Patent Publication Number: US-11032965-B2

Title: Pneumatic spreading machine and method for controlling or regulating the metering elements thereof by carrying out calibration tests

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a United States National Phase Application of International Application PCT/EP2017/001203, filed Oct. 11, 2017, and claims the benefit of priority under 35 U.S.C. § 119 of German Application 10 2016 012 254.4, filed Oct. 14, 2016, the entire contents of which are incorporated herein by reference. 
     TECHNICAL FIELD 
     The invention relates to a method for controlling and/or regulating a metering element of a pneumatic spreading machine, comprising
         at least one transfer chamber which is arranged downstream of the metering element and which serves for the transfer, into at least one conveying line, of material for spreading that has been metered by means of the metering element;   at least one blower for charging the conveying line with an air stream; and   at least one spreading element arranged downstream of the conveying line,       

     wherein at least one calibration test is performed by virtue of the metering element, charged with a particular type of material for spreading, being actuated over a predetermined test duration with a predetermined operating parameter and the mass of material for spreading metered during the calibration test being gravimetrically detected, following which, from the mass of material for spreading thus obtained in relation to the test duration and the operating parameters of the metering element, a functional relationship between the operating parameter of the metering element and the actual mass flow of material for spreading metered by means of said metering element is calculated, and the metering element is then controlled and/or regulated to a setpoint mass flow of material for spreading in a manner dependent on this functional relationship. The invention also relates to a pneumatic spreading machine designed in particular for carrying out a method of said type, comprising
         at least one metering element;   at least one transfer chamber which is arranged downstream of the metering element and which serves for transferring, into at least one conveying line, material for spreading that has been metered by means of the metering element;   at least one blower for charging the conveying line with an air stream;   at least one spreading element arranged downstream of the conveying line; and   at least one weighing device to which a particular type of material for spreading which is to be dispensed can be fed by actuation of the metering element over a predetermined test duration with a predetermined operating parameter during a calibration test, in order to gravimetrically detect the mass of material for spreading thus metered.       

     TECHNICAL BACKGROUND 
     Pneumatic spreading machines of the above-mentioned type are widely used in the agricultural sector for dispensing predominantly pulverulent and/or particulate material for spreading, such as in particular seeds and/or fertilizer. Here, the material for spreading, which is generally stored in a container, is metered by means of one or more metering elements, which are commonly arranged below an outlet opening of the container, and the metered mass flow of material for spreading is transferred to a multiplicity of spreading elements arranged downstream of the metering element. For the transfer of the material for spreading to the spreading elements, a blower is used which feeds the generated conveying air into a conveying line, in the interior of which—and generally in a line portion thereof below the metering element—there is situated a transfer chamber in order for the flow of material for spreading metered by means of the metering element to be dispersed into the conveying air stream flowing in the conveying line and to be fluidized. For the latter purpose, the conveying line is, in the region of the transfer chamber, commonly although not imperatively equipped with a so-called injector which comprises a nozzle arranged upstream of the transfer chamber in the conveying line and a diffuser, in the form of an expansion nozzle, arranged downstream of the transfer chamber in the conveying line. This transfer chamber is in this case consequently formed between the nozzle and the diffuser. In particular in the case of so-called drill ploughs, the conveying line finally opens out, downstream of the transfer chamber, into a distributor unit, which is designed for example in the form of a distributor head and which has a multiplicity of outlets. The latter are generally arranged so as to be distributed around the circumference of the distributor unit and are adjoined by in each case one spreader line which serves for feeding the flow of material for spreading in partial flows, corresponding to the number of spreader lines, to in each case one spreading element, which spreading elements are arranged with different lateral spacings to the spreading machine. Furthermore, other types of distributor units are also customary, for example in the form of cyclones which separate the particles of material for spreading out of the conveying air stream and which are used predominantly in spreading machines in the form of precision seeding machines. 
     If the pneumatic spreading machine is for example a fertilizer spreader, such as is known for example from DE 10 2004 030 240 B4, then the spreading elements may be formed for example by impact plates situated at the end of the spreader lines. By contrast, if the pneumatic spreading machine is for example a sowing machine, then the spreading elements may for example comprise sowing coulters for introducing the seeds into the ground. Such spreading machines are known inter alia from DE 44 34 963 A1, DE 197 47 029 A1 or DE 10 2010 053 883 A1. 
     The container, which is heavy in particular when filled with the material for spreading, is commonly arranged, in the case of known pneumatic spreading machines, on a support structure which extends below the container and which supports the latter. Here, the support structure may be held either by a three-point hitch of a prime mover, such as a tractor, or the spreading machine is in the form of a towed machine which is itself supported on the ground during operation. The housing of the transfer chamber, in particular if it is equipped with an injector with the nozzle and diffuser which each open into said transfer chamber and are commonly arranged coaxially, is for space reasons often arranged transversely with respect to the direction of travel (that is to say the central axis of nozzle and diffuser extends perpendicular to the direction of travel). Furthermore, in particular for large working widths, so-called twin configurations are known which comprise in each case one container, which serves for accommodating the material for spreading, and in each case one pneumatic transport system of the type described above. In this case, the transfer chamber is generally arranged parallel to the direction of travel. 
     The one or more metering elements of pneumatic spreading machines generally have, depending on the material for spreading that is to be dispensed, cellular wheels or cam wheels which can be controlled and/or regulated with regard to their operating parameters, such as in particular the rotational speed, wherein it is furthermore known for the cellular wheels or cam wheels to be exchangeable for one another in order to adapt the spreading machine to different materials for spreading (cf. for example EP 2 786 649 A2). However, it is basically also possible for use to be made of metering elements equipped with metering slides activatable by activator means, which metering elements interact with a metering opening, wherein, as an operating parameter of such metering elements, the relative position of the metering slide in relation to the metering opening can be controlled and/or regulated. 
     In order to regulate the one or more metering elements of generic pneumatic spreading machines to a desired set point mass flow of material for spreading, DE 10 2014 115 020 A1 for example describes a regulation method in which the actual mass flow of the particles of material for spreading dispersed into the conveying air stream is detected in the conveying line by means of a sensor, such as a piezo sensor, and is transmitted to a regulating device of the spreading machine, which determines a manipulated variable in a manner dependent on the set point mass flow, and correspondingly regulates the metering elements to the set point mass flow. In this regard, it is the intention to continuously determine a corrective factor as a ratio of the actual mass flow in relation to the actual rotational speed or frequency of the metering element, such that the set point mass flow can, with the aid of the corrective factor, be converted into a setpoint rotational speed or frequency of the metering element. The regulating device determines the manipulated variable acting on the metering element—in this case the rotational speed or frequency—in a manner dependent on a control error which is determined as a difference between the setpoint rotational speed and the actual rotational speed. However, such methods have hitherto not been able to become established on the market because the detection of the actual mass flow of fluidized particles of material for spreading using sensor means is error-prone and also susceptible to faults, wherein even local deposits and/or fouling can lead to failure of the mass flow regulation. 
     This also applies to DE 100 37 713 A1 which describes a spreading machine in the form of a drill plough, which comprises a metering element in the form of a sowing wheel which meters the metered seeds into a transfer chamber arranged below the metering element, which metering chamber is adjoined by a conveying line charged with an air stream. Downstream of the metering element, there is provided a counter device which is in the form of a light barrier, a sensor device or an impact device and which counts a partial quantity of the seeds to be dispensed, in order to regulate the sowing quantity in a manner dependent on this and on the working speed. Aside from the above-mentioned disadvantages generally associated with a corresponding sensor arrangement, there is also the problem here that only a partial quantity of the total mass flow of material for spreading that is to be metered can be fed to the counter device, in order that the particles of material for spreading can form a countable layer. Owing to the commonly non-linear dependency of the metered mass flow in relation to the rotational speed of the metering element, there are consequently scattering errors in the dispensing of the (total) setpoint mass flow of material for spreading. 
