Centrifuge, method of operating a centrifuge and computer readable medium

Description

TECHNICAL AREA OF INVENTION

[0001] The invention relates to a centrifuge.

[0002] The centrifuge is preferably a flow-through centrifuge in which at least one medium is at least temporarily supplied to and / or discharged from a centrifugation chamber while the chamber rotates. The at least one medium is, in particular, the medium to be centrifuged, a rinsing liquid, a buffer solution, a modified medium extracted from the centrifuged medium, or a sediment in the centrifugation chamber. To give only a few examples not limiting the invention, the flow-through centrifuge can be a blood centrifuge in which the medium to be centrifuged is blood and the extracted modified medium or sediment is blood cells or particles, or it can be a centrifuge used to obtain cells, microcarriers, or other particles contained in a medium from that medium.It is also possible that the centrifuged medium is not a pure liquid, but rather a solution or suspension containing particles such as cells, cell debris, or cell parts. Such a flow centrifuge is used, for example, in the production of biopharmaceutical or biotechnological products in biopharmaceutical companies or in bioprocessing applications. The flow centrifuge can be used, for instance, to obtain and / or clarify cells or microcarriers, with the resulting cells then being used for cell therapy. Other applications include (but are not limited to) the production of vaccines or the processing of blood for the extraction of blood cells. Such flow centrifuges are distributed, for example, by Sartorius AG, Otto-Brenner-Straße 20, 37079 Göttingen, Germany, and affiliated companies under the trademark "Ksep" (registered trademark), see [reference].also www.sartorius.com / en / products / process-filtration / cell-harvesting / ksep-systems (Date accessed: 28.06.2022).

[0003] The rotor of such a flow centrifuge has, in particular, four centrifugation chambers, which can be designed as bags attached to the rotor body and are evenly distributed around the circumference. The centrifugation chambers are arranged radially spaced from the rotor's axis of rotation. A first connecting line opens radially inside a centrifugation chamber, while a second connecting line opens radially outside the centrifugation chamber. In a first operating phase, a first medium, for example, blood, is fed into the centrifugation chamber via the second connecting line while the centrifugation chamber rotates with the rotor.In the centrifugation chamber, particles contained in the medium are deposited radially outwards as a result of centrifugation, while the remaining medium (i.e., the medium supplied radially outwards minus the particles forced radially outwards) is discharged radially inwards via the first inlet line. In this first operating phase, the first inlet line is therefore a discharge line, while the second inlet line is a feed line. As this operation continues, the proportion and concentration of particles in the centrifugation chamber increase until it is largely or completely filled with particles. In a subsequent, optional second operating phase, the particles in the centrifugation chamber are washed. For this purpose, a washing or buffer solution is introduced into the centrifugation chamber via the second inlet line.The washing or buffer solution flows through the centrifugation chamber and is discharged radially internally via the first connecting line. During this operating phase, the centrifugation chamber rotates with the rotor, so that the centrifugal force prevents the particles from exiting the chamber with the washing or buffer solution via the first connecting line. During the second operating phase, the first connecting line serves as both the discharge and supply line for the washing or buffer solution. In a subsequent third operating phase, the centrifugation chamber continues to rotate with the rotor.In the third operating phase, the flow direction through the centrifugation chamber is reversed, and the particles are removed from the centrifugation chamber via the second inlet line, while washing or buffer solution is added to the centrifugation chamber via the first inlet line. The third operating phase ends when all particles have been removed from the centrifugation chamber. This is followed successively by further cycles with the three operating phases described above.

[0004] Such flow centrifuges, for which the invention can be applied, are known, for example, from EP 3 936 601 A1, EP 2 310 486 B1, EP 2 485 846 B1, US 4,216,770, US 4,419,089, US 4,389,206 and US 5,665,048.

[0005] It is possible that the centrifuge covered by the invention has a horizontal axis of rotation, whereby an exchange of the media (e.g., blood, a washing fluid, and particles) can occur during centrifugation in the area of ​​the rotating rotor shaft. Such a flow centrifuge could, for example, be a blood centrifuge in which blood is centrifuged as the medium.

