Abstract:
A metering system for a row unit for individual dispensing of grains comprises metering devices having a chamber for carrying grains, whereby a defined pressure level in the chamber is higher than ambient pressure. At least two metering elements establish a border to the chamber, whereby the metering elements are arranged within the housing so that they can be turned and the metering elements consist of cut-outs arranged along a curved path for picking up grains. At least one grain dispensing area is intended, which is defined by the chamber and the metering elements. The grain dispensing area includes a seed inlet element for transporting separated grains to a seed metering pipe to dispense the separated grains into a furrow, whereby a pressure application device is arranged at the seed inlet element or the seed metering pipe, to produce an air stream for the acceleration of the grains.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims priority from German Application Nos. DE 10 2015 101 255.3 filed Jan. 28, 2015 and DE 10 2015 101 256.1 filed Jan. 28, 2015, the contents of which are incorporated herein by this reference. 
       FIELD 
       [0002]    The present invention relates to a metering system for a row unit of an agricultural machine for an individual dispensing of granular material with the characteristics of the independent claim  1 . 
       BACKGROUND 
       [0003]    A variety of procedures, methods or machines are known in agriculture for dispensing or distributing of seeds and fertilizer in granular form in a most even way on a farmland area. One kind of these machines is called a seed singulating machine. In the case of seed singulating machines, it is possible to single out grains by means of metering devices and to place these in regular intervals into a seed furrow. Generally, the seed furrow is produced by means of appropriate furrowing tools. In this way, almost all the seeds are provided with about the same growing space, which ensures a uniform development of the plants. 
         [0004]    In addition to the growing space, the selection of the best suited seeds for the respective location is also crucial for the development of the plants. For example, there are some kinds of seeds that are better suited for rather dry and others for moist soil conditions. Some kinds of seeds are also better suited for heavy clay-like soils and others for rather light sandy soils. But since the soil conditions can often be varied, in particular in the case of fields that cover a large area, it would be advantageous if the kinds of seeds could be adapted within the field according to the respective soil condition. 
         [0005]    A variety of approaches to solve this are known from prior art. U.S. Pat. No. 6,672,228 B1, for example, describes a metering system for a row unit, wherein the metering system consists of two metering devices. For example, by means of a carousel, it is possible to supply different kinds of seeds to the respective metering devices. After separating the seeds, the individual grains are placed in a seed pipe so that the seeds can be transported into the seed furrow. When there is a change of the seeds dispensing into the seed pipe from the first metering device to the second metering device, these can be respectively moved in an axial direction by means of a slider. The device is characterized in that when individual seed dispensing is performed in the first metering device, the second metering device does not perform any separation or vice versa, which means that only one respective metering device is active at a time. 
         [0006]    Although it is thus possible to dispense different kinds of seeds, the moving of the metering device and of the carousel makes a quick change between the two metering devices or between the different kinds of seeds impossible. At faster driving speeds and frequent changes of seeds, it is possible that there are inaccuracies in the seed dispensing due to the time that is necessary for changing of the metering devices. The design of the row unit with slider and carousel is also often very extensive and thus also correspondingly costly. Furthermore, there is a problem with the seed dispensing because it occurs in the seed pipe in a free fall. Due to vibrations and impacts which can occur in the row unit during driving in the field, it is possible that the seeds are misplaced within the seed pipe or that the seeds collide within the seed pipe. This can also result in an uneven grain dispensing. 
         [0007]    Another metering device by means of which seeds can be dispensed in a metered or individual manner is known from U.S. Pat. No. 7,765,943 B2. In this device, the seeds can be volumetrically metered by means of a rotary valve or it can be separated by means of a metering unit. The supply of the seeds is regulated by a slide, whereby either a volumetric metering or a separation of the seeds is performed, depending on the position of the slide. 
         [0008]    A further agricultural machine with two metering devices has been known through the US-based company “Kinze Manufacturing Inc.”. In their so-called Multi-Hybrid Planter 4900, two metering devices comprise one common seed dispensing area. The metering devices are operated by means of low pressure systems respectively. After the grains are dispensed from one metering unit, they are placed into the seed furrow by means of a free fall through a seed metering pipe. The switching between the metering devices or the kinds of seeds is performed, for example, by means of GPS-data. Yet, low pressure metering devices have the disadvantage that they are very susceptible to dirt. In particular, dirt particles can be sucked in by means of the low pressure in the metering device, which can lead to malfunctions. 
         [0009]    From WO 2014 113 803 A1, a further metering system for a row unit is known. This metering system can be supplied with at least two different kinds of seeds, whereby only one kind of seed can be dispensed with the respective metering device. However, this system has the disadvantage that a quick switching between the kinds of seeds is not possible because there is only one metering device. Rather, a respective waiting-time must be defined, in order to take into account the time that is required for the grains to reach from the central seed tank to the metering device. But such a system is very complex and it is also error-prone if the timings are not chosen correctly. 
         [0010]    Another metering system is known from WO 2014/205454 A1, which comprises two metering devices. The two metering devices are arranged with a distance between each other and both use the vacuum principle. It is thus possible that the seeds can be accommodated by the cut-outs of the metering elements. The seeds that are captured by the cut-outs can then subsequently fall into one common seed metering pipe or into two separate seed metering pipes by means of gravity. 
         [0011]    Other systems are also known from prior art, in which two streams of seeds are connected by means of a Y-piece, whereby these are generally metered volumetrically. Also, a connection of the streams of seeds is not yet synchronized, which means that single grain dispensing cannot be guaranteed. It is also already known that, for example, micro granules are added into a stream of individual grains. Up to now, a separated grain dispensing of these two compounds can also not be guaranteed in this case. Additionally, the stream of individual grains can possibly be affected, by means of which a sufficiently accurate seed dispensing can no longer be ensured. 
