Differential dosing scale for liquids and methods for dosing liquids

Description

[0001] The present invention relates to a differential dosing scale for dosing liquid, comprising a submersible container in which the liquid to be dosed is contained and / or can be received and / or from which the liquid to be dosed can be drawn off for metered withdrawal, a dip tube which is immersed into the submersible container for metered withdrawal of the liquid to be dosed from the submersible container, and a metering pump with which the liquid to be dosed can be drawn from the submersible container via the dip tube and discharged from the differential dosing scale. The present invention also relates to a method for dosing liquid.

[0002] Differential dosing scales for liquid dosing are already known in the prior art. For example, WO 2015 / 158764 A1 discloses a differential dosing scale for liquid dosing with a funnel-shaped container for the liquid to be dosed, with a dosing pump, with a line connected to the dosing pump for extracting the liquid from the container, with a load cell connected to the container for determining the weight of the container, and with a control device, wherein the container-side end of the line is led into the container from above and arranged at a distance from the container.

[0003] However, known differential dosing scales based on the principle of dip tube-based liquid sampling from a weighed container have the disadvantage that the dip tube immersing in the weighed container exerts a buoyant force, which distorts the weighing result. This buoyancy-related error depends on the density of the liquid and the volume displaced by the dip tube.Since the volume displaced by the immersion tube changes with its depth, and the immersion depth of the immersion tube in turn depends on the changing fill level of the weighed container due to liquid withdrawal, the buoyancy-induced error is proportional to the fill level for a constant, approximately cylindrical container cross-section, variable over time for a continuously changing, approximately conical container cross-section, and abrupt for a discontinuously changing container cross-section, such as one equipped with internal components like probes or heating elements. Particularly in differential dosing scales with controlled weight loss, these effects are undesirable and must be corrected computationally, which requires knowledge of the precise, time-varying fill level as well as the fill-level-dependent container cross-section.Another disadvantage of such known differential dosing scales is that the immersion tube must be positioned sufficiently deep in the immersion tank to ensure that liquid can continue to be drawn in even as the fill level decreases. However, as the immersion depth increases, so does the suction lift of the dosing pump, thus limiting the selection of dosing pumps, pumpable liquids, or the maximum tank height. Furthermore, the pressure conditions on the suction side of the dosing pump change with the changing fill level, which in turn shifts the operating point on the pump characteristic curve and consequently impairs the controllability of the control loop.

[0004] The object of the present invention is therefore to avoid or at least reduce the disadvantages of the prior art. In particular, a differential dosing scale is to be provided which exhibits good weighing decoupling and whose weighing result can be determined precisely and easily.

[0005] The problem is solved by a differential dosing scale with the features of claim 1. Advantageous embodiments are claimed in the dependent claims and are explained in more detail below.

[0006] Thus, the object of the invention in a generic differential dosing scale is solved according to the invention by the fact that the differential dosing scale is designed structurally and / or control-wise in such a way that a liquid level of the liquid to be dosed present in the immersion container is kept at a constant predetermined and / or predeterminable level relative to the immersion tube.

[0007] The invention is based on the surprising finding that the weighing result can be improved by keeping the immersion depth of the dip tube in the liquid being metered in the immersion container practically constant. According to the invention, this is achieved by keeping the liquid level in the immersion container relative to the dip tube constant. This allows the immersion depth of the dip tube to be set and maintained, at least temporarily, in a particularly simple yet reliable manner.

[0008] The immersion vessel (and optionally a storage container described in more detail below) and the liquid it contains preferably form a closed system, for example, a permanently connected system (weighed system), the weight of which is recorded in order to determine the liquid drawn from the immersion vessel based on the decreasing weight of the weighed system. The immersion tube preferably extends into the immersion vessel / below the liquid level, so that the liquid to be drawn can be drawn in via the immersion tube by means of the metering pump connected to the immersion tube and metered into a subsequent process. The immersion tube is preferably arranged at a distance from the wall of the immersion vessel and preferably enters the immersion vessel from above, so that the immersion tube is not supported by the immersion vessel and there is no force transmission between the immersion tube and the immersion vessel or the weighed system.This means that preferably the immersion tube and the metering pump are not part of the weighing system and their weight is not recorded. According to the invention, the differential metering scale can have structural and / or control measures designed to maintain the surface level of a quantity of liquid present in the immersion tank at a constant level relative to the immersion tube, regardless of the liquid withdrawal / the delivery rate of the metering pump. This means that the differential metering scale is preferably designed such that the position of the liquid level relative to the immersion tube does not change, even when liquid is drawn from / drawn in from the immersion tank via the immersion tube, or that any change in the liquid level is compensated for by the structural and / or control measures.

[0009] This has the advantage that by keeping the level relative to the immersion tube constant, the disadvantages associated with a changing immersion depth can be avoided. Even though the buoyant force itself is independent of the container geometry, since it depends solely on the amount of displaced volume, the container geometry plays a role when the immersion depth changes over time, because the liquid level changes over time with a constant withdrawal rate. Every time-dependent change in force (here, the buoyant force) is included in the calculated delivery rate of the differential dosing scale. Accordingly, with the present invention, it is no longer necessary to know the container geometry in order to calculate the change in the buoyant force, since the buoyant force remains unchanged or practically unchanged due to the constant immersion depth of the immersion tube.Due to the constant immersion depth, not only does the buoyancy force of the immersion tube remain constant during operation of the differential dosing scale, but advantageously, the operating point of the dosing pump can also remain constant, resulting in good controllability of the system. Furthermore, the constant immersion depth allows for a shallower immersion depth for the immersion tube, which in turn reduces the buoyancy force of the immersion chamber and the resulting error either to a potentially acceptable level or minimizes the effort required for its computational compensation. The weighing system can be adjusted using standard methods with test weights while the chamber is filled with liquid.

[0010] Furthermore, it is particularly important to reliably avoid or at least significantly reduce the buoyancy force acting on the dip tube that varies during dosing.

[0011] When operating the differential dosing scale, the immersion tube is preferably at least partially immersed in the liquid contained in the immersion container.

[0012] The level of the liquid surface is preferably specified along the world coordinate system and / or along an axis parallel or antiparallel to the direction of gravity.

[0013] The liquid level is preferably kept at a constant level during the operation of the differential dosing scale and / or during the dosing of the liquid.