     In practice, calibration tests are therefore performed, as before, by virtue of the metering element, charged with a particular type of material for spreading, being actuated over a predetermined test duration with a predetermined operating parameter—commonly the rotational speed of the metering element designed as a cellular wheel or cam wheel—and the mass of material for spreading metered during the calibration test being gravimetrically detected. From the mass of material for spreading thus obtained in relation to the test duration and the operating parameters of the metering element, it is then possible to calculate a functional relationship between the operating parameter of the metering element and the mass flow of material for spreading metered by means of said metering element, and the metering element can then be controlled and/or regulated in a manner dependent on this functional relationship to a setpoint mass flow of material for spreading. Here, for the calibration test, it is essential that all of the material for spreading metered during the execution of said test can be collected, and no fractions thereof remain for example in components of the spreading machine, in order to ensure high accuracy of the adjustment of the metering element during the later working step of fertilizing/sowing and in order, both for economic reasons and for environmental protection reasons, to avoid incorrect metering, also referred to as “calibration errors”, in particular over-metering, owing to material for spreading being only partially collected during a calibration test. 
     Whereas, in many cases, such calibration tests are performed manually before the commencement of spreading work by virtue of the metering element being actuated in the above manner and material for spreading metered during the operation test being collected in a test container to be placed below the metering element, following which the test container with the collected mass of material for spreading is manually weighed, and a characteristic value that identifies the desired spread quantity of material for spreading per unit of metering time is input into a control device of the spreading machine (cf. for example EP 0 635 195 A1, DE 44 31 288 A1, EP 2 022 308 A1, DE 10 2007 044 178 A1 or DE 20 2014 009 404 U1), such an approach is firstly relatively cumbersome for the farmer, and secondly, the metering accuracy achieved in this way leaves something to be desired, because the actual mass flow of the same material for spreading may change in the case of a constant rotational speed of the metering element during the ongoing spreading work, in particular owing to moisture. Moreover, manual inputting of values into the control device basically also exhibits high susceptibility to errors. 
     Therefore, generic pneumatic spreading machines are also known in which the calibration tests can be performed firstly in automated fashion and secondly at various points in time during the spreading work, for example as the spreading machine is turning at the headland etc., in order to keep the functional relationship between the rotational speed of the metering element and the actual mass flow of material for spreading metered by means of said metering element up-to-date at all times and to consequently ensure continuously high metering accuracy. 
     For example, DE 101 34 991 A1 describes a pneumatic drill plough with a seed container, with a metering element designed in the form of a cellular wheel, and with a counting device for counting the particles of material for spreading that have been metered during automated calibration tests. The counting device is designed as a pneumatic counting device and comprises a cellular wheel with bores arranged spaced apart from one another in the outer region thereof, a suction device that sucks the particles of material for spreading into the bores, and a particle separating device which separates the sucked-in particles out of the bores. Two sensors which are arranged in each case in front of and behind the particle separating device in a direction of rotation of the cellular wheel serve for counting the particles of material for spreading metered during the calibration test, wherein the result of this count is transmitted to a regulating device which regulates the metering element in accordance with the desired spreading. The counting device is arranged in the interior of the seed container, wherein, in a portion of the conveying line arranged between the metering element and the distributor head, there is provided a switch which, during the execution of a calibration test, diverts the metered particles of material for spreading to the counting device, whereas, during the spreading work, said switch conducts said particles to the distributor unit designed in the form of a distributor head. Aside from the cumbersome design of the particle counting device from a structural aspect, a disadvantage consists in particular in that the particles of material for spreading that are conducted in a circuit to the counting device during a calibration test can accumulate or remain at numerous locations in the spreading machine, for example in the injector or in the conveying line itself, such that there is the risk of metering errors if not all of the particles of material for spreading can be counted. Moreover, the calibration test is relatively time-consuming. 
     EP 2 420 121 B1 describes a pneumatic spreading machine designed in particular in the form of a sowing machine, having a storage container for accommodating the material for spreading, having a metering element and having transfer chamber, arranged below said metering element, with an injector, which opens into a conveying line for the fluidized flow of material for spreading. Furthermore, the spreading machine comprises a weighing container arranged below the injector, which weighing container serves for the selective weighing of a metered fraction of material for spreading from the storage container during a calibration test and can be connected to or separated from said storage container by means of a calibration valve. In order to carry out a calibration test, the calibration valve has consequently opened, such that the material for spreading metered by means of a predefined number of rotations of the metering element falls into the weighing container, where the mass of said material for spreading is gravimetrically detected by means of a weighing cell. By contrast, during the spreading work, the calibration valve is closed, such that the metered material for spreading is released from the metering element directly to the injector. It has proven to be disadvantageous in particular that the material for spreading collected in the weighing container must, after every calibration test, be recirculated into the storage container by means of an additional recirculation line, which is equipped with an additional blower. Furthermore, the housing of the transfer chamber of pneumatic spreading machines, whether or not equipped with an injector, should basically, in order to achieve as low as possible a center of gravity of the machine and in order to satisfy the demands for realizing as large as possible a capacity of the storage container, be arranged at a very low height below the metering element, which is possible only to a limited extent with the weighing container, including its recirculation line, provided below the injector. In order to be able to combine the working processes of fertilizing and/or sowing with working processes of cultivation in a space-saving manner, generic pneumatic spreading machines, in particular in the form of so-called drill ploughs, are furthermore commonly equipped with active or passive cultivation units such as for example packer rollers, rotary harrows and the like, which additionally restricts the structural space required for the weighing container. 
     SUMMARY 
     The invention is therefore based on an object of further developing a pneumatic spreading machine and a method for controlling and/or regulating the metering element thereof of the type mentioned in the introduction while at least substantially avoiding the above-stated disadvantages, such that automated execution of calibration tests with high accuracy is ensured. 
     With regard to a method, said object is achieved, in the case of a method for controlling and/or regulating a metering element of a pneumatic spreading machine of the type mentioned in the introduction, in that the mass of material for spreading metered during the calibration test is gravimetrically detected downstream of the metering element and upstream of the transfer chamber or in the transfer chamber, following which said material for spreading is transferred to the conveying line and dispensed. 
     With regard to a device, to achieve said object in the case of a pneumatic spreading machine of the type mentioned in the introduction, the invention furthermore provides that the weighing device is arranged downstream of the metering element and upstream of the transfer chamber, in or at the transfer chamber, such that the mass of material for spreading metered during the calibration test can be transferred to the conveying line and dispensed. 
     Owing to the fact that the gravimetric detection of the material for spreading metered during a calibration test performed in automated fashion is weighed downstream of the metering element and upstream of the transfer chamber or in the latter, wherein the weighing device is consequently likewise arranged downstream of the metering element and upstream of the transfer chamber or in or at the transfer chamber itself, the embodiment according to the invention firstly eliminates the need for additional recirculation lines for the material for spreading into the storage container thereof, such that there is also no risk of contamination of the material for spreading that is stored therein. In particular, however, the risk of metering errors is minimized since the gravimetric detection of the material for spreading is performed directly downstream of the metering element, such that it is ensured that all of the material for spreading metered during a calibration test is also actually weighed and does not, on the path to a weighing device provided spaced apart from the metering element, for example a weighing device in the interior of the container, remain partially disregarded owing to deposits in various components of the pneumatic spreading machine. This is also associated with a time-saving, such that the calibration test can be performed relatively quickly and consequently even during short interruptions in the spreading work. The gravimetric detection of the material for spreading may in this case be performed when the blower is deactivated, because said blower is not necessarily required for transporting the material for spreading from the metering element to the weighing device. A particular advantage of the embodiment according to the invention furthermore consists in that material for spreading that is metered and weighed during a calibration test can subsequently be dispensed in controlled fashion via the transfer chamber and via the spreader lines adjoining said transfer chamber via the conveying line, for example by activation of the blower, such that the dead times that basically exist during the commencement of operation of generic spreading machines—be it at the start of the spreading work or after interruptions thereof, for example when traveling from the headland into the field interior—(the material for spreading metered by the metering element must be fed by means of the activated blower to the transfer chamber and pass from there via the conveying and spreader lines and, after having possibly passed a distributor unit, to the spreading elements) can be bridged. 
