Abstract:
A valve assembly for spraying devices for agricultural technology having a plurality of valves, wherein the valves each include a valve body, which is capable of assuming at least one enable position and one disable position relative to a valve seat, an electric motor for moving the valve seat and/or the valve body into the enable position and the disable position, and an electric energy storage device for providing electric energy for the electric motor, wherein a voltage converter is provided and configured, in a first operation mode, to convert a first voltage provided by the energy storage device into a second, higher voltage to be applied to the electric motor during moving the valve body and/or the valve seat and, in a second operation mode, to charge the energy storage device with low power input.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the priority of the German patent application DE 10 2013 222 743.4 the disclosure of which is hereby incorporated into this application by reference. 
       FIELD AND SUMMARY OF THE INVENTION 
       [0002]    The invention relates to a valve assembly for spraying devices for agricultural technology, wherein the valves each include a valve body, which is capable of assuming at least one enable position and one disable position relative to a valve seat, an electric motor for moving the valve seat and/or the valve body into the enable position and the disable position, and an electric energy storage device for providing electric energy for the electric motor. The invention also relates to a field sprayer including a valve assembly according to the invention. 
         [0003]    The aim of the invention is to provide an improved valve assembly for spraying devices for agricultural technology and an improved field sprayer. 
         [0004]    Therefore, the valve assembly according to the invention comprises a plurality of valves, each including a valve body, which is capable of assuming at least one enable position and one disable position relative to a valve seat, an electric motor for moving the valve seat and/or the valve body into the enable position and the disable position, and an electric energy storage device for providing electric energy for the electric motor, wherein a voltage converter is provided and configured, in a first operation mode, to convert a first voltage provided by the energy storage device into a second, higher voltage to be applied to the electric motor during moving the valve body and/or the valve seat and, in a second operation mode, to charge the energy storage device with low energy input. The invention is based on the finding that in case of a failure of the wired or external power supply for an electric valve, even the voltage provided by an energy storage device on the valve itself is not in all conditions sufficient to displace the valve into a predefined position by means of the electric motor. Depending on requirements, this may be the enable position or the disable position. For example, a higher torque of the electric motor is needed temporarily, in order to move the valve body and/or the valve seat counter the actual liquid pressure. To produce such a higher torque of the electric motor, a voltage converter is provided which in a first operation mode, also referred to as boost operation mode, converts a first voltage provided by the energy storage device into a second, higher voltage to be applied to the electric motor during moving the valve body and/or the valve seat. Owing to the higher output voltage of the voltage converter, the electric motor can provide a sufficiently high torque and/or a sufficiently high number of revolutions to reliably close the valve even in case of a failure of the wired or external energy supply. Thus, the energy storage device as such can be comparatively small and low cost in structure, for example, using lower nominal voltage than the electric motor, and all the same allows to ensure that, in case of failure of the wired or external energy supply, the valve assumes the predetermined emergency position reliably. Furthermore, by means of the energy storage device can be ensured that even during normal operation, but without failure of the power supply of the field sprayer, all valves of the field sprayer can be opened or closed simultaneously, without overloading of the power supply. 
         [0005]    The voltage converter is configured to charge the energy storage device with low power input in a second operation mode. 
         [0006]    In such a so-called buck operation mode, the energy storage device can then be charged during a somewhat longer period of time using lower defined power input, so that the energy supply of the spraying device is not overloaded. Specifically, this allows a solution to the problem that with large spraying devices, for example, field sprayers, the electric system of a tractive vehicle does not have sufficiently high performance in order to supply the high number of valves simultaneously with sufficient electric energy to effect a simultaneous switching operation of all valves. Field sprayers may, for example, have a working width of 42 m, and commonly, there is a nozzle with a valve provided every 50 cm. With the simultaneous power consumption of 84 valves during an opening operation or a closing operation, the electric system of a tractive vehicle for the field sprayer will, in general, be overchallenged. Thus, using the invention ensures not only the simultaneous operation of all electric valves on a field sprayer, furthermore, in case of a failure of the electric energy supply, it still also allows displacing every valve into a predefined emergency position. Charging of the energy storage device is accomplished during the buck operation mode with low power input, so that the electric system of a tractive vehicle is not overloaded. 
         [0007]    In an advanced embodiment of the invention, the voltage converter is configured to control or to regulate power input in a second operation mode. 