[0014] In the context of the present application, the fact that the level of the liquid is kept constant relative to the immersion tube preferably means that the vertical distance between the immersion tube (or a reference point of the immersion tube) and the liquid level is kept constant.

[0015] In In one embodiment, the immersion tube is stationary. Preferably, the immersion tube is arranged along an axis parallel to the direction of gravity.

[0016] According to a preferred embodiment, the liquid level of the liquid to be metered in the immersion chamber can be maintained at a constant, predetermined and / or predeterminable level relative to an intake opening of the immersion tube. The opening can, for example, be located in a plane parallel or perpendicular to the liquid level.

[0017] In the context of the present application, the fact that the level of the liquid level is kept constant relative to the immersion tube preferably means that the vertical distance between the plane within which the intake opening lies and the plane of the liquid level is kept constant.

[0018] According to a preferred embodiment, the immersion vessel can be moved along at least one path of movement, preferably along a direction parallel to the normal vector of the liquid level and / or to the direction of gravity. By making the immersion vessel movable, a falling liquid level within the immersion vessel relative to the immersion tube can be maintained in position relative to the immersion tube when liquid is being withdrawn.

[0019] The immersion container can preferably be moved back and forth along the path of movement.

[0020] According to a preferred embodiment, the immersion tube can be moved along at least one path of movement, preferably along a direction parallel to the normal vector of the liquid level and / or to the direction of gravity. By making the immersion tube movable, a falling liquid level within the immersion chamber relative to the immersion tube can be maintained in position when liquid is being withdrawn.

[0021] The immersion tube can preferably be moved back and forth along the path of movement.

[0022] According to a preferred embodiment, the metering pump can be moved along at least one path of motion, preferably along a direction parallel to the normal vector of the liquid level and / or to the direction of gravity, and preferably the differential metering scale is configured such that the metering pump moves in the same direction and / or simultaneously with the dip tube and / or is held at a constant predetermined and / or determinable level relative to the dip tube and / or the liquid level. This allows the relative distance between the metering pump and the suction head (e.g., at the suction opening of the dip tube facing the liquid during metering and / or located within the liquid) to be kept constant, and the metering pump to be operated at a defined or definable operating point.

[0023] This is advantageous because the characteristic curve of a metering pump typically depends on the height difference between the position of the pump itself and the suction position.

[0024] A "coordinated" movement of the metering pump and dip tube means that while the metering pump moves in one direction, the dip tube moves in the same direction (and vice versa). If the direction of the metering pump changes, the direction of the dip tube also changes.

[0025] According to a preferred embodiment, the differential dosing scale can have a detection device for detecting the position of the liquid level and / or the fill level of the liquid in the immersion chamber, the detection device in particular comprising an optical sensor, an ultrasonic sensor, and / or a microwave sensor. In this way, the position of the liquid level (in particular along a direction parallel or antiparallel to the direction of gravity) can be determined particularly advantageously and precisely. Preferably, the position of the liquid level is determined in the world coordinate system (z-direction) and / or relative to a reference, such as the intake opening of the immersion tube.

[0026] Based on the position of the liquid level, and given knowledge of the position and design of the immersion tank, the fill level of the liquid in the immersion tank can be determined. Other methods for determining the fill level of the liquid in the immersion tank are also known to those skilled in the art.

[0027] Preferably, the detection device operates without contact, i.e., in particular without contact with the liquid and / or the immersion container.

[0028] According to a preferred embodiment, the differential dosing scale can be configured to move the immersion container, the immersion tube, and / or the dosing pump depending on the position of the liquid level and / or the fill level of the liquid in the immersion container, wherein the position and / or fill level is preferably determined by means of the detection device. In this way, it is particularly advantageous to control the immersion depth of the immersion tube into the liquid to be dosed.

[0029] This means that despite the removal of liquid, the buoyant force acting on the dip tube does not change, or only changes to a minimal extent. The same applies, but with the opposite sign, when liquid is added (for example, when filling the immersion chamber).

[0030] Preferably, the process of the immersion tank, immersion tube and / or metering pump is carried out along the respective path of movement.

[0031] Advantageously, the constant level is maintained at least temporarily during the operation of the scale and / or during the dosing of the liquid.

[0032] In In one embodiment, the immersion tank is operated accordingly.

[0033] In In one embodiment, the immersion tube is moved accordingly.

[0034] In In one embodiment, the immersion container and the immersion tube are moved accordingly.

[0035] In In one embodiment, the immersion tube and the metering pump are moved accordingly.

[0036] In In one embodiment, the immersion tank, the immersion tube and the metering pump are moved accordingly.

[0037] If the immersion tank is also moved, one or more of the following options are particularly advantageous: In the case of net liquid removal from the immersion tank (i.e., when more liquid flows out of the immersion tank than enters it), the immersion tank is preferably moved parallel to the normal vector of the liquid level and / or antiparallel to the direction of gravity, especially in the case of a stationary immersion tube.

[0038] In the case of a net liquid inflow into the immersion tank (i.e., when more liquid enters the immersion tank than flows out of it), the immersion tank is preferably moved antiparallel to the normal vector of the liquid level and / or parallel to the direction of gravity, especially in the case of a stationary immersion tube.

[0039] If the immersion tube is also moved, one or more of the following options are particularly advantageous: In the case of net liquid removal from the immersion container (i.e., when more liquid flows out of the immersion container than enters it), the immersion tube is preferably moved antiparallel to the normal vector of the liquid level and / or parallel to the direction of gravity.

[0040] In the case of a net liquid inflow into the immersion tank (i.e., when more liquid enters the immersion tank than flows out of it), the immersion tube is preferably moved parallel to the normal vector of the liquid level and / or antiparallel to the direction of gravity.

[0041] This allows the liquid level relative to the immersion tube to be reliably kept at a constant level, even if it changes as a result of a change, in particular a decrease or increase, in the amount of liquid in the immersion container, especially if it falls or rises.

[0042] According to a preferred embodiment, the differential dosing scale can be configured to move the immersion container and / or the immersion tube, in particular to maintain the constant level of the liquid level relative to the immersion tube.

[0043] The previously mentioned options apply individually and in any combination here as well. In particular, it is advantageous to maintain a constant level, at least temporarily, during operation of the scale and / or during the dosing of the liquid.

[0044] According to a preferred embodiment, the differential dosing scale can be configured such that the immersion chamber and the immersion tube, particularly for maintaining a constant liquid level relative to the immersion tube, can both be moved, preferably at least temporarily simultaneously and / or in opposite directions. This ensures that a constant immersion depth of the immersion tube into the liquid being dosed can be reliably achieved even with large changes in the liquid level, since the changing fill level of the immersion chamber can be compensated for by two movement paths simultaneously. Furthermore, this allows the individual movement paths of the immersion tube and immersion chamber to be shorter, thus enabling a more compact design of the differential dosing scale.

[0045] In one embodiment, the simultaneous movement of the immersion tank and immersion tube is carried out only at least temporarily during the filling of the immersion tank, and in particular, when metering the liquid, only the immersion tank or only the immersion tube is moved.

[0046] According to a preferred embodiment, at least the immersion container can be part of a weighed system of the differential dosing scale.

[0047] Such a differential dosing scale, which is based on the principle of immersion tube-based liquid extraction from a weighed container, here the immersion tank, is distinguished from weighing systems that use a flexible decoupling element by the fact that it has good force decoupling between the weighed part of the differential dosing scale (here at least the immersion tank and / or any storage container, which will be discussed in detail below) and the non-weighed part of the differential dosing scale (here at least the immersion tube and the dosing pump).

[0048] The liquid in the immersion container is preferably also included as part of the weighed system of the differential dosing scale.

[0049] According to a preferred embodiment, the differential dosing scale can be configured to adjust the speed and / or direction of movement of the immersion tank, the immersion tube, and / or the dosing pump in response to changes in the position of the liquid level and / or the fill level of the liquid in the immersion tank and / or in response to changes in the results of weighings of the system being weighed. This allows for particularly reliable control of the liquid level. In particular, an inflow of liquid, for example from the storage tank, can be taken into account, and the constant level relative to the immersion tube can be maintained even during this inflow.

[0050] For example, a change in position can be a change in the level rate. This can be determined, for instance, from the detection results. This also allows for responses to different speeds at which the liquid level moves (especially during dosing and / or while filling the immersion chamber).

[0051] In In one embodiment, the speed and / or direction of the immersion tank's movement is adjusted accordingly.

[0052] In In one embodiment, the speed and / or direction of the immersion tube's movement is adjusted accordingly.

[0053] In In one embodiment, the speed and / or direction of the process is carried out according to the immersion tank and the immersion tube, respectively.

[0054] In In one embodiment, the speed and / or direction of the process is adjusted according to the dip tube and the metering pump, respectively.

[0055] In In one embodiment, the speed and / or direction of the process is carried out according to the immersion tank, the immersion tube and the metering pump.

[0056] This allows the liquid level relative to the immersion tube to be kept at a constant level, particularly if it changes due to a change, especially a decrease or increase, in the amount of liquid in the immersion tank, especially if it falls or rises.

[0057] According to a preferred embodiment, the differential dosing scale can have a reservoir in which the liquid to be dosed is contained and / or can be received, wherein the immersion chamber is fluidically connected to the reservoir for supplying the liquid to be dosed from the reservoir into the immersion chamber. This allows, for example, liquid to be supplied to the immersion chamber when the liquid level in the immersion chamber falls below a critical level. Preferably, the liquid is then supplied to the immersion chamber accordingly, for which the differential dosing scale can be designed.

[0058] For example, the immersion tank can be refilled at specific intervals, at least temporarily. During refilling, the travel path of the immersion tank and / or metering pump can be reversed compared to the metering process, and / or the adjustable volume described below can be increased during refilling.

[0059] In particular, a differential dosing scale is a differential dosing scale with a corresponding storage container.

[0060] According to a preferred embodiment, the reservoir can be included in the weighed system of the differential dosing scale. This advantageously prevents the weighing result from changing when liquid is redistributed from the reservoir to the immersion tank.

[0061] According to a preferred embodiment, the differential dosing scale can be structurally and / or control-wise designed such that the liquid level of the liquid to be dosed in the immersion tank is maintained at a constant, predetermined, and / or predeterminable level, particularly during operation of the differential dosing scale and / or during dosing. To compensate for the liquid to be dosed from the immersion tank, the immersion tank can be connected to the reservoir via a connecting line and supplied from it.

[0062] According to the invention, the differential dosing scale can incorporate structural and / or control measures designed to maintain the liquid level in the immersion tank at a constant / predetermined level, regardless of the liquid withdrawal / delivery rate of the dosing pump. This means that the differential dosing scale is preferably designed such that its liquid level in the immersion tank does not change, even when liquid is drawn from / drawn in via the immersion tube, or that any change in the liquid level is compensated for by the structural and / or control measures.

[0063] This has the advantage that keeping the immersion tank level constant avoids the disadvantages associated with a changing level. In particular, it is no longer necessary to know the tank geometry to calculate changes in buoyancy, as the buoyancy remains unchanged due to the constant immersion depth of the immersion tube. The constant level not only keeps the buoyancy of the immersion tube constant during operation, but also allows the operating point of the metering pump to remain constant, resulting in good controllability. Furthermore, the constant level allows for a shallower immersion depth for the immersion tube, which in turn reduces the buoyancy of the immersion tank and the resulting error to either an acceptable level or minimizes the computational effort required for its correction.The weighing system can be adjusted using a known method with test weights and liquid inside.

[0064] According to a preferred embodiment, the differential dosing scale can have a float valve arranged in a fluidic connection between the reservoir and the immersion chamber, and a float located in the immersion chamber. Since such float valves and floats are already used in other applications besides differential dosing scales, it is possible to implement such a design modification to the differential dosing scale without significant effort. Because the reservoir and the immersion chamber are already connected via a connecting line / fluid line to supply / replenish liquid in the immersion chamber, integration is straightforward.

[0065] The float valve can be controlled by the float in such a way that it opens the fluidic connection when the predetermined fill level is reached and closes it when the predetermined fill level is reached. This means that the flow rate via the float valve and float into the immersion tank is controlled to ensure the predetermined fill level is maintained. Thus, the fill level in the immersion tank is kept constant by a technically simple device, requiring no additional actuating energy or control for the mechanically operated float valve. In other words, the float valve limits the minimum fill level to the predetermined level.

[0066] According to a further development of the preferred embodiment, the immersion tank can be arranged below the reservoir in the direction of gravity, so that the liquid to be metered can be fed from the reservoir into the immersion tank by gravity. This means that no separate pump is required to move the liquid from the (considerably larger) reservoir into the immersion tank; it is sufficient to open the fluidic connection between the reservoir and the immersion tank.

[0067] According to a further development of the preferred embodiment, the fluidic connection to the immersion tank via the float valve can have a gravity-driven delivery rate that is higher than the delivery rate of the metering pump. This means that opening the float valve allows at least as much liquid per unit of time to be supplied as is drawn from the immersion tank by the metering pump. This ensures that the inflow rate equals the outflow rate and prevents any delayed level equalization.

[0068] According to a preferred embodiment, the volume that can be held by the immersion vessel can be adjusted, in particular by making a bottom section and / or a wall section of the immersion vessel at least partially movable and / or shape-changeable. By changing the amount of liquid that the immersion vessel can potentially hold through altering its holding volume, a liquid level within the immersion vessel that is rising or falling relative to the immersion tube can be maintained in position. Thus, despite a net withdrawal or net inflow of liquid, the buoyant force acting on the immersion tube does not change, or changes only to a minimal extent.

[0069] A movable floor and / or wall section can be achieved, for example, by a floor and / or wall section that can be rotated and / or folded around an axis. A movable floor and / or wall section can also be achieved, for example, by a sliding floor and / or wall section, such as one that is height-adjustable and / or a side wall that can be moved inwards and / or outwards.

[0070] A floor and / or wall area that can be modified in its shape can, for example, reduce the volume of the immersion tank to varying degrees depending on the strength and / or direction of the force acting on it from the outside.

[0071] A shape-reducible base and / or wall area can be achieved, for example, by using a base and / or wall area that, at least in part, comprises a reversibly deformable material, such as a membrane-like surface. A rubber membrane or a gas bladder, similar to a diaphragm expansion vessel in heating systems, can be used here. By changing the pre-charge pressure on the gas side of the membrane, the fill level can be adjusted to compensate for different liquid densities. Applying a force to this surface area from outside the immersion vessel can push it inwards, thus reducing the holding volume, and / or reducing the pressure can increase the holding volume.

[0072] According to a preferred embodiment, the differential dosing scale can be configured to adjust the volume that can be absorbed by the immersion container depending on the position of the liquid level and / or the fill level of the liquid in the immersion container.

[0073] In this process, the volume is preferably reduced when net liquid is withdrawn from the immersion container.

[0074] In this process, the volume is preferably increased when there is a net inflow of liquid into the immersion tank.

[0075] This allows the liquid level relative to the immersion tube to be reliably kept at a constant level, even if it changes as a result of a change, in particular a decrease or increase, in the amount of liquid in the immersion tank, especially if it falls or rises.

[0076] According to a preferred embodiment, the differential dosing scale can have an overflow fluidically connected to the immersion tank. The overflow can be designed such that the liquid to be dosed flows out of the immersion tank via the overflow when the predetermined fill level is exceeded. The general provision of an overflow is a known design that prevents the immersion tank from overflowing uncontrollably. In the preferred embodiment, the overflow is designed such that it ensures the fill level does not exceed the predetermined level. Thus, if more liquid is continuously supplied to the immersion tank than is discharged from it, the fill level can be maintained at the predetermined level at all times. In other words, the overflow limits the maximum fill level to the predetermined level.Furthermore, the differential dosing scale is designed so that at any given time at least as much liquid is fed into the immersion container as flows out via the overflow.

[0077] According to a further development of the preferred embodiment, the differential dosing scale can have an overflow container to which the overflow is fluidically connected for collecting the liquid that flows above the predetermined fill level. This has the advantage that the overflowing liquid is collected and can be fed back into the immersion tank.

[0078] In particular, the immersion tank can be positioned above the overflow tank in the direction of gravity. This has the advantage that the liquid flows from the immersion tank into the overflow tank by gravity alone, without the need for a pump or similar device.

[0079] According to a further development of the preferred embodiment, the differential dosing scale can have an overflow pump with which the liquid to be dosed can be drawn from the overflow container and fed to the immersion tank. Thus, the overflowed liquid can be returned to the immersion tank. Alternatively, the liquid can be drawn from the overflow container and returned to the reservoir, from which it is then fed back into the immersion tank. Crucially, the overflow container is part of the weighing system, and the liquid can be fed to the immersion tank (directly or via the reservoir). Therefore, the overflow pump serves to pump the liquid from the overflow container against gravity to a higher level in order to supply the immersion tank.

[0080] The overflow pump can preferably have a higher delivery rate than the metering pump, or be operated at a higher delivery rate. This means that a larger quantity of liquid is constantly supplied to the immersion tank than is discharged from it, with the difference between the inflow and outflow rates being discharged via the overflow.

[0081] According to a further development of the preferred embodiment, the overflow tank can be formed by the reservoir. This means that the reservoir is arranged below the immersion tank in the direction of gravity, and the liquid is fed into the immersion tank via the overflow pump. Thus, only two tanks are required if the reservoir also serves as the overflow tank. However, for space reasons, it may be necessary to provide a separate overflow tank. In this case, the reservoir is arranged above the immersion tank and the overflow tank and serves to feed the liquid into the immersion tank, while the overflow tank is arranged below the immersion tank to collect the overflow liquid, which is then either fed directly back into the immersion tank or into the reservoir.

[0082] According to a preferred embodiment, the differential dosing scale can have a control valve arranged in a fluidic connection between the reservoir and the immersion chamber. This control valve is controlled and / or regulated such that it supplies a quantity of liquid from the reservoir to the immersion chamber that corresponds to the quantity of liquid discharged from the differential dosing scale via the immersion tube. This means that the fill level can be kept constant by means of control measures, by ensuring that at any given time exactly the same quantity of liquid is supplied to the immersion chamber as is discharged from it. Because the weight of the liquid discharged is already measured, the control / regulation of the control valve can be implemented in a simple manner.

[0083] According to a preferred embodiment, the dip tube can have a suction opening for drawing the liquid to be metered from the immersion chamber. This can be, in particular, the suction opening already mentioned above. The dip tube can preferably be arranged in the immersion chamber such that the suction opening is immersed in the liquid at a depth below the predetermined fill level, which is between 1 and 10 times the diameter of the dip tube. This means that the immersion depth should be as shallow as possible to minimize the increasing buoyancy and the increasing suction head that must be overcome with increasing immersion depth, thus keeping the resulting error to a minimum. The wall thickness of the dip tube should also be as shallow as possible to minimize the increasing buoyancy and the resulting error with increasing wall thickness.

[0084] According to a preferred embodiment, the differential dosing scale can have a weighing device designed to detect the weight of one and / or the (permanently connected) system, in particular the reservoir, the immersion tank, and the liquid to be dosed contained therein (i.e., without the pump and immersion tube). The amount of liquid dispensed by the metering pump can then be determined gravimetrically from the weight loss. This allows for a particularly precise determination of the delivery rate.

[0085] According to a preferred embodiment, the differential dosing scale can have a control and / or regulating device designed to control and / or regulate the metering pump based on the weight of the system detected by the weighing device and based on a control variable for the quantity of liquid to be discharged from the differential dosing scale via the immersion tube. This allows the delivery rate to be metered with particular precision for a subsequent process.

[0086] According to a preferred embodiment, the immersion container and / or the storage container can have a downwardly tapered (i.e. in the direction of gravity), for example conical, cross-sectional shape to improve residual emptying.

[0087] Furthermore, the invention relates to a method for dosing liquid. According to the invention, the method comprises the liquid to be dosed being provided in an immersion tank of a differential dosing scale, in particular according to one of the preceding claims, from which the liquid to be dosed is drawn for metered withdrawal by a metering pump via a dip tube that is immersed in the immersion tank and discharged from the differential dosing scale, wherein a liquid level of the liquid to be dosed in the immersion tank is maintained at a constant predetermined and / or predeterminable level relative to the dip tube, in particular an intake opening of the dip tube, in particular during the operation of the differential dosing scale and / or during the dosing of the liquid.

[0088] All the advantages and options described above regarding the differential dosing scale also apply here, individually and in any combination. Therefore, reference can be made to the previous explanations at this point.

[0089] In particular, all features of the differential dosing scale described above can be provided in the differential dosing scale used in the process, individually or in any combination. Furthermore, all features with respect to which the differential dosing scale described above is designed can be implemented within the process. Above all, the options highlighted again in the following embodiments are particularly advantageously also achievable in the process.

[0090] According to a preferred embodiment of the method, the immersion vessel and / or the immersion tube can be moved, in particular to maintain the constant level of the liquid level relative to the immersion tube.

[0091] According to a preferred embodiment of the method, depending on the position of the liquid level and / or the fill level of the liquid in the immersion vessel, the immersion vessel, the immersion tube and / or the metering pump can be moved, wherein the position and / or fill level is preferably determined by means of a detection device.

[0092] According to a preferred embodiment of the method, the liquid level of the liquid to be dosed, present in the immersion container, can be maintained at a constant predetermined and / or predeterminable fill level, particularly during the operation of the differential dosing scale and / or during the dosing of the liquid.

[0093] According to a preferred embodiment of the method, a fluidic connection between a reservoir containing the liquid to be metered and the immersion tank can be opened, in particular by actuating a float valve arranged in the fluidic connection, when the predetermined fill level is undershot and the fluidic connection can be disconnected when the predetermined fill level is reached, wherein preferably the fluidic connection is provided for supplying the liquid to be metered from the reservoir to the immersion tank.

[0094] In summary, the invention relates to a differential dosing scale in which the known weighing decoupling method using a dip tube is combined with a device that ensures a low, constant immersion depth in the liquid. This avoids the disadvantages of a decoupling element (such as low force shunt, good chemical, thermal and pressure resistance, electrostatic dissipation, low thermal expansion and simple, reproducible assembly).Furthermore, the invention avoids the disadvantage of the immersion tube, namely that the amount of liquid displaced by the immersion tube generates a weighing error that must be computationally compensated and which depends on the medium density, the tube geometry, and the tank level, and the disadvantage of the immersion tube, namely that its length is largely determined by the tank height, and that with greater tank heights the required suction head of the pump increases, thus limiting the selection of meterable pumped media / liquids and pump types. This is achieved by maintaining a constant immersion depth of the immersion tube, for example, by keeping the level in the immersion tank at a predetermined level, regardless of the amount of liquid discharged. Preferably, a float valve is provided to maintain the level in the immersion tank at a constant level.Another preferred solution provides for an immersion tank whose fill level is kept constant by an overflow. In this case, it is necessary to pump the overflowing medium back to a higher level using an overflow pump so that it can be fed back into the immersion tank. The invention also relates to a method for dosing liquid. The invention is explained below with reference to the drawings. These show: . Fig. 1 a schematic representation of a first embodiment of a differential dosing scale according to the invention, Fig. 2 a schematic representation of a second embodiment of the differential dosing scale according to the invention, Fig. 3 a schematic representation of the first embodiment of the differential dosing scale with a control device, Fig. 4 a schematic representation of a third embodiment of a differential dosing scale according to the invention, and Fign. 5 bis 7 Various schematic representations of a dipping container and a dipping tube of the differential dosing scale for understanding the invention.

[0095] The figures are purely schematic and serve solely to illustrate the invention. The same elements are identified by the same reference numerals. Features of different embodiments can be combined according to the invention.

[0096] Fign. 1 bis 3 Figure 1 shows schematic views of a differential dosing scale 1 according to the invention. The differential dosing scale 1 is used for dosing liquid 2. The differential dosing scale 1 has a reservoir 3 containing the liquid 2 to be dosed, and a dip tube 4, which is fluidically connected to the reservoir 3 for supplying the liquid 2 to be dosed from the reservoir 3 into the dip tube 4 and from which the liquid 2 to be dosed can be drawn for metered withdrawal. The differential dosing scale 1 also has a dip tube 5, which dips into the dip tube 4 for metered withdrawal of the liquid 2 from the dip tube 4. The dip tube 5 dips into the dip tube 4 in such a way that no force bypass occurs and the dip tube is not supported by the dip tube 4. In particular, the dip tube 5 is arranged at a distance from a wall of the dip tube 4.Furthermore, the differential dosing scale 1 has a dosing pump 6, with which the liquid 2 to be dosed can be drawn from the immersion container 4 via the immersion tube 5 and discharged from the differential dosing scale 1 (for a subsequent process).

[0097] According to the invention, the differential dosing scale 1 is structurally and / or control-technically designed in such a way that the liquid level of the liquid 2 to be dosed, which is present in the immersion container 4, is kept at a constant predetermined fill level 7 (i.e., in particular, the level of the liquid level is kept constant relative to the preferably stationary immersion tube).

[0098] In the illustrated embodiments, the storage tank 3 is connected to the immersion tank 4 via a connecting line / fluid line 8, and the immersion tube 5 or the metering pump 6 is connected to the downstream process via a discharge line 9. The storage tank 3, the immersion tank 4, and the connecting line 8 are part of a balanced system, while the immersion tube 5, the metering pump 6, and the discharge line 9 are not part of the balanced system but are supported separately. Furthermore, a service valve 10 can be arranged in the connecting line 8, allowing the fluidic connection between the storage tank 3 and the immersion tank 4 to be closed / disconnected for maintenance purposes.

[0099] In the first, in Fig. 1 In the illustrated embodiment, maintaining the predetermined fill level 7 is achieved by arranging a float valve 11 in the connecting line 8 and a float 12 in the immersion tank 4. The float valve 11 is controlled by the float 12 such that it opens the fluidic connection when the predetermined fill level 7 is undershot and closes the fluidic connection when the predetermined fill level 7 is reached.

[0100] In the in Fig. 1 In the illustrated embodiment, the immersion tank 4 is arranged below the reservoir 3 in the direction of gravity, so that the liquid 2 to be metered can be fed from the reservoir 3 into the immersion tank 4 by gravity. The gravity-driven delivery rate achievable via the float valve 11 into the immersion tank 4 can preferably be higher than the delivery rate of the metering pump 6 in order to ensure sufficient refilling.

[0101] In addition, the immersion container 4 can have a drain valve 13, through whose opening the liquid 2 can be drained to completely empty the immersion container 4, and / or an overflow 15, through which the liquid 2 can drain from the immersion container 4 when an overflow level is exceeded.

[0102] Furthermore, the differential dosing scale 1 has a weighing device 14 which is designed to weigh the system being weighed, i.e. in Fig. 1 to measure the volume of the storage tank 3, the immersion tank 4, the connecting line 8, the float valve 11, the float 12, the drain valve 13, the overflow 15, and the liquid 2 contained in the storage tank 3, the connecting line 8, and the immersion tank 4. Preferably, the quantity of liquid 2 discharged via the metering pump 6 can be determined gravimetrically from this measurement.

[0103] In the first, in Fig. 1 In the illustrated embodiment, maintaining the predetermined fill level 7 is achieved by the differential dosing scale 1 having an overflow 15 fluidically connected to the immersion tank 4, which is designed such that the liquid 2 to be dosed flows out of the immersion tank 4 via the overflow 15 when the predetermined fill level 7 is exceeded. Furthermore, the differential dosing scale 1 is designed such that at any given time at least as much liquid 2 is supplied to the immersion tank 4 as flows out via the overflow 15.

[0104] Furthermore, the differential dosing scale 1 can preferably have an overflow container located in the Fig. 2 In the illustrated embodiment, the reservoir 3 is formed by the overflow 15, which is fluidically connected to the overflow 15 for collecting the liquid 2 flowing over the predetermined fill level 7. The immersion tank 4 can preferably be arranged above the overflow tank 3 in the direction of gravity. In particular, the differential dosing scale 1 can have an overflow pump 16 with which the liquid 2 to be dosed can be drawn from the overflow tank 16 and supplied to the immersion tank 4, the overflow pump 16 having a higher delivery rate than the metering pump 6. This ensures that at any given time at least as much liquid 2 can be supplied to the immersion tank 4 as flows over the overflow 15.

[0105] Alternatively or additionally, the differential dosing scale 1, even if not shown in the figures, can have a control valve arranged in a fluidic connection between the reservoir 3 and the immersion tank 4, which is controlled and / or regulated in such a way that it supplies a quantity of liquid from the reservoir 3 to the immersion tank 4 which corresponds to a quantity of liquid discharged from the differential dosing scale 1 via the immersion tube 5.

[0106] In Fig. 3 The figure shows that the differential dosing scale 1 has a control and / or regulating device 17, which is designed to control and / or regulate the dosing pump 6 depending on the weight of the system detected by the weighing device 14 and depending on a control variable for a quantity of liquid 2 to be discharged from the differential dosing scale 1 via the immersion tube 5. Thus, a desired dosed quantity of liquid 2 can be supplied to the subsequent process.

[0107] In Fig. 4 A differential dosing scale 1 is shown in a third embodiment. Features are identical to those of the embodiment described above. Fig. 1 The differential dosing scales described above are designated with the same reference numerals. Therefore, only the differences between differential dosing scale 1 and the one described below are described. Fig. 1 The described differential dosing scale is described.

[0108] In the third Fig. 4 In the illustrated embodiment, maintaining the predetermined level 7 of the liquid level is achieved by moving the immersion container 4 along a straight path of movement parallel to the direction of gravity R (which is shown in Fig. 4 (pointing downwards) is movable, which in Fig. 4 as indicated by a double arrow. During the (net) discharge of fluid from the immersion vessel 4 as a result of the metering process, the immersion vessel 4 then becomes antiparallel to the direction of gravity R (in Fig. 4 (i.e., proceed upwards).

[0109] In this way, the falling liquid level in immersion chamber 4 can be kept at a constant level relative to the immersion tube. In other words, the immersion depth of the immersion tube 5 in the liquid in immersion chamber 4 remains constant, since the falling liquid level 7 within immersion chamber 4 is compensated for by an equal and opposite upward movement of the immersion chamber 4.

[0110] The differential dosing scale 1 has a detection device 17a with which the position of the liquid level in the immersion tank 4 is detected relative to a reference (e.g., the intake opening of the immersion tube 5). In this case, the detection device 17a is, for example, an ultrasonic sensor. This can detect the corresponding position of the liquid level 7, for example, by evaluating the two-way travel time of an emitted ultrasonic signal until the echo is received.

[0111] Thus, the differential dosing scale 1 is designed to move the immersion container 4 depending on the fill level of the liquid in the immersion container 4.

[0112] In this third embodiment, liquid is temporarily transferred from the reservoir 2 to the immersion tank 4. For this purpose, the float valve 11 is controlled by the float 12 such that it opens the fluidic connection between the reservoir 2 and the immersion tank 4 when a lower fill level limit is reached and closes the fluidic connection when a second fill level limit is reached.

[0113] While the liquid is transferred from the storage container 2 into the immersion container 4, the immersion container 4 is moved parallel to the direction of gravity R (in Fig. 4 (i.e., downwards) if the net amount of liquid in the immersion tank 4 increases, meaning more liquid is added from the reservoir 2 than is drawn from the immersion tank 4 via the immersion tube 5. Otherwise, for example, the travel speed (antiparallel to the direction of gravity R) could simply be adjusted, in particular reduced. This ensures that the immersion depth of the immersion tube 5 remains constant even while the immersion tank 4 is being filled.

[0114] In Fign. 5 bis 7 To put it simply, it can be seen that the fill level in the immersion tank 4, especially when a large quantity is drawn through the immersion tube 5, cannot change linearly and an angle of repose β can form. To prevent the formation of such an angle of repose β from affecting the buoyancy force of the immersion tube 5, the immersion tube 5 can be positioned as shown in Fig. 6 The dip tube 5 is shown to be angled. This means that an intake opening 18 of the dip tube 5 is spaced apart from an immersion section of the dip tube 5, so that even when the angle of repose β is formed, the buoyancy force of the dip tube 5 does not change, since the same part of the dip tube 5 remains covered by liquid. According to the inventive solution (see Figure 1), the dip tube 5 is designed to be angled. Fig. 7 However, the fill level is kept constant at the predetermined level 7, so a straight design of the dip tube 5 is suitable. The dip tube 5 should have an immersion depth 19 that is as small as possible, while simultaneously preventing turbulence at the surface of the liquid 2 from affecting the suction behavior at the intake opening 18. Therefore, it has proven advantageous if the immersion depth 19 of the dip tube 5 corresponds to 1 to 10 times the diameter of the dip tube 20. Reference symbol list

[0115] 1 Differential dosing scale 2 Liquid 3 Reservoir 4 Immersion tank 5 Immersion tube 6 Dosing pump 7 Predetermined fill level 8 Connecting line 9 Discharge line 10 Maintenance valve 11 Float valve 12 Float body 13 Drain valve 14 Weighing device 15 Overflow 16 Overflow pump 17 Control device 17a Detection device 18 Suction opening 19 Immersion depth 20 Immersion tube diameter R Gravity direction

Claims

1. Differential dosing scale (1) for dosing of liquid (2), comprising an immersion vessel (4), in which the liquid to be dosed is contained and / or receivable and / or from which the liquid (2) to be dosed is dischargeable for metered withdrawal of the liquid (2), an immersion tube (5), which for metered withdrawal of the liquid (2) to be dosed from the immersion vessel (4) immerses into the immersion vessel (4), and a dosing pump (6), with which the liquid (2) to be dosed is suckable in via the immersion tube (5) from the immersion vessel (4) and dischargeable from the differential dosing scale (1), characterized in that the differential dosing scale (1) is configured structurally and / or in terms of control technology such that a liquid level present in the immersion vessel (4) of the liquid (2) to be dosed is maintained at a constant predetermined and / or predeterminable level relative to the immersion tube (5), by the differential dosing scale comprising a detection device for detecting a position of the liquid level and / or for detecting a fill height of the liquid in the immersion vessel (4) or an overflow (15) fluidically connected with the immersion vessel (4).

2. Differential dosing scale (1) according to claim 1, wherein the liquid level present in the immersion vessel (4) of the liquid (2) to be dosed is maintained at a constant predetermined and / or predeterminable level relative to a suction opening of the immersion tube (5).

3. Differential dosing scale (1) according to any of the preceding claims, wherein the immersion vessel (4) is movable along at least one, preferably along a direction extending parallel to the normal vector of the liquid level and / or to the direction of gravity, movement path.

4. Differential dosing scale (1) according to any of the preceding claims, wherein the immersion tube (5) is movable along at least one, preferably along a direction extending parallel to the normal vector of the liquid level and / or to the direction of gravity, movement path.

5. Differential dosing scale (1) according to claim 4, wherein the dosing pump (6) is movable along at least one, preferably along a direction parallel to the normal vector of the liquid level and / or to the direction of gravity, movement path, and preferably the differential dosing scale (1) is configured such that the dosing pump (6) is moved in the same direction and / or simultaneously with the immersion tube (5) and / or is maintained at a constant predetermined and / or predeterminable level relative to the immersion tube (5) and / or the liquid level.

6. Differential dosing scale (1) according to any of the preceding claims, characterized in that the detection device comprises an optical sensor, an ultrasonic sensor and / or a microwave sensor.

7. Differential dosing scale (1) according to any of the preceding claims, wherein the differential dosing scale (1) is configured to, depending on a position of the liquid level and / or a fill height of the liquid in the immersion vessel (4), move the immersion vessel (4), the immersion tube (5) and / or the dosing pump (6), wherein preferably the position and / or fill height is determined by means of the detection device.

8. Differential dosing scale (1) according to any of the preceding claims, wherein the differential dosing scale (1) is configured such that the immersion vessel (4) and / or the immersion tube (5), in particular for maintaining the constant level of the liquid level relative to the immersion tube (5), is or are moved.

9. Differential dosing scale (1) according to claim 8, wherein the differential dosing scale (1) is configured such that the immersion vessel (4) and the immersion tube (5), in particular for maintaining the constant level of the liquid level relative to the immersion tube (5), both, preferably at least temporarily simultaneously and / or in opposite directions, are moved.

10. Differential dosing scale (1) according to any of the preceding claims, wherein at least the immersion vessel (4) is counted as part of a weighed system of the differential dosing scale (1).

11. Differential dosing scale (1) according to any of the preceding claims, wherein the differential dosing scale (1) is configured to carry out the speed and / or the direction of movement of the immersion vessel (4), the immersion tube (5) and / or the dosing pump (6) in each case depending on a change of the position of the liquid level and / or the fill height of the liquid in the immersion vessel (4) and / or depending on a change of the results of weighings of the weighed system.