[0006] Furthermore, the invention relates to a method for operating such a centrifuge and a computer-readable medium. STATE OF THE ART

[0007] EP 2 814 617 B1 provides the following information on the state of the art for cooling a laboratory centrifuge: During centrifugation, especially in very high-speed laboratory centrifuges, heat is generated in the centrifuge drum during the rotation of the centrifuge rotor due to air friction and the introduction of electrical power losses. Since the centrifuge drum is sealed with a lid to prevent the centrifuged material from escaping, this heat cannot be easily dissipated and leads to an increase in the temperature of the centrifuged material. This temperature increase is undesirable, however, as it can lead to the destruction or unusability of the centrifuged samples. Typically, the samples must be kept at a defined temperature, for example, at temperatures of 4 °C, 22 °C, or 37 °C, depending on the application.Therefore, precautions have been taken in the past to prevent an increase in the temperature of the material being centrifuged, often employing indirect cooling. With this indirect cooling, the rotor is usually enclosed within the centrifuge vessel under the lid, and no cooling channel or similar mechanism is used. The air thus circulates only within the centrifuge vessel. Cooling is achieved by a second medium that is routed along the outside of the vessel or within the vessel wall. For this purpose, a refrigerant circuit with a compressor, pipes, and a heat exchanger is often used. A special refrigerant is circulated around the vessel via pipes that, for example, are arranged in a spiral pattern along the sides and bottom of the centrifuge vessel to dissipate heat.Unlike "coolants," such as those used in the cooling water circuit of passenger cars, a refrigerant undergoes phase changes during its passage through the refrigerant circuit, typically from liquid to gaseous. With such a refrigerant, it is also possible to temperature-control a sample that is below ambient temperature. A refrigerant circuit can also be used to cool the sample to a temperature below the ambient air temperature. Such laboratory centrifuges are known, for example, from DE 38 18 584 A1 or JP 2011 255330 A. These refrigerant circuits 1 have an evaporator 2, which is usually arranged in a ring around the centrifuge vessel 3, a compressor 4, a condenser 5, and an expansion device 6 (see [reference]). Fig. 1The expansion device 6 is designed for the maximum possible load case, i.e., the maximum speed of the centrifuge rotor (not shown). It is already known that the expansion device 6 (pressure equalization element between the high- and low-pressure sections of the refrigerant circuit 1 when the compressor 4 is at rest) is designed as a capillary tube or thermostatic injection valve 7 (abbreviated as "TEV"). In conjunction with a pressure-controlled temperature sensor 8 downstream of the evaporator 3, this thermostatic injection valve 7 is used to automatically increase or decrease the refrigerant flow in the refrigerant circuit 1 at the evaporator inlet VE, depending on the measured temperature. For this to occur, the refrigerant at the evaporator outlet VA needs to be superheated, creating an overpressure that is directly applied to a spring 9 of the thermostatic injection valve 7 to actuate it.More precisely, a certain temperature exists at the evaporator outlet VA. The sensor 10 of the thermostatic injection valve 7 is attached to the evaporator outlet VA. This sensor also contains a refrigerant, which can correspond to the refrigerant of the refrigerant circuit 1. Due to the temperature at the evaporator outlet VA, the refrigerant has a corresponding pressure, which then acts on the thermostatic injection valve 7 and the counterforce of the spring 9, thus opening or closing the thermostatic injection valve 7. Other load cases can be partially, but usually only imprecisely, controlled by another control element, in this case a frequency- or speed-controlled compressor 4. Because the refrigerant requires superheating for the thermostatic injection valve 7 to function, the evaporator capacity cannot be fully utilized; only approximately 95% of the evaporator surface area can be used.Due to the required superheating, there is a temperature difference of approximately 7 K between the evaporator inlet (VE) and the evaporator outlet (VA). Another significant disadvantage of such known refrigerant circuits 1 in centrifuges is that the compressors 4 can only be controlled relatively imprecisely and within certain limits, so that in various partial and low-load conditions, the compressor 4 may have to be switched off completely. However, this is not always possible because compressors 4 typically have a minimum runtime to ensure the internal oil circuit is maintained.Conversely, due to the increased heating of the compressor 4's drive motor during start-up and the necessary pressure equalization or reduction of the pressure differential between the high- and low-pressure sections, a certain minimum idle time is required for such compressors 4. Therefore, the control options via the compressor 4 are severely limited, particularly in the lower capacity range. A further disadvantage is that vibrations occur when the compressor 4 of a refrigerant circuit 1 starts or stops. These vibrations affect the centrifuge's operating behavior, increase the mixing rate in the rotor after the centrifuge has stopped, and impact adjacent laboratory equipment and the like. Finally, frequent switching on and off of the compressor 4 reduces its service life.

