Dosing device and dosing system and method for dosing a fluid

Abstract

A dosing device (20) for dosing a fluid has a fine dosing valve (24), a coarse dosing valve (26), and a valve block (22). The dosing device (20) is designed such that, in a first position, in which the fine dosing valve (24) is in an open position and the coarse dosing valve (26) is in a closed position, a fluid flows from a fluid inlet (28) through a fine dosing chamber (32) via a fine dosing valve seat (34) into a fine dosing outlet channel (40) during operation. In a second position, in which the fine dosing valve (24) is in a closed position and the coarse dosing valve (26) is in an open position, a fluid flows from the fluid inlet (28) via a coarse dosing chamber (36) and a coarse dosing valve seat (38) into a coarse dosing outlet channel (42). Furthermore, a dosing system with such a dosing device (20) and a dosing method are proposed.

Description

The invention relates to a metering device for metering a fluid, having a fine metering valve, a coarse metering valve and a valve block. The invention further relates to a dosing system with such a dosing device and to a method for dosing a fluid with the aid of the dosing device.Such metering devices and metering systems are known.In order to meter a fluid efficiently and precisely, large quantities of fluid are dispensed or filled via the coarse metering valve and small quantities are dispensed or filled via the fine metering valve.The disadvantage of the known metering devices is that they are very complicated to clean.It is an object of the invention to provide a dosing device which can be cleaned with little effort. It is a further object of the invention to provide a dosing system with such a dosing device and a method for dosing fluid.The first object is achieved by a metering device for metering a fluid, having a fine metering valve, a coarse metering valve and a valve block. The fine metering valve has a fine metering chamber and a fine metering valve seat which are formed in the valve block. Furthermore, the coarse metering valve has a coarse metering chamber and a coarse metering valve seat which are formed in the valve block. Furthermore, a connecting channel is provided which connects the fine metering chamber and the coarse metering chamber to one another in terms of flow. The valve block has a fluid inlet which opens into one of the fine metering chamber and the coarse metering chamber and is connected in terms of flow to the other via the connecting channel, a fine metering outlet channel which is arranged downstream of the fine metering valve seat in the flow direction, and a coarse metering outlet channel which is arranged downstream of the coarse metering valve seat in terms of flow in the flow direction. The metering device is configured such that in a first position, in which the fine metering valve is in an open position and the coarse metering valve is in a closed position, a fluid flows from the fluid inlet through the fine metering chamber via the fine metering valve seat into the fine metering outlet channel during operation, and in a second position, in which the fine metering valve is in a closed position and the coarse metering valve is in an open position, a fluid flows from the fluid inlet via the coarse metering chamber and the coarse metering valve seat into the coarse metering outlet channel during operation.It has been recognized according to the invention that with a metering device configured in this way, in positions in which only one of the two metering valves is opened, i.e. either the fine metering valve or the coarse metering valve, the fluid flows via the connecting channel through the metering chamber of the closed metering valve, i.e. through the fine metering chamber or the coarse metering chamber, and flushes the latter. Thus, the dosing device at least partially self-cleans during operation, so that the effort for cleaning the dosing device is reduced overall. In addition, it is possible with the metering device according to the invention to remove air bubbles from the system by flushing air out of the cavities with liquid when the coarse metering valve is open at the beginning of the metering process. Thereafter, for example, a fine dosing free of air bubbles can take place directly.In this case, the fine metering valve can have a bellows for separating media, which bellows is arranged in the fine metering chamber and can press against the fine metering valve seat. Additionally or alternatively, the coarse metering valve can have a bellows for separating media, which bellows is arranged in the coarse metering chamber and can press against the coarse metering valve seat.In particular, the bellows of the fine metering valve and / or the bellows of the coarse metering valve are formed from polytetrafluoroethylene (PTFE) or a fluorine-free material. As a result of this configuration with resistant materials and media-separated drives, the metering device meets high hygiene requirements and is suitable in particular for use in the chemical, pharmaceutical and food sectors.Furthermore, the fine metering valve and / or the coarse metering valve can each have a pneumatically actuated piston drive, as a result of which the metering device is suitable for use in demanding environments, in particular for hazardous and / or rough environments.In