     If the spreading machines has multiple metering elements with in each case one transfer chamber arranged downstream thereof, then it is self-evidently possible for a weighing device designed in the manner according to the invention to be arranged downstream of each metering element, in order to operate the metering elements in each case correspondingly to the functional relationship, obtained by means of the calibration tests, between the operating parameter of the respective metering element and the actual mass flow metered by means of said metering element. However, on the other hand, it is also conceivable for only one weighing device to be provided for carrying out the calibration tests by means of the mass of material for spreading metered by means of one of the metering elements, and for the other metering elements that are not equipped with a weighing device to be operated correspondingly to the functional relationship, obtained from this, between the operating parameter of the one metering element and the actual mass flow metered by means of said metering element, by virtue of the functional relationship consequently being “transferred” to the other metering elements. 
     In order that, after each calibration test, the spreading machine can automatically control and/or regulate the desired mass flow of material for spreading, without the mass of material for spreading detected during the calibration test, or a value representative of this, having to be manually input, the spreading machine may preferably have a control and/or regulating device which is operatively connected both to the weighing device and to the metering element and which is designed to, from the mass of material for spreading detected by means of the weighing device in relation to the test duration and the operating parameter of the metering element, such as for example the rotational speed, the number of rotations, the number of emptied cells or cam troughs of the metering wheel or the like, during the calibration test, calculate a functional relationship between the operating parameter of the metering element and the actual mass flow of material for spreading metered by means of said metering element, and to subsequently control and/or regulates the metering element to a setpoint mass flow of material for spreading in a manner dependent on this functional relationship. The functional relationship may furthermore, in a manner known per se, involve a factor, a characteristic line or curve, a characteristic map or the like. 
     As already indicated, the invention provides in particular that the material for spreading metered during the calibration test
         is collected downstream of the metering element and upstream of the transfer chamber, the mass thereof is gravimetrically detected, and it is then released to the transfer chamber; or   is collected in the transfer chamber when the blower is decoupled from said transfer chamber and/or deactivated, and the mass thereof is gravimetrically detected, following which the injector is coupled to the blower and/or the latter is activated, such that the material for spreading metered during the calibration test is, in both cases, dispensed in controlled fashion at the start of the spreading work.       

     With regard to a device, for this purpose, various design embodiments may be provided, wherein the weighing device should always be closed on all sides or “encapsulated” and/or accommodated entirely in the interior of the conveying components situated between the metering element and the transfer chamber, so as to protect the material for conveying against external action and so as not to falsify the measurement result. Accordingly, according to a first advantageous embodiment, it may be provided for example that the weighing device is arranged downstream of the metering element and upstream of the transfer chamber, wherein the material for spreading can be fed selectively either to the weighing device or, past the latter, to the transfer chamber. The weighing device is consequently arranged in particular parallel to a line connecting the metering element to the transfer chamber, from which line it can be transferred selectively directly to the transfer chamber (during spreading work) or firstly to the weighing device (during a calibration test) and from there to the transfer chamber (after the calibration test at the start of the spreading work). 
     In this context, according to one design variant, provision may be made for the weighing device to comprise a weighing container which, by means of a switch arranged in a line connecting the metering element to the transfer chamber, is selectively connectable to the metering element or separable therefrom, wherein the weighing container in particular
         has at least one weighing cell arranged in the interior thereof; or   is mechanically decoupled from the line connecting the metering element to the transfer chamber, and is connected to an external container balance.       

     As already mentioned, the switch, which is designed for example in the form of a guide flap, is consequently set, during a calibration test, such that it conducts the metered particles of material for spreading directly to the weighing container, wherein the particles of material for spreading are, after the weighing that is performed there at the start of the spreading work, transferred from the weighing container into the injector for example by means of a flap that can be set into an open position and into a closed position, whereas, during the spreading work, the switch transfers the particles of material for spreading past the weighing container directly to the transfer chamber, such that the particles of material for spreading do not have to pass through the weighing container. In the case of a weighing container connected to an external container balance, the mechanical decoupling thereof on the one hand from the line which connects the metering element to the transfer chamber and which is equipped with the switch, and on the other hand from the connection, which is to be opened and closed, of the weighing container to the transfer chamber, may be realized for example in a manner known per se by means of flexible line pieces, composed for example of elastically flexible materials, such as silicone, rubber etc., composed of flexibly pliable materials, such as (filter) fabrics and the like, by means of bellows etc. 
     According to a further design variant, provision may be made in this context for the weighing device to have a weighing container with at least one weighing cell arranged in the interior thereof and to be mounted so as to be pivotable, in relation to a line connecting the metering element to the transfer chamber, between at least one weighing position, in which said line opens into the weighing container, and at least one transfer position, in which the weighing container opens into the transfer chamber, wherein the transfer chamber in particular
         is arranged on a rotary slide by means of which said transfer chamber is rotatable between the at least one weighing position, in which said transfer chamber is arranged outside the line connecting said transfer chamber to the metering element, and the at least one transfer position, in which both the weighing container and the line connecting the metering element to the transfer chamber open into said transfer chamber; or   is itself mounted so as to be pivotable, in relation to the line connecting said transfer chamber to the metering element, between the at least one weighing position, in which said transfer chamber is pivoted away from the line connecting said transfer chamber to the metering element, and the at least one transfer position, in which both the weighing container and the line connecting the metering element to the transfer chamber open into said transfer chamber.       

     In the former case, the transfer chamber can consequently, by means of the rotary slide, be rotated out of its operating position, in which it is connected via the line to the metering element, into the weighing position, in which it is arranged outside the line connecting it to the metering element in the operating position. In the operating position, in turn, the weighing container, which is for example pivotable articulated on the circumference of the line, can be connected to the line which connects the metering element to the transfer chamber in the operating position, by virtue of said weighing container being pivoted into the cross section of said line, such that the calibration test can be performed. Subsequently, the weighing container is pivoted out of its weighing position again, and the transfer chamber is rotated by means of the rotary slide into the transfer position, which corresponds in particular to its operating position, in which firstly the material for spreading metered by means of the metering element can pass into the transfer chamber, and in which secondly the material for spreading received in the weighing container can be transferred into the transfer chamber. The latter may in turn be performed for example by means of a closure flap, in the open state of which the material for spreading falls from the weighing container into the transfer chamber at the start of spreading work after the calibration test. 
     In the latter case, both the weighing container and the transfer chamber are, for example at substantially oppositely situated pivot bearings on the circumference of the line which connects the metering element to the transfer chamber in the operating position, articulated pivotably on said line, such that they can each be connected to the line by pivoting in order to perform a calibration test or in order to dispense the material for spreading during the spreading work. After the calibration test has ended, the transfer chamber is consequently pivoted into its transfer position, which corresponds in particular to the operating position, in which the material for spreading received in the weighing container can be transferred into the transfer chamber. This may in turn be performed for example by means of a closure flap, in the open state of which the material for spreading falls from the weighing container into the transfer chamber at the start of the spreading work after the calibration test. 