         [0008]    This is to ensure that even with numerous valves present, there is no overloading of the power supply and all energy storage devices are charged at the same rate. 
         [0009]    In an advanced embodiment of the invention, in a second operation mode, a third voltage for charging the energy storage device is lower than a supply voltage of the voltage converter. 
         [0010]    These ways and means are also to ensure that the energy supply during charging of the plurality of energy storage devices is not overloaded, and specifically, that only part of the total power provided is used for charging of the energy storage devices. 
         [0011]    In an advanced embodiment of the invention, the voltage converter is a direct current (DC) voltage converter. 
         [0012]    Appropriate DC voltage converters are referred to as DC choppers, two-quadrant choppers, synchronous rectifiers, step-up/step-down choppers, or predominantly also as buck/boost converters. An essential feature is that, during motoric operation, the current flow passes from the energy storage device via the DC voltage converter to the electric motor, however, during charging operation, the current flow passes from an electric energy supply via the DC voltage converter to the energy storage device. 
         [0013]    In an advanced embodiment of the invention, the energy storage device is a capacitor, in particular a supercapacitor. 
         [0014]    Capacitors, in particular supercapacitors, are comparatively compact in structure and, nonetheless, provide a high electric energy density. Supercapacitors can be so-called supercaps, electric double-layer capacitors (EDLCs), electrochemical capacitors, or hybrid capacitors. A common feature with all capacitors is that they can be charged during a somewhat longer period of time with lower power input, but they are adapted to provide high electric power in the short-run for motoric operation. 
         [0015]    In an advanced embodiment of the invention, a valve housing is provided, wherein the electric motor, the voltage converter and a valve control circuit for the electric motor and the voltage converter are arranged within the valve housing, and wherein the voltage converter, the energy storage device and the valve control circuit are encased by a water-tight potting compound. 
         [0016]    In this manner, very short signal pathways can be realized during transmission of signals. This also allows arrangement of the electric motor, the voltage converter and the valve control circuit for the electric motor and the voltage converter protected within the valve housing. Advantageously, the energy storage device itself is also arranged within the valve housing. By potting the electronics, they are reliably shielded from atmospheric exposure, but also from adverse effects of agricultural pesticides or cleaning agents, for example, during high-pressure cleaning. 
         [0017]    In an advanced embodiment of the invention, a cover of the valve housing is sealed by means of the potting compound. 
         [0018]    By potting the cover and the housing, the electric motor disposed within the valve housing can also be shielded from external impacts. 
         [0019]    In an advanced embodiment of the invention, the valve housing is provided with a ventilation hole, wherein the ventilation hole is closed using a water-tight but air-permeable membrane. 
         [0020]    Attaching an air-permeable but water-impermeable membrane allows pressure compensation, for example, in the presence of severe temperature variations. Formation of condensed water within the housing is prevented. Thereby, the electric motor disposed within the valve housing is protected. The membrane is attached to the housing in such a manner, for example, sunk-in below a perforated protective cover, that cleaning of the field sprayer by means of a high-pressure cleaner may not damage the membrane. 
         [0021]    In an advanced embodiment of the invention, the electric motor is a step motor. Advantageously, a screw spindle driven by the electric motor is provided for moving the valve body. 
         [0022]    By means of a screw spindle, high breakaway torques and high holding forces for the valve body and/or the valve seat can be generated. Advantageously, the screw spindle is self-locking. The use of a step motor allows adjusting the rotational position of the step motor to a predetermined value using the valve control circuit without additional sensors. 
         [0023]    In an advanced embodiment of the invention, the valve housing is provided with two electric plug connectors. 
         [0024]    In this manner, valves arranged side by side on a field sprayer can be interconnected by easily to be plugged-in cables. Thereby, a modular construction is obtained. Thus, for equipment of a field sprayer with the valves according to the invention and, in particular, for wiring these valves, standardized cables each including two plug connectors can be used, and there is no need for a specific cable assembly. Typically, in field sprayers, the nozzle supports with the valves are spaced 50 cm apart. In case pre-assembled cables each including two plug connectors are available, an arbitrary number of valves can be mutually interconnected by means of these pre-assembled cables. 
