). 
     A display or a report of such processes, e.g. the start, the end or the status of a charging process or the status of the rechargeable battery unit  8 , occurs by a display device or by a signaling device which is arranged as a lamp such as an LED, or an acoustic element such as a signal buzzer or a piezo beeper. 
     If the rechargeable battery voltage lies above the minimum voltage, e.g. 22 V, and beneath the end-of-charge voltage U 3  of 29.4 V, a charging process is performed with a specific charging current I according to charging characteristics which can be adapted to the type of chargeable battery (these values can be preset in the charging device  22  in a manner not shown here). A charging current I is 350 mA for example and is kept constant from a point of time t 0  at which the charging process is started with the start-of-charge voltage U 1  up to a point of time t 2  at which the end-of-charge voltage U 3  is reached. If the end-of-charge voltage U 3  of 29.4 V is reached at point of time t 2 , this voltage is kept constant and the charging current I is respectively reduced in the course of the further charging process. 
     The charging voltage U rises from the start-of-charge voltage U 1  from the point of time t 0  up to the point of time t 1  at which the nominal voltage U 2  is reached, and rises further until reaching the end-of-charge voltage U 3  at point of time t 2 . 
     The charging device  22  principally comprises a so-called step-up converter if the rechargeable battery can be charged with a charging voltage of more than 29 V, or if the rechargeable battery can be charged with a charging voltage which is higher than the supply voltage provided by the main supply device  9 . This is the case from point of time t 1  in the diagram in  FIG. 3 . 
     From the point of time t 1  to the point of time t 2 , the charging device  22  acts as a step-up converter, but with constant charging current I, whereas it acts from the point of time t 2  as a step-up converter with constant charging current U. 
     The step-up converter acts from the point of time t 0  until reaching the nominal voltage U 2  at point of time t 1  as a so-called step-down converter and reduces the charging current U while the charging current I is kept constant. 
     An optional deactivation of the charging current U after a previously determinable time for example is not shown. 
     As already described above,  FIG. 3  shows the curve progression of the charging current I, which remains constant up to the point of time t 2 .  FIG. 3  and  FIG. 3 a    further show exemplary curves of the charging current I after the point of time t 2 . 
     In accordance with the illustration of  FIG. 3  and according to a first exemplary embodiment of a charging device  22 , a diagram curve of the charging current I after the point of time t 2  is provided, wherein the charging current I decreases more and more with progressing time, thus providing a falling curve which is similar to a decreasing parabola branch. 
     In accordance with the illustration of  FIG. 3 a    and according to a further exemplary embodiment of a charging device  22 , a diagram curve of the charging current I after the point of time t 2  is provided, wherein the charging current I at the point of time t 2 , or in the range around the point of time t 2 , decreases very rapidly and steeply, so that the curve progression at the point of time t 2  or in the range around point of time t 2  is arranged to decrease in the manner of a sharp bend. In the further progression over time, the charging current I decreases steeply at first, wherein the charging current I approaches in the subsequent time progression a predetermined value, i.e. a charge retention current. In one embodiment of the charging device  22  and the rechargeable battery unit  8 , the charge retention current will never become zero and approaches a predetermined value asymptotically, for example. In accordance with another embodiment and similar to one of the other initially described embodiments, an isolation of the charging voltage U occurs by a timer element after a predetermined period of time, wherein the charging current I will then also become zero. 
     Since the mains power supply device  9  only provides a maximum voltage of 29 V, the charging device  22  operates in the voltage range of 29 V up to the end-of-charge voltage U 3  of 29.4 V as a step-up converter. 
     If the charging current drops beneath a preset charging current (e.g. 1/40 to 1/20 of the nominal capacity of the rechargeable battery of the rechargeable battery unit  8 ) the charging process will be deactivated. Alternatively, deactivation can also occur after a preset time. 
     Automatic recharging occurs when the rechargeable battery voltage drops beneath a preset value of 27 V for example. 
     The charging device  22  and/or the coupling apparatus  10  comprise electric/electronic fuses (not shown). 
     The reference device  23  is discretely arranged in one embodiment as a voltage divider  27  and is shown in an exemplary schematic circuit diagram in  FIG. 4 . 
     The voltage divider  27  comprises at least three resistors R 1 , R 2  and R 3 , which are switched in series and whose middle connection forms the connection a 5  for connection to the charging device  22  ( FIG. 2 ). The other connection of the resistance R 1  is arranged as the connection a 1  ( FIG. 2 ) and the other end of the resistor R 2  is connected to ground by a further resistor R 3 . 