[0008] Against this background, EP 2 814 617 B1 proposes a refrigerant circuit 1 (see Fig. 2), in which the expansion device 6 is configured as an electronically continuously or discretely controllable throttle (which can also be configured as an electronic injection valve 11). Temperature sensors 12, 13, 14 detect the temperatures of the refrigerant at the inlet VE of the centrifuge vessel 3, the actual temperature in the centrifuge vessel 3, and the temperature at the outlet VA of the centrifuge vessel 3. The temperature signals from the temperature sensors 12, 13, 14, a setpoint temperature of the centrifuge vessel 3, and a tolerance range of the actual temperature of the centrifuge vessel 3 with respect to the setpoint temperature (in particular ±5 K) are supplied to an electronic control unit. The electronic control unit controls the electronic injection valve 11 and the controllable compressor 4 for temperature control.A bypass line 15 connects the connecting line 16 between the electronic injection valve 11 and the evaporator 2 with the connecting line 17 between the outlet of the compressor 4 and the evaporator 2. An electronic injection valve 18 is located in the bypass line 15. It is possible that the electronic control unit also controls the electronic injection valve 18. According to EP 2 814 617 B1, switching between coarse and fine control occurs as needed, as follows: Coarse control is used when the laboratory centrifuge is started until the actual temperature remains within the tolerance range for a predetermined period. Then, the system switches to and generally maintains fine control during further operation. Coarse control is only resumed if the actual temperature leaves the tolerance range despite fine control.During coarse control, only the compressor 4 is controlled, without any control of the electronically controlled injection valves 11, 18. In contrast, during fine control, the output of the compressor 4 remains unchanged. Control is then achieved via the electronic injection valve 11. During fine control, the electronic injection valve 11 is controlled based on three different criteria. First, the electronic injection valve 11 is reduced [or increased] if the actual temperature of the centrifugal vessel 3 decreases [or increases] within a predefined period, thereby reducing [or increasing] the refrigerant flow.The electronic injection valve 11 is also controlled to open if the refrigerant temperature at the evaporator 2 inlet VE is lower than a predefined temperature threshold at the evaporator 2 inlet VE. This opening is maintained until the temperature again exceeds the predefined threshold. This prevents the compressor 4 from operating in a vacuum. Finally, the temperature difference between the compressor outlet VA and the compressor inlet VE is also monitored. This difference should be between 0 K and 1 K to maximize the utilization of the evaporator 2 and prevent liquid refrigerant from entering the compressor 4. If this difference falls below the specified range, the electronic injection valve 11 is closed further and / or the compressor frequency is reduced.

[0009] JP 2010 008022 A discloses a refrigerant circuit for a centrifuge in which, in a normal operating mode without control options, the refrigerant flows from a compressor via a condenser, a dryer, and two capillary tubes arranged in series to an evaporator. If the cooling of the centrifuge tank thus results in an excessively low temperature, a bypass valve is opened, allowing refrigerant to flow from the compressor outlet to the evaporator via the bypass line through the downstream capillary tube, bypassing the condenser and the upstream capillary tube. To control the refrigerant flow rates in the parallel lines when the solenoid valve is open, the diameter of the upstream capillary tube is smaller than the diameter of the downstream capillary tube.