         [0025]    In an advanced embodiment of the invention, the valve housing is provided with two electric connector cables, wherein each connector cable is provided with an electric plug connector, and wherein the plug connectors are of mutually matching design. 
         [0026]    The cables are, for example, for standard nozzle distances of 50 cm provided on each valve. Thereby, the feed throughs of the connector cables traversing the valve housing can be sealed reliably, since they are attached already during production of the valve. During installation of the valve assembly on a field sprayer, errors are prevented in that the plug connectors of different valves can be inserted one into the other only in the correct way. Thus, the installation effort is reduced and a simple and faultless installation is ensured. Furthermore, there is less effort and expenditure for storage and logistics on the side of the manufacturer. Extension cables are provided for installation on joints on the linkage of the field sprayer or for connection of the valves to a central control unit of the field sprayer. In addition to the reduced effort and expenditure in installation, the valve thereby also has an easy to maintain design. In case a valve needs to be replaced, there is no risk of incorrect valve connection. By appropriate design of the valve control, there is automatic configuration. 
         [0027]    In an advanced embodiment of the invention, a valve control is arranged within the housing and configured for operation on a bus line. 
         [0028]    The operation on a bus line facilitates control of the valves according to the invention considerably. The individual valves can be interconnected serially, and are then controlled using bus signals. For example, a four-wire cable can be used. The individual valves can be configured in a simple and user-friendly manner by means of relaying on the circuit board after installation on the machine or after a repair intervention. The control unit automatically conducts a query of the individual positions of the valves and stores them. Furthermore, there is also a possibility to allow signal exchange between the individual valves during a status check. In this manner, a cable failure or a disconnected plug connection may also be located. For example, when ten valves are serially connected and during a status check only the first five valves respond, then it can be assumed that there is a cable failure or a disconnection between the fifth and the sixth valve. The valve control receives signals from a superior control unit, for example, on a tractive vehicle, and converts them into control signals for the step motor. The valve control also monitors the input voltage and output voltage of the valve, for example. If the valve control detects that the input voltage has decreased below a predefined value, an emergency operation is initiated, in that a second, higher voltage is applied to the electric motor in a boost operation mode, and then the motor can displace the valve body and/or the valve seat into a predefined emergency position. By means of the valve control, the charging condition of the energy storage device is monitored as well, and a buck operation mode for charging the energy storage device using low power input is adjusted, as required. 
         [0029]    The problem underlying the invention is also solved by a field sprayer comprising the valve assembly according to the invention. Advantageously, the valves are mutually interconnected electrically by means of a cable supply line, wherein the cable supply line from a first valve to a second adjacent valve is plugged into the first plug connector and the cable supply line from the first valve to a third adjacent valve is plugged into the second plug connector. 
         [0030]    In this manner, a modular construction can be obtained, and valves arranged adjacently on the linkage of the field sprayer can be connected by means of pre-assembled cables without difficulty. 
         [0031]    In an advanced embodiment of the invention, each valve housing is provided with two electric connector cables, each including an electric plug connector, wherein the valves are mutually interconnected by means of the connector cables, and wherein a first connector cable of a first valve leads to a connector cable of a second, adjacent valve and a second connector cable of the first valve leads to a connector cable of a third, adjacent valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0032]    Further features and advantages of the invention will become apparent from the claims and the description hereinbelow of preferred embodiments of the invention in connection with the drawings. Individual features of the different embodiments and their illustration in the drawings can be combined in any arbitrary way without exceeding the scope of the invention. In the drawings: 
           [0033]      FIG. 1  shows a front view of a valve according to the invention according to a first embodiment; 
           [0034]      FIG. 2  shows a side view of the valve according to  FIG. 1 ; 
           [0035]      FIG. 3  shows a rear view of the valve according to  FIG. 1 ; 
           [0036]      FIG. 4  shows a front view of the valve according to  FIG. 1 ; 
           [0037]      FIG. 5  shows a view on sectional plane A-A in  FIG. 2 ; 