       SUMMARY 
       [0012]    It is the objective of the present invention to present a metering system for a row unit of an agricultural machine, which is arranged with at least two metering devices and/or metering units for an individual dispensing of the grains. The metering system should thereby be designed in such a way that a switching of the individual seeds dispensed from the at least one first to the at least one second metering device can be accomplished as quickly as possible. At the same time, a bouncing of the grains within the seed pipe should be prevented as much as possible. These objectives of the invention are achieved by means of the characteristics of the independent claim  1 . Characteristics of advantageous developments of the invention are derived from the dependent claims. To achieve the above-mentioned objectives, the present invention presents a metering system for a row unit of an agricultural machine, preferably in the form of a seed singulating machine. The row unit is connected to the agricultural machine by means of a frame, whereby the connection between the row unit and the frame is accomplished by means of a support device. The support device can be designed, for example, in the form of a rhomboid. 
         [0013]    The metering system consists of at least two metering devices, which can be mounted onto the row unit. Alternatively, the at least two metering devices can also be set at a distance to the row unit and can be arranged to the machine and/or to the frame of the machine instead. It is possible to supply the at least two metering devices with seeds from a seed reservoir via certain seed supply lines. Preferably at least two metering devices are supplied with different kinds of seeds, so that the seeds can be adapted to the different soils while driving on the field. 
         [0014]    The at least two metering devices consist of at least one chamber for receiving the grains for dispensing. Depending on the embodiment, the at least two metering devices can consist of one common chamber or of one respective chamber, whereby each one of the respective chambers is supplied with the seeds from the seed reservoir that are to be dispensed. If the metering devices consist of one common chamber, they are separated by means of a dividing element. The purpose of the dividing element is to prevent the mixing of the different kinds of seeds. Various elements can serve as dividers, preferably such that prevent the different kinds of seeds from being mixed but that still allow air to flow from one chamber into the next. 
         [0015]    The at least one chamber is further characterized by a defined pressure level that is higher than the ambient pressure. Thus, the at least one chamber is pressurized, which can be accomplished by means of a corresponding pressure application device, for example, in form of a high pressure blower. It would also be possible to apply the opposite side of the chamber with a lower pressure by means of a vacuum blower. In any case, the at least one chamber or the two chambers should be designed in such a way that the pressure level P 1  in the chamber is greater than the pressure level P 2 , which prevails in the area that is opposite of the chamber. 
         [0016]    So if a pressure application device is mentioned in connection with the present description, it refers to any kind of high pressure or vacuum device, which can produce the desired high or low pressure within the chambers. Whether this high pressure or vacuum is produced by means of a blower or any other means is not of primary importance in the present context. 
         [0017]    The metering system according to the invention further consists of at least two metering elements. The at least two metering elements are arranged in such a way within the housing of the at least two metering devices that they can be turned, or that the at least two metering elements can rotate around a respective rotational axis. The at least two metering elements can be preferably designed in a disc- and/or drum- and/or plate-like manner. It is also possible that the at least two metering devices are arranged with different metering elements. The at least two metering elements are equipped with cut-outs, which are arranged along a curved path at regular intervals. These cut-outs can be designed in the shape of bore holes and/or elongated holes and/or slots, or the like, so that they can receive individual grains which were supplied to the at least two respective metering devices. The cut-outs can further be arranged in different sizes and contours which are adapted to or chosen according to the respective materials that are to be dispensed. 
         [0018]    A border for at least one of the chambers is formed by the at least two metering elements, which means that the metering element is the border of the respective chambers. The metering system further consists of at least one grain dispensing area which is defined by the at least one chamber and by the at least two metering elements. A respective connection to an area with a lower pressure level P 2  than that of the chambers is achieved by means of the cut-outs. Thus, a pressure difference occurs in the cut-outs of the at least two metering elements. The pressure difference assists the receiving of grains by the respective cut-outs. The grains which are in the chamber can thus be picked up by the respective cut-outs of a metering element and can be transported to the at least one seed dispensing area by the rotation of the metering element. A pressure difference at the cut-outs can subsequently be interrupted by means of appropriate interrupting elements, whereby the grains are then pushed out of the cut-outs into the seed inlet element or into the seed metering pipe. 
         [0019]    While only one grain dispensing area is formed for the metering system according to the invention with one common chamber, two respective grain dispensing areas are formed for the metering system with two chambers. 
         [0020]    A separating device and/or a separating element can preferably be arranged between the grain pick up and the grain dispensing area. The separating device and/or the separating element ensures that excess grains which are sticking to the cut-outs can be expelled. This separating device can be designed in a variety of ways, whereby this one corresponds to the preferred embodiment as it is known from EP 1 928 223 B1, whereby also other separating devices would be possible. 
         [0021]    The present object is characterized in that at least one grain dispensing area is arranged at at least one seed inlet element for receiving and transporting the separated grains to a seed metering pipe in order to dispense the separated grains into a seed furrow in the soil which was prepared by means of soil cultivation tools. Hereby, the at least one seed inlet element and/or the seed metering pipe is arranged at a pressure application device by means of which an air stream for the acceleration of the grains can be produced. 
         [0022]    If the metering system according to the invention forms at least one common chamber and thus also one common grain dispensing area, then only one seed inlet element is necessary. This seed inlet element is defined by the upper section of the seed metering pipe. 
         [0023]    For a metering system with one common chamber and thus with one common seed dispensing area this particularly means the following: 
         [0024]    The invention intends that the at least two metering devices consist of one common seed dispensing area, which means that different kinds of seeds are separated by the respective metering devices and then transported to the common seed dispensing area. Afterwards, the separated material is led into the seed metering pipe, whereby the upper section of the seed metering pipe is defined as the seed inlet element. The seed dispensing can be accomplished by means of only one respective metering device, or also by means of two metering devices. The advantage of such an arrangement is that it is possible to quickly switch between the metering devices or between the kinds of seeds. Furthermore, the row unit or the metering system can be designed in a simple way, since no further tools are needed for the switching or changing of the kinds of seeds. A switching can be accomplished, for example, by means of a turning off of the motor of one of the metering devices. The common seed dispensing area can be pressurized with a defined pressure level that is higher than the ambient pressure, for example, in form of some kind of high pressure. The defined pressure level can be produced, for example, by means of a separate connector or by a connection with the chambers. By means of this defined pressure level, an air flow is produced within the seed metering pipe, by means of which the grains are accelerated after being released from the metering element and after being dispensed into the seed metering pipe. This largely prevents a bouncing of the grains within the seed metering pipe or at least reduces it to such an extent that it does not have any, or at least only an insignificant influence on the dispensing accuracy. 
