Patent Publication Number: US-2019193100-A1

Title: Metering device and metering method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a 35 U.S.C. §§ 371 national phase conversion of PCT/EP2017/062603, filed May 24, 2017, which claims priority of European Patent Application No. 16171963.8, filed May 30, 2016, the contents of which are incorporated by reference herein. The PCT International Application was published in the German language. 
    
    
     TECHNICAL FIELD 
     The invention relates to a metering device for metering a fluid, comprising a common supply line and a plurality of discharge lines. 
     TECHNICAL BACKGROUND 
     The metering of fluids plays an important part in many various application sectors when specific quantities of a fluid are required. Metering is generally understood to be measuring or assessing a specific quantity. For example, specific quantities of lubricant are required in a rolling mill, so that the lubricant is metered. The required quantity of lubricant is presently conveyed by a pump in a rolling mill. That quantity then is distributed among a plurality of nozzles. The nozzles then spray the lubricant onto the rollers of the rolling mill, or into a roller gap of the rolling mill, respectively. 
     The lubricant herein can be sprayed in its pure form or else as a mixture with a carrier medium. When it is sprayed as a mixture, the lubricant can be mixed with the carrier medium already prior to passing the pump, or the lubricant is mixed with the carrier medium only in the nozzle. All variants of spraying have in common that the quantity of lubricant used is to be precisely metered. If too little lubricant is used, increased wear arises on the rollers and an increase in the energy required in the rolling procedure in the rolling mill arises. In order for inaccuracies in the metering by way of a conventional pump to be equalized, more lubricant than is absolutely required is presently used. This is at the expense of lower operating costs and/or representing a risk to the rolling process because issues relating to grip can arise on account of the reduced friction in the rolling gap. 
     A lubricating system having a common supply line and at least one conveying device is shown in document WO 2010/085489 A1. A specific quantity of lubricant is guided to a machine injection point by means of the lubricating system. In order for the flow of lubricant to be able to be precisely monitored, the lubricant system comprises an infeed pump which on the discharge side is connected to the supply line, and a throughflow measuring apparatus which is disposed on the inlet side of the conveying device. The lubricant flow can be monitored and set by a computer. 
     US 4 520 902 A discloses a lubricant impingement system having a lubricant reservoir, a pump driven in a motorized manner, and a plurality of conveying devices, wherein the plurality of conveying devices are connected among one another and to the pump and to the lubricant reservoir by way of a common line for the lubricant. The common line functions both for supplying the lubricant that is to be dispensed by the conveying devices as well as for returning non-consumed lubricant. As a hydraulic fluid, the lubricant pressurized by the pump simultaneously drives the movable pistons of the individual conveying devices. 
     SUMMARY OF THE INVENTION 
     It is an object of the invention to provide a metering device having improved metering. 
     The object is achieved by a metering device of the type mentioned above. The metering device according to the invention comprises a plurality of conveying devices each having one cavity for receiving the fluid and one piston for displacing the fluid. The plurality of conveying devices on the inlet side are in each case connected to the common supply line and on the outlet side are in each case connected to one of the plurality of discharge lines. 
     The metering device preferably comprises a drive unit. At least two of the conveying devices can be connected to the drive unit. Furthermore, the drive unit can drive at least two of the conveying devices. The drive unit is advantageously a common drive unit. The plurality of conveying devices are expediently mechanically connected to the common drive unit. It is moreover purposeful for the common drive unit to drive the plurality of conveying devices. In particular, the plurality of conveying devices can be driven/moved in a synchronous manner, for example while using the common drive unit. 
     The invention proceeds from the concept that a single pump as has been used to date can only inaccurately meter the required quantities of fluid. More fluid than necessary is typically consumed by way of such a pump in particular in the case of small required quantities. 
     On account of the plurality of conveying devices the fluid quantity is now split among the plurality of conveying devices. Each of the plurality of conveying devices has a cavity volume that is smaller than the aforementioned pump. The maximum volume of the respective cavity can be considered the cavity volume. By virtue of the smaller cavity volume each conveying device can measure a required quantity better than the afore-mentioned pump. Each of the conveying devices can convey a specific volumetric flow which then can be dispensed by the respective discharge line. Improved metering, in particular a more precise metering, can be guaranteed in this way. Moreover, the operating costs can be lowered by virtue of the improved metering. 
     The plurality of conveying devices furthermore enable a variable volumetric flow of fluid in a wide range. That volume of fluid which can be conveyed by a respective conveying device can be understood to be the volumetric flow. In particular, the volumetric flow which can be conveyed by one of the conveying devices can for example be at least 1 ml/min and/or at most 100 l/min, in particular at most 14 l/min. The volumetric flow can depend, for example, on the respective construction mode of the conveying device, in particular on a diameter of the conveying device, and/or on a drive speed. 
     At least one, in particular each, of the conveying devices can have an angular cross section. At least one, in particular each, of the conveying devices expediently has a round cross section. At least one, in particular each, of the conveying devices is preferably cylindrical. At least one, in particular each, of the conveying devices is (in each case) preferably embodied as a metering cylinder. At least one, in particular each, of the conveying devices can (in each case) be a piston pump, for example. Furthermore, at least one, in particular each, of the conveying devices can (in each case) have one piston, for example. Furthermore, the respective cavity which each of the conveying devices comprises can at least be a cylindrical chamber. 