     According to a further design variant, provision may be made for the weighing device to have a weighing container with at least one weighing cell arranged in the interior thereof, and both the transfer chamber and the weighing container are arranged on a linear slide which acts in particular substantially perpendicularly with respect to a line connecting the metering element to the transfer chamber, wherein the transfer chamber and the weighing container are displaceable between at least one weighing position, in which the line connecting the metering element to the transfer chamber opens into the weighing container and the transfer chamber is arranged outside the cross section of said line, and at least one operating position, in which the line connecting the metering element to the transfer chamber opens into the transfer chamber and the weighing container is arranged outside the cross section of said line, and wherein furthermore, the weighing container is, in particular by means of a flap, selectively connectable to the transfer chamber and separable therefrom. In this case, the transfer chamber and the weighing container can consequently be displaced, in particular jointly, by means of the linear slide, in order to either connect the weighing container to the metering element in order to carry out a calibration test or connect the transfer chamber to the metering element during spreading work. The transfer of the material for spreading received in the weighing container after a calibration test into the transfer chamber may in turn be performed by means of a closure flap, in the open state of which the material for spreading falls from the weighing container into the transfer chamber at the start of spreading work. 
     In all of the above mentioned design variants, the transfer of the material for spreading metered during a calibration test from the weighing container into the transfer chamber may be performed preferably under the action of gravitational force, by virtue of the weighing container, at least in its transfer position, being arranged at a corresponding height at least partially above the transfer chamber. Alternatively or in addition, it is for example also conceivable for the transfer of the material for spreading metered during a calibration test from the weighing container into the transfer chamber to be performed by means of the air stream generated by the blower, by virtue of the material for spreading being for example suctioned from the weighing container into the transfer chamber. 
     In an alternative design variant, which does not require a separate weighing container, provision may for example also be made whereby the weighing device
         has a flap which is arranged in the line connecting the metering element to the transfer chamber and which is pivotable between a weighing position, in which it closes the line cross section, and an operating position, in which it at least partially opens up the line cross section, wherein the flap is equipped with a weighing cell and/or the pivot axle thereof is equipped with a torque or torsion sensor; or   has a slide arranged in the a line connecting the metering element to the transfer chamber, which slide is displaceable between a weighing position, in which it closes the line cross section, and an operating position, in which it at least partially opens up the line cross section, wherein the slide is equipped with a weighing cell.       

     The material for spreading metered during a calibration test is consequently, with the flap closed or with the slide closed, collected directly in the line connecting the metering element to the transfer chamber, in order for the mass of said material for spreading to be gravimetrically detected, following which the flap is opened, or the slide is pulled out of the line, in order for the collected material for spreading to be transferred to the transfer chamber and dispensed at the start of the “normal” spreading work. The displacement direction of the slide in this case expediently extends approximately perpendicular to the line connecting the metering element to the transfer chamber. Said line may preferably be equipped with suitable sealing lips which, when the flap or the slide is in the closed position, bear against the flap or against the slide, such that weighing errors can be avoided even if the transfer chamber below the flap or the slide is impinged on with the conveying air stream by the blower whilst the calibration test is being performed. 
     In a second advantageous embodiment, which likewise does not require a separate weighing container and in the case of which the material for spreading metered during a calibration test is collected directly in the transfer chamber with the blower decoupled from said transfer chamber and/or deactivated, in order for the mass of said material for spreading to be gravimetrically detected, following which the transfer chamber is coupled to the blower and/or said blower is activated in order to dispense the material for spreading, one design variant may provide for the weighing device to comprise a weighing cell which is arranged in the interior of the transfer chamber, in particular at the base thereof, wherein the weighing cell can in particular be exposed and covered by means of a slide situated at the inside. The weighing cell is consequently positioned in the interior of the transfer chamber such that the material for spreading metered by means of the metering element falls directly onto said weighing cell, without the possibility of losses occurring which are not gravimetrically detected. In order to protect the weighing cell during spreading work, said weighing cell may preferably be covered by means of the slide, and exposed only for the purposes of performing a calibration test. 
     In a further design variant, it may be provided in this context that at least one lower portion of the transfer chamber is connected
         by means of at least one weighing cell; or   by means of at least one pivot bearing equipped with a torque or torsion sensor to the line connecting the metering element to the transfer chamber. The entire transfer chamber, or else only one—lower—part thereof, can consequently be connected either by means of the weighing cells, or by means of the pivot bearing equipped with the sensor, to the line connecting the metering element to the transfer chamber, such that the material for spreading metered during a calibration test is in turn collected in the transfer chamber itself in order for its mass to be gravimetrically detected.       

     To ensure that, during the execution of calibration tests, the blower does not introduce any air stream into the transfer chamber in the manner mentioned above, the control and/or regulating device may expediently deactivate the blower or separate said blower from the transfer chamber, for example by means of a shut-off flap or the like, wherein it is alternatively or additionally for example also possible for a warning message to be generated if, for example in the event of a fault, in the case of the blower being active during a calibration test, the weighing device detects the mass of material for spreading hereby metered. 
     In order to be able to access the functional relationships, determined by means of a multiplicity of calibration tests, between the operating parameter of the metering element and the actual mass flow, metered by means of said metering element, of particular materials for spreading at a later point in time, and in order to preferably keep the functional relationship up-to-date at all times during spreading work, in order to thereby take into consideration in particular physical changes of the material for spreading, such as may arise for example owing to an ingress of moisture, provision may be made, in an advantageous embodiment of the method according to the invention, whereby the functional relationship, obtained from the mass of a particular type of material for spreading gravimetrically detected during a calibration test in relation to the test duration and the operating parameter of the metering element, between the operating parameter of the metering element and the actual mass flow of material for spreading is stored, in particular in the form of a metering factor, in order for said functional relationship to be retrievable when required, wherein it is updated in particular when a further calibration test is carried out. 
     In the case of a correspondingly designed spreading machine, provision may accordingly be made, in an advantageous refinement, whereby the control and/or regulating device is designed to store the functional relationship, obtained from the mass of a particular type of material for spreading gravimetrically detected during a calibration test in relation to the test duration and the operating parameter of the metering element, between the operating parameter of the metering element and the actual mass flow of material for spreading, in particular in the form of a metering factor, or is connected to a memory device suitable for this purpose, in order for said functional relationship to be retrievable when required, wherein the control and/or regulating device is in particular designed to update the functional relationship when a further calibration test is carried out. 
     With regard to the bridging, mentioned in the introduction, of the dead times upon the commencement of operation of generic spreading machines—be it at the start of spreading work or be it for example after traveling through the headland—it may prove to be expedient in particular if the mass of material for spreading metered during the calibration test is transferred to the conveying line and dispensed as or immediately before the metering element is, after the end of the calibration test, returned to its normal operating state, in which it is controlled and/or regulated in accordance with the desired setpoint mass flow. In this way, the mass of material for spreading metered during the calibration test can consequently be dispensed at a point in time before the material for spreading newly metered by the metering element upon the commencement (resumption) of the spreading work can pass to the transfer chamber and from there via the conveying or spreader line(s) to the spreading elements, such that a spontaneous start of operation is ensured and local deficiencies in the supply of material for spreading to the ground to be covered are avoided. 
     In the case of a spreading machine configured for this purpose, provision may consequently preferably be made whereby the control and/or regulating device is designed to set the metering element into its normal operating state, in which it controls and/or regulates the metering element in accordance with the desired setpoint mass flow, as or immediately after the mass of material for spreading metered during the calibration test is, after the end of the calibration test, transferred to the conveying line and dispensed. The latter may for example be realized in a simple manner by virtue of the quantity of material for spreading metered during the calibration test, which either is already situated in the transfer chamber or has for example been transferred from a weighing container to said transfer chamber, being fluidized, and introduced into the conveying line, in order to feed the material for spreading via the spreader lines to the respective spreading elements, by activation of the blower or opening of a shut-off flap in a blowing air line which connects the blower to the transfer chamber. 