           [0038]      FIG. 6  shows a view on sectional plane B-B in  FIG. 3 ; 
           [0039]      FIG. 7  shows a view on sectional plane C-C in  FIG. 4 ; 
           [0040]      FIG. 8  shows a diagrammatic illustration of a field sprayer according to the invention; 
           [0041]      FIG. 9  shows a diagrammatic equivalent circuit diagram of a valve according to the invention; 
           [0042]      FIG. 10  shows a diagrammatic illustration of a field sprayer according to the invention according to another embodiment of the invention; 
           [0043]      FIG. 11  shows a side view of a valve according to the invention according to a second embodiment; 
           [0044]      FIG. 12  shows a front view of the valve according to  FIG. 11 ; 
           [0045]      FIG. 13  shows a top view of the valve according to  FIG. 11 ; 
           [0046]      FIG. 14  shows a partial sectional view of the valve according to  FIG. 13 ; 
           [0047]      FIG. 15  shows a partial sectional view of the valve according to  FIG. 12 ; 
           [0048]      FIG. 16  shows a partial sectional view of the valve according to  FIG. 11 ; and 
           [0049]      FIG. 17  shows an illustration of portions of a valve assembly according to the invention including a plurality of valves according to the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0050]      FIG. 1  shows a valve  10  according to the invention disposed on a nozzle support  12 . The nozzle support  12  is attached to a not illustrated feed pipe and has a connector unit  14  for mounting a not illustrated spray nozzle. Liquid to be sprayed passes from the nozzle tube through the nozzle support  12  to the connector unit  14  and to the spray nozzle. This flow communication between the nozzle tube and the spray nozzle can be disabled or enabled by means of the valve  10 . 
         [0051]    The valve  10  has a valve housing  16 , wherein a valve body, a valve seat, a step motor for moving the valve body, an electric energy storage device, and a valve control circuit are arranged, as will be further explained with reference to  FIGS. 5 to 7 . The valve housing  16  is provided with two electric plug connectors  18  and  20 , and into each thereof a cable supply line can be plugged in. The valve housing  16  is attached to a matching exterior threaded flange of the nozzle support  12  by means of a lock nut  22 . 
         [0052]    The illustration of  FIG. 2  shows a view of the valve  10  and the nozzle support  12  from below. Apparent are the connector unit  14  for the spray nozzle and a channel  24  within the nozzle support  12 , which channel can be enabled or disabled by means of the valve body of the valve  10 , as explained above. 
         [0053]    The illustration of  FIG. 3  shows a side view of the valve  10  and the nozzle support  12 . According to this view, the connector unit  14  for the spray nozzle is arranged at the bottom. 
         [0054]    The illustration of  FIG. 4  shows a rear view of the valve  10  and the nozzle support  12 . The nozzle support  12  has a collar  26  which can be placed around a not illustrated feed pipe, in order to fix the nozzle support  12  to said feed pipe. The feed pipe has an opening on its bottom side and a tube adaptor  28  of the nozzle support  12  engages therein. Via said tube adaptor  28  the liquid to be sprayed passes into the nozzle support  12  and finally to the connector unit  14  for a spray nozzle. 
         [0055]    In the illustration of  FIG. 4  the plug connector  18  is indicated. The plug connector  18  includes a total of four contacts and is provided for a four-wire cable. 
         [0056]    Referring to the views of  FIGS. 1 to 4 , it is apparent that the valve housing  16  is closed, in order to accommodate the components of the valve  10  therein protected against contamination and liquid. 
         [0057]      FIG. 5  shows a view on the sectional plane A-A of  FIG. 2 . The nozzle support  12  is illustrated merely in portions and, specifically, only an exterior threaded flange  28  of the nozzle support  12  is illustrated, where the lock nut  22  of the valve is screwed thereon and a connector adaptor  30  of the nozzle  10  is placed thereon. In the illustration of  FIG. 5  is apparent that the liquid to be sprayed flows into an annular channel  40  of the exterior threaded flange  28  in the direction of the arrows  41 , and thus passes to a valve seat  36  of the valve  10 . Starting from the valve seat  36 , the liquid to be sprayed flows via two transverse holes  38  into a central channel  32  which is surrounded by the annular channel  40 . In the central channel  32 , the liquid flows in the direction of the arrow  34 . The valve seat component  36  includes the actual valve seat  42 , which seat is adapted to be closed or enabled by means of a valve body  44 . In the illustration of  FIG. 5 , the valve seat is enabled and liquid to be sprayed can pass from the annular channel  40  through the valve seat  42  and enter into the central channel  32 . When moving the valve body  44  from the enable position in the illustration of  FIG. 5  to the left hand side in  FIG. 5  until the rounded front end of the body abuts on the valve seat  42 , a flow communication between the central channel  32  and the annular channel  40  is discontinued. Thus, the valve  10  is in a disable position. 