         [0025]    If the metering system according to the invention forms two chambers and thus also two seed dispensing areas, two corresponding seed inlet elements are necessary. By means of a corresponding embodiment it is possible to join the two seed inlet elements into one seed metering pipe. 
         [0026]    To accomplish this, the invention intends that the at least two metering devices and/or the at least two metering elements are arranged with some distance between each other and that they are possibly not mounted directly on the row unit. The metering devices consist of one respective seed dispensing area with a seed metering pipe or with a seed inlet element that is arranged at it, which means that each seed dispensing area is arranged with one respective seed inlet element. The two seed inlet elements are hereby united into one common seed metering pipe within their further course. A Y-shaped element can preferably be used as connecting piece. Other connecting pieces would also be possible, whereby their respective shape should be designed in such a way that the at least two seed inlet elements are united into a common seed metering pipe. The joining into one seed metering pipe can also be performed at some distance from the other. The seed inlet elements can also be made with different lengths. The seed metering pipe can also be designed in such a way that it forms a seed inlet element and that at least one second seed inlet element is connected to it, by means of which only one additional pipe would be needed. This connection can also be made in a Y-shape and can be described as connecting piece. It is thus possible that the separated grains can be dispensed via one common seed metering pipe into the furrow in the field that was produced by the soil cultivation tools. 
         [0027]    The connection can be done directly after the metering devices or at some distance to these. If, for example, the metering devices are arranged with some distance between the row units, a connection could be done at the row unit. The advantage of such an arrangement is that it is possible to quickly switch between the metering devices or the kinds of seeds. Furthermore, the row unit or the metering system according to the invention can be designed in a simple way, since no further tools are needed for the switching or changing of the kinds of seeds. As in the case with the embodiment with one common chamber or with one common seed dispensing area, a quick switching can be performed by turning off of the motor of the respective metering element. 
         [0028]    Furthermore, it is possible that one seed dispensing area is pressurized by a defined pressure level that is higher than the ambient pressure, for example, in the form of a high pressure blower. Comparable to the embodiment with one common chamber, the defined pressure level that is higher than the ambient pressure can be produced by means of a separate connector or by a connection of the chambers. By means of this defined pressure level, an air flow is produced within the seed metering pipe, by means of which the grains are accelerated after being released from the metering element and after being dispensed into the seed metering pipe. Furthermore, this largely prevents a bouncing of the grains within the seed metering pipe or at least reduces it to such an extent that it does not have any or at least only an insignificant influence on the dispensing accuracy. 
         [0029]    It is also possible that the at least two metering devices are designed in the form of vacuum metering devices, in which the pressure level P 2  is a vacuum and the pressure level P 1  is greater than the pressure level P 2 . In order that the grains can also be accelerated within the seed metering pipe in this case, it is possible that the common seed dispensing area or at least one seed dispensing area from the two seed dispensing areas is equipped with a separate air supply. It would also be possible that the seed metering pipe or the at least one seed inlet element is arranged with a pressure application device. For example, this can be accomplished in the form of a Venturi or a ring nozzle, by means of which the grains are accelerated within the seed metering pipe. The air flow or the air pressure can preferably be regulated, by means of which the speed of the grains within the seed metering pipe can be influenced. 
         [0030]    The invention further intends that the air flow within the seed metering pipe can be adapted. To accomplish this, different solutions are possible. For one, the seed dispensing area can be actively connected to at least one chamber, so that the pressure level in the metering device on the side facing towards the grains is almost equal. It would also be possible that the seed dispensing area is connected to the pressure generator or to the air supply pipe of the chambers by means of a separate pressure connection. It is thus possible that there are different pressure levels between the chamber and the at least one seed dispensing area or the one seed dispensing area. The additional connection may also consist of an adjusting element, by means of which the air stream or the air pressure within the seed metering pipe can be adjusted. 
         [0031]    In one preferred embodiment, at least one seed dispensing area is connected to a chamber or the seed inlet is arranged within the chamber of the metering device, by means of which the pressure in the chamber is also used to produce the air stream within the seed metering pipe. 
         [0032]    The cut-outs in the metering elements are arranged along a circular or curved path, whereby the seed metering pipe or the seed inlet element is arranged at least partially in a tangential way towards at least one of the curved paths. The seed metering pipe consists of one seed inlet and one seed outlet, whereby these preferably feature a round cross section. But other cross sections would also be possible, for example, square or rectangular shapes. The cross section of the seed metering pipe can also change within its course. It can become bigger or smaller. It is thereby possible to change the speed of the grains within the seed metering pipe. The seed metering pipe can also feature different radii, by means of which the grains can be led along the seed metering pipe, which can prevent a bouncing of the grains. In the present object, the seed metering pipe is curved in a sickle- and/or bow-shape at least in some sections. 
         [0033]    In the case of one common chamber or one common seed dispensing area, the invention further intends that the seed metering pipe or the seed inlet is designed in such a way that it enlarges within the seed dispensing area and then narrows down in its further course. The advantage of this is that there is sufficient space for the grains in the dispensing area to be securely received by the seed metering pipe. In the center of the widened area, it is possible, for example, to arrange for an intermediate piece which divides the seed metering pipe. In this way it is possible to achieve a suction effect by means of the air stream that occurs in the area of the grain dispensing, which ensures a smooth grain dispensing. 