     Furthermore, it may self-evidently be advantageous if, in the control and/or regulation of the metering element, in a manner dependent on the functional relationship between the operating parameter of the metering element and the mass of material for spreading metered during the preceding calibration test, to the desired setpoint mass flow of material for spreading, at least one spreading parameter from the group comprising
         working width,   traveling speed and   actual position of the spreading machine is also taken into consideration.
 
The actual position of the spreading machine may in this case be determined, in a manner known per se, by means of a GPS receiver connected to the control and/or regulating device, such that it is possible, in particular in the case of dispensing of fertilizer, to allow for different setpoint mass flows of material for spreading in accordance with an electronic application map. The traveling speed may likewise be determined for example by means of GPS or by means of sensors that are customary for this purpose, or else may be input into the control and/or regulating device. The latter indeed also applies to the desired working width, including partial width switching configurations.
       

     In the case of a spreading machine configured for carrying out such a method, provision may accordingly preferably be made whereby, in the control and/or regulation of the metering element, in a manner dependent on the functional relationship between the operating parameter of the metering element and the mass of material for spreading metered by means of said metering elements during the preceding calibration test, to the desired setpoint mass flow of material for spreading, also takes into consideration at least one spreading parameter from the group comprising
         working width,   traveling speed and   actual position of the spreading machine.
 
For this purpose, said control and/or regulating device is equipped in particular with a GPS receiver, which is operatively connected to the control and/or regulating device, and/or to corresponding sensors of the above-stated type.
       

     Finally, in particular with regard to the first execution of a calibration test after the storage container of the spreading machine has been filled with fresh material for spreading and spreading work is to be commenced, it may be expedient if, for the calibration test, a predetermined test duration is taken into consideration, at the start of which the metering element was already actuated, wherein, for the detection of the mass of material for spreading metered during the calibration test, the difference between the mass at the end of the test duration and at the start of the test duration is determined. In this way, it is ensured that the cells or the cam troughs of a metering wheel of the metering element are fully filled with the relevant material for spreading in the predetermined test duration, and it is not for example the case that cells or cam troughs of the metering wheel which are initially still (partially) empty or are (partially) filled with “old” material for spreading with a different density falsify the calibration test. Here, the metering wheel may for example be rotated with the operating parameter predetermined for the calibration test, for example at least one half of one rotation, such that it is fully filled with the “present” material for spreading, following which the calibration test itself begins for the first time. The residual material for spreading that is possibly metered here however remains disregarded for the calibration test owing to the fact that, for the detection of the mass of material for spreading metered during the calibration test, only the difference between the mass at the end of the test duration and at the start of the test duration is determined. This may be realized in a manner known per se by means of known so-called “tare functions” of the weighing cells used, or else by means of electronic calculation of the difference between the measured value of the mass of material for spreading at the end of the test duration and at the start of the test duration. 
     Further features and advantages of the invention will emerge from the following description of exemplary embodiments with reference to the drawings. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which preferred embodiments of the invention are illustrated. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  is a schematic view of an embodiment of a pneumatic spreading machine, designed in the form of a drill plough, viewed from the rear; 
         FIG. 2  is a schematic perspective view of the distributor unit, designed in the form of a distributor head, of the spreading machine as per  FIG. 1 , including the metering element, the housing of the transfer chamber and the pneumatic conveying components; 
         FIG. 3  is a schematic, partially sectional detail view of an embodiment of a transfer chamber of the spreading machine as per  FIGS. 1 and 2 , which is formed between the nozzle and the diffuser of an injector, but without the metering element; 
         FIGS. 4A and 4B  are each schematic sectional views of the metering element and of the transfer chamber of the spreading machine as per  FIGS. 1 to 3  with a first embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a weighing container with weighing cells arranged in the interior thereof, in different operating situations; 
         FIGS. 5A and 5B  are each schematic sectional views, substantially corresponding to  FIGS. 4A and 4B , with a second embodiment, modified in relation thereto, of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a weighing container connected to an external container balance, in different operating situations; 
         FIGS. 6A and 6B  are each schematic sectional views of the metering element and of the pivotably mounted transfer chamber of the spreading machine with a third embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a likewise pivotably mounted weighing container with weighing cells arranged in the interior thereof, in different operating situations; 
         FIGS. 7A, 7B and 7C  are each schematic sectional views of the metering element and of the transfer chamber, arranged on a rotary slide, of the spreading machine with a fourth embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a pivotably mounted weighing container with weighing cells arranged in the interior thereof, in different operating situations; 
         FIGS. 8A, 8B and 8C  are each schematic sectional views of the metering element and of the transfer chamber, arranged on a linear slide, of the spreading machine with a fifth embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a weighing container arranged on the same linear slide and which has weighing cells arranged in the interior thereof, in different operating situations; 
         FIGS. 9A and 9B  are each schematic sectional views of the metering element and of the transfer chamber of the spreading machine with a sixth embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a flap arranged in the line connecting the metering element to the transfer chamber, which flap has weighing cells arranged on the top side thereof or has torque or torsion sensors arranged on the pivot axle thereof, in different operating situations; 
         FIGS. 10A and 10B  are each schematic sectional views of the metering element and of the transfer chamber of the spreading machine with a seventh embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and upstream of the transfer chamber and which comprises a slide arranged in the line connecting the metering element to the transfer chamber, which slide has weighing cells arranged on the top side thereof, in different operating situations; 
         FIG. 11  is a schematic sectional view of the metering element and of the transfer chamber of the spreading machine with an eighth embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and at the transfer chamber and which comprises a pivot bearing, equipped with a torque or torsion sensor, of the transfer chamber; 
         FIG. 12  is a schematic sectional view of the metering element and of the transfer chamber of the spreading machine with a ninth embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and at the transfer chamber and which comprises a connection, equipped with weighing cells, of the transfer chamber to the line connecting the metering element to the transfer chamber; 
         FIG. 13  is a schematic view, substantially corresponding to  FIG. 12 , with a tenth embodiment, modified in relation thereto of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and at the transfer chamber and in the case of which only the lower portion of the transfer chamber is connected by means of weighing cells to an upper portion thereof; and 
         FIGS. 14A and 14B  are each schematic sectional views of the metering element and of the transfer chamber of the spreading machine with an eleventh embodiment of a weighing device which serves for the automated execution of calibration tests and which is arranged downstream of the metering element and in the transfer chamber and which has weighing cells arranged on the base of the transfer chamber, in various operating situations. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     Referring to the drawings,  FIG. 1  schematically shows an exemplary embodiment of a pneumatic spreading machine which, in the present case, is designed in the form of a sowing machine or drill plough and which can be detachably fixed for example to a conventional three-point linkage of a prime mover, such as a tractor. Said spreading machine comprises a storage container  1  for accommodating material for spreading, such as for example seeds and/or fertilizer, having a cover  2 , which are supported on supports  3  of a frame. To the latter there is also fixed a blower  4  for generating an air stream. Below an outlet of the container  1 , which for example tapers downward in funnel-shaped form, there is situated a housing  5 , which can be seen in more detail in  FIG. 2  and in particular in  FIG. 3 , of a transfer chamber  14 , which serves for the transfer of the material for spreading to a conveying line  6 . The latter is charged with an air stream by the blower  4  in order to convey the material for spreading upward into a distributor unit  7 . The distributor unit  7  is in the present case formed by a distributor head and comprises a multiplicity of connectors, which are arranged so as to be distributed around the circumference of said distributor head and which in the present case extend approximately radially outwards and to which in each case one spreader line  8  is connected. The connection of the spreader lines  8  may be realized for example by means of in each case one housing  18  (c.f.  FIG. 2 ), which is expediently equipped with in each case one shut-off element for interrupting the fluidized flow of material for spreading in accordance with demand, in order to be able to provide different working widths or also partial width switching configurations. The spreader lines  8  which extend from the distributor head of the distributor unit  7  and which may for example be formed in the manner of hoses, and which are illustrated in cutaway form in  FIG. 1  for the sake of clarity, are led downward and rearward, wherein, at their free ends averted from the distributor unit  7 , said spreader lines are equipped with spreading elements. In the case of the sowing machine shown by way of example in  FIG. 1 , said spreading elements are sowing coulters (not visible in detail) with furrow closers  9 , so-called harrows, which are arranged downstream of said sowing coulters. The frame of the spreading machine may furthermore be supported on the ground  11 , and in particular lifted off therefrom, by means of support wheels  10 . 