one embodiment, the fine metering valve and the coarse metering valve are of identical design. The use of identical parts has a wide variety of advantages in logistics, production and maintenance of the dosing device.In a further embodiment, the fine metering outlet channel has a smallest cross section which is smaller than a smallest cross section of the coarse metering outlet channel. Thus, at a given pressure, the volume flow flowing through the fine dosing outlet channel is smaller than the volume flow flowing through the coarse dosing outlet channel, so that small quantities of fluid can be dosed precisely via the fine dosing outlet channel, while large quantities of fluid can be dosed in a short time via the coarse dosing outlet channel.In this case, it can be provided that the smallest cross section of the fine metering outlet channel is smaller than the smallest cross section of the coarse metering outlet channel by at least a factor of ten, in particular even by a factor of 50, in order to provide particularly efficient metering. A further advantage is that containers of widely different sizes can be filled accurately and quickly by the opening times of the coarse metering valve and fine metering valve being able to be adapted accordingly.As already explained above, the coarse metering valve and the fine metering valve are in particular identical parts, i.e. their valve seat has the same nominal width.According to an alternative embodiment, the fine metering valve seat has a nominal width which is smaller than a nominal width of the coarse metering valve seat, in particular by at least 50% or by at least 75%. In this way, at a given pressure, the volume flow flowing through the fine metering valve seat is smaller than the volume flow flowing through the coarse metering valve seat, so that small amounts of fluid can be metered precisely via the fine metering valve seat, while large amounts of fluid can be metered in in a short time via the coarse metering valve seat.Furthermore, the fine metering outlet channel and the coarse metering outlet channel can be connected in terms of flow to a common outlet which is formed in the valve block. Compared to separate outlets for the fine dosing outlet channel and the coarse dosing outlet channel, this design has the advantage that during operation the high volume flow of the coarse dosing valve flows through the common outlet and thus also flushes the outlet which is associated with the fine dosing outlet channel.Furthermore, it can be provided that the dosing device has a connecting piece attached to the valve block with a filling channel. The filling channel is in this case connected in terms of flow to the fine metering outlet channel and the coarse metering outlet channel, in particular via a common outlet which is formed in the valve block and is connected in terms of flow to the fine metering outlet channel and the coarse metering outlet channel. By means of the connecting piece, the metering device is of modular construction and can be adapted to different requirements with little effort by selecting or using a matching connecting piece.According to a further embodiment, the fluid inlet opens into the fine metering chamber and fluid can flow via the connecting channel to the coarse metering chamber. During operation, a fluid thus flows in the second position from the fluid inlet via the fine metering chamber through the connecting channel into the coarse metering chamber and from the coarse metering chamber via the coarse metering valve seat into the coarse metering outlet channel. In this way, the fine metering chamber is flushed or cleaned particularly effectively by the high volume flow which flows through it in this case.According to the invention, in order to achieve the object mentioned above, a metering system having a metering device according to the invention with the advantages mentioned above, a control unit and a scale or a gravimetric or volumetric measuring unit is also provided, wherein the scale or the measuring unit is coupled to the control unit by signal technology, so that the control unit can process the measured values and correspondingly actuates the valves.The control unit can optionally be programmed in such a way that it controls the opening times of the fine and coarse valves as a function of the quantity of the fluid to be metered, so that containers of exactly different sizes can be filled very quickly and accurately by means of the metering system.The further object is achieved by a method for metering a fluid, in particular a liquid, by means of the aforementioned metering device. Before the beginning of a metering process, one of the two is opened after both the fine metering valve and the coarse metering valve have been closed beforehand. Fluid, in particular liquid, is thus introduced into the dosing system in order to flush it. After this flushing, the metering takes place by selective opening and closing of the coarse metering valve and of the fine metering valve.Because more fluid can flow through the device via the coarse metering valve, it is appropriate to carry out the flushing process when this valve is opened.By intermittently opening and closing the corresponding valve during flushing populations are created, over which for example air in dead spaces is captured and entrained. The same applies to impurities.Further advantages and features will become apparent from the following description and from the attached drawings. In these show:FIG. 1 shows a schematic illustration of a metering system according to the invention with a metering device according to the invention, andFIG. 