         [0034]    It can further be intended that the seed inlet is aligned at the disc in such a way that the disc touches and slides on it. In the case of one common chamber or of one common seed dispensing area, this would mean that the distance of the at least two metering elements towards each other at the seed dispensing area is lesser than the diameter or the cross section of the seed metering pipe or of the seed inlet. In both embodiments it would also be possible that the seed metering pipe features a round cross section, which would then be interrupted on the side that faces towards the disc. The grain dispensing of the metering element into the seed metering pipe can thus be greatly improved, since possibly interfering edges, which would otherwise be present between the seed metering pipe and the metering element are omitted in this way. 
         [0035]    In the case of two chambers or of two seed dispensing areas, it would also be possible that the metering element does not touch and slide on the seed inlet element. But in order to prevent any edges of the seed inlet element at the metering element in such an arrangement, it can be aligned at an angle. It would also be possible that the seed inlet element is designed with a beveled edge and thus the thickness of the edge would also be reduced. 
         [0036]    As mentioned earlier, the two metering devices and/or the at least two metering elements can consist of one common housing or can be arranged within one common housing. Thus, the two metering elements would be integrated in one constructional unit. The chambers of the metering device are separated by a dividing wall in this case in order to prevent a mixing of the different kinds of seeds. The kinds of seeds are stored in a seed reservoir and can be supplied to the chambers at any time. The dividing wall is preferably designed in such a way that air can pass through it. Thus, only one central air supply is needed for the at least two metering devices, so that the piping effort of the machine can be reduced. 
         [0037]    In the course of the seed metering pipe and/or of the at least one seed inlet element, at least one sensor element can be arranged for, by means of which the grain dispensing or the grain transport can be monitored. The at least one sensor element is preferably designed as an optical sensor element. The derived values of the at least one sensor or of the sensors can among others be used to adjust the speed of the metering elements accordingly and thus it is possible to improve the dispensing accuracy. In like manner, many different other applications are possible as well. 
         [0038]    The at least two metering devices may include many different embodiments. Thus, metering devices which work according to the high pressure and/or the vacuum principle or which feature a combination of the high pressure and the vacuum principle are conceivable. Mechanically working metering devices would also be possible, in which the grain separation is performed, for example, by the so-called “finger pick up”. Also centrifugal-based metering devices are conceivable or possible, in which the acceleration of the grains can be achieved by the rotation speed of the metering element. 
         [0039]    The at least two metering devices can work according to the same principle and may consist of basically the same setup. It is thus possible that the metering devices feature a respective first area in which the grains are picked up by means of a pressure difference from the cut-outs in the metering element. The at least two metering devices further consist of a second area in which a transport of the grains towards the seed dispensing area is performed by means of the metering element. To accomplish this, a rotation of the metering element by means of some kind of drive is necessary. This drive for the metering element can be a motor, an electric or hydraulic drive, etc. This area is equipped with a separating device and/or with separating elements. One of the purposes of the separating device or of the separating elements is to expel excess grains from the cut-outs. This is done in such a way that only one respective grain remains in the cut-outs. The at least two metering devices feature a third area, which is arranged with at least one interrupting element for the interruption of the pressure difference at the cut-outs. The at least one interrupting element can be designed, for example, in the form of a roller. An interruption of the pressure difference has the effect, that the grains, which are located in the cut-outs, fall into the seed metering pipe by means of the seed inlet element. Alternatively, it is also possible that an air blast pushes the grains out of the cut-outs. A fourth area is characterized in that the grains and/or the air stream are redirected from a circular path and from a perpendicular air stream into a guided transporting direction and a guided air stream in the direction of the seed metering pipe. Furthermore, there is a fifth area that is arranged with a seed inlet of the seed metering pipe and with a section of the seed metering pipe for transporting the grains towards a seed furrow. 
         [0040]    In the case of one common chamber, at least two of the third, fourth and fifth areas or in the case of two chambers, the third, fourth and fifth area, can hereby form the common seed dispensing area. For example, the areas thereby encompass an area that amounts to at least 75°. But bigger or smaller angles would also be possible. 
         [0041]    The at least two metering devices can be arranged facing towards each other in a mirror image-inverted way and/or twisted about their respective axes, or preferably the axis of the seed metering pipe and/or parallel relative to each other and/or at an angle and/or in a combination thereof. The sides with the chambers are preferably facing each other. 
         [0042]    The invention intends that at least one of the at least two metering devices or at least one metering element is arranged with a motor drive. Thus at least one of the at least two metering devices or at least one metering element can be powered with a motor drive. Electrically, hydraulically or mechanically working drives would also be conceivable. It is further possible that transmission devices are used to transmit the motion of the at least one powered metering device to the second metering device. Clutches or belts or transmissions or gear wheels can be preferably used as transmission devices. It would also be possible that the at least two metering devices are arranged with a respective separate drive, which means that each metering device can be powered by means of a separate drive. This would have the advantage that the metering devices could be operated at different speeds depending on the kind of seeds used. Additional aids, such as transmission gear boxes or the like would not be necessary in this case. 
         [0043]    In order to create an energy efficient row unit or an energy efficient metering system, it would be necessary that the motor drives of the metering elements are coupled in such a way that the braking energy of the one first drive can be used as starting energy for the second drive and vice versa. In the same manner, the motion of one metering device could also be used as energy producer for the other metering device. 
         [0044]    The at least two metering devices are coupled in such a way that an individual grain dispensing can be performed into the seed inlet element or into the seed metering pipe by means of at least one metering device, respectively. The speeds of the at least two metering elements are adapted relative to each other in such a way that when the grain dispensing is switched from one metering element to the other, the grain dispensing is synchronized, which means that the desired spacing of the grains can also be maintained during a switching process. In order to improve this ability, the at least two metering devices or the cut-outs of the at least two metering elements can be filled with grains until directly before the interrupting element or up to the seed dispensing area. But there is only one grain dispensing or one interruption of the pressure difference at one metering device, respectively, which means that the interrupting element pushes the grains only out of the cut-outs of one metering element, respectively. In like manner, it is possible that for a simultaneous grain dispensing of the at least two metering elements, respectively, these are synchronized in such a way that the grains are dispensed into the seed inlet element alternately. Thus, in the case of a simultaneous grain dispensing, the interrupting elements of both chambers also have to be adapted relative to each other, which would mean that the interrupting elements would have to produce a respectively alternate interruption of the pressure difference. For example, this can be accomplished by means of a corresponding sensor arrangement in connection with a control device. 