       FIG. 2  shows the pneumatic conveying components of the spreading machine as per  FIG. 1 , which serve for the transfer of the material for spreading from the transfer chamber  14 , which is situated in the interior of the housing  5 , into the distributor unit  7 , which is designed in the form of a distributor head, via the conveying line  6 . The latter has, at its end averted from the distributor unit  7 , a connecting piece  12  for the fluidic contacting of the blower  4  (see  FIG. 1 ), wherein, downstream of the connector piece  12 , the outlet of the metering housing  13  of a metering element (described in more detail further below) opens into the transfer chamber  14 , which is extended through by the conveying line  6 . From there, the material for spreading dispersed in the air stream passes firstly via an approximately horizontal portion of the conveying line  6  into a riser pipe portion thereof, which opens into the center of the distributor head of the distributor unit  7  from below, around the circumference of which the radial connectors for the housings  18  are arranged, which are in turn adjoined by in each case one spreader line  8  which is not illustrated again in the drawing in  FIG. 2 . 
     As can also be seen from  FIG. 2  and in particular  FIG. 3 , in the interior of the housing  5  of the transfer chamber  14  which is arranged below the metering housing  13  and which in the present case is extended through, for example transversely with respect to the direction of travel, by the conveying line  6 , there are accommodated both a nozzle  15  and a diffuser  16 , designed in the form of an expansion nozzle, of an injector, which nozzle and diffuser are arranged coaxially and for example perpendicularly with respect to the direction of travel of the spreading machine at the lowest point thereof. The transfer chamber  14  is in this case situated in the intermediate space between the nozzle  15  and the diffuser  16  of the injector. Whereas the nozzle  15  of the injector is connected, at the left-hand end of the housing  5  of the transfer chamber  14  in  FIG. 2 , to the blower  4  (see  FIG. 1 ), the diffuser  16  of the injector is adjoined at the right-hand end of the housing  5  of the transfer chamber  14  in  FIG. 2  by the conveying line  6 . In this way, the material for spreading, after having been metered in a desired mass flow by means of the metering element accommodated in the metering housing  13 , is transferred, in the transfer chamber  14  arranged between the nozzle  15  and the diffuser  16  of the injector, into the diffuser  16  by means of the gas stream flowing in via the nozzle  15 , and passes from there into the conveying line  6 . 
     The spreading machine shown in  FIGS. 1 to 3  is furthermore equipped with a control and/or regulating device (not illustrated in the drawing) which controls and/or regulates the functional components of the spreading machine and is operatively connected inter alia to a weighing device  100  (discussed in detail further below with reference to  FIGS. 4 to 14 ) to which a respective type of material for spreading which is stored in the storage container  1  and which is to be dispensed can be fed by actuation of the metering element  17  over a predetermined test duration with a predetermined operating parameter during a calibration test, in order for the mass of material for spreading thus metered to be gravimetrically detected. The control and/or regulating device is furthermore operatively connected to the metering element  17 , in order to, from the mass of material for spreading detected by means of the weighing device  100  in relation to the test duration and the operating parameter of the metering element  17  during the calibration test, calculate a functional relationship between the operating parameter of the metering element  17  and the actual mass flow of material for spreading metered by means of said metering element, and to subsequently control and/or regulate the metering element  17  to a setpoint mass flow of material for spreading in a manner dependent on this functional relationship, for example in the form of a metering factor. 
     Here, the control and/or regulating device may expediently be designed to store the functional relationship, obtained from the mass of a particular type of material for spreading gravimetrically detected during the calibration test, between the operating parameter of the metering element  17  and the actual mass flow of material for spreading, or is connected to a memory device (likewise not shown) suitable for this purpose, in order for said functional relationship to be retrievable when required. Furthermore, said functional relationship may in particular also be updated during the execution of one or more further calibration tests, such that physical changes to the material for spreading during ongoing spreading work, such as may arise in particular owing to an ingress of moisture, do not lead to metering errors. Furthermore, provision may be made whereby, in the control and/or regulation of the metering element  17 , in a manner dependent on the functional relationship between the operating parameter of the metering element  17  and the mass of material for spreading metered by means of said metering element during the preceding calibration test, to the desired setpoint mass flow of material for spreading, the control and/or regulating device also takes into consideration further spreading parameters, in particular the working width—for example input by means of an input device, for example in the form of an operating terminal (not shown), assigned to the control and/or regulating device—including possibly provided partial width switching configurations, the traveling speed—likewise for example input or detected by sensor means or using GPS—and/or the actual position of the spreading machine—likewise detected in particular by means of GPS. 
     The metering element  17  may furthermore be designed in any known manner, wherein, in the present case, it has in each case a metering wheel which can be set in rotation in a controlled and/or regulated manner and which, depending on the type of material for spreading to be dispensed, may be designed for example in the manner of cellular or cam wheels. The operating parameter of the metering element  17  which is taken into consideration during the calibration tests and which serves for the determination of the functional relationship that is definitive for the control and/or regulation of said metering element to the desired setpoint mass flow of material for spreading, such as a metering factor, may consequently be for example the rotational speed, the rotational frequency, the number of rotations, the number of emptied cells or cam troughs of the metering wheel of the metering element  17  or the like. It is likewise for example conceivable for the number of cells or cam troughs of the metering wheel of the metering element  17  emptied during a calibration test to be counted by means of a suitable sensor. 
     As is also evident from the following description of various embodiments of weighing devices  100  which serve for the gravimetric detection of the material for spreading metered during automated calibration tests, with reference to  FIGS. 4 to 14 , the metering housing  13  of the metering element  17  has for example an upper inlet  19 , which faces toward an outlet of the storage container  1  (see  FIG. 1 ), and a lower outlet  20 , which is adjoined by a line  21  which connects the outlet  20  of the metering housing  13  of the metering element  17  to the housing  5  of the transfer chamber  14 . 
     The exemplary embodiments of a weighing device  100 , which serves for the automated execution of calibration tests, shown in  FIGS. 4 to 8  have in common the fact that said weighing device comprises in each case one weighing container  101  arranged on the one hand directly downstream of the metering element  17  and on the other hand directly upstream of the transfer chamber  14 , to which weighing container the material for spreading can be selectively fed during a calibration test, or past which weighing container the material for spreading can be conducted during “normal” spreading work, such that the material for spreading metered by means of the metering element  17  passes from the outlet  20  of the metering housing  13  via the line  21  directly into the transfer chamber  14 . The weighing container  101 , which may for example have a capacity from approximately 0.5 1 to approximately 5 1 and which may possibly additionally be equipped with fill level sensors (not shown) is in this case arranged at such a height level that, firstly, the material for spreading can, during a calibration test, fall from the outlet  20  of the metering housing  13  into the weighing container  101  purely owing to gravitational force, whereas the material for spreading that has collected in the weighing container  101  during a calibration test can, after the calibration test has ended, be conducted to the transfer chamber  14  again purely under gravitational force, such that the mass of material for spreading metered during the calibration test can be transferred to the conveying line  6  and dispensed via the distributor unit  7  and the spreader lines  8  (see  FIG. 1 ), in order to hereby in particular bridge dead times upon the commencement (resumption) of spreading work and avoid resulting local deficiencies in the supply to the ground. 