     In one preferred design embodiment of the invention, the plurality of conveying devices are identically configured. Alternatively, the plurality of conveying devices can at least in part differ from one another, for example in terms of the cross-sectional area thereof, in terms of the cavity volume thereof, and/or in terms of other properties. 
     The common supply line advantageously opens into the plurality of conveying devices. Furthermore, each of the discharge lines can open into a respective discharge. 
     It is expedient for at least two of the conveying devices, in particular all conveying devices, to be intercoupled. For example, the intercoupled conveying devices can be coupled by way of a coupling unit. 
     Two elements can be understood to be “intercoupled” when the two elements are in interaction with each other. Furthermore, in the case of two (inter)coupled elements, the state of the one element can influence the state of the other element. 
     The metering device can furthermore comprise at least one linear guide by which the coupling element is expediently guided. In this way, the linear guide can have a mechanically stabilizing effect. 
     It is furthermore advantageous for at least two of the conveying devices, in particular all conveying devices, to be mechanically interconnected/connected among one another by way of a mechanical connection. The mechanical connection is expediently a rigid mechanical connection. The mechanical connection can be established by way of the coupling unit, for example. 
     The drive unit can comprise a linear drive. The linear drive can convert a rotary movement to a linear movement, for example. The drive unit can furthermore be a hydraulic, electric, and/or pneumatic drive unit. The drive unit can moreover have a gearbox or be free of any gearing. 
     A sensor can be disposed on the drive unit and/or on the mechanical connection, in particular on the coupling unit. The sensor can furthermore be integrated in the drive unit. The sensor can be a position sensor and/or a rotation speed sensor, for example. A drive speed of the driving unit, a speed of the piston, and/or a momentary volumetric flow can be determined with the aid of the sensor, for example. 
     At least one of the conveying devices can be embodied as a single-action metering cylinder. In one advantageous design embodiment of the invention, each of the conveying devices is in each case embodied as a single-action metering cylinder. Each of the single-action metering cylinders expediently comprises a single cylinder chamber which, in particular successively, can receive and discharge the fluid. 
     Furthermore, at least one of the conveying devices can be embodied as a double-action metering cylinder. In one preferred design embodiment of the invention, each of the conveying devices is in each case embodied as a double-action metering cylinder. Each of the double-action metering cylinders expediently comprises two cylinder chambers. While the first cylinder chamber of a respective double-action metering cylinder can receive the fluid, the second cylinder chamber of the same metering cylinder can preferably, in particular simultaneously, discharge the fluid, and/or vice versa. A double-action metering cylinder can be, for example, a double-rod cylinder, also referred to as a synchronous cylinder, or a differential cylinder. 
     At least one of the conveying devices, in particular each of the conveying devices, can have a leakage bore, in particular for identifying any leakage. Moreover, the metering device can comprise a collector line. Furthermore, the at least one conveying device, in particular each of the conveying devices, can be connected to the collector line by way of the respective leakage bore. 
     The metering device can comprise a return line, in particular a common return line. Moreover, the metering device can comprise at least one pressure control valve, in particular a plurality of pressure control valves. The metering device can furthermore comprise at least one switch valve, in particular a plurality of switch valves. One of the switch valves can in each case be disposed in each discharge line, for example. 
     At least one of the conveying installations is expediently connected to the return line. In particular, each of the conveying devices can be connected to the return line. Furthermore, each of the conveying devices can in each case be connected to the return line by way of one of the plurality of pressure control valves and/or by way of one of the plurality of switch valves. 
     Each of the switch valves can comprise in each case two positions, for example. The first position can be a passing position at which the respective conveying device is expediently connected to the respective discharge of the metering device. The second position can be a return flow position at which the respective conveying device is expediently connected to the return line. 
     The metering device can furthermore comprise a check unit. The switch valves can be connected to the check unit. Furthermore, the switch valves can be actuated and/or switched while using the check unit. 
     The metering device can have at least one check valve. The metering device expediently has a plurality of check valves. At least one of the plurality of check valves can in each case be disposed on the inlet side and/or on the outlet side of a respective conveying device. 
     The metering device preferably comprises at least one measuring coupling, also referred to as a mini measuring connector. The metering device can furthermore comprise at least one measuring sensor. The measuring coupling and/or the measuring sensor can be disposed in at least one of the plurality of discharge lines. The measuring sensor can be, for example, a pressure sensor, a temperature sensor, and/or a volumetric flow sensor. 
     The metering device comprises in particular a plurality of measuring couplings and/or a plurality of measuring sensors. At least one of the plurality of measuring couplings and/or at least one of the plurality of measuring sensors can be disposed in at least one of the plurality of discharge lines. At least one of the plurality of measuring couplings and/or at least one of the plurality of measuring sensors are/is preferably disposed in each of the plurality of discharge lines. For example, at least one of the plurality of measuring sensors, in particular each of the measuring sensors, can (in each case) be a pressure sensor, temperature sensor, and/or volumetric flow sensor. 
     The metering device can comprise a check unit and/or a controller unit, in particular for monitoring and/or controlling a parameter of the outgoing fluid. 
     The controller can be at least a controller without feedback, in particular a controller with feedback. The outgoing fluid is expediently the fluid going out by way of at least one of the discharge lines. The parameter can be, for example, a pressure, temperature, and/or a volumetric flow. 
     The check unit and/or the controller unit are/is expediently connected to at least one of the measuring sensors. 
     Furthermore, the check unit and/or the controller unit can be connected to each of the measuring sensors. 