         [0045]    The desired switching between the kinds of seeds or between the at least two metering devices is preferably done my means of GPS-data or by means of any other satellite system or position detecting system. The switching positions could also be stored in a computer unit, and a switching could be accomplished in this way. A manual switching by an operator would likewise be possible. The switching between the at least two metering devices is necessary in order that it is possible to switch between the different kinds of seeds. 
         [0046]    In order to prevent a possible collision of the grains after a switching of the grain dispensing from one metering device to the other, it is possible that the metering elements of the at least two metering devices are turning in the opposite direction of the respective other one, at least for a certain time. This means that the metering element by means of which a grain dispensing is to be done would turn, for example, clockwise, while the other metering element, which should no longer dispense any grains, would at least for a short time turn counter clockwise. A collision of the grains can be prevented in this way. Afterwards, a metering element could be fully deactivated by means of turning off the motor. Due to the working together of the two metering elements, different kinds of grains can be dispensed while driving on the field. 
         [0047]    Furthermore, the at least two metering devices can be designed in such a way that the sides with the respectively lower pressure level are connected to the respective chambers of the other metering device and/or to the air supply. It would also be possible that the areas with a lower pressure level are in turn connected to a vacuum area of the pressure application device. It is further possible that the sides of the at least two metering elements with the lower pressure level, or the sides of the at least two metering elements that are facing away from the grains, are equipped with some means so that the cut-outs in the areas where no grains are to be transported can be covered, or that the pressure difference can be stopped or reduced in these areas. Such areas could be located, for example, between the grain dispensing and the grain pick up. But it is also possible that other parts could be covered, for example, in the case when no grains should be transported or separated. 
         [0048]    For example, the supply of the at least two metering devices with seeds can be done by means of a pneumatic conveyor system. An additional container for receiving and storing grains can also be arranged for each metering device. It would likewise be conceivable that at least one metering device is supplied by a pneumatic conveyor system and the second metering device is supplied by an additional container. This would be advantageous if, for example, much more would be needed from one kind of seeds than from the other kind, so that the seeds with the heavy consumption would be supplied by a pneumatic conveyor system, wherein these seeds are provided in a big tank that is attached to the machine. The activation of the at least two metering devices could likewise be performed in such a way that when an interruption occurs during the supply of the seeds for the first metering device, the one second metering device will be automatically activated. Furthermore, the air supply for the pneumatic conveyor system could also be used to support the defined pressure level in the chamber. 
         [0049]    In addition to the metering system, which is arranged at it, the row unit also consists of furrowing tools, preferably two coulters which are aligned towards each other at an angle. They form a so-called double disc pair. But it would also be possible to use the present invention with a so-called single disc coulter or with a tine coulter. The seed metering pipe is arranged, for example, between the two or next to the one disc, whereby the seed outlet on the other hand is arranged within or directly next to the at least one outer contour of the at least one disc. A catching element is further arranged directly behind the coulters or the tines or it reaches into these and/or it is arranged next to it and it is designed, for example, in the shape of a roller. It is arranged in such a way that the stream of grains and/or the air stream is basically directed tangentially with regards to the outer contour or the catching element. 
         [0050]    A change of direction of the grains occurs in the seed dispensing area, which means that the grains are redirected from a circular motion along a curved path into a mainly tangential and/or straight direction with regards to the curved path. This is accomplished by means of a change of direction of the air streams which are directed as respective perpendicular air streams towards the cut-outs inside the chambers, into a guided air stream. This air stream is directed along the seed metering pipe and/or along the guiding element that is arranged at the at least one seed dispensing area. Additionally, the guiding element features a guiding path which at least partially follows the same direction as the at least one seed inlet element. A good air stream can be produced in this way, whereby the air stream can also be produced, for example, by an active connection with at least one chamber. But a separate air supply would also be possible. 
         [0051]    Furthermore, the curved path, the guiding element and the seed metering element are arranged in such a way that any element, such as grains, dirt particles or the like, which reach the grain dispensing area, are forcibly dispensed via the guiding path into the seed metering element. This reduces the susceptibleness to dirt tremendously. In order to further improve the susceptibleness to dirt, a push-out roller or a push-out element can be arranged for the at least two metering elements or for the seed dispensing areas on the respective side that is facing away from the grains. By means of these, any grains and/or dirt particles that possibly remain in the cut-outs after the grain dispensing, can be removed and dispensed into the seed metering pipe. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0052]    Subsequently, the invention and its advantages will be further explained by means of the embodiments and the attached figures. The ratio of the sizes of the individual elements in relation to each other in the figures does not always correspond to the real size ratios since some shapes have been simplified and other shapes have been enlarged in relation to other elements for better illustration. 
           [0053]      FIG. 1  depicts a schematic side view of a row unit of an agricultural machine according to a first embodiment. 
           [0054]      FIG. 2  depicts a perspective view of an embodiment of the metering system according to the invention. 
           [0055]      FIG. 3  depicts a cross sectional side view of one embodiment of the metering system according to  FIG. 2 . 
           [0056]      FIG. 4  depicts a cross sectional top view of the metering system according to  FIG. 2 . 
           [0057]      FIG. 5  depicts a cross sectional front view of the metering system according to  FIG. 2 . 
           [0058]      FIG. 6A  depicts an angled arrangement of the metering elements towards each other in a simplified perspective view and  FIG. 6B  is a simplified top view thereof. 
           [0059]      FIG. 7  depicts a schematic side view of a row unit of the agricultural machine according to a second embodiment. 
           [0060]      FIG. 8  depicts a side view of an embodiment of the metering system according to the invention according to  FIG. 7 . 