[0010] EP 0 295 377 A2 discloses a refrigerant circuit of a centrifuge in which the output of a compressor is connected to a cooling coil of the centrifuge tank via a parallel connection of a hot line and a cold line, in which a condenser is arranged. A pulse-width modulated valve is arranged in each of the hot and cold lines, and these valves are operated in opposite directions. The heat supplied to the cooling coil depends on the pulse width, which is controlled based on the measured temperature in the centrifuge tank. TASK OF INVENTION

[0011] The invention is based on the objective of improving the design of a centrifuge and a method for operating it with regard to the possibilities of reacting to an undesired decrease in temperature in the centrifuge vessel. Furthermore, the invention is based on the objective of proposing a computer-readable medium with control logic for a correspondingly improved method. SOLUTION

[0012] The object of the invention is achieved according to the invention by the features of the independent claims. Further preferred embodiments of the invention can be found in the dependent claims. DESCRIPTION OF THE INVENTION

[0013] The invention relates to a centrifuge comprising a centrifuge tank. Furthermore, the centrifuge includes a refrigerant circuit in which a refrigerant circulates, preferably undergoing a phase change within the refrigerant circuit. The refrigerant circuit serves to cool the centrifuge tank in order to maintain a target temperature within a tolerance range within the centrifuge tank.

[0014] In the centrifuge, the temperature in the centrifuge vessel is detected (directly or indirectly) by means of a temperature sensor. To name just a few examples that do not limit the invention, the temperature sensor can be arranged in a wall of the centrifuge vessel or in a lid of the centrifuge, in particular as close as possible to the centrifuge chamber of the centrifuge vessel or in direct proximity to it. It is also possible, however, for the temperature sensor to be integrated into the rotor or a centrifuge container for the material to be centrifuged that is held on the rotor (see also the disclosure in EP 3 560 592 A1).

[0015] The refrigerant circuit used in the invention includes a compressor whose speed, frequency, and / or power are adjustable. Furthermore, the refrigerant circuit includes a condenser. An adjustable expansion device is also arranged in the refrigerant circuit. The refrigerant circuit also includes an evaporator that transfers cooling to the centrifuge boiler. For example, the evaporator can be surrounded by a duct or integrated into a wall of the centrifuge boiler. The adjustable expansion device is preferably arranged upstream of the evaporator in the refrigerant circuit.The adjustable expansion device allows control of the refrigerant flow and / or expansion, thereby influencing the pressure and temperature conditions of the refrigerant in the low-pressure section and in the evaporator area. The adjustable expansion device can be passive, in particular a thermostatic injection valve, or active, in particular an electronically controlled throttle or other electronically controlled expansion device.

[0016] According to the invention, a connecting line from the compressor to the condenser is connected via a bypass line to the connecting line between the expansion device and the evaporator. Preferably, the bypass line bypasses the condenser and the adjustable expansion device. The bypass line can thus create a connection between the high-pressure and low-pressure sections of the refrigerant circuit. To control this connection, an electronically controlled valve is arranged in the bypass line, regulating the flow through the bypass line.

[0017] The invention proposes that the centrifuge be equipped with an electronic control unit and control logic. This control logic monitors the difference between a predetermined target temperature in the centrifuge vessel and the temperature measured by the temperature sensor, i.e., the actual temperature in the centrifuge vessel. If this difference exceeds a predetermined threshold, the control unit actuates the valve located in the bypass line to increase the flow rate through the bypass line. This is preferably the case when the control unit has already set a minimum compressor output and / or the expansion device has been actuated by the control unit to maximize heat absorption by the evaporator.Thus, the valve is preferably activated to increase the flow rate through the bypass line when conventional measures to prevent a decrease in the temperature of the centrifuge vessel have already been exhausted and the temperature still falls below the setpoint by the threshold value (which, without the measures according to the invention, might necessitate the compressor shutdown). In this case, the valve activation results in more refrigerant flowing from the high-pressure side to the low-pressure side at a point on the evaporator's inlet. This increases the amount of warmer refrigerant on the high-pressure side that is mixed into the low-pressure side at the evaporator's inlet, ultimately resulting in less heat being dissipated from the centrifuge vessel by the evaporator.In this way, an excessive reduction in temperature in the centrifuge vessel can be counteracted, which is also possible without having to switch off the compressor or requiring a further or excessive reduction in the compressor's power.