2 shows a schematic illustration of the metering device from FIG. 1.The following detailed description, taken in conjunction with the accompanying drawings, in which like numerals refer to like elements, is intended to describe various embodiments of the disclosed subject matter and is not intended to represent the only embodiments. Each embodiment described in this disclosure is merely illustrative and should not be construed as preferred or advantageous over other embodiments.All features disclosed below with respect to the embodiments and / or the accompanying figures may be combined alone or in any sub-combination with features of the aspects of the present disclosure, including features of preferred embodiments, provided the resulting combination of features is appropriate to a person skilled in the art.FIG. 1 shows a dosing system 10 with a control unit 12, a scale 14 and a dosing device 20.The dosing system 10 is configured here to control the dosing device 20 by means of the control unit 12 such that a fluid to be dosed is dispensed from the dosing device 20 in a precise amount. The quantity is determined by the scale 14, which here forms the measuring unit of the dosing system 10.For this purpose, the dosing device 20 and the scale 14 are connected to the control unit 12 in a signal-transmitting manner. These connections are shown in broken lines in FIG. 1.In an alternative embodiment, the dosing system 10 can have any desired measurement unit instead of the scale 14, in particular a gravimetric or volumetric measurement unit.The metering device 20 (see FIG. 2 ) has a valve block 22, as well as a fine metering valve 24 and a coarse metering valve 26, which are mounted on the valve block 22.The valve block 22 has a fluid inlet 28, an outlet 30, a fine metering chamber 32 with a fine metering valve seat 34 and a coarse metering chamber 36 with a coarse metering valve seat 38.In the present embodiment, the fluid inlet 28 opens into the fine metering chamber 32.The fine metering chamber 32 and the coarse metering chamber 36 are preferably designed free of dead spaces in order to facilitate cleaning.The valve block 22 further comprises a fine metering outlet channel 40, which opens upstream via the fine metering valve seat 34 into the fine metering chamber 32 and downstream into the outlet 30, and a coarse metering outlet channel 42, which opens upstream via the coarse metering valve seat 38 into the coarse metering chamber 36 and downstream into the outlet 30.Furthermore, the valve block 22 has a connecting channel 44 by means of which the fine metering chamber 32 is connected in terms of flow to the coarse metering chamber 36 and is connected in series in the flow direction.In the illustrated embodiment, the fine metering valve seat 34 and the coarse metering valve seat 38 have an identical nominal width and an identical cross section, respectively.In principle, the fine metering valve seat 34 and the coarse metering valve seat 38 can each have any desired size nominal width and any desired cross section.In an alternative embodiment, the fine metering valve seat 34 has a nominal width which is smaller than the nominal width of the coarse metering valve seat 38, in particular by at least 50% or by at least 75%.The fine metering outlet channel 40 has a diameter d of, for example, 2.5 mm, which forms the smallest cross section q of the fine metering outlet channel 40, while the coarse metering outlet channel 42 has a diameter D of, for example, 10 mm, which forms the smallest cross section Q of the coarse metering outlet channel 42.Generally, the fine metering outlet channel 40 and the coarse metering outlet channel 42 may each have a smallest cross section q, Q of any size or diameter.In an alternative embodiment, the smallest cross section q of the fine dosing outlet channel 40 is smaller than the smallest cross section Q of the coarse dosing outlet channel 42 by at least a factor of 10, in particular even by at least a factor of 50.Returning to the metering valves 24, 26, the fine metering valve 24 has a drive 46 and a bellows 48, which is coupled in terms of drive to the drive 46, for example via a tappet.The drive 46 is here a pneumatically actuated piston drive.The bellows 48 is made of PTFE or polytetrafluoroethylene or a fluorine-free material, for example.In all embodiments, the bellows 48 is arranged in the fine metering chamber 32 and seals the drive 46 with respect to the fine metering chamber 32 in a fluid-tight manner, such that a media separation is provided between the drive 46 and the fluid which flows through the fine metering chamber 32 during operation.By means of the drive 46, the bellows 48 can be adjusted between a closed position, in which the bellows 48 presses against the fine metering valve seat 34 and tightly closes it, and an open position, in which the bellows 48 releases, i.e. does not close, the fine metering valve seat 34.The coarse metering valve 26 has a drive 50 and a bellows 52, which is coupled in terms of drive to the drive 50, for example via a tappet.The drive 50 is here a pneumatically