     Moreover, the check unit and/or the controller unit can be connected to the aforementioned sensor. For example, the check unit and/or the controller unit can monitor the drive speed of the drive unit, the speed of a piston/the pistons, and/or a determined volumetric flow, in particular while using the sensor. 
     The check unit and/or the controller unit can furthermore be connected to the drive unit, in particular for controlling a drive speed of the drive unit. The check unit and/or the controller unit can comprise the above-mentioned check unit, or be a unit that is separate from the check unit. 
     The check unit and/or the controller unit can furthermore operate at least in a partially automatic manner. In the case of partially automatic monitoring and/or controlling, a part-step of monitoring and/or controlling can be carried out other than by the check unit and/or the controller unit per se, for example by a person in charge. Furthermore, monitoring and/or controlling can be carried out fully automatically by means of the check unit and/or the controller unit, in particular without any manual intervention by a person. 
     In one advantageous design embodiment of the invention, the metering device comprises a material block. A material block can be understood to be a block of solid material. The material block can have a plurality of bores and/or clearances. The plurality of conveying devices are in each case at least partially expediently disposed in the material block, in particular in the bores and/or clearances of the material block. Moreover, the pressure control valves, the switch valves, the check valves, the measuring coupling, the sensors, and/or further elements can at least partially be disposed in the material block and/or on the material block. 
     The material block can enable compact and/or robust construction mode of the metering devices. Lines or ducts, respectively, between the individual components can be kept short on account of the construction mode. Sealing locations can thus be reduced and/or avoided. Moreover, leakages can be reduced and/or avoided in this way. 
     The invention is furthermore directed toward a metering system having the metering device according to the invention, in particular having one of the refinements of the metering device described above. 
     The metering system expediently comprises a pump unit. The pump unit can have an initial pressure pump. The pump unit on the discharge side is preferably connected to the supply line. Moreover, the pump unit on the entry side can be connected to the return line. 
     It is furthermore advantageous for the metering system to comprise a fluid tank. The fluid tank on the discharge side in a purposeful manner is connected to the pump unit. The fluid tank on the entry side can furthermore be connected to the pump unit. The pump unit can comprise a pressure control valve. 
     The metering system can furthermore comprise a spray device, in particular having a plurality of nozzles. 
     The fluid can be a lubricant, for example. 
     The metering device and/or the metering system can in particular be a metering device/a metering system in rolling mill. Issues relating to grip by virtue of insufficient friction in a rolling gap of the rolling mill can be avoided by virtue of the improved metering. 
     The invention furthermore relates to a method for metering a fluid, wherein a metering device comprises a common supply line and a plurality of discharge lines, in which method the fluid is supplied by way of the common supply line and is dispensed by way of the plurality of discharge lines. 
     In order for improved metering to be enabled, the metering device according to the invention comprises a plurality of conveying devices having in each case one cavity and one piston, and the fluid in the case of the method is supplied to the plurality of conveying devices, wherein the cavities of the plurality of conveying devices receive the fluid, and each of the conveying devices dispenses a predetermined volumetric flow to, in each case, one of a plurality of discharge lines, wherein the pistons of the plurality of conveying devices displace the fluid. 
     The fluid when being displaced can in particular be dispensed from the plurality of conveying devices. 
     The metering device mentioned in the context of the method can in particular be the above-described metering device. Consequently, the elements mentioned hereunder of the metering device can be the aforementioned elements. 
     The plurality of conveying devices are expediently mechanically interconnected/connected among one another. It is furthermore preferable for the plurality of conveying devices to be driven in a common manner. In particular, the plurality of conveying devices can be driven and/or moved in a synchronous manner. 
     For example, the volumetric flow can be set in temporal terms in particular for metering the fluid. 
     The volumetric flow preferably is at least 1 ml/min. It is furthermore advantageous for the volumetric flow to be at most 100 l/min, in particular at most 14 l/min. 
     Furthermore, a spatial spray profile can be set, for example, by way of the choice of the conveying devices, in particular of the cavity volume thereof, by the switching mode of the conveying devices with the discharge lines and/or with a spray device and/or by the disposal of nozzles in the spray device. 
     In one preferred design embodiment of the invention, receiving of the fluid and displacing of the fluid take place successively. “Successively” can be understood to be in direct succession and/or by way of a temporal spacing. Each of the conveying devices can be designed in each case as a single-action metering cylinder having in each case a single cylindrical chamber, for example. Displacing can take place at the same speed as receiving, for example, and can take place up to 280 times more slowly than receiving. The design embodiment of the plurality of conveying devices as in each case a single-action metering cylinder can be particularly cost-effective. 
     In one further advantageous design embodiment of the invention, receiving the fluid and displacing the fluid take place simultaneously. In this case, each of the conveying devices can be designed as a double-action metering cylinder having in each case two cylinder chambers, for example. In particular, receiving the fluid and displacing the fluid take place simultaneously in different cylinder chambers of a respective conveying device, in particular in the different cylinder chambers of a respective double-action metering cylinder. For example, the first cylinder chamber of a respective double-action metering cylinder can receive the fluid, and the second cylinder chamber of the same metering cylinder can simultaneously displace the fluid, and vice versa. Continuous metering becomes possible in this way. 