         [0058]    The valve body  44  has a rod shape and is moved by means of an electric step motor  46 . The step motor  46  rotates a screw spindle  48 , which spindle in turn is arranged in a matching internal thread of a blind hole of the valve body  44 . Rotation of the step motor  46  causes an axial movement of the screw spindle  48  and a shifting movement of the valve body  44 , starting from the illustration of  FIG. 5  to the left hand side in the direction towards the valve seat  42 . Starting from the disable position, the screw spindle  48  is turned in the inverse direction, in order to move the valve body  44  away again from the valve seat  42  and to move the valve  10  into the enable position. 
         [0059]    Within the valve housing  16 , a circuit board  50  is arranged besides the step motor  46 , where on the board, a valve control circuit  54  is arranged besides a supercapacitor  52  and visible merely in portions in  FIG. 5 .  FIG. 5  illustrates that the circuit board  50  together with the supercapacitor  52  and the valve control circuit  54  is arranged within the valve housing  16 . The step motor  46  is also disposed within the valve housing  16 . The entirety of electric and electronic components of the valve  10  is, thus, disposed and shielded within the valve housing  16 . The valve control circuit  54  is designed for bus operation, in particular for operation using a CAN (controller area network) bus. The connector units of the plug connectors  18 ,  20  are connected to the valve control circuit  54 . 
         [0060]      FIG. 6  shows a view on the sectional plane B-B in  FIG. 3 . Illustrated within the valve housing  16  are the step motor  46  and the circuit board  50  with the valve control circuit  54 . The valve control circuit  54  includes a voltage converter which, in a first operation mode, also referred to as boost operation mode, can convert a first voltage provided by the supercapacitor  52  acting as an energy storage device into a second, higher voltage to be applied to the step motor  46 . Owing to this higher output voltage, the step motor  46  can provide a higher torque, in order to reliably move the valve body  44 —starting from an enable position into a disable position—or vice versa. 
         [0061]    Said boost operation mode of the valve control circuit  54  is adjusted in any case, when a failure of an external energy supply of the valve  10  has been detected. During normal operation, an external supply voltage is applied to the step motor, which voltage is provided by the electric system of a tractive vehicle, for example. The boost operation mode is adjusted in that, using the valve control circuit  54 , the input voltage and the output voltage of the valve  10  are monitored. If the input voltage decreases below a predefined value, then a failure of the external energy supply is assumed and the voltage converter is shifted to the boost mode and the valve  10  is moved into the disable position. Typically, upon a failure of the external energy supply, the valve  10  is moved into the disable position. However, there are definitely country-specific directives demanding that in case of a failure of the external energy supply, the valve  10  is moved into an enable position. Even said movement into the enable position would be performed in the boost operation mode of the valve control circuit  54 . However, the boost operation mode can be adjusted always in case the valve  10  is to be closed or opened, in particular in case that a plurality of valves  10  is to be opened simultaneously. The boost operation mode then ensures that an electric energy supply, for example, of a field sprayer, is not overloaded even during simultaneous actuation of a plurality of valves. 
         [0062]    By means of the valve control circuit  54  even the charging condition of the supercapacitor  52  is monitored. If the valve control circuit  54  detects that the supercapacitor  52  falls below a predetermined charging condition, then the valve control circuit  54  adjusts a so-called buck operation mode, wherein the supercapacitor  52  is charged during a somewhat longer period of time using a low power input. To that end, the voltage converter is a so-called buck/boost converter and, thus, allows power flow in two opposite directions, namely, during a boost operation mode, from the supercapacitor  52  via the voltage converter to the step motor  46 , and during a buck operation mode, from the external electric energy supply to the supercapacitor  52 . 
         [0063]    The illustration of  FIG. 7  shows a view on the sectional plane C-C in  FIG. 4 . In this illustration, the circuit board  50  arranged within the valve housing  16  together with the supercapacitor  52  and the valve control circuit  54  is clearly apparent. Also apparent is that between the plug connectors  18 ,  20  and the circuit board  50  there are merely very short lengths to be bridged. The electric signals are transmitted from the input plug connector  20  to the output plug connector  18  by means of a relaying on the circuit board. 