           [0061]      FIG. 9  depicts a front view of the metering system according to  FIG. 7  in a cross section. 
           [0062]      FIG. 10  depicts a front view of the metering system according to  FIG. 7  in a cross section, wherein the metering elements touch and slide on the seed inlet elements. 
       
    
    
     DETAILED DESCRIPTION 
       [0063]    For elements of the invention that are the same or that function in the same way, identical reference numbers will be used in the  FIGS. 1 to 10 . Additionally, for a better overview, only reference numbers which are needed for the description of the respective figure are depicted in the individual figures. The depicted embodiments only represent illustrations of how the metering system according to the invention can be designed, and do not represent any final limitation. 
         [0064]      FIG. 1  depicts a side view of a row unit  10  of an agricultural machine in the form of a seed singulating machine. Such machines are used in agriculture for an individual dispensing of granular grains such as seeds and/or fertilizer. Row unit  10  is connected to frame  14  of the machine via a support device  12  in form of a rhomboid. Row unit  10  further consists of furrowing tools, which form in particular two coulters  16  that are aligned at an angle towards each other. A catching element  18  is arranged subordinately to the coulters  16  or in such a way that it reaches in between these. It is designed as a roller that should catch and slow down the grains that are to be dispensed after they have been placed in the furrow. At the rear end of the row unit  10 , two rollers  20  are arranged as furrow closing tools. 
         [0065]    A metering system  22  is arranged at row unit  10  in the embodiment, which consists of two metering devices  24 ,  26 . Metering system  22  is part of row unit  10  in the depicted illustration. But it would also be possible that it could be set at a distance from the row unit  10  and that it could be arranged, for example, at the frame of the machine. A seed metering pipe  28  is arranged at the lower end of metering system  22 , by means of which the grains, which were separated by the metering devices  24 ,  26 , can be transported into the seed furrow. The section of the seed metering pipe  28  that reaches into the metering elements can also be described as seed inlet element  27 . 
         [0066]    Metering system  22  according to the invention is depicted in a perspective view in  FIG. 2 . Metering system  22  is made up of a front and a rear metering device  24 ,  26 . In the depicted embodiment of  FIG. 2 , the two metering devices  24 ,  26  are constructed in an identical way. But metering devices  24 ,  26  are arranged facing towards each other in way that they are twisted about their respective axes. Metering devices  24 ,  26  consist of a respective multipart housing  30 , which may comprise, for example, a front and a rear housing part. The housing parts are connected by means of hinges  32  and/or locking elements. Housing  30  features a respective air inlet  38 , by means of which its metering devices  24 ,  26  can be supplied with the appropriate pressure level. The metering devices  24 ,  26  are supplied with material that needs to be dispensed in form of grains via a seed supply line  34  or via a not depicted seed reservoir  36 . The seeds are preferably different kinds of materials. The supply of the metering devices  24 ,  26  can be accomplished, for example, by means of a container or by means of a pneumatic conveyor system that is attached to the row unit. In order to be able to vary the amount of seeds that will be transported, additional sliders  40  are arranged on the metering devices  24 ,  26 . Slider  40  can be used to open or close the seed reservoir  36  in gradual stages. Each metering devices  24 ,  26  is powered by a drive motor  42 . Electrical or hydraulical versions or motor drives can be used. 
         [0067]      FIGS. 3, 4 and 5  depict different respective views of the combination of the two metering devices  24 ,  26  according to  FIG. 2 . Parts of housing  30  or parts that are not needed for the description are accordingly not shown or depicted in cross section for a better understanding. 
         [0068]    Metering system  22  consists of two metering devices  24 ,  26 . They are constructed in the same manner, but are arranged facing towards each other in way that they are twisted about their respective axes. The metering devices  24 ,  26  consist of one respective chamber or of one common chamber  44 , which is supplied with the seeds that are to be dispensed or with the corresponding grains  46 . In an embodiment with one common chamber  44 , they are divided by means of a dividing element. This ensures that the different kinds of seeds will not be mixed. Preferably, dividing elements are used which allow air to pass through. 
         [0069]    Chambers  44  or the common chamber  44  is pressurized with a pressure level P 1 , which is produced, for example, by a pressure application device that is attached to the machine. For example, it is possible to use high pressure blowers for this purpose. 
         [0070]    A metering element  48  is rotating within metering devices  24 ,  26 , which is designed in the form of a disc in the present embodiment. Cut-outs  52  are arranged in regular intervals along at least one curved path  50  on the respective metering element  48 . The cut-outs  52  are made in the form of bore holes in the present example. But it is also possible that the cut-outs  42  are designed as elongated holes and/or slots, or the like. Furthermore, the cut-outs  52  in the metering devices  24 ,  26  can feature different sizes and contours which can be adapted to or chosen according to the grain sizes that are to be dispensed. Metering element  48  forms a respective border to chamber  44 , whereby a connection to the area with a lower pressure level P 2  is created by means of the cut-outs  52 . A pressure difference is thus created at each one of the cut-outs  52 . As a result, grains  46  can be received in each cut-out  52 . The grains which were picked up by the cut-outs  52  can be transported to one seed dispensing area  54  by the rotation of the metering element  48 . 
         [0071]    A separating device or a separating element  56  is arranged between the seed reservoir  36  and the seed dispensing area  54 . These correspond to the object of EP 1 928 223 B1, as was already mentioned earlier. But it would also be possible to use a variety of other separating elements  56 . By means of these separating devices  56 , excess grains  46  and grains which are sticking to the cut-outs  52  can be expelled, so that only one respective grain remains in the cut-outs  52 . 
         [0072]    The metering devices  22  consist of one common seed dispensing area  54 , which means that different kinds of seeds are separated by the metering devices  24 ;  26 , respectively. The grains which are held by the cut-outs are transported to the common seed dispensing area  54  by the rotation of the metering elements  48 . By means of an interruption of the pressure difference by interrupting elements  58 , the grains are pushed into a seed metering pipe  28  that is arranged at the seed dispensing area  54  via a seed inlet element  27 . For example, the interrupting elements  58  can be designed as a roller. The seed inlet element  27  defines a section of the seed metering pipe  28 , which merges into the common seed dispensing area  54 . 