     The previously provided description of advantageous embodiments of the invention contains numerous features, which in the individual dependent claims partially are presented combined as a plurality of features. Said features can however expediently also be considered individually and can be combined to form further purposeful combinations. In particular, said features can each be combined individually and in any arbitrary suitable combination with the method according to the invention and the metering device according to the invention, or the metering system according to the invention, respectively. Thus, method features may also be regarded as worded in substantive terms as properties of the corresponding device unit and vice versa. 
     Even though some terms are used in each case in the singular or in combination with a numeral in the description or in the claims, the scope of the invention is not intended to be limited to the singular or the respective numeral for these terms. 
     The properties, features and advantages of the invention described above and the manner in which they are achieved will be more clearly and distinctly comprehensible in conjunction with the following description of the exemplary embodiments, which are explained in greater detail in conjunction with the drawings. The exemplary embodiments are used to explain the invention and do not restrict the invention to the combination of features, including functional features, that is specified therein. For this purpose, it is furthermore also possible for suitable features of each exemplary embodiment to be considered explicitly in isolation, removed from one exemplary embodiment, introduced into another exemplary embodiment in order to supplement the latter and combined with any one of the claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings: 
         FIG. 1  shows a circuit diagram of a metering system; 
         FIG. 2  shows a circuit diagram of a metering device; 
         FIG. 3  shows an exemplary design embodiment of the metering device from  FIG. 2 ; 
         FIG. 4  shows the exemplary design embodiment of the metering device from  FIG. 3  in another perspective; 
         FIG. 5  shows a sectional view of the metering device from  FIG. 3  and  FIG. 4 ; 
         FIG. 6  shows a schematic longitudinal section through one of the conveying devices from  FIG. 2  to  FIG. 4 ; 
         FIG. 7  shows a schematic longitudinal section through an alternative design embodiment of the conveying devices; 
         FIG. 8  shows a circuit diagram of another metering system; 
         FIG. 9  shows a circuit diagram of another metering device; 
         FIG. 10  shows a schematic longitudinal section through one of the conveying devices from  FIG. 8 ; and 
         FIG. 11  shows a circuit diagram of a further metering system. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
       FIG. 1  shows a schematic circuit diagram of a metering system  2 . The metering system  2  has a metering device  4 , having a supply line  6  and a return line  8 , for metering a fluid. The metering system  2  furthermore comprises a pump unit  10  which on the discharge side is connected to the supply line  6  and on the entry side is connected to the return line  8 . The pump unit  10  comprises an initial pressure pump  12  as well as a pressure control valve  14 . 
     The metering system  2  moreover comprises a fluid tank  16  which on the discharge side as well as on the entry side is connected to the pump unit  10 . 
     The fluid tank  16  as well as the pump unit  10  supply the metering device  4  with fluid. For example, the fluid on the discharge side of the initial pressure pump  12  of the pump unit  10  is pressurized to approx. 1 bar to 3 bar. 
     The metering system furthermore can comprise a spray device (not illustrated) (cf.  FIG. 11 ). 
     The metering system  2  in this exemplary embodiment is a metering system  2  in a rolling mill. The fluid is in particular a lubricant, in particular for lubricating rollers of the rolling mill and/or of a rolling gap of the rolling mill. For example, the rolling mill can be a rolling mill for hot rolling and/or cold rolling. 
       FIG. 2  shows a circuit diagram of the metering device  4  from  FIG. 1 . The metering device  4  comprises a plurality of conveying devices  18 . The supply line  6  is a common supply line  6 . 
     The plurality of conveying devices  18  on the inlet side are in each case connected to the common supply line  6 . In particular, the common supply line  6  opens into the plurality of conveying devices  18 . 
     The metering device  4  furthermore comprises a plurality of discharge lines  20 . Each of the discharge lines opens into a discharge  21 . One of the plurality of conveying devices  18  on the discharge side is in each case connected in each case to one of the plurality of discharge lines  20 . 
     Each of the conveying devices  18  has a round cross section and is cylindrical. Each of the conveying devices  18  is in each case furthermore embodied as a metering cylinder. Moreover, each of the conveying devices  18  is in each case a piston pump. 
     The plurality of conveying devices  18  are of identical configuration and have an identical cross-sectional area and an identical cavity volume. 
     Each of the conveying devices  18  is in each case embodied as a double-action metering cylinder  22  (cf.  FIG. 6 ). Each of the double-action metering cylinders  22  comprises two cylinder chambers  24 . The two cylinder chambers  24  form the cavity of the respective double-action metering cylinder  22 . Each of the double-action metering cylinders  22  furthermore comprises in each case one piston  26  which delimits the respective first cylinder chamber  24  in relation to the respective second cylinder chamber  24 . Each of the pistons  26  has a piston seal  27 . 
     Each of the double-action metering cylinders  22  is configured as a double-rod cylinder, also referred to as a synchronous cylinder. Moreover, each of the double-action metering cylinders  22  (cf.  FIG. 6 ) has a continuous piston rod  28 . The piston  26  is fixedly connected to the piston rod  28 . 
     The plurality of conveying devices  18  (that is all of the latter) are furthermore intercoupled, in particular by way of a coupling unit  30 . The coupling unit  30  is embodied as a coupling plate. 
     The plurality of conveying devices  18  (that is all of the latter) are in particular mechanically interconnected/connected among one another by way of a rigid mechanical connection  32 . The mechanical connection  32  is established by way of the coupling unit  30 . 
     The metering device  4  moreover comprises a drive unit  34  which is embodied as a common drive unit  34 . 