         [0064]    The illustration of  FIG. 8  shows diagrammatically a field sprayer  60  according to the invention including a total of eight valves  10  according to the invention. Liquid conduits are not illustrated. What is illustrated is merely one CAN bus line  62  serially interconnecting the individual valves  10  and coming from an individual nozzle control unit  64 . The individual nozzle control unit  64  is provided, during normal operation, to control the valves  10  individually or commonly or in groups in such a manner that the valves move from the enable position to the disable position or vice versa. The individual nozzle control unit  64  sends signals to the individual valves  10  and also receives signals from the valves  10 . For that purpose, the valve control circuits  54  of the individual valves  10  are designed such that, for example, in response to status requests of the individual nozzle control unit  64 , they give a feedback on their status, for example, whether or not they are in operation, actually indeed a feedback on the fact whether the respective valve  10  is in an enable position or in a disable position. 
         [0065]    By means of such a status request the individual nozzle control unit  64  can assess, whether or not all the valves  10  on the bus line  62  are ready for operation. In case, for example, the feedbacks of individual valves  10  are missing or an increased power consumption is measured on an individual valve, then not only failure of the respective valve, as the case may be, but also breakage of a cable or a short-circuit can be concluded therefrom, for example. In case, for example, during a status request there is no feedback given to the individual nozzle control unit  64  from the last three valves  10  arranged on the left hand side in  FIG. 8 , then a cable breakage between the fourth to last and the third to last valve  10  can be concluded therefrom. If the valves  10  do not receive a feedback from the control unit  64 , for example, due to a defect in the bus line, then the emergency stop control can also be activated. 
         [0066]    In case an energy supply of the individual valves  10  fails, which supply is also via the CAN bus line  62 , then the individual valve control circuits  54  detect the failure, as explained above, and said control circuits then cause moving of the valves  10  into the emergency position, in particular the disable position, exclusively using the energy provided by means of the supercapacitor  52 . 
         [0067]    The field sprayer  60  further includes a central control unit  66  which sends and receives signals to and from the individual nozzle control unit  64  via an ISO bus line  68 . The central control unit  66  includes, for example, a navigation module and decides, based on the current position of the field sprayer  60 , which of the valves  10  are to be switched on and off. The corresponding commands are then sent to the individual nozzle control unit  64 , then, the commands are implemented by the control unit and transmitted to the valves  10 . If need be, the individual nozzle control unit  64  can also be integrated in the central control unit  66 . 
         [0068]    In  FIG. 9  is illustrated a diagrammatic equivalent circuit diagram of a valve  10  according to the invention. The valve  10  includes the valve control circuit  54  which is provided with the voltage converter  55 , wherein the supercap is coupled via the buck/boost control. The supercapacitor  52  and also the step motor  46  are connected to the voltage converter  55 . Furthermore, the voltage converter  55  is connected to an external energy supply having a supply voltage U v  which is provided, for example, by the electric system of a tractive vehicle. 
         [0069]    During normal operation the valve control circuit  54  receives a signal from the individual nozzle control unit  64 , cf.  FIG. 8 , and then applies the supply voltage U v  to the electric motor, here implemented as step motor  46 , in order to open or close the valve  10  thereby. Thus, it is possible to apply voltage to the electric motor while bypassing the buck/boost control of the voltage converter  55 , even though the diagrammatic illustration of  FIG. 9  does not reveal this. Therefore, during normal operation, the supercapacitor  52  is not used, instead the step motor  46  is driven exclusively by means of the external energy supply. 
         [0070]    The external supply voltage U v  is permanently monitored by means of the valve control circuit  54 . In case the valve control circuit  54  detects that the supply voltage U v  has decreased below a predefined value, then a failure of the external energy supply is assumed and the buck/boost converter is shifted to a boost operation mode, wherein the voltage provided by the supercapacitor  52  is converted into a higher voltage to be applied to the electric motor  46 . During said boost operation the valve  10  is then closed exclusively using the electric energy provided by the supercapacitor  52 . As explained above, according to country-specific directives, there can be enabling of the valve  10  provided in an emergency operation. 