     The middle connection of the resistors R 1  and R 2  to the connection a 5  is connectable via a switching element (a transistor T 1  in this case) to a resistor R 4  connected to ground. The input of the switching element, i.e. the base of the transistor T 1 , forms the connection a 4  ( FIG. 2 ) for the charging supply voltage detection  26 . 
     The transistor T 1  is shown as an NPN type, but it can also be a PNP type for example. It is further possible that the resistor R 4  is arranged in the collector line of the transistor T 1 . Furthermore, the transistor T 1  can also be arranged as an adjustable resistor in form of a MOS-FET. Other arrangements (e.g. combinations) are obviously also possible. 
     The connecting point between the resistor R 2  and the resistor R 3  is connectable to ground via a further switching element (transistor T 2  here) on the one hand and to ground via a resistor R 5  and a capacitor C on the other hand. The base of the transistor T 2  forms the connection a 3  ( FIG. 2 ) for the at least one current detection device  24 . 
     Furthermore, said connecting point between the resistor R 2  and the resistor R 3  is connectable to ground via a further switching element (transistor T 3  here), e.g. for current limitation of the charging current I, wherein the basis of the transistor T 3  forms a connection a 6  for a further parameter for the reference device  23  which will be explained below in closer detail. 
     The transistors (switching elements) T 1 , T 2  and T 3  influence the voltage divider  27  in such a way that they bridge or change the resistors of the voltage divider  27 , thereby changing the voltage value at the reference connection a 5  against ground. As a result, the different parameters of rechargeable battery voltage, charging supply voltage, charging current can have an influence on the charging device  22 . 
     As a result, a voltage value on the base of the transistor T 1  can place the resistor R 4  in parallel to the resistors R 2  and R 3  switched in series depending on the charging supply voltage at connection a 4 . This also allows recognizing whether the mains power supply device  9  is connected and supplies voltage. 
     Transistor T 2  can bridge the resistor R 3  and R 5  (which is parallel to R 3 ) on the basis of a voltage value at connection a 3  depending on the charging current and therefore place R 2  to ground. 
     When the mains power supply device  9  is connected, the capacitor C forms a short circuit to ground for a time interval depending thereon, thus bridging the resistor R 5  and the transistor T 2 . A charging process can thus be started. 
     The capacitor C can be discharged again when the transistor T 3  switches to ground by a signal at the further connection a 6 . This signal can be triggered for example by a specific voltage value of the rechargeable battery voltage. Furthermore, at least one of the three resistors R 1 , R 2 , R 3  which are switched in series are connected to a capacitor C for temporarily changing the voltage divider. 
     The embodiments described above do not limit the invention. They can be modified within the scope of the enclosed claims. 
     The stated voltage values for the charging voltage U and the end-of-charge voltage U 3  are only provided by way of example; it is understood that they can have other values in connection with other types of rechargeable batteries. 
     It is possible that the voltage divider  27  is not influenced by transistors as switching elements but by electromechanical switches. 
     It is also possible to use other configurations of the reference device  23  instead of the voltage divider  27 , e.g. fully integrated circuits. 
     The rechargeable battery of the rechargeable battery unit  8  can also be a type of battery other than lithium-ion batteries, e.g. a lead-gel battery, NiCd battery, etc. 
     If the rechargeable battery comprises rechargeable batteries with separate integrated safety circuits with terminal connections, they can be connected by means of an additional cable to the coupling apparatus  10  and its functional units. 
     Furthermore, a further advantage of the coupling apparatus  10  as a component arranged in a modular fashion needs to be mentioned, which is arranged to be easily and simply mountable during mounting of the electromotive furniture drive  1  and is especially designed for a group of similar types of rechargeable batteries, e.g. a group of lithium-ion batteries, and with similar storage capacity. 
     The embodiment shown in the drawings comprises a common negative line by way of example, which line is associated at least to the motor controller  6  and the rechargeable battery unit  8  and also the mains power supply device  9 , whereas the respective positive line is effectively connected to diodes and/or at least to the charging device  22 . In its electrical reversion, another embodiment (not shown in closer detail) comprises a common positive line which is associated at least with the motor controller  6  and the rechargeable battery unit  8  and also the main supply device  9 , whereas its respective negative line is effectively connected to diodes and/or at least the charging device  22 .