     The plurality of conveying devices  18  are mechanically connected to the drive unit  34 . The drive unit  34  drives the plurality of conveying devices  18  in a synchronous manner. In particular, the piston rod  28  by the drive unit  34  is in each case driven or moved, respectively, conjointly with the piston  26 . 
     The drive unit  34  comprises a linear drive  36  which can convert a rotary movement to a linear movement. The drive unit  34  furthermore has a shaft  38  which is embodied as a spindle. The drive unit  34  by way of the shaft  38  is mechanically connected to the coupling unit  30 . 
     A sensor  40  is integrated in the drive unit  34 . The sensor  40  is configured as a rotation speed sensor. A drive speed of the drive unit  34  can first be determined with the aid of the sensor  40 . Furthermore, a speed of one of the pistons  26 , in particular of all pistons  26 , and thus a momentary volumetric flow, can be determined with the aid of the sensor  40 . 
     The metering device  4  moreover comprises a plurality of pressure control valves  42 . The return line  8  is a common return line  8 . Each of the conveying devices  18  by way of one of the plurality of pressure control valves  42  is connected to the return line  8 . Should a pressure in one of the discharge lines  20  exceed a threshold value, the respective pressure control valve  42  ensures that the fluid can run off by way of the return line  8 . 
     Fluid which is dispensed by/conveyed out of the respective conveying device  18  but is not dispensed by way of the respective discharge line  20  is returned to the pump unit by the common return line  8 . 
     The metering device  4  furthermore comprises a plurality of switch valves  44 . For example, one of the switch valves  44  is in each case disposed in each discharge line  20 . Each of the switch valves  44  has an electric solenoid  46  by which the respective switch valve  44  is switched. 
     Each of the switch valves  44  in each case has two positions. The first position of the switch valve  44  is a passing position at which the respective conveying device  18  is connected to the respective discharge  21  of the metering device  4 . The second position of the switch valve  44  is a return flow position at which the respective conveying device  18  is connected to the return line  8 . Accordingly, each of the conveying devices  18  by way of the respective switch valve  44 , and depending on the position of the respective switch valve  44  can be connected to the return line  8 . 
     The metering device  4  furthermore comprises a check unit  48  which is connected to the plurality of switch valves  44  by a data connection  50 . The data connection  50  can be established by a cable and/or in a wireless manner. The switch valves  44  are actuated and/or switched while using the check unit  48 . 
     When rolling a wide strip, for example, all switch valves  44  can be at the passing position. Furthermore, when rolling a narrow strip, for example, the switch valves  44  that are located on the right and the left according to the drawing can be moved to the return flow position, while the switch valves  44  that are disposed in the center according to the drawing are at a passing position. Moreover, in the event of maintenance of the rolling mill and/or in the event of maintenance of the metering device, for example, all switch valves can be moved to the return flow position. 
     The metering device  4  has a plurality of check valves  52  which are in each case disposed on the inlet side or on the outlet side of a respective conveying device  18 . 
     The metering device  4  furthermore comprises a plurality of measuring couplings  54  and a plurality of measuring sensors  56 . One of the plurality of measuring couplings  54  and one of the plurality of measuring sensors  56  are in each case disposed in each of the plurality of discharge lines  20 . Each of the measuring sensors  56  is in each case a volumetric flow sensor, for example. Furthermore, a further measuring sensor  58  which is a pressure sensor and/or a temperature sensor, for example, is disposed on/connected to one of the measuring couplings  54 . In principle, a further measuring sensor  58  can in each case be disposed on each of the measuring couplings  54 . 
     The metering device  4  comprises a controller unit  60  for monitoring and/or controlling a parameter of the outgoing fluid. The parameter can be a pressure, a temperature, and/or a volumetric flow, for example. 
     The controller unit  60  is connected to each of the volumetric flow sensors  56  by a data connection  50 . In this way, the volumetric flow can be monitored at each of the discharge lines  20 , in particular while using the controller unit  60 . The controller unit  60  is furthermore connected to the drive unit  34  by a data connection  50 , in particular for controlling a drive speed of the drive unit  34 . The volumetric flow can be set or regulated, respectively, in this way. 
     The controller unit  60  is furthermore connected to the further measuring sensor  58  which is a pressure sensor and/or a temperature sensor. The pressure and/or the temperature at one of the discharge lines  20  can be monitored in this way, in particular while using the controller unit  60 . A malfunction, for example an increase in pressure by virtue of clogging, and/or a drop in pressure by virtue of leaking, can be identified in a timely manner in this way. 
     The previously mentioned sensor  40  is also connected to the controller unit  60  by way of a data connection  50 . The sensor measures the current rotations of the drive unit  34 , or the drive speed of the drive unit  34 , respectively. The rotations or drive speed are monitored by the control unit  60 . 
     The controller unit  60  in this exemplary embodiment comprises the above-mentioned check unit  48  for setting the switch valves  44 . 
     The width of a rolled strip which is to be rolled/is being rolled is known to the controller unit  60 , or to the check unit  48 , respectively. The switch valves are switched in a corresponding manner. Furthermore, a rolling speed is known to the controller unit  60 , from which the controller unit  60  can draw a conclusion in terms of a required volumetric flow of fluid. A required drive speed of the drive unit  34  is calculated from the required volumetric flow. The controller unit  60  actuates the drive unit  34  in a corresponding manner. The drive speed set is verified and optionally readjusted by means of the sensor  40 . If a volumetric flow that deviates from the required volumetric flow is measured by means of one of the volumetric flow sensors  56 , the controller unit  60  in this instance can in turn readjust the drive speed of the drive unit  34 . 