         [0071]    In addition to adjusting the boost operation mode to move the valve  10  into an emergency position in case of failure of the external power supply, the valve control circuit  54  also monitors the output voltage and/or the charging condition of the supercapacitor  52 . In case the valve control circuit  54  detects that the charging condition of the supercapacitor  52  is below a predefined limit value, then the buck/boost control of the voltage converter  55  is shifted to a buck operation mode, wherein the supercapacitor  52  is then charged by means of the buck/boost control of the voltage converter  55  using the external energy supply mains. During said buck operation, the buck/boost converter  55  provides for a low power input during charging the supercapacitor  52 , so that the external energy supply will not be overloaded even in case that, for example, all supercapacitors  52  of the plurality of valves  10  are charged simultaneously. 
         [0072]      FIG. 10  shows a diagrammatic illustration of a field sprayer  80  according to another embodiment of the invention. Issuing from the individual nozzle control unit  64 , the valves  10  are mounted to the linkage of the field sprayer, each valve with a line to the left and to the right hand side. Configuration is then performed automatically starting from one side. In contrast to the field sprayer  60  according to  FIG. 8 , the bus line and/or the cable  82  do not have to be passed from one end of the linkage to the other, but the bus line extends starting from the middle of the linkage to the left and to the right hand side. The field sprayer  80  includes a central control unit  66  which is connected via a line  68  or also a plurality of lines to the individual nozzle control unit  64 . 
         [0073]    The illustration of  FIG. 11  shows a side view of a valve  100  for a valve assembly according to the invention. The valve  100  is provided with a valve housing  102  which is attached to a matching thread of a nozzle support  106  by means of a lock nut  104 . The nozzle support  106  is attached to a not illustrated feed pipe, as explained with reference to the nozzle support  12  in  FIG. 1 , and has a connector unit  108  for attaching a not illustrated spray nozzle. A flow communication between the feed pipe and the spray nozzle and the connector unit  108 , respectively, can be disabled or enabled by means of the valve  100 . 
         [0074]    The valve  100  has, similar to the valve  10  according to  FIG. 1 , a valve body, a valve seat, a step motor for moving the valve body, an electric energy storage device, and a valve control circuit. To avoid repetitions, merely those components of the valve  100  are explained that differ from the valve  10  according to  FIG. 1 . 
         [0075]    Specifically, the valve  100  is provided with two connector cables  110 ,  112 , wherein the first connector cable  110  is provided with an electric plug connector  114  and the second connector cable  112  is provided with a second plug connector  116 . The first plug connector  114  is a plug, the second plug connector  116  is a socket, wherein the two plug connectors  114 ,  116  are of matching design. However, the two plug connectors  114 ,  116  are not intended to be inserted one into the other. In fact, the first plug connector  114  of the valve  100  is to be connected to a second plug connector of an identical, adjacent valve. The second plug connector  116  of the valve  100  is to be connected to the first plug connector of a further, adjacent valve. A valve assembly obtained thereby will be further explained with reference to  FIG. 17 . The two connector cables  110 ,  112  are provided for standard nozzle distances of 50 cm and integral on the valve  100 . A feed through of the two connector cables  110 ,  112  into the valve housing  102  can thus be sealed reliably. Since the connector cables  110 ,  112  are already fixed to the valve housing  102 , mounting of the valve  100  is significantly facilitated and, especially, errors during installation or repair of a valve assembly according to the invention on a field sprayer are virtually excluded. Also, the expenditure for stock-keeping is reduced, since there is no need to keep separate connector cables ready for the valves  100 . Merely in the region of articulations on the linkage of a field sprayer or for connection of the valves to an individual valve control unit, cf.  FIG. 17 , there may be need for extension cables. 
         [0076]    The valve housing  102  has a bottom part  118  and a cover  120 . The bottom part  118  and the cover  120  are potted together, what will be explained further hereinafter. The cover  120  is provided with a ventilation hole  122  which allows pressure compensation between the interior of the housing  102  and the environment. Therein, the ventilation hole  122  is closed by an air-permeable but water-impermeable membrane. The membrane is not visible in the illustration of  FIG. 11 , since it is in a recessed position, in order to prevent damage of the membrane by external impact, for example, during blasting using a high-pressure cleaner. 