[0018] In principle, there are numerous possibilities for the valve arranged in the bypass line with regard to its design (e.g., poppet valve, spool valve, etc.), operating positions (continuous operating positions; discrete operating positions of any number), and control options, as long as the valve can be controlled by the electronic control unit. Any suitable valve known from the prior art can be used for this purpose. In one embodiment of the invention, the valve is designed as a 2 / 2-way solenoid valve, which has a larger opening position and a smaller opening position. For example, the smaller opening position could be a closed position and the larger opening position a flow position. In this case, the valve is always in the closed position, in which the bypass line is closed.Only when the difference between the target temperature in the centrifuge vessel and the temperature measured by the temperature sensor exceeds the threshold value, is the 2 / 2-way solenoid valve switched to the open position by the control unit. In this case, the 2 / 2-way solenoid valve can assume its closed position without electrical excitation from the control unit, while electrical excitation is required to switch it to the open position. However, the valve can also be configured in reverse, so that it is switched to the closed position by electrical excitation. In this case, the stable position of the valve, which can only be changed by electrical excitation, can be secured by a spring.In another embodiment, the valve can be designed as a bistable valve, which maintains a previously established open position and a closed position without requiring any further activation of the valve. Electrical activation of the valve is then only necessary to change its position in either direction.

[0019] There are various possibilities for the criteria for controlling the 2 / 2-way solenoid valve to the open position. For example, the 2 / 2-way solenoid valve could be controlled to the open position until the difference between the setpoint temperature in the centrifuge vessel and the temperature detected by the temperature sensor is less than the threshold value or any other temperature correlated with the setpoint temperature. In a particularly simple embodiment of the invention, the control logic controls the 2 / 2-way solenoid valve from the closed position to the open position for a predetermined period of time.The predetermined time interval can depend on operating parameters of the centrifuge, such as the centrifuge speed, the ambient temperature, the material being centrifuged, and / or the type of rotor used, to name just a few examples that do not limit the invention. It is also possible that the time interval for which the valve is controlled in the open position by the control logic is learned during centrifuge operation and potentially over a multitude of operating cycles.

[0020] Within the scope of the invention, any expansion device can be used, which can therefore also be an electronically controlled expansion valve or an electronically controlled throttle. For a particularly simple embodiment of the invention, a passive thermostatic injection valve is used as the expansion device. A compressor of any design can be used in the centrifuge according to the invention. Preferably, a rotary piston compressor is used, the operation of which has proven to be very advantageous with regard to undesirable vibrations and can also be advantageous with regard to the use of environmentally friendly refrigerants.

[0021] For one solution to the invention, instead of designing the valve as a 2 / 2-way solenoid valve, a valve with several different opening cross-sections can be used. In this case, the valve can have several discrete operating positions that correlate with the different opening cross-sections. It is also possible for the valve to have continuously varying opening cross-sections, whereby the different opening cross-sections may or may not represent a fully closed position and / or a fully open position. For example, the valve can be designed as a proportional valve, which allows continuously varying opening cross-sections depending on the electrical excitation.It is also possible for the valve to provide several different opening cross-sections by being designed as a pulse-width modulated valve, where the duty cycle for pulse-width modulation correlates with the opening cross-section. For such configurations, the control unit incorporates control logic that increases the opening cross-section if the difference between the target temperature in the centrifuge vessel and the temperature measured by the temperature sensor exceeds a threshold value. In this case, the increase in the opening cross-section depends on the magnitude of the difference, the rate of change of the difference, and / or the duration for which the difference exceeds the threshold value. For example, it is possible that initially only a slight increase in the valve opening is implemented.If the control logic of the control unit then determines that the temperature in the centrifuge vessel remains too low, the opening can be further enlarged. Within the scope of the invention, the opening cross-section or its size can also be controlled based on the operating parameters of the centrifuge, in particular the actual temperature in the centrifuge vessel.

[0022] According to the invention, the control logic of the control unit operates in two different modes: A normal operating mode is present when the difference between the setpoint temperature in the centrifuge vessel and the temperature detected by the temperature sensor is less than the threshold value (or a second threshold value). In the normal operating mode, the control logic performs control or regulation exclusively by means of the adjustable expansion device and / or the adjustable compressor. In the normal operating mode, the valve is in a first position.

[0023] An exceptional operating mode occurs when the difference between the setpoint temperature in the centrifuge vessel and the temperature detected by the temperature sensor exceeds the threshold (or the aforementioned second threshold). In this exceptional operating mode, the control logic moves the valve to a second position that differs from the first position. According to the invention, no additional control or regulation by the compressor takes place in this exceptional operating mode, and preferably, no control or regulation by the adjustable expansion device takes place either. For this aspect of the invention, the valve's opening cross-section in the first position is smaller than the valve's opening cross-section in the second position.