     In the case of the embodiment as per  FIGS. 4A and 4B , the weighing container  101  of the weighing device  100  is arranged in a radial direction laterally adjacent to the line  21  connecting the metering housing  13  of the metering element  17  to the housing  5  of the transfer chamber  14 , wherein, in the line  21 , there is provided a switch  102  designed in the form of a guide flap articulated pivotably on said line, which switch is situated, in  FIG. 4 , in a position in which it feeds all of the metered material for spreading to the weighing container  101  (the calibration test is performed), whereas, in  FIG. 4B , said switch is situated in a position in which it feeds all of the metered material for spreading to the transfer chamber  14 , such that the weighing container  101  is consequently bypassed (spreading work is performed). On the base of the weighing container  101 , there are situated one or more weighing cells  103  for gravimetrically detecting the mass of the material for spreading metered during a calibration test and transmitting this to the control and/or regulating device of the spreading machine. In its base-side region, the weighing container  101  is furthermore connected via a transfer line  104  to the housing  5  of the transfer chamber  14 , wherein the transfer line  104  can be closed (see  FIG. 4A ; the calibration test can be performed) and opened (see  FIG. 4B ; the material for spreading passes, after the calibration test, into the transfer chamber  14  in order for said material for spreading to be transferred to the conveying line  6  and dispensed) by means of a shut-off element, such as for example a shut-off flap  105 . 
     The embodiment of a weighing device  100  illustrated in  FIGS. 5A and 5B , in which components which are identical and of identical action are denoted by the same reference designations, differs from that as per  FIGS. 4A and 4B  primarily in that, instead of the weighing cells  103  arranged in the interior of the weighing container  101  (see  FIGS. 4A and 4B ), an outer container balance  106  is provided, on which the weighing container  101  is mounted. In order to mechanically decouple said weighing container firstly from the line  21  connecting the metering housing  13  of the meeting element  17  to the housing  5  of the transfer chamber  14  and secondly from the transfer line  104  which opens directly into the housing  5  of the transfer chamber  14 , compensation elements  107 , for example bellows or hose portions composed of flexible elastic or pliable materials, such as silicone, rubber textile or filter fabric and the like, are arranged between said lines  21 ,  104  and the weighing container  101 . 
     In the case of the embodiment as per  FIGS. 6A and 6B , the weighing container  101  of the weighing device  100  is in turn—similarly to  FIGS. 4A and 4B —equipped on its base with one or more weighing cells  103  and, in relation to the line  21  connecting the metering housing  13  of the metering element  17  to the housing  5  of the transfer chamber  14 , is mounted so as to be pivotable about a pivot axle S 1  between a weighing position ( FIG. 6A ; the calibration test is performed), in which said line opens into the weighing container  101 , and a transfer or normal operating position ( FIG. 6B ; the calibration test is ended and the spreading work can be performed), in which the weighing container  101  opens into the transfer chamber  14 . The pivot axle S 1  of the weighing container  101  is in the present case arranged at the lower end of the line  21  in the region of the circumference thereof and extends substantially horizontally, that is to say perpendicularly with respect to the line  21 . The housing  5  of the transfer chamber  14  is in turn, in relation to the line  21  connecting it to the metering housing  13  of the metering element  17 , mounted so as to be pivotable about a pivot axle S 2  between the weighing position ( FIG. 6A ), in which it has been pivoted away from the line  21 , and the transfer or normal operating position ( FIG. 6B ), in which both the weighing container  101  and the line  21  connecting the outlet  20  of the metering housing  13  to the housing  5  of the transfer chamber  14  open into the transfer chamber  14 . The latter pivot axle is in the present case likewise arranged at the lower end of the line  21  in the region of the circumference thereof and extends substantially horizontally, that is to say perpendicularly with respect to the line  21 , and in particular parallel to the pivot axle S 1  of the weighing container  101 . In this case, a separate transfer line  104  (see  FIGS. 4 and 6 ) that connects the weighing container  101  to the transfer chamber  14  can be omitted, because, after the ending of the calibration test, the weighing container  101  is, in an overhead position, emptied into the transfer chamber  14  ( FIG. 6B ) in order for the material for spreading that has been collected during the calibration test to be transferred to the conveying line  6  and dispensed. The housing  5  of the transfer chamber  14  has, for this purpose, that is to say for the purposes of “docking” the weighing container  101  onto the transfer chamber  14  in the situation illustrated in  FIG. 6B , an opening  108  which is adapted with regard to its circumferential cross section to the opening cross section of the weighing container  101  and which is furthermore arranged on the upper region of the transfer chamber  14 , such that the material for spreading can fall from the weighing container  101  into the transfer chamber  14  purely owing to gravitational force (see  FIG. 6B ). The opening  108  is expediently closable by means of a suitable cover (not illustrated in the drawing) in order that, in the operating position of the housing  5  equipped with the injector ( FIG. 6B ), the flow conditions prevailing in the transfer chamber  14  thereof are not influenced in the case of the blower  4  being active. 
     The embodiment of a weighing device shown in  FIGS. 7A to 7C , in the case of which components which are identical and of identical action are denoted by the same reference designations, differs from that as per  FIGS. 6A and 6B  primarily in that the housing  5  of the transfer chamber  14  is not articulated on the line  21  by means of a pivot bearing S 2  (see  FIGS. 6A and 6B ) but is rather arranged on a rotary slide which is situated outside the plane of the drawing and is consequently not illustrated in detail and by means of which the transfer chamber  14  is rotatable in the direction of the arrow D ( FIG. 7B ) between the weighing position ( FIG. 7A ; the calibration test is performed), in which said transfer chamber is arranged outside the line  21  that connects it to the metering element  5 , and the transfer or normal operating position ( FIG. 7C ), in which both the weighing container  101  and the line  21  open into said transfer chamber. It is likewise possible in this case to see the cover  109 , assigned to the opening  108  provided for the “docking” of the weighing container  101  onto the housing  5  of the transfer chamber  14 , of the weighing container  101 , which cover is open in the situations shown in  FIGS. 7A  (the calibration test is performed) and  7 C (after the end of the calibration test, the material for spreading that has collected in the weighing container  101  is emptied, in an overhead configuration, into transfer chamber  14 ), whereas said cover closes the opening cross section of the weighing container  101  when said weighing container is pivoted ( FIG. 7B ) between the weighing position ( FIG. 7A ) and the transfer or normal operating position ( FIG. 7C ) and when, after the transfer of the material for spreading from the weighing container  101  into the transfer chamber  14 , the spreading work is performed again with the blower  4  activated (cf.  FIG. 1 ). 