actuated piston drive.Here too, the bellows 52 consists, for example, of PTFE or polytetrafluoroethylene or a fluorine-free material.In all embodiments, the bellows 52 is arranged in the coarse metering chamber 36 and seals the drive 50 with respect to the coarse metering chamber 36, such that a media separation is provided between the drive 50 and the fluid which flows through the coarse metering chamber 36 during operation.By means of the drive 50, the bellows 52 can be adjusted between a closed position, in which the bellows 52 presses against the coarse metering valve seat 38 and tightly closes it, and an open position, in which the bellows 52 releases, i.e. does not close, the coarse metering valve seat 38.The fine metering valve 24 and the coarse metering valve 26 can be of identical design, i.e. identical parts.The metering device 20 has a first position in which the fine metering valve 24 is in the open position and the coarse metering valve 26 is in the closed position, and a second position in which the fine metering valve 24 is in the closed position and the coarse metering valve 26 is in the open position.In this connection, the dosing device 20 is designed such that, during operation, a fluid flows via the fluid inlet 28 into the fine dosing chamber 32 and from the fine dosing chamber 32 via the fine dosing valve seat 34 through the fine dosing outlet channel 40 into the outlet 30 when the dosing device 20 is in the first position. The direction of flow of the fluid is shown by arrows in FIG. 2.In the second position, during operation, the fluid flows from the fluid inlet 28 via the fine metering chamber 32 through the connecting channel 44 into the coarse metering chamber 36 and from the coarse metering chamber 36 via the coarse metering valve seat 38 through the coarse metering outlet channel 42 into the outlet 30.Thus, in the first position, the fluid flows through the fine dosing outlet channel 40 and not via the coarse dosing outlet channel 42. Due to the smaller smallest cross section q of the fine dosing outlet channel 40, only a comparatively small amount of fluid per unit time flows to the outlet 30, whereby small amounts can be dosed particularly precisely.Furthermore, in the second position, the fluid flows through the coarse metering outlet channel 42 and not via the fine metering outlet channel 40. Due to the large smallest cross section Q of the coarse metering outlet channel 42, a comparatively large amount of fluid per unit time flows to the outlet 30, whereby large amounts can be metered in in a short time.In principle, the metering device 20 can have a third position in which both the fine metering valve 24 and the coarse metering valve 26 are each in the open position in order to conduct a particularly high volume flow to the outlet 30.Further, the metering device 20 is operated in a fourth position, in which both the fine metering valve 24 and the coarse metering valve 26 are each in the closed position, so as not to direct fluid to the outlet 30.In order to deliver the fluid in a defined manner, the metering device 20 has a connecting piece 54 with a filling channel 56, which is fastened to the valve block 22.The connecting piece 54 is designed in the present case in the form of a filling nozzle.The filling channel 56 is connected in terms of flow to the outlet 30.Furthermore, a seal 58 ensures that the outlet 30 is connected to the filling channel 56 in a fluid-tight manner.In an alternative embodiment, the fine metering outlet channel 40 and the coarse metering outlet channel 42 do not open into a common outlet 30, as shown in FIG. 2, but rather each have a separate outlet in the valve block 22.Preferably, these separate outlets are arranged adjacent to each other so that they each open into the filling channel 56 when the connecting piece 54 is attached to the valve block 22.In all embodiments, a dosing device 20 is provided in this way, which can be cleaned with little effort. The same applies to the dosing system 10 with a corresponding dosing device 20.In particular, the present design of the metering device 20 results in the fine metering chamber 32 and the bellows 48 arranged therein being flushed in the second position when the fluid flows from the fluid inlet 28 via the coarse metering outlet channel 42 to the outlet 30. The large volume flow, which in the second position flows through the fine metering chamber 32, in comparison with the small volume flow, which in the first position flows via the fine metering outlet channel 40, ensures a particularly high cleaning effect during operation.Not only for cleaning, i.e. flushing, but also for removing air from the system, it is appropriate to open either the fine metering valve or the coarse metering valve, for example pulsing, before the beginning of a metering process after the fine metering valve and the coarse metering valve have been previously closed, so that fluid, in particular liquid, is introduced into the metering system in order to flush the metering system and remove air.When the coarse metering valve is opened for flushing, a larger amount of fluid for flushing can flow through the metering device, which improves the quality of the flushing operation.Air bubbles can be removed particularly well if the fine metering valve or the coarse metering valve is opened and closed intermittently during the flushing.