[0024] If a 2 / 2-way solenoid valve is used, the first position can be the closed position, while the second position can be the open position. However, if other valve designs with a continuously or discretely variable opening cross-section are used, any partial opening can occur in the first and / or second position.

[0025] In one embodiment of the invention, the compressor in the centrifuge is operated continuously during operation of the laboratory centrifuge, with the rotational speed always corresponding to at least a minimum speed. The inventive design thus avoids the need to switch off the compressor, which is advantageous both with regard to the operation, service life, and lubrication of the compressor, and also to prevent undesirable mixing of the centrifuged material resulting from stopping and restarting the compressor.

[0026] Another solution to the problem underlying the invention is a method for operating a centrifuge. Here, the centrifuge is fundamentally constructed as previously described in the various embodiments and further developments. In one process step, a test is first performed to determine whether the difference between the target temperature in the centrifuge vessel and the temperature detected by the temperature sensor exceeds a threshold value. If this test shows that the difference is greater than the threshold value, the flow rate through the bypass line is increased in the method according to the invention.

[0027] In one aspect of the invention, the flow of the refrigerant through the evaporator is controlled or regulated (also or exclusively) by a passive thermostatic injection valve.

[0028] It is possible that in the inventive method the refrigerant is conveyed in the refrigerant circuit by means of a rotary piston compressor.

[0029] Furthermore, in the method according to the invention, it is possible that the valve is controlled to several different opening cross-sections (continuously or in discrete stages). If the difference between the target temperature in the centrifuge vessel and the temperature detected by the temperature sensor is greater than a threshold value, the opening cross-section is enlarged. The enlargement and its extent depend on the magnitude of the detected difference, the rate of change of the difference, and / or the time period during which the difference exceeds the threshold value.

[0030] According to the invention, a test is performed to determine whether the amount of the difference between the target temperature in the centrifuge vessel and the temperature detected by the temperature sensor is smaller than the threshold value (or a second other threshold value).

[0031] If this is the case, the centrifuge operates in normal mode. In normal mode, control is achieved via the adjustable expansion device and / or the compressor. In normal mode, the valve is in its first position.

[0032] If, however, the difference is greater than the threshold (or the second threshold), the centrifuge operates in an emergency mode. In this emergency mode, the valve is controlled to a second position that differs from the first position. In this emergency mode, no control or regulation is performed by the compressor, and preferably, no control or regulation is performed by the adjustable expansion device either. For the embodiment of the method according to the invention, the opening cross-section of the valve is smaller in the first position than the opening cross-section of the valve in the second position.

[0033] In a further embodiment of the method according to the invention, the compressor is operated continuously during the operation of the centrifuge, whereby the rotational speed always corresponds to at least a minimum rotational speed during this operation.

[0034] Another solution to the problem underlying the invention is a computer-readable medium that includes control logic for carrying out a method for operating a centrifuge, as previously described. The control logic on such a computer-readable medium can, for example, enable the subsequent implementation of the method according to the invention on an existing centrifuge or allow for an upgrade of the control software.

[0035] Advantageous further developments of the invention result from the patent claims, the description and the drawings.

[0036] The advantages of features and combinations of features mentioned in the description are merely exemplary and can have an effect alternatively or cumulatively, without the advantages necessarily having to be achieved by embodiments according to the invention.

[0037] Regarding the disclosure content—not the scope of protection—of the original application documents and the patent, the following applies: Further features can be derived from the drawings—in particular, the geometries depicted and the relative dimensions of several components to one another, as well as their relative arrangement and functional connection. The combination of features from different embodiments of the invention or from features of different claims is also possible, deviating from the chosen cross-references of the claims, and is hereby encouraged. This also applies to features that are illustrated in separate drawings or mentioned in their description. These features can also be combined with features from different claims.Likewise, features listed in the patent claims may be omitted for further embodiments of the invention, but this does not apply to the independent patent claims of the granted patent.