     In the case of the embodiments of a weighing device  100  shown in  FIGS. 8A to 8C , in which, again, components which are identical or of identical action are denoted by the same reference designations and will not otherwise be described again, both the housing  5  of the transfer chamber  14  and the weighing container  101  which is equipped on its base with one or more weighing cells  103  are arranged on a linear slide  110 , which in the present case extends substantially horizontally or substantially perpendicularly with respect to the line  21  connecting the metering housing  13  of the metering element  17  to the housing  5  of the transfer chamber  14 , at the lower end of said line. Both the housing  5  of the transfer chamber  14  and the weighing container  101  are in this case displaceable jointly between a weighing position ( FIG. 8A ; the calibration test is performed), in which the line  21  opens into the weighing container  101  and the transfer chamber  14  is arranged laterally outside the cross section of said line  21 , and an operating position ( FIG. 8C ; spreading work can be performed), in which the line  21  opens into the transfer chamber  14  and the weighing container  101  is arranged laterally outside the cross section of said line  21 . In order, after a calibration test is performed ( FIG. 8A ) and before the start of spreading work ( FIG. 8C ), for the material for spreading that has collected in the weighing container  101  to be transferred into the transfer chamber  14  and then, when the blower  4  is activated, dispensed by the conveying line  6 , the weighing container  101  can be selectively connected to and separated from the housing  5 , situated adjacent thereto, of the transfer chamber  14 . For this purpose, in the lower region of the wall that separates the weighing container  101  from the housing  5  of the transfer chamber  14 , there is provided a pivotable flap  111  which is opened ( FIG. 8B ) during the transfer of the material for spreading accommodated in the weighing container  101  into the transfer chamber  14  after the end of the calibration test. Whereas the material for spreading may in this case also be transferred purely under the action of gravitational force into the transfer chamber  14 , in the present case a stripper  112  is used for this purpose, which stripper is for example fixed in static fashion to the linear guide  110  or in the region of that end of the line  21  which is averted from the metering housing  13  with the metering element  17  and which stripper extends from above to the base of the weighing container  101 . 
     The weighing device  100 —which is again arranged in each case directly downstream of the metering element  17  and upstream of the metering chamber  14 —both the embodiment as per  FIGS. 9A and 9B  and the embodiment as per  FIGS. 10A and 10B  require no dedicated weighing container  101  (cf.  FIGS. 3 to 8 ), by contrast to the preceding exemplary embodiments. In the embodiment shown in  FIGS. 9A and 9B , the weighing device  100  instead comprises a flap  113  which is arranged in the line connecting the metering housing  13  of the metering element  17  to the housing  5  of the transfer chamber  14 , which flap is pivotable between a weighing position ( FIG. 9A ; the calibration test is performed), in which said flap closes the cross section of the line  21  and the metered material for spreading is collected on the top side of the flap  113 , and an operating position ( FIG. 9B ; after the calibration test has been performed, the material for spreading that has collected on the flap  113  is transferred into the transfer chamber  14 , in order to be able to dispense said material for spreading via the conveying line  6 ), in which said flap at least partially or in particular entirely opens up the line cross section. The latter indeed also applies for the normal operating position, in which the flap  113  has the task of ensuring an unhindered passage of the metered material for spreading through the line  21  into the transfer chamber  14 . In order to gravimetrically detect the mass of material for spreading that has been metered during the execution of calibration tests, the flap  113  may on the one hand be equipped on a flap pivot axle S 3  with a torque or torsion sensor; on the hand, it is alternatively also conceivable for the flap  113  to be equipped, at its upper side facing toward the metering element  17 , with one or more weighing cells (not shown). The stop or seat, arranged in the interior of the line  21 , of the flap  113  in the closed position thereof should furthermore be equipped with corresponding sealing lips so as not to cause any air-pressure-induced calibration errors in the event of the transfer chamber  14  being charged with a blowing air stream during the execution of a calibration test. 
     In the case of the embodiment illustrated in  FIGS. 10A and 10B , the weighing device  100  comprises, instead of the flat  113  (see  FIGS. 9A and 9B ), a slide  118  which is arranged in the line  21  connecting the metering housing  13  of the metering element  17  to the housing  5  of the transfer chamber  14 , which slide is displaceable between a weighing position ( FIG. 10A ; the calibration test is performed), in which said slide closes the cross section of the line  21  and the metered material for spreading is collected on the top side of the slide  118 , and an operating position ( FIG. 10B ; after the calibration test has been performed, the material for spreading that has collected on the slide  118  is transferred into the transfer chamber  14 , in order to be able to dispense said material for spreading via the conveying line  6 ), in which said slide at least partially or in particular entirely opens up the line cross section. The latter indeed also applies for the normal operating position, in which the slide  118  has the task of ensuring an unhindered passage of the metered material for spreading through the line  21  into the transfer chamber  14 . In order to gravimetrically detect the mass of material for spreading that has been metered during the execution of calibration tests, the slide  118  is equipped, at its upper side facing toward the metering element  17 , with one or more weighing cells (not shown). In the present case, the slide  118  is displaceable back and forth along a linear guide  119  which extends substantially perpendicularly with respect to the line  21 , that is to say substantially horizontally, wherein, in its closed or weighing position as per  FIG. 10A , said slide abuts against sealing lips  120  provided in the interior of the line  21 . The displacement of the slide  118  is expediently realized, like the pivoting of the flap  113  ( FIGS. 9A and 9B ), by means of suitable, for example motor-type or actuator-type drives (not shown) which are commanded by the control and/or regulating device of the spreading machine. 
     The embodiments of weighing devices  100  schematically illustrated in  FIGS. 11 to 13 , which are positioned directly downstream of the metering element  17  on the housing  5  of the transfer chamber  14 , likewise provide no additional weighing container, but instead, the housing  5  of the transfer chamber  14  itself serves as a “weighing container”, that is to say, during the execution of calibration tests, the material for spreading metered by means of the metering element  17  is collected directly in the transfer chamber  14 . The transfer chamber  14  must for this purpose indeed be decoupled from the blower  4  (cf.  FIG. 1 ), or said blower must be deactivated, which can expediently be triggered by means of the control and/or regulating device. After the ending of the calibration test, the blower  4  can then be activated again in order for the material for spreading to be transferred from the transfer chamber  14  into the conveying line  6  and dispensed when or before the “normal” spreading work begins again. 
     Accordingly, in the embodiment of the weighing device  100  shown in  FIG. 11 , provision is made for the housing  5  of the transfer chamber  14 —similarly to the flap  113  of the exemplary embodiment shown in  FIGS. 9A and 9B —to be articulated, so as to be pivotable about the axle S 4 , on the circumference of the lower end of the line  21 , by means of a pivot bearing, wherein the pivot bearing is in turn equipped with a torque or torsion sensor  115  in order to gravimetrically detect the mass of material for spreading that has been collected in the transfer chamber  14  during a calibration test. Instead of the pivot bearing equipped with sensors  115 , the housing  5  of the transfer chamber  14  in the case of the embodiment of the weighing device  100  shown in  FIG. 12  is, for the same purpose, connected by means of weighing cells  116  to the lower end of the line  21 . The exemplary embodiment of the weighing device  100  illustrated in  FIG. 13  differs from this basically merely in that only a lower portion of the housing  5  of the transfer chamber  14  is connected by means of the weighing cells  116  to an upper portion of said housing. 
     Finally, the weighing device  100  as per the embodiment shown in  FIGS. 14A and 14B  is arranged downstream of the metering element  17  in the interior of the housing  5  of the transfer housing  14 —or more specifically on the base of the transfer chamber  14 —and comprises one or more weighing cells  117 . Whereas the weighing cells  117  are exposed during the execution of calibration tests with the blower  4  deactivated or decoupled from the transfer chamber  14 , such that the material for spreading metered by means of the metering element  17  is collected on said weighing cells ( FIG. 14A ), the weighing cells  117  are preferably assigned a slide  117   a  which acts for example in the direction of the arrow P of  FIG. 14A  and by means of which the weighing cells  117  can be covered when the “normal” spreading work is being performed or also when, at the start of said spreading work, the material for spreading that has collected in the transfer chamber  14  during the prior calibration test is to be dispensed via the conveying line  6  by activation of the blower  4  or coupling of said blower to the housing  5  of the transfer chamber  14  ( FIG. 13B ), such that the weighing cells  117  are not exposed to the air stream laden with particles of material for spreading. 
     While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.