     The metering device  4  is used for rolling a continuous rolled strip, for example. 
       FIG. 3  schematically shows an exemplary design embodiment of the metering device  4  from  FIG. 2 .  FIG. 4  shows the same exemplary design embodiment of the metering device  4  as in  FIG. 3 , but from another perspective. 
     The metering device  4  in  FIG. 3  and  FIG. 4  comprises a material block  62 . The material block is a block of solid material, for example of steel, in particular of stainless steel. The plurality of conveying devices  18  are in each case at least in part disposed in the material block  62 . The material block  62  comprises in particular cylindrical bores  64  (cf.  FIG. 5  and  FIG. 6 ) which penetrate the material block  62 . One of the conveying devices  18  is disposed in each of the bores  64 . 
     Each of the conveying devices  18  furthermore comprises two fixing elements  66  which are in each case configured as a cylinder head. Each of the conveying devices  18  at both ends of the bore  64  is in each case fixed or held, respectively, by one of the fixing element  66 . The fixing elements  66  are connected, in particular screw-fitted, to the material block  62 . A simple and rapid replacement of the individual conveying devices  18  or of parts thereof is enabled in this way. 
     The material block  62  furthermore comprises clearances which are in each case configured as a blind bore. Moreover, the pressure control valves  42 , the switch valves  44 , the check valves  52 , the measuring coupling  54 , the measuring sensors  56  are at least in part disposed, for example screw-fitted, in the material block  62 , in particular in the clearances. 
     The material block  62  is in this way configured as a cylinder and valve housing. 
     The material block  62  enables a compact and robust construction mode of the metering device  4 . Lines or ducts, respectively, between individual components are embodied by bores in the material block  62 , and on account of this construction mode, are kept short such that leakages can be reduced and/or avoided. 
     The metering device  4  furthermore comprises linear guides  68 . The coupling unit  30  is guided with the aid of the linear guides  68 . The linear guides  68  increase the mechanical stability of the metering device  4  in this way. 
     The coupling unit in  FIG. 3  and  FIG. 4  is illustrated so as to be transparent in order for the linear guides  68  and the piston rods  28  to be better visible. 
     The material block  62  having the bores  64  and clearances thereof can be manufactured in a cost-effective and automated manner. 
       FIG. 5  shows a section through the metering device  4  from  FIG. 3  and  FIG. 4  along two conveying devices  18 . 
     The material block  62  in this image is illustrated so as to be transparent. Furthermore, hatching of the sectioned elements has been dispensed with for the sake of better clarity. 
     The cylindrical bores  64  which penetrate the material block  62  can be seen in this image. One of the conveying devices  18  is disposed in each of said bores  64 . 
     It can be further seen in this image that the pressure control valves  42 , the switch valves  44 , check valves  52 , and the measuring coupling  54  are at least in part disposed in the material block  62 , in particular in the clearances which are in each case configured as a blind bore. 
     The check valves  52  are disposed completely in the material block  62 . In the case of the switch valves  44 , a part, in particular the electrical part (solenoid  46  and the electrical connector) of the switch valves protrudes from the material block  62 . The pressure control valves  42  also protrude in part from the material block  62 , in particular so as to be able to set the threshold value, or the switching time, respectively, of the pressure control valves  42 . The measuring couplings  54  likewise protrude in part from the material block  62 . A measuring sensor  58  (cf.  FIG. 2 ) can thus be connected to the respective measuring coupling  54 . 
       FIG. 6  shows a schematic longitudinal section through one of the conveying devices  18  from  FIG. 2  to  FIG. 5 . The conveying device  18  is disposed in the cylindrical bore  64  which penetrates the material block  62 . 
     The conveying device  18  is embodied as a double-action metering cylinder  22 . The double-action metering cylinder furthermore comprises the piston rod  28  which is fixedly connected to the piston  26 , and a cylinder tube  70  which forms the external wall. The piston  26  within the cylinder tube  70  moves in a reciprocating manner in the direction of the longitudinal axis of the cylinder tube  70 . According to the drawing, the piston  26  within the cylinder tube  70  moves in the vertical direction toward the right and the left. 
     The double-action metering cylinder  22  comprises two cylinder chambers  24 . The piston  26  separates the first cylinder chamber  24  from the second cylinder chamber  24 . Each of the cylinder chambers by way of an inlet  72  is connected to the supply line  6 , and by way of an outlet  74  is connected to the respective discharge line  20 . While the first cylinder chamber  24  of the double-action metering cylinder  22  receives the fluid, the second cylinder chamber  24  of the same metering cylinder  22  simultaneously dispenses the fluid, and vice versa. 
     The conveying device  18  is fixed with the aid of the two fixing elements  66  (here cylinder heads). The fixing elements  66  are screw-fitted to the material block  62 . Each of the fixing elements  66  furthermore comprises a plurality of seals  76  which are configured as annular seals. The seals guarantee a tightness of the conveying device  18 . Moreover, each of the fixing elements  66  comprises a scraper  78 . The respective scraper  78  is configured as a rubber ring. The scrapers  78  likewise ensure a tightness of the conveying device  18 . The cylinder tube  70  also comprises a seal  76  which seals the fixing element  66  in relation to the material block  62 . 