Claims

Metering device (20) for metering a fluid, having a fine metering valve (24), a coarse metering valve (26) and a valve block (22), wherein the fine metering valve (24) has a fine metering chamber (32) and a fine metering valve seat (34) which are formed in the valve block (22), wherein the coarse metering valve (26) has a coarse metering chamber (36) and a coarse metering valve seat (38) which are formed in the valve block (22), wherein a connecting duct (44) connects the fine metering chamber (32) and the coarse metering chamber (36) to one another in terms of flow, wherein the valve block (22) has a fluid inlet (28) which opens into one of the fine metering chamber (32) and the coarse metering chamber (36) and is connected to the other in terms of flow via the connecting duct (44), and a fine metering outlet duct (40), which is arranged downstream of the fine metering valve seat (34) in the flow direction and has a coarse metering outlet duct (42) which is arranged downstream of the coarse metering valve seat (38) in the flow direction, wherein the metering device (20) is configured such that, in a first position, in which the fine metering valve (24) is in an open position and the coarse metering valve (26) is in a closed position, a fluid flows during operation from the fluid inlet (28) through the fine metering chamber (32) via the fine metering valve seat (34) into the fine metering outlet duct (40); and in a second position, in which the fine metering valve (24) is in a closed position and the coarse metering valve (26) is in an open position, a fluid flows from the fluid inlet (28) via the coarse metering chamber (36) and the coarse metering valve seat (38) into the coarse metering outlet channel (42) during operation.Metering device (20) according to Claim 1, characterized in that the fine metering valve (24) has a bellows (48) for media separation which is arranged in the fine metering chamber (32) and can press against the fine metering valve seat (34), and / or the coarse metering valve (26) has a bellows (52) for media separation which is arranged in the coarse metering chamber (36) and can press against the coarse metering valve seat (38), in particular wherein the bellows (48) of the fine metering valve (24) and / or the bellows (52) of the coarse metering valve (26) are formed from polytetrafluoroethylene (PTFE) or a fluorine-free material.Metering device (20) according to Claim 1 or 2, characterized in that the fine metering valve (24) and / or the coarse metering valve (26) each have a pneumatically actuated piston drive.Metering device (20) according to one of the preceding claims, characterized in that the fine metering valve (24) and the coarse metering valve (26) are of identical design.Metering device (20) according to one of the preceding claims, characterized in that the fine metering outlet channel (40) has a smallest cross section (q) which is smaller than a smallest cross section (Q) of the coarse metering outlet channel (42).Metering device (20) according to Claim 5, characterized in that the smallest cross section (Q) of the coarse metering outlet channel (42) is greater than the smallest cross section (q) of the fine metering outlet channel (40) by at least a factor of 10, in particular greater by at least a factor of 50.Metering device (20) according to one of the preceding claims, characterized in that the fine metering valve seat (34) has the same nominal width as the coarse metering valve seat (38) or the nominal width of the fine metering valve seat (34) is smaller than the nominal width of the coarse metering valve seat (38), in particular by at least 50% or by at least 75%.Metering device (20) according to one of the preceding claims, characterized in that the fine metering outlet channel (40) and the coarse metering outlet channel (42) are connected in terms of flow to a common outlet (30) which is formed in the valve block (22).Metering device (20) according to one of the preceding claims, characterized in that the metering device (20) has a connecting piece (54), which is attached to the valve block (22) and has a filling channel (56), wherein the filling channel (56) is connected in terms of flow to the fine metering outlet channel (40) and the coarse metering outlet channel (42), in particular via a common outlet (30) which is formed in the valve block (22) and is connected in terms of flow to the fine metering outlet channel (40) and the coarse metering outlet channel (42).Metering device (20) according to one of the preceding claims, characterized in that the fluid inlet (28) opens into the fine metering chamber (32) and fluid can flow via the connecting channel (44) to the coarse metering chamber (36).Dosing system (10) having a dosing device (20) according to one of the preceding claims, a control unit (12) and a scale (14) or a gravimetric or volumetric measuring unit, wherein the scale (14) or the measuring unit is coupled to the control unit (12) by signal technology.Dosing system (10) according to claim 11, characterised in that the control unit (12) is programmed in such a way that it controls the opening times of the fine dosing valve (24) and coarse dosing valve (26) as a function of the quantity of the fluid to be dosed.Method for metering a fluid, in particular a liquid, with a metering device (20) according to one of Claims 1 to 10, characterized in that, before the start of a metering process, after the fine metering valve (24) and the coarse metering valve (26) have been closed, either the fine metering valve (24) or the coarse metering valve (26) is opened and fluid, in particular liquid, is introduced into the metering system in order to flush the metering system, and wherein fluid is subsequently metered by selective opening and closing of the fine metering valve (24) and of the coarse metering valve (26).Method according to claim 13, characterised in that the coarse dosing valve (26) is opened for the flushing.Method according to claim 13 or 14, characterised in that during the flushing the fine dosing valve (24) or the coarse dosing valve (26) is opened and closed intermittently.

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