[0038] The features mentioned in the claims and the description are to be understood, with regard to their number, as meaning that exactly that number or a greater number than the stated number is present, without the need for the explicit use of the adverb "at least". Thus, for example, if a valve or a release device is mentioned, this is to be understood as meaning that exactly one valve or release device, two valves or two release devices, or more valves or more release devices are present. The features listed in the claims may be supplemented by further features or may be the only features that the subject matter of the respective claim possesses.

[0039] The reference numerals contained in the patent claims do not constitute a limitation of the scope of the subject matter protected by the patent claims. They serve only the purpose of making the patent claims easier to understand. BRIEF DESCRIPTION OF THE FIGURES

[0040] The invention will now be further explained and described with reference to preferred embodiments shown in the figures. Fig. 1 The figure schematically shows a laboratory centrifuge with a refrigerant circuit according to the state of the art. Fig. 2 The figure schematically shows a laboratory centrifuge with a refrigerant circuit according to EP2814 617 B1. Fig. 3 schematically shows a centrifuge with a refrigerant circuit. Fig. 4 schematically shows a method for operating a centrifuge with a refrigerant circuit. FIGURE DESCRIPTION

[0041] Fig. 3Figure 1 schematically shows a centrifuge 19 with a centrifuge tank 3 and a refrigerant circuit 1 in which a compressor 4, a condenser 5, an expansion device 6 (which can be configured as a thermostatic injection valve 7 or an electronically controlled expansion device or throttle 11), and an evaporator 2 are connected in that order in a circuit. A connecting line 17 between the compressor 4 and the condenser 5 is connected via a bypass line 15 with an electronically controlled valve 20 arranged therein to a connecting line 16 between the expansion device 6 and the evaporator 2. If the expansion device 6 is configured as a thermostatic injection valve 7, it preferably has a spring 9 and the pressure-controlled temperature sensor 8 with the sensor 10 (see Figure 1). Fig. 1 and the state of the art mentioned at the beginning).

[0042] An inventive method is described in Fig. 4As shown, the process begins (possibly after the centrifuge 19 has started up) with the centrifuge 19 operating in a normal operating mode 21. In normal operating mode 21, the temperature in the centrifuge vessel 3 is regulated in a process step 22. This regulation initially involves controlling the refrigerant flow and the size of the opening or throttling effect of the expansion device 6. This can be done passively, as shown, if a thermostatic injection valve 7 is used as the expansion device 6. However, it is also possible for the temperature in the centrifuge vessel 3 to be determined by means of a temperature sensor 23, and for an electronic injection valve or an electronic throttle 11 to be controlled as needed by a control unit. Alternatively or additionally, the temperature can be controlled by controlling the variable-speed compressor 4 by means of the control unit.In process step 24, which can take place during the aforementioned control or regulation, a difference is determined between a predefined target temperature (for example, entered by the user and stored in the control unit or read from a characteristic map for the selected operating data) in the centrifuge vessel and the temperature recorded by temperature sensor 23 (i.e., an actual temperature, whereby the measured temperature can also be corrected or converted into the actual temperature in the centrifuge chamber within the centrifuge vessel 3 or an estimate of this actual temperature). In process step 25, this difference is then compared with a threshold value, which can be, for example, 5 K, 3 K, or 1 K.If the difference is smaller than the threshold value and thus the actual temperature is less than the target temperature by the threshold value, normal operating mode 21 can be continued, in which the process step 22 is returned.

[0043] If, however, the difference between the setpoint temperature and the actual temperature is greater than the threshold value, and thus the actual temperature is lower than the setpoint temperature by more than the threshold value, a switch occurs from normal operating mode 21 to an exceptional operating mode 26. In exceptional operating mode 26, in process step 27, the control unit actuates valve 20 such that the flow rate in the bypass line 15 is increased. It is possible that valve 20 is designed as a 2 / 2-way solenoid valve. In this case, in process step 27, the 2 / 2-way solenoid valve 28 is actuated such that it is switched from the closed position to the open position. Optionally, in process step 29, further measures can be taken to increase the actual temperature, for example by appropriately controlling the adjustable compressor 4 and / or controlling the expansion device 6.It is possible that this state is then maintained for a predetermined period of time. Immediately or after this period, in process step 30, it is checked whether the difference between the target temperature and the actual temperature is still greater than the threshold value. If this is the case, the exceptional operating mode 26 is maintained, and in process step 27, the valve 20 is opened, opened further than before, or the open state of the valve 20 is maintained. If, on the other hand, the actual temperature has risen to such an extent that it is at most a threshold value lower than the target temperature, a return to normal operating mode 21 occurs, in which case process steps 22, 24, and 25 are executed again.