     In  FIG. 6  the left cylinder chamber  24  according to the drawing, which represents the first cylinder chamber  24 , is completely filled. Furthermore, the right cylinder chamber  24  according to the drawing, which represents the second cylinder chamber  24 , is completely emptied. The piston  26  accordingly is located in the terminal position on the right according to the drawing. The piston rod  28 , conjointly with the piston  26 , is subsequently moved by the drive unit toward the left according to the drawing, such that the left, first cylinder chamber  24  of the double-action metering cylinder dispenses the fluid by way of the left outlet  74  according to the drawing. The right, second cylinder chamber  24  simultaneously receives the fluid by way of the right inlet  72  according to the drawing. The piston rod  28 , conjointly with the piston  26 , is thus moved to the left until the left, first cylinder chamber  24  is completely emptied and the right cylinder chamber is completely filled. 
     The piston rod  28 , conjointly with the piston  26 , then moves toward the right such that the left, first cylinder chamber  24  of the double-action metering cylinder receives the fluid by way of the left inlet  72  according to the drawing, and the right, second cylinder chamber  24  simultaneously dispenses the fluid by way of the right outlet  74  according to the drawing, until the left, first cylinder chamber  24  according to the drawing is completely filled, and the right, second cylinder chamber  24  according to the drawing is completely emptied. The procedure is repeated as a circulatory system. Continuous metering is possible in this way. 
     The piston  26  in an exemplary manner has an external diameter of 14 mm. The piston rod  28  in a furthermore exemplary manner has a diameter of 10 mm. The so-called stroke of the conveying device  18  is, for example, 160 mm. The distance which the piston  26  can cover at most in one direction can be referred to as the stroke. The cavity volume of the conveying device  18  is thus 12 ml, for example. 
     The fluid that is received by the respective cylinder chamber  24  is pressurized to 1 bar to 3 bar, for example. Furthermore, the fluid that is dispensed by the respective cylinder chamber is pressurized to 5 bar to 10 bar, for example. The threshold value of the check valves  52  is adapted to the pressure conditions of the fluid in a corresponding manner. Accordingly, the respective check valve  52  that is disposed on the outlet side of the respective cylinder chamber  24  has a higher threshold value than the respective check valve  52  that is disposed on the inlet side of the respective cylinder chamber  24 . 
     The volumetric flow which can in each case be conveyed by a conveying device  18  (hereunder simply referred to as “the volumetric flow”) in this exemplary embodiment corresponds to the volumetric flow which in each case can be dispensed by way of one of the discharge lines  20 . The volumetric flow can be set so as to depend on the drive speed of the drive unit  34 . For example, the volumetric flow can be set in a range from 3.5 ml/min to 64 ml/min. 
       FIG. 7  shows a schematic longitudinal section through an alternative design embodiment of the conveying devices  18  from  FIG. 6 . The description hereunder is substantially limited to the points of differentiation in relation to the conveying devices  18  from  FIG. 6 , to which reference is made in terms of features and functions that remain the same. Elements that substantially remain the same are in principle identified by the same reference signs, and features which are not mentioned are incorporated in the following exemplary embodiment without being described once again. 
     Each of the cylinder chambers  24  has an inlet  72  which simultaneously functions as an outlet  74 . 
       FIG. 8  shows a schematic circuit diagram of a further metering system  80  having another metering device  82  for metering a fluid. The description hereunder is substantially limited to the points of differentiation in relation to the exemplary embodiment from  FIG. 1  to  FIG. 6 , reference being made to the latter in terms of features and functions that remain the same. Elements that substantially remain the same are in principle identified by the same reference signs, and features which are not mentioned are incorporated in the following exemplary embodiment without being described once again. 
     The supply line  6  of the metering device  82  simultaneously functions as a return line  8 . In principle, a design embodiment in which the supply line  6  and the return line  8  are present so as to be separate from one another (in a manner analogous to that of the first exemplary embodiment) would in principle also be possible. 
       FIG. 9  shows a circuit diagram of the metering device  82  from  FIG. 8 . 
     Each of the conveying devices  18  is in each case embodied as a single-action metering cylinder  84  (cf.  FIG. 10 ). Each of the single-action metering cylinders  84  expediently comprises a single cylinder chamber  24 . Each of the single-action metering cylinders  84  furthermore comprises in each case one piston  26  and one piston rod  86 . The piston  26  is fixedly connected to the piston rod  86 , wherein the piston rod  86  is located only on one side of the piston  26 . 
     Each of the conveying devices  18  has one leakage bore  88 . The metering device  82  furthermore comprises a collector line  90  which is connected to the leakage bores  88 . 
     A sensor  92  is disposed on the mechanical connection  32 , in particular on the coupling unit  30  (instead of the sensor  40  on the drive unit  34  in the first exemplary embodiment). The sensor  92  is a position sensor. The sensor  92  can determine the position of the coupling unit  30  and thus the speed of the coupling unit  30  or the speed of the pistons  26 , respectively, and/or the volumetric flow. 
     The sensor  92  is also connected to the controller unit  60  by way of a data connection  50 . The sensor  92  measures the position of the coupling unit  30  and thus the speed of the coupling unit  30 , or the speed of the pistons  26 , respectively, said speed being monitored by means of the control unit  60 . 
     The metering device  82  in this exemplary embodiment does not comprise any pressure control valves (as opposed to the first exemplary embodiment in  FIG. 1  to  FIG. 6 ), although this would be possible in principle. 