         [0077]    In the illustration of  FIG. 12  the valve  100  is illustrated in a front view. Apparent are the nozzle support  106  and the two-part housing  102  having the cover  120  and the bottom part  118 . The bottom part  118  overlaps the cover  120  in portions, wherein the cover  120  is potted with the housing  118  in this region, as already explained. The connector cables  112 ,  110  are led out of the bottom part  118 . In the illustration of  FIG. 12  the second electric plug connector  116  is visible from the front side. 
         [0078]    The illustration of  FIG. 13  shows a view of the valve  100  according to  FIG. 11  from above. In this view the cover  120  and an upper edge of the bottom part  118  are apparent, where the upper edge overlaps the cover  120  in portions, cf.  FIG. 12 . 
         [0079]    The illustration of  FIG. 14  shows a sectional view of the valve  100  in the position according to  FIG. 13 , that is, in a top view. The sectional plane extends through the drive shaft of an electric motor  124  in the valve housing  102 . The structures of the electric motor  124  and of the valve mechanism  126  do, however, not differ from the embodiment according to  FIGS. 1 to 7 , see especially  FIG. 5  and  FIG. 7 , so that a repeated explanation is omitted. 
         [0080]    Apparent in  FIG. 14  is the structure of the ventilation hole  122 . A through hole is closed by a membrane  128  in the interior of the housing, which membrane is, as explained above, air-permeable but water-impermeable. An insert  130  in the through hole is in a meander shape and, thereby, allows passage of air, but prevents that, for example, a water jet of a high-pressure cleaner may directly impact on the membrane  128 . Via the ventilation hole  122 , the interior of the valve housing  102  can be vented, and thus, for example, formation of condensed water in the interior of the housing  102  can also be prevented. 
         [0081]    A circuit board  132  is visible in the interior of the housing  102 , whereon electronic components are illustrated merely diagrammatically, which components are a voltage converter and a valve control circuit. As well arranged on the circuit board  132  is a supercapacitor  134 . 
         [0082]    The interior of the housing  102  is also apparent in the illustration of  FIG. 15 . The bottom part  118  is provided with a groove-type texture  136  on the top surface thereof, and the cover  120  engages in said texture. Said groove  136  is potted after inserting the cover  120 , so that the valve housing  102  is reliably sealed against external impacts, with the exception of the ventilation hole  122 . 
         [0083]    The circuit board  132  is arranged in the bottom part  118 . Apparent in  FIG. 15  is a feed through  138  for one of the connector cables. The circuit board  132  together with the electronic components arranged thereon and the supercapacitor  134  and also the through holes  138  for the connector cables are potted using a potting compound  140 . The potting compound  140  extends up to a plane  142 . Merely the electric motor  124  is disposed above the potting compound  140 . The complete electronics and also the supercapacitor  134  as an energy storage device and the cable feed throughs  138  are disposed within the potting compound  140 , and thereby are reliably water-tight. 
         [0084]    In the illustration of  FIG. 16  another sectional view in a lateral position is illustrated. 
         [0085]    The illustration of  FIG. 17  shows a valve assembly  150  according to the invention composed of a total of three valves  100 . The valve assembly  150  is illustrated merely in portions, for example, 48 valves can be mutually interconnected by the ways and means as illustrated in  FIG. 17 . Using the plug connector  114 , a first connector cable  110  of the middle valve  100  in  FIG. 17  is inserted into the plug connector  116  of the second connector cable  112  of the left hand valve  100  in  FIG. 17 . Using its plug connector  116 , the second connector cable  112  of the middle valve  100  is inserted into the plug connector  114  on the first connector cable  110  of the right hand valve  100  in  FIG. 17 . The second connector cable  112  of right hand valve  100  in  FIG. 17  is connected to an individual nozzle control unit  64 , which can be connected to a central control unit on a field sprayer, cf.  FIG. 10 . Connection to the individual nozzle control unit  64  is via the plug connector  116  on the second connector cable  112  of right hand valve  100  in  FIG. 17 . Evidently, the valve assembly  150  can be constructed in a very simple manner and errors during electric connection of the valves  100  can be virtually excluded. Even replacing of one of the valves  100  can be done in a very simple manner. During replacement of one of the valves  100  and during the first installation of the valve assembly  150 , there is an automatic configuration of the valves  100  using the individual nozzle control unit  64 . The valves  100  are connected by means of a bus line and communicate via a bus protocol.