         [0073]    Just like the chambers  44 , seed dispensing area  54  can also be pressurized. In the present embodiment, this is accomplished by means of an active connection between the chambers  44  and the seed dispensing area  54 , which means that no further air supply is needed and the pressure level in the chambers  44  and in the seed dispensing area  54  is basically the same. 
         [0074]    By means of the air pressure within seed dispensing area  54 , an air stream is created due to the lower pressure in the seed metering pipe  28 . After the grains  46  are released from the metering element  48 , they are picked up by the air stream, by means of which the grains  46  are actively accelerated within the seed metering pipe  28  by a seed inlet element  27 . This largely prevents a bouncing of the grains  46  within the seed metering pipe  28  or at least reduces it to such an extent that it does not have any or at least only an insignificant influence on the dispensing accuracy. 
         [0075]    The seed metering pipe  28  or the seed inlet  60  is designed in such a way that it enlarges within the seed dispensing area  54  and then narrows down in its further course. The advantage of this is that there is sufficient space for the grains  46  in the seed dispensing area  54  to be securely received by the seed metering pipe  28 . 
         [0076]    A change of direction of the grains  44  occurs in the seed dispensing area  54  from a circular motion along a curved path  50  into a mainly tangential and/or straight direction with regards to the curved path  50 . This is accomplished via a redirecting of the air streams, which are directed as respective perpendicular air streams  68  towards the cut-outs  52  inside the chambers  44  into a guided air stream  66 , which is guided along the seed metering pipe  28  and/or the guiding element  64  that is arranged to the seed dispensing area  54 . Additionally, the guiding element  64  features a guiding path  70 , which follows at least partially the same direction as the seed metering pipe  28 . A guided air stream  66  can thus be produced. The air stream can also be produced by an active connection with at least one chamber  44 . But a separate air supply would also be possible. 
         [0077]    Furthermore, the curved path  50 , the guiding element  64  and the seed metering pipe  28  are arranged in such a way that any element, such as grains  44 , dirt particles or the like, which reach the grain dispensing area  54 , are forcibly dispensed via the guiding path into the seed metering pipe  28 . This reduces the susceptibility to dirt tremendously. In order to further improve this, a push-out roller  58  is arranged for the metering elements  48  or for the seed dispensing areas  54  on the respective side that is facing away from the grains  46 . In this way, any grains  46  and/or dirt particles that possibly remain in the cut-outs  52  after the grain dispensing, can be removed and dispensed into the seed metering pipe  28  via the seed inlet element  27 . 
         [0078]    In the embodiment of  FIGS. 3 to 5 , only one respective grain dispensing is performed by only one metering device  24 ,  26 . But the other metering device  24 ,  26  is filled with grains  44  until directly before the seed dispensing area  54  or up to the interrupting element. This enables a quick switching between the metering devices  24 ,  26 , so that the metering devices  24 ,  26  do not need any waiting time before they can dispense the grain. 
         [0079]    In  FIGS. 1 to 5 , the metering devices  24 ,  26  are twisted about their respective axes and arranged in parallel with an offset between each other. In  FIGS. 6A and 6B , another possible arrangement of the metering devices  24 ,  26  or of the metering elements  48  is made evident in a perspective view and in a top view. 
         [0080]    The metering elements  48  are arranged at a respective angle towards each other. A seed metering pipe  28 , which consists of a seed inlet  60  merges towards the lower right side. The upper section of the seed metering pipe  28  defines the seed inlet element  27 . The metering elements  48  directly touch and slide on the respective seed inlet  60  or the seed metering pipe  28 . This means that the distance of the metering elements  48  towards each other at the seed dispensing area  54  is less than the diameter of the seed metering pipe  28 . As a result, the respective bow-shaped contour  62  of the seed metering pipe  28  is interrupted on the side that is facing towards the metering elements  48 . The advantage of this is that there are no edges of the seed metering pipe  28  that touch the metering element  48 . This leads to an improvement of the grain dispensing. 
         [0081]      FIG. 7  also depicts a side view of an embodiment of a row unit  10  according to a second design form. This design form also consists of metering system  22 . While one of the two metering systems is a direct part of row unit  10 , the other one is intended to be mounted onto frame  14 . One respective seed inlet element  27  is assigned to both metering devices  24 ,  26 . The two seed inlet elements  27  can be connected to one seed metering pipe  28  by means of a connecting piece  29 . The connecting piece  29  is designed in a Y-shape. But a variety of other connecting pieces or connecting possibilities would also be conceivable. But in any case, the connecting pieces are designed in such a way that the at least two seed inlet elements  27  are joined into a common seed metering pipe  28 . The joining of the respective seed inlet elements  27  is done at row unit  10 , whereby other locations would also be possible or conceivable, in particular directly after the metering devices  24 ,  26 . The advantage of such a joining is that only one respective seed metering pipe  28  has to be placed at the row units  10  and not two seed inlet elements  27 . 
         [0082]    Metering system  22  is depicted in a side view in  FIG. 8 . Metering system  22  is made up of a front and a rear metering device  24 ;  26 . In the depicted embodiment of  FIG. 8 , the two metering devices  24 ,  26  are constructed in an identical way. But they are arranged towards each other in way that they are twisted around their respective axes. Metering devices  24 ;  26  consist of a respective multipart housing  30 , which may, for example, comprise a front and a rear housing part. The housing parts are connected by means of hinges  32  and/or locking elements. Housing  30  features a respective air inlet  38 , so that the metering devices  24 ,  26  can be supplied with the appropriate pressure level. The metering devices  24 ,  26  are supplied with material that needs to be dispensed in form of grains via a seed supply line  34  or via a seed reservoir  36  which is not depicted. The materials are preferably of different kinds. The supply of the metering devices  24 ,  26  can be accomplished, for example, by means of a container or by means of a pneumatic conveyor system that is attached to the row unit. In order to be able to vary the amount of seeds that will be transported, additional sliders  40  are arranged on the metering devices  24 ,  26 . Sliders  40  can be used to open or close the seed reservoir  36  in gradual stages. Each metering device  24 ,  26  is powered by a drive motor  42 . This can be a mechanical, an electrical or hydraulic drive, etc. 