[0044] It is also possible that the valve 20 is connected in parallel in the bypass line 15 with a line section having a predetermined flow cross-section or a throttle with a predetermined throttle cross-section, thus ensuring a permanent flow through the bypass line 15 by means of this line section. In this case, the flow thus ensured can be further influenced depending on the opening position of the valve 20. Again, the valve 20 can be designed as a 2 / 2-way solenoid valve or as any other discretely or continuously adjustable valve.

[0045] Preferably, the compressor 4 is designed as a rotary piston compressor 31. REFERENCE MARK LIST

[0046] 1 Refrigerant circuit 2 Evaporator 3 Centrifuge tank 4 Compressor 5 Condenser 6 Expansion device 7 Thermostatic injection valve 8 Pressure-controlled temperature sensor 9 Spring 10 Filler 11 Electronically controlled expansion device or electronically controlled throttle 12 Temperature sensor 13 Temperature sensor 14 Temperature sensor 15 Bypass line 16 Connecting line 17 Connecting line 18 Electronically controlled injection valve 19 Centrifuge 20 Valve 21 Normal operating mode 22 Process step 23 Temperature sensor 24 Process step 25 Process step 26 Emergency operating mode 27 Process step 28 2 / 2-way solenoid valve 29 Process step 30 Process step 31 Rotary compressor

Claims

1. Centrifuge (19), in particular flow-through centrifuge, biotechnical centrifuge or blood centrifuge, comprising a) a centrifuge vessel (3), b) a cooling medium circuit (1) with a circulating cooling medium and c) a temperature sensor (23) which senses a temperature which at least correlates with the temperature in the centrifuge vessel (3), wherein c) the cooling medium circuit (1) comprises ca) a controllable compressor (4), cb) a liquefier (5), cc) an adjustable relaxing device (6) and cd) an evaporator (2) delivering cold energy to the centrifuge vessel (3), d) a connecting line (17) of the compressor (4) to the liquefier (5) is connected by a bypass line (15) to a connecting line (16) between the relaxing device (6) and the evaporator (2) and e) an electronically controlled valve (20) controlling the flow is arranged in the bypass line (15), characterized in that f) an electronic control unit is provided which comprises control logic which in the case that a difference - of the desired temperature in the centrifuge vessel (3) and - of the temperature sensed by the temperature sensor (23) exceeds a threshold value controls the valve (20) such that the flow through the bypass line (15) is increased and g) the control unit comprises control logic which ga) in a normal operation mode (21) in which the absolute value of the difference - of the desired temperature in the centrifuge vessel (3) and - of the temperature sensed by the temperature sensor (23) is smaller than the threshold or than a second threshold provides a control by means of the relaxing device (6) and / or by means of the compressor (4) when the valve (20) is in a first position and gb) in an extraordinary operation mode (26) in which the absolute value of the difference: - of the desired temperature in the centrifuge vessel (3) and - the temperature sensed by the temperature sensor (23) exceeds the threshold value or the second threshold value controls the valve (20) in a second position differing from the first position, wherein in the extraordinary operation mode (26) there is no control by means of the compressor (4), wherein preferably in the extraordinary operation mode (26) there is also no control by means of the relaxing device (6), gc) wherein in the first position of the valve (20) the opening cross section of the valve (20) is smaller than the opening cross section of the valve (20) in the second position, the steps f), g), ga), gb) and gc) being part of the control logic of the electronic control unit.

2. Centrifuge (19) of claim 1, characterized in that a) the valve (20) is a 2 / 2-way solenoid valve (28) comprising a larger opening position and a smaller opening position, in particular an open position and a closed position and b) the control unit comprises control logic which in the case that a difference - of the desired temperature in the centrifuge vessel (3) and - of the temperature sensed by the temperature sensor (23) exceeds a threshold controls the 2 / 2-way solenoid valve (28) from the smaller opening position into the larger opening position, wherein the control logic preferably controls the 2 / 2-way solenoid valve (28) for a predetermