ROTARY EVAPORATOR AND METHOD FOR CONTROLLING A ROTARY EVAPORATOR

Description

[0001] The present invention relates to a rotary evaporator with an evaporator piston, a heating bath and an immersion control device, in particular a rotary evaporator with a control device, and a method for controlling this rotary evaporator.

[0002] WO 2010 / 043283 A1 describes a rotary evaporator with a control system for regulating the distillation quantity. Rotary evaporators are known from US 4,738,295 A and DE 35 22 607 A1.

[0003] In DE 10 2009 006 819 A1 a rotary evaporator is described which has a control and regulation unit for controlling the rotary drive, a heating bath or a lift via a remote control, so that intervention by the operator is also possible over a spatial distance.

[0004] A perceived disadvantage of the rotary evaporators in the prior art was that they had to be monitored during operation in order to be able to intervene if necessary.

[0005] The object of the present invention was therefore to provide a rotary evaporator that avoids the disadvantages of the prior art, as well as a method for its operation.

[0006] This problem is solved according to the invention by the features of the independent claims. Advantageous embodiments are specified in the dependent claims.

[0007] In particular, the problem is solved by a rotary evaporator comprising an evaporator piston and a heating bath, wherein the evaporator piston is immersible in the heating bath, preferably via a lift with which the evaporator piston is vertically movable, further comprising an immersion control device for controlling the immersion depth of the evaporator piston in the heating bath, wherein the immersion control device is configured to determine the level of the heating bath and wherein the immersion control device is configured to control the immersion depth of the evaporator piston in the heating bath as a function of the level of the heating bath. The immersion control device is configured to determine the bottom of the heating bath and to control the immersion depth of the evaporator piston in the heating bath as a function of the bottom of the heating bath. The immersion control device includes sensors by which the level of the heating bath can be determined.The rotary evaporator includes a movement device for vertical movement of the evaporator piston and a device for tilting the evaporator piston relative to the horizontal.

[0008] A rotary evaporator typically comprises an evaporator piston that can be immersed in a heating bath. This immersion process can consist of lowering the evaporator piston into the heating bath and / or raising the heating bath. The immersion process is preferably carried out by means of a lift that allows the evaporator piston to be moved vertically and thus immersed in the heating bath located beneath it. Preferably, the heating bath is movable vertically upwards, allowing the evaporator piston to be immersed in the heating bath. Particularly preferably, both the evaporator piston and the heating bath are movable vertically. The immersion depth of the evaporator piston in the heating bath is therefore a relative value, determined by the lowering of the evaporator piston and the raising of the heating bath.The evaporator flask is rotated around its longitudinal axis by a rotary drive, thereby evaporating the components introduced into the evaporator flask in a temperature-dependent manner. These evaporated components are directed into a vertical condenser, where they condense and are collected in a receiving flask connected to it. A control unit is preferably provided for the heating bath, allowing its temperature to be regulated. A refilling device is also preferably provided, enabling the metered replenishment of the heating bath medium, preferably water or oil, particularly silicone oil. This makes it possible to compensate for losses in the heating bath, which can occur over time due to evaporation, for example, without interrupting the evaporation process of the rotary evaporator. The rotary evaporator preferably also includes a control unit for regulating the rotation of the evaporator flask.

[0009] The rotary evaporator features an immersion control device for controlling the immersion depth of the evaporator piston in the heating bath. The immersion control device preferably includes a processor for controlling the immersion process. The immersion control device can also be combined with other control units, such as a control unit for regulating the heating bath or a control unit for controlling the rotation of the evaporator piston.

[0010] The immersion control device is designed to determine the level of the heating bath. Both the heating bath level and the fill level of the evaporator flask are variable parameters. This is because the mixture in the evaporator flask decreases due to the evaporation of the component to be removed, and the heating bath level increases when the evaporator flask is lowered into the heating bath. Lowering the evaporator flask raises the level of the medium in the heating bath by the amount it displaces. Simultaneously, the system may also be designed to introduce additional medium into the heating bath during operation, thereby increasing the level of the heating bath.

[0011] The immersion control device is designed to control the immersion depth of the evaporator piston in the heating bath depending on the bath level. This allows the rotary evaporator to be operated automatically with an optimal immersion depth of the evaporator piston in the heating bath, even if the level of the medium in the heating bath changes, particularly when the level of the medium in the heating bath rises due to displacement during the immersion process of the evaporator piston. With a small piston, the displacement is less than with a large piston, and therefore the rise in the level of the medium in the heating bath is also smaller. This control is preferably implemented via a lift mechanism that allows the evaporator piston to be moved vertically. By controlling the lift, the immersion control device can achieve, control, and regulate the predetermined or optimal immersion depth.In this form, the immersion control device is also an immersion regulating device.

[0012] The level of the heating bath can be calculated based on the originally added amount of heating medium or determined by sensors.

[0013] The immersion control device is additionally equipped to determine the bottom of the heating bath and also to control the immersion depth of the evaporator piston in the heating bath depending on the bottom of the heating bath.

[0014] The bottom of the heating bath is the lowest level within the bath. In a heating bath with a horizontal base plate, the bottom of the bath is the upper boundary of this base plate. The evaporator flask cannot be lowered below this level, as it would then come into contact with the bottom and could not be lowered further. Therefore, the bottom of the heating bath is a useful parameter for controlling the immersion depth of the evaporator flask.

[0015] Preferably, the immersion control device is configured to determine the fill level of the evaporator flask and to control the immersion depth of the evaporator flask into the heating bath as a function of the fill level of the evaporator flask. This can be done either only in combination with controlling the immersion depth of the evaporator flask into the heating bath as a function of the level of the heating bath or also as a function of the bottom of the heating bath.

[0016] The filling level of the evaporator flask is the level to which the evaporator flask is filled. It is the horizontal level formed by the mixture present in the evaporator flask during operation of the rotary evaporator. This level is parallel to the surface of the liquid in the heating bath, where it maintains a predetermined level.

[0017] At the same time, it can also be provided that further mixture is fed into the evaporator flask during operation, which leads to an increase in the filling level in the evaporator flask.

[0018] The immersion control device is preferably configured to control the immersion depth of the evaporator piston in the heating bath as a function of the fill level of the evaporator piston and the level of the heating bath. This allows the rotary evaporator to be operated automatically with an optimal immersion depth of the evaporator piston in the heating bath, even if the fill level in the evaporator piston or the level of the medium in the heating bath changes. This control is preferably implemented via a lift mechanism that allows the evaporator piston to be moved vertically. By controlling the lift mechanism, the immersion control device can achieve, control, and regulate the predetermined or optimal immersion depth.

[0019] The fill level of the evaporator flask can be calculated directly based on the initial fill quantity, or determined by sensors (thus independent of the type). Similarly, the level of the heating bath can be calculated based on the initial quantity of heating medium added, or determined by sensors.

[0020] A preferred embodiment of the rotary evaporator has sensors that can be used to determine the fill level of the evaporator flask and / or the level of the heating bath. The sensors preferably operate according to one or more of the following principles: optical, mechanical, thermoelectric, resistive, piezoelectric, capacitive, inductive, or magnetic. Optical, mechanical, thermoelectric, resistive, or piezoelectric sensors are preferably used for determining the fill level in the evaporator flask, with the fill level preferably determined optically, by weight, or by conductivity. Optical, mechanical, thermoelectric, resistive, piezoelectric, capacitive, inductive, or magnetic sensors are preferably used for determining the level of the heating bath, with the level preferably determined optically, by weight, by moisture, or by conductivity.

[0021] Preferably, the rotary evaporator has sensors comprising one or more elements from the following group: light barrier, preferably an analog light barrier, weight sensor, photosensor, camera, infrared LED Ultrasonic sensor, microwave transmitter and receiver, radar sensor, humidity sensor, level gauge, float, level sensor, vibration sensor, electromechanical plumb system, pressure sensor, conductivity sensor, temperature sensor.

[0022] The fill level can preferably be determined using a light barrier by moving the filled piston past the light barrier via the lift and measuring the fill level at that point. It is also preferably possible to move the light barrier and detect the fill level in the process. An analog light barrier is particularly preferred.

[0023] A weight sensor can be used to detect the weight of the heating bath or the evaporator flask, and thus the size of the evaporator flask. This makes it possible to determine the fill level or, by measuring the increase in the weight of the heating bath due to displacement when the evaporator flask is immersed, to determine the rise in the heating bath level. Furthermore, it is also possible to determine the weight (or level) of the evaporated component collected in the receiving flask and to draw conclusions by comparing this to the current fill level in the evaporator flask.

[0024] A photosensor, particularly a camera, can capture an image that can be analyzed to detect the fill level. Similarly, the level of the heating bath can be determined in this way. Preferably, the heating bath has at least a partially transparent area through which the level of the medium in the heating bath can be visually observed. This can be achieved, for example, by constructing the heating bath with a transparent material (glass / acrylic / etc.) so that the entire side wall, towards which the camera is directed, is transparent, or at least a strip on the wall of the heating bath, preferably in the vertical direction, is transparent, allowing the level to be visually detected from the outside. A marking is also preferably provided to facilitate reading the level or evaluating its magnitude.

[0025] Infrared LEDs can also be used to detect fill levels and volumes, for example in the form of light barriers or motion detectors. Ultrasonic sensors, microwave transmitters and receivers, or radar sensors are also suitable for this purpose.

[0026] The moisture level in the heating bath can be determined using a humidity sensor, preferably arranged vertically within the bath. This can also be achieved using a different type of level gauge, such as one equipped with a float or level sensor. This could also include a vibration sensor or an electromechanical leveling system.

[0027] A pressure sensor can be used to determine the weight and thus the level or fill level can be inferred. A conductivity sensor, preferably located at the edge of the heating bath, can be used to determine the level of the heating bath.

[0028] Furthermore, a moving device for vertical movement of the evaporator piston, in particular a moving device integrated into a lift, is provided.

[0029] A lift mechanism allows the evaporator piston to be lowered vertically into the heating bath. Additionally, the evaporator piston, in its mounting on the rotary evaporator, can assume an angle to the horizontal, preferably approximately 30°. The lift moves the entire evaporator piston vertically without changing its angle to the horizontal. Thus, the lift mechanism allows the evaporator piston to be lowered into the heating bath, and preferably, the lift is used to lower and raise the evaporator piston.

[0030] It is also preferably possible to change the immersion depth of the evaporator piston by changing the angle of the evaporator piston to the horizontal. Thus, the immersion depth can be changed by tilting the evaporator piston into the heating bath.

[0031] The object of the present invention is also achieved by a method for controlling a rotary evaporator, wherein the rotary evaporator comprises an evaporator piston and a heating bath, wherein the evaporator piston is immersible in the heating bath, preferably via a lift with which the evaporator piston is vertically movable, further comprising an immersion control device for controlling the immersion depth of the evaporator piston in the heating bath, comprising the steps of: Determining the fill level of the evaporator flask; determining the level of the heating bath; controlling the immersion depth of the evaporator flask in the heating bath depending on the fill level of the evaporator flask (10) and depending on the level of the heating bath; determining the bottom of the heating bath; controlling the immersion depth of the evaporator flask in the heating bath depending on the bottom of the heating bath; determining the level of the heating bath by a sensor and vertical process and tilting of the evaporator piston relative to the horizontal depending on the level of the heating bath.

[0032] The level of the heating bath is the surface of the medium in the heating bath. This is horizontally oriented due to gravity.

[0033] By determining the level of the heating bath, it is known at what level or height the surface of the medium in the heating bath is located.

[0034] InThe immersion depth of the evaporator flask is controlled based on this parameter. Preferably, a maximum level is defined that must not be exceeded. Once this maximum level is reached, the evaporator flask is not lowered further to prevent increasing the level of the medium in the heating bath. Alternatively, the level can be lowered by releasing some medium from the heating bath, allowing the evaporator flask to be lowered further.

[0035] The procedure includes the following steps: Determining the bottom of the heating bath; controlling the immersion depth of the evaporator piston in the heating bath depending on the bottom of the heating bath.

[0036] This allows the lowering of the evaporator piston to be additionally controlled, taking into account the lowest value that the piston should not fall below, as it could otherwise be damaged by contact with the bottom of the heating bath.

[0037] The following steps are still preferred: Determining the fill level of the evaporator flask; controlling the immersion depth of the evaporator flask in the heating bath depending on the fill level of the evaporator flask.

[0038] These steps can be carried out either in combination with the control system, depending on the type of heating bath, or without it.

[0039] The filling level is the upper level formed by the mixture in the evaporator flask. It extends parallel to the surface of the medium in the heating bath, i.e., the level of the heating bath. Both are horizontally aligned due to gravity.

[0040] By determining the filling level, with reference to the evaporator flask on the one hand and the known height of the evaporator flask above the bottom of the heating bath on the other hand, it is also known with reference to this bottom of the heating bath at what level, i.e. at what height, this upper edge or boundary of the mixture is located inside the evaporator flask.

[0041] In The immersion depth of the evaporator flask is controlled based on these two parameters. Preferably, a target configuration is chosen in which the filling level of the evaporator flask is a predetermined amount below the level of the heating bath. This predetermined amount is preferably between 0.5 and 2 cm, more preferably between 0.8 and 1.2 cm, and most preferably approximately 1 cm. InIn this configuration, the heating bath heats an area of ​​the evaporator flask above the filling level but below the level directly through the heating bath medium, before this area of ​​the evaporator flask comes into contact with the mixture in the evaporator flask during rotation, and on the other side of the evaporator flask, the mixture is carried along by adhesion into a particularly heated area, so that the component to be separated can be particularly well evaporated from the mixture here.

[0042] Preferably, the control system can also react to changes in the fill level and / or the liquid level, so that the immersion depth can be adjusted during operation to achieve the target configuration. It is also preferably possible to ensure that a minimum distance is maintained between the lower edge of the evaporator flask and the bottom of the heating bath. If this distance is at risk of being breached, the control system can preferably meter the amount of medium added to the heating bath, thus raising the liquid level and reducing the immersion depth to ensure the required distance to the bottom is maintained. Preferably, a minimum distance is also maintained between the upper edge of the heating bath and the neck of the evaporator flask, i.e., an area that is not immersed in the heating bath.

[0043] Preferably, the fill level or level of the heating bath is continuously monitored or at least determined at predetermined time intervals, so that changes in the fill level (due to evaporation of the component in the mixture) as well as the level (due to evaporation of the medium of the heating bath) can be reacted to.

[0044] The procedure includes the following step: determining the level of the heating bath using a sensor.

[0045] Preferably, the procedure comprises the following steps: Determining the fill level of the evaporator flask by means of a sensor, and controlling the immersion depth of the evaporator flask in the heating bath depending on the fill level of the evaporator flask and depending on the level of the heating bath.

[0046] Several technical implementation options are available for determining the fill level or level using a sensor. Optical sensors, such as a light barrier, a photoelectric sensor, or a camera, are preferred.

[0047] In In another preferred method, the following further step is provided: re-dosing of medium for the heating bath depending on the filling level of the evaporator flask.

[0048] This makes it possible to replenish the medium for the heating bath after it has evaporated or been lost over time, thus compensating for these losses.

[0049] A top-up dose can also consist of withdrawing medium from the heating bath if, for example, the level of the heating bath rises above a predetermined value due to the immersion process of the evaporator flask, thus preventing the heating bath from overflowing.

[0050] Further details and advantages of the invention will now be explained in more detail with reference to an exemplary embodiment shown in the drawings.

[0051] They show: Fig. 1a a schematic representation of an evaporator flask and a heating bath of a rotary evaporator in a starting position and Fig. 1b a schematic representation of an evaporator flask and a heating bath of a rotary evaporator made of Figure 1a in a lowered position.

[0052] Figure 1a Figure 1 is a schematic representation of an evaporator piston 10 and a heating bath 20 of a rotary evaporator 1 in a starting position in which the evaporator piston 10 is located above the heating bath 20 and is not immersed in it.

[0053] The rotary evaporator 1, of which only a section is shown here, primarily depicting the evaporator flask 10, the heating bath 20, and a lift 30, also features an immersion control device 40. This device is connected to the rotary evaporator by wire or radio link, or wirelessly. This immersion control device 40 allows the evaporator flask 10 to be moved vertically by means of the lift 30, thus controlling the immersion depth of the evaporator flask 10 in the heating bath 20. The fill level of the mixture in the evaporator flask 10 is indicated on the right by the reference numeral N15a and denotes the upper edge of the mixture in the evaporator flask 10. The lower limit of the evaporator flask is indicated by the reference numeral BK and denotes the level at which the bottom of the flask is located. The level of the medium in the heating bath 20 in the configuration of the Figure 1aThis is indicated by the reference number P25a. It is the level of the medium in the heating bath that is reached when the piston is not immersed in the heating bath. This is the minimum level, as immersing the piston in the heating bath will always increase this level.

[0054] Two sensors, 45.1 and 45.2, are shown, which detect the fill level N15a and the level P25a. Sensor 45.1 is preferably an optical sensor, in particular a camera, which determines the fill level N15a. The position of the bottom of the piston BK can also be determined via sensor 45.1. Sensor 45.1 can also be configured to determine the level P25a of the heating bath. Alternatively or additionally, a sensor 45.2, which is configured here as a level sensor, can be provided and determines the fill level of the heating bath or the level of the heating bath P25a.

[0055] Figure 1bFigure 1 is a schematic representation of an evaporator flask 10 and a heating bath 20 of a rotary evaporator 1 as shown in Figure 2. Figure 1a shown, but in a lowered position.

[0056] Based on the situation in Figure 1a The immersion control device 40, via the control of the lift 30, lowered the evaporator flask 10 vertically downwards into the heating bath. This resulted in a lower fill level of N15b inside the evaporator flask 10. As the evaporator flask 10 was immersed in the heating bath 20, the level of the heating bath P25b increased because the flask displaced medium from the heating bath 20. The bottom BK of the evaporator flask 10 was also lowered and is now located above the bottom BH of the heating bath 20. However, the distance between the bottom BK of the evaporator flask 10 and the bottom BH of the heating bath 20 is now greater than in the initial state. Figure 1aThe immersion control device 40 has lowered the evaporator piston 10 via the lift 30 to such an extent that the difference between level N15b and level P25b reaches a predetermined value, in this case -1cm.

[0057] If, when lowering the evaporator piston 10, the level of the heating bath P25b rises too high and there is a risk that the heating bath will overflow, this can be detected by monitoring the level and prevented by the control system.

[0058] If, during operation, the level P25b or the level N15b changes, the immersion depth can be adjusted via the immersion control device 40 so that the difference between the level N15b and the level P25b reaches the desired value again. This can be achieved during continuous evaporation of a component from the mixture in the evaporator piston 10 by moving the evaporator piston 10 vertically upwards as the fill level P25b falls, so that the difference between the level N15b and the level P25b reaches the predetermined value again. Should excessive amounts of medium evaporate from the heating bath 20, it is also possible to refill the heating bath 20 with medium so that the level P25b rises again - if necessary, an excessively high level P25b must then be compensated for by raising the evaporator piston 10 via the lift 30, so that the predetermined value between the level N15b and the level P25b is reached again.Preferably, additional medium can also be supplied to the heating bath 20 if the distance between the bottom BK of the evaporator flask 10 and the bottom BH of the heating bath 20 falls below a critical value, since the evaporator flask 10 will then also be raised to restore the desired difference.

[0059] Typically, the lift is in the upper position before distillation. Once the user has placed the flask 10 (containing the mixture) on the lift, they lower it into the heating bath 20. It is recommended that the flask 10 be filled to a maximum of 50% (1000 ml flask -> 500 ml mixture). The optimal immersion depth is preferably reached when the filling level of the evaporator flask N15b is approximately 1 cm, preferably approximately 2 cm, and most preferably more than 3 cm below the heating bath level P25b.

[0060] The immersion control device 40 preferably also takes into account that the piston does not rest on the bottom BH of the heating bath 20. The optimal immersion depth therefore depends on the evaporator piston used, the filled volume, and the level of the medium in the heating bath 20.

[0061] The invention described here provides a rotary evaporator that is easy to operate. With the rotary evaporator according to the invention, the user simply places the piston on the device and presses start. The system then automatically adjusts to the optimal immersion depth via the immersion control device, without requiring any further input such as piston size, fill volume, or heating bath condition.

[0062] The sensors employed allow for the implementation of various immersion control devices via a multitude of operating mechanisms. As soon as the evaporator piston immerses itself in the heating medium, the level of the medium in the heating bath rises—in this example, the water level. This can be monitored preferably using a level sensor. The level rise, combined with the distance traveled, yields a displaced volume from which the piston size can be calculated.

[0063] As soon as the evaporator piston enters the heating medium, a buoyant force is generated. This buoyant force corresponds to the weight of the displaced water. Using force sensors in the feet of the heating bath (scales), this weight increase can be detected. Here, too, the piston size can be inferred from the distance traveled.

[0064] Preferably, the evaporator flask passes through a light barrier on its way to the heating bath. Using a light barrier, preferably an analog light barrier, it is possible to deduce the shape of the flask and the volume inside it from the shape of the curve, and thus to determine the fill level in the evaporator flask.

[0065] The immersion control device can preferably also monitor and take into account other conditions during control, such as dry running, overflow of the heating bath and the control of the supply (or removal) of heating bath medium.

[0066] This provides a rotary evaporator which, through its control system, enables simplified operation, in particular a control system that can react independently to changing conditions when the level of medium from the heating bath changes or when the fill level in the evaporator flask changes. Reference symbol list

[0067] 1 Rotary evaporator 10 Evaporator piston 15 Evaporator piston filling level 20 Heating bath 25 Heating bath level 30 Lift 35 Vertical movement device for the evaporator piston 40 Immersion control device 45 Sensor

Claims

1. A rotary evaporator (1) comprising an evaporator flask (10) and a heated bath (20), wherein the evaporator flask (10) can be immersed in the heated bath (20), further comprising an immersion control unit (40) for controlling the immersion depth of the evaporator flask (10) in the heated bath (20), wherein the immersion control unit (40) is set up so as to determine the level (25) of the heated bath (20), and wherein the immersion control unit (40) is arranged so as to control the immersion depth of the evaporator flask (10) in the heated bath (20) as a function of the level (25) of the heated bath (20) wherein the immersion control unit (40) is arranged so as to determine the base of the heated bath (20) and wherein the immersion control unit (40) is arranged so as to control the immersion depth of the evaporator flask (10) in the heated bath (20) as a function of the base of the heated bath (20), wherein the immersion control unit (40) comprises sensors (45) via which the level (25) of the heated bath (20) can be determined, wherein the rotary evaporator (1) comprises a traversing unit (35) for vertically moving the evaporator flask (10) and a unit for tilting the evaporator flask (10) with respect to the horizontal plane.

2. The rotary evaporator (1) according to claim 1, wherein the immersion control unit (40) is set up so as to determine the filling level (15) of the evaporator flask (10), and wherein the immersion control unit (40) is set up so as to control the immersion depth of the evaporator flask (10) in the heated bath (20) as a function of the filling level (15) of the evaporator flask (10).

3. The rotary evaporator (1) according to any of the preceding claims, wherein the immersion control unit (40) comprises sensors (45), via which the filling level (15) of the evaporator flask (10) and of the heated bath (20) can be determined.

4. The rotary evaporator (1) according to claim 3, wherein the sensors (45) operate according to one or a plurality of the following principles: optical, mechanical, thermoelectric, resistive, piezoelectric, capacitive, inductive, magnetic.

5. The rotary evaporator (1) according to any of the claims 3 or 4, wherein the sensors (45) comprise one or a plurality of elements of the following group: Light barrier, weight sensor, photo sensor, camera, infrared LED, ultrasonic sensor, microwave transmitter and receiver, radar sensor, humidity sensor, level measuring unit, float gauge, level sensor, vibration sensor, electromechanical plumb bob system, pressure sensor, conductivity sensor, temperature sensor.

6. A method for controlling a rotary evaporator (1), wherein the rotary evaporator comprises an evaporator flask (10) and a heated bath (20), wherein the evaporator flask (10) can be immersed in the heated bath (20), further comprising an immersion control unit (40) for controlling the immersion depth of the evaporator flask (10) in the heated bath (20), with the steps:Determination of the filling level (15) of the evaporator flask (10)Determination of the level (25) of the heated bath (20) Control of the immersion depth of the evaporator flask (10) in the heated bath (20) as a function of the filling level (15) of the evaporator flask (10) and as a function of the level (25) of the heated bath (20),Determination of the base of the heated bath Control of the immersion depth of the evaporator flask in the heated bath as a function of the base of the heated bath,Determination of the level (25) of the heated bath (20) via a sensor (45') and vertical movement and tilting of the evaporator flask (10) relative to the horizontal plane as a function of the level (25) of the heated bath (20).

7. A method of controlling a rotary evaporator (1) according to claim 8, wherein the immersion control unit (40) comprises sensors (45), and the method comprises the following steps: Determination of the filling level (15) of the evaporator flask (10) via a sensor (45), Control of the immersion depth of the evaporator flask (10) in the heated bath (20) as a function of the filling level (15) of the evaporator flask (10) and as a function of the level (25) of the heated bath (20).

8. A method according to any of the preceding method claims further comprising the steps: Determination of the filling level of the evaporator flask Control of the immersion depth of the evaporator flask in the heated bath as a function of the filling level of the evaporator flask.

9. A method according to any of the preceding claims, further comprising the step: Additional dosing of medium for the heated bath as a function of the filling level of the evaporator flask and / or as a function of the level of the heated bath.