         [0083]      FIG. 9  depicts the arrangement of the two metering devices  24 ,  26  in a frontal cross section. Parts of housing  30  or parts that are not needed for the description are accordingly not shown or depicted in cross section for a better understanding. 
         [0084]    Metering system  22  consists of two metering devices  24 ,  26 . In the depicted embodiment, the two metering devices  24 ,  26  are constructed mainly in an identical way. Furthermore, the metering devices  24 ,  26  are arranged towards each other in way that they are twisted about their axes or about the axis of the seed metering pipe  28 . The metering devices  24 ,  26  each consist of one respective chamber  44 . Each chamber  44  can be supplied with seeds that are to be dispensed or with corresponding grains  46 . 
         [0085]    Chambers  44  are pressurized with a respective pressure level P 1 , which is produced, for example, by a pressure application device in form of a high pressure or vacuum blower that is attached to the machine. 
         [0086]    A metering element  48  is rotating within each of the metering devices  24 ,  26 , which are designed in the form of a disc in the present embodiment. The respective metering element  48  consists of cut-outs  52  that are arranged in regular intervals along at least one curved path  50 . The cut-outs  52  are made in form of bore holes. But it is also possible that the cut-outs are designed as elongated holes and/or slots or the like. Furthermore, the cut-outs  52  in the metering devices  24 ,  26  can feature different sizes and contours which can be adapted to or chosen according to the grain sizes that are to be dispensed. Metering elements  48  form a border to chamber  44 , respectively. A respective connection to an area with a lower pressure level P 2  is achieved by means of the cut-outs  52 . A pressure difference is thus created at each one of the cut-outs  52 . Among other things, the pressure difference assists the receiving of grains by the respective cut-outs  52 . The picked up grains can subsequently be transported to one seed dispensing area  54  by the rotation of the metering elements  48 . 
         [0087]    The metering devices  22  consist of one respective seed dispensing area  54 , which means that different kinds of seeds are separated by the respective metering devices  24 ,  26  and then transported to the seed dispensing area  54  by the rotation of the metering elements  48 . The grains that are held in the cut-outs  52  are subsequently released into a seed inlet element  27  that is arranged at the seed dispensing area  54  and/or into a seed metering pipe  28  by means of an interruption of the pressure difference by interrupting elements  58 . The interrupting elements  58  can be designed, for example, in the form of a roller. Depending on the embodiment, the interrupting elements  58  can work alternately, so that one respective grain is released from the first seed dispensing area and subsequently one grain from the second seed dispensing area into the seed metering pipe  28 . It is also possible that only one interrupting element  58  of one chamber  44  is active, by means of which only the same kind of seeds can be dispensed into the ground. 
         [0088]    Just like the chambers  44 , seed dispensing area  54  can also be pressurized. In the present embodiment, this is accomplished by means of an active connection between the chambers  44  and the seed dispensing area  54 . This means that no further air supply is needed and the pressure level in the chambers  44  and in the seed dispensing area  54  is basically the same. 
         [0089]    By means of the air pressure that is present in at least one seed dispensing area  54 , an air stream is created due to the lower pressure in the seed metering pipe  28 . After the grains  46  are released from the metering element  48  they are picked up by the air stream. Thus, the grains  46  are actively accelerated within the seed metering pipe  28 . Furthermore, this largely prevents a bouncing of the grains  46  within the seed metering pipe  28  or at least reduces it to such an extent that is has no or at least only an insignificant influence on the dispensing accuracy. 
         [0090]    The seed metering elements  27  are arranged at an angle towards metering element  48 , so that their seed inlet  40  also features an angle towards it. In order to avoid interfering edges or the like and to keep the distance between metering element  48  and seed inlet  40  as small as possible, seed inlet elements  27  are beveled on the respective side that is facing the metering elements  48 . 
         [0091]      FIG. 10  depicts a front view of the metering system  22  in a cross section, wherein the metering elements  48  directly touch and slide on the seed inlet elements  27 . By means of such an arrangement, edges between metering elements  48  and the seed inlet elements  27  are prevented. Thus, the grain dispensing can be improved accordingly. The diameter of the seed inlet elements  27  in the seed dispensing area is furthermore adapted to correspond to the touching and sliding, which can also improve the grain intake by means of the seed inlet elements  27 . The invention was described with reference to a preferred embodiment. But it is still possible for a skilled person to make adaptations and changes to the invention without leaving the scope of protection of the following claims. 
       LIST OF REFERENCE SIGNS 
       [0092]      10  row unit 
         [0093]      12  support device 
         [0094]      14  frame 
         [0095]      16  coulter 
         [0096]      18  catching element 
         [0097]      20  roller 
         [0098]      22  metering device 
         [0099]      24  front metering device 
         [0100]      26  rear metering device 
         [0101]      27  seed inlet element 
         [0102]      28  seed metering pipe 
         [0103]      29  connecting piece 
         [0104]      30  housing 
         [0105]      32  hinge 
         [0106]      34  seed supply line 
         [0107]      36  seed reservoir 
         [0108]      38  air supply 
         [0109]      40  slider 
         [0110]      42  motor 
         [0111]      44  chamber 
         [0112]      46  grains 
         [0113]      48  metering element 
         [0114]      50  curved path 
         [0115]      52  cut-outs 
         [0116]      54  grain dispensing area 
         [0117]      56  separating device, separating element 
         [0118]      58  push-out roller 
         [0119]      60  seed inlet 
         [0120]      62  bow-shaped contour 
         [0121]      64  guiding elements 
         [0122]      66  guided air stream 
         [0123]      68  perpendicular air stream 
         [0124]      70  guiding path