12. Differential dosing scale (1) according to any of the preceding claims, comprising a supply vessel (3), in which the liquid (2) to be dosed is contained and / or receivable, wherein the immersion vessel (4) is fluidically connected with the supply vessel (3) for supplying the liquid (2) to be dosed from the supply vessel (3) into the immersion vessel (4).

13. Differential dosing scale (1) according to claim 12, wherein the supply vessel (3) is counted as part of the weighed system of the differential dosing scale (1).

14. Differential dosing scale (1) according to any of the preceding claims, wherein the differential dosing scale (1) is configured structurally and / or in terms of control technology such that a liquid level present in the immersion vessel (4) of the liquid (2) to be dosed, in particular during operation of the differential dosing scale and / or during dosing of the liquid, is maintained at a constant predetermined and / or predeterminable fill level (7).

15. Differential dosing scale (1) according to any of the preceding claims, characterized in that the differential dosing scale (1) comprises a float valve (11) arranged in a fluidic connection between the supply vessel (3) and the immersion vessel (4) and a float body (12) arranged in the immersion vessel (4), wherein the float valve (11) is controlled by the float body (12) such that it opens the fluidic connection when the predetermined fill level (7) is undershot and disconnects the fluidic connection when the predetermined fill level (7) is reached.

16. Differential dosing scale (1) according to any of the preceding claims, characterized in that the immersion vessel (4) is arranged in the direction of gravity below the supply vessel (3), so that the liquid (2) to be dosed is supplyable from the supply vessel (3) into the immersion vessel (4) by gravity.

17. Differential dosing scale (1) according to claim 16, characterized in that the fluidic connection determined via the float valve (11) into the immersion vessel (4) has a gravity-induced delivery rate, which is higher than a delivery rate of the dosing pump (6).

18. Differential dosing scale (1) according to any of the preceding claims, wherein the volume receivable by the immersion vessel (4) is adjustable, in particular in that a bottom region and / or a wall region of the immersion vessel (4) is at least partially movable and / or configured to be shape changeable.

19. Differential dosing scale (1) according to any of the preceding claims, wherein the differential dosing scale (1) is configured to, depending on a position of the liquid level and / or a fill height of the liquid in the immersion vessel (4), adjust the volume receivable by the immersion vessel (4).

20. Differential dosing scale (1) according to any of the preceding claims, characterized in that the overflow (15) fluidically connected with the immersion vessel is configured such that the liquid (2) to be dosed, when the predetermined fill level (7) is exceeded, flows out of the immersion vessel (4) via the overflow (15).

21. Differential dosing scale (1) according to claim 20, characterized in that the differential dosing scale (1) comprises an overflow vessel (3), with which the overflow (15) is fluidically connected for collecting the liquid (2) flowing out above the predetermined fill level (7), wherein the immersion vessel (4) is arranged in the direction of gravity above the overflow vessel (3).

22. Differential dosing scale (1) according to claim 21, characterized in that the differential dosing scale (1) comprises an overflow pump (16), with which the liquid (2) to be dosed is suckable in from the overflow vessel (16) and is supplyable to the immersion vessel (4), wherein the overflow pump (16) has a higher delivery rate than the dosing pump (6).

23. Differential dosing scale (1) according to any of the preceding claims, characterized in that the differential dosing scale (1) comprises a control valve arranged in a fluidic connection between the supply vessel (3) and the immersion vessel (4), which is controlled and / or regulated such that it supplies an amount of liquid from the supply vessel (3) into the immersion vessel (4), which corresponds to an amount of liquid discharged via the immersion tube (5) from the differential dosing scale (1).

24. Differential dosing scale (1) according to any of the preceding claims, characterized in that the immersion tube (5) comprises a suction opening (18) for sucking in the liquid (2) to be dosed from the immersion vessel (4), which is arranged such that it immerses with an immersion depth (19) below the predetermined fill level (7) into the liquid (2), which lies between 1 and 10 times an immersion tube diameter (20).

25. Differential dosing scale (1) according to any of the preceding claims, characterized in that the differential dosing scale (1) comprises a weighing device (14), which is designed to detect the weight of a and / or the weighed system, in particular from the supply vessel (3), the immersion vessel (4) and the liquid (2) to be dosed contained therein, wherein the differential dosing scale (1) comprises a control and / or regulation device (17), which is designed to control and / or regulate the dosing pump (6) depending on the weight of the system detected by the weighing device (14) and depending on a control variable for an amount to be discharged via the immersion tube (5) from the differential dosing scale (1) of the liquid (2).

26. Method for dosing of liquid, the method comprising that the liquid to be dosed is provided in an immersion vessel of a differential dosing scale, from which immersion vessel the liquid to be dosed for metered withdrawal of the liquid is sucked in with a dosing pump via an immersion tube immersing into the immersion vessel for metered withdrawal of the liquid to be dosed and is discharged from the differential dosing scale, wherein a liquid level of the liquid to be dosed in the immersion vessel, in particular during operation of the differential dosing scale and / or during dosing of the liquid, is maintained at a constant predetermined and / or predeterminable level relative to the immersion tube, in particular a suction opening of the immersion tube, wherein the differential dosing scale comprises a detection device for detecting a position of the liquid level and / or for detecting a fill height of the liquid in the immersion vessel (4) or an overflow (15) fluidically connected with the immersion vessel (4).

27. Method according to claim 26, wherein the immersion vessel and / or the immersion tube, in particular for maintaining the constant level of the liquid level relative to the immersion tube, is or are moved.

28. Method according to any of claims 26 or 27, wherein a liquid level present in the immersion vessel of the liquid to be dosed, in particular during operation of the differential dosing scale and / or during dosing of the liquid, is maintained at a constant predetermined and / or predeterminable fill level.

29. Method according to any of claims 26 to 28, wherein a fluidic connection between a supply vessel containing the liquid to be dosed and the immersion vessel, in particular by actuating a float valve arranged in the fluidic connection, is opened when the predetermined fill level is undershot and the fluidic connection is disconnected when the predetermined fill level is reached, wherein preferably the fluidic connection is provided for supplying the liquid to be dosed from the supply vessel into the immersion vessel.