     The metering device  82  is used in a hot-rolling process, for example, in particular for rolling individual rolled strips from slabs. If the respective conveying devices  18  are completely filled with fluid, the quantity of fluid is sufficient for an entire rolled strip. The filling of the conveying devices  18  in this instance can be performed between rolling a first strip and rolling a second strip, for example. 
       FIG. 10  shows a longitudinal section through one of the conveying devices  18  from  FIG. 9 . The conveying device  18  is embodied as a single-action metering cylinder  84  and comprises a single cylinder chamber  24 . The cylinder chamber  24  forms the cavity of the single-action metering cylinder  84 . The cylinder chamber  24  can successively receive and dispense the fluid. 
     The cylinder chamber  24  in  FIG. 10  is partially filled. The piston  26  is located in the center according to the drawing. 
     The piston rod  86 , conjointly with the piston  26 , subsequently moves to the right such that the cylinder chamber  24  receives the fluid by way of the inlet  72  until the cylinder chamber  24  is completely filled. 
     The piston rod  86 , conjointly with the piston  26 , is subsequently moved by the drive unit to the left according to the drawing such that the cylinder chamber  24  dispenses the fluid by way of the outlet  74 . The metering of the fluid is performed in this way. The piston rod  86 , conjointly with the piston  26 , can move to the left until the cylinder chamber  24  is completely emptied. The cylinder chamber  24  subsequently has to be refilled. The procedure is repeated as a circulatory system. Discontinuous metering is possible in this way. 
     The cylinder chamber  24  can be completely filled in 11 s, for example. Furthermore, the cylinder chamber is completely emptied in, for example, 11 s to 205 s, depending on the volumetric flow set. 
     The conveying device  18  has a leakage bore  88  for identifying leakages. Furthermore, the conveying device  18  is connected to the collector line  90  of the metering device  82  by way of the leakage bore  88 . 
     In the event of a leakage from the conveying device  18 , some fluid exits by way of the leakage bore  88 . The fluid that has exited by virtue of the leakage accumulates in the collector line  90  and can be detected visually and/or by way of a measuring apparatus. In the event of a defect in one of the conveying devices  18 , a timely replacement of the defective conveying device  18  can be guaranteed in this way. 
       FIG. 11  shows a further metering system  94  having a metering device  96 . The description hereunder is substantially limited to the points of differentiation in relation to the exemplary embodiment from  FIG. 8  to  FIG. 10 , reference being made to the latter in terms of features and functions that remain the same. Elements that substantially remain the same are in principle identified by the same reference signs, and features which are not mentioned are incorporated in the following exemplary embodiment without being described once again. 
     Some elements (such as, for example, a pump unit, a fluid tank, a drive unit, a return line, pressure control valves, switch valves, measuring couplings, measuring sensors, etc.) are not shown in  FIG. 11  but could in principle be incorporated individually or in any arbitrary combination from the other exemplary applications. 
     The metering system  94  comprises a spray device  98  having a plurality of nozzles  100 . The spray device  98  is furthermore connected to the plurality of discharge lines  20  of the metering device  96 . 
     The metering device  96  comprises a plurality of conveying devices  18  which at least in part differ from one another, for example in terms of the cross-sectional area thereof and in terms of the cavity volume thereof. For example, the respective cross-sectional area and the respective cavity volume of the conveying devices  18  disposed on the right and on the left according to the drawing is smaller than in the conveying devices  18  disposed in the center according to the drawing. The cross-sectional areas of the conveying devices  18 , or the different cavity volumes of the conveying devices  18 , respectively, enable different volumetric flows. 
     Furthermore, more nozzles  100  of the spray device are connected to the conveying devices  18  that are disposed in the center according to the drawing than are connected to the conveying devices  18  that are disposed on the right and on the left according to the drawing. 
     A desired spatial spray profile can be set by way of a corresponding circuit design including the nozzles  100  and of a corresponding disposal of the nozzles  100 . 
     Even though the invention has been illustrated and described in more detail by way of the preferred exemplary embodiments, the invention is not restricted by the examples disclosed, and other variations may be derived therefrom by a person skilled in the art without departing from the scope of protection of the invention. 
     LIST OF REFERENCE SIGNS 
       2  Metering system 
       4  Metering device 
       6  Supply line 
       8  Return line 
       10  Pump unit 
       12  Initial pressure pump 
       14  Pressure control valve 
       16  Fluid tank 
       18  Conveying device 
       20  Discharge line 
       21  Discharge 
       22  Metering cylinder 
       24  Cylinder chamber 
       26  Piston 
       27  Piston seal 
       28  Piston rod 
       30  Coupling unit 
       32  Mechanical connection 
       34  Drive unit 
       36  Linear drive 
       38  Shaft 
       40  Sensor 
       42  Pressure control valve 
       44  Switch valve 
       46  Solenoid 
       48  Check unit 
       50  Data connection 
       52  Check valve 
       54  Measuring coupling 
       56  Measuring sensor 
       58  Measuring sensor 
       60  Controller unit 
       62  Material block 
       64  Bore 
       66  Fixing element (cylinder head) 
       68  Linear guides 
       70  Cylinder tube 
       72  Inlet 
       74  Outlet 
       76  Seal 
       78  Scraper 
       80  Metering system 
       82  Metering device 
       84  Metering cylinder 
       86  Piston rod 
       88  Leakage bore 
       90  Collector line 
       92  Sensor 
       94  Metering system 
       96  Metering device 
       98  Spray device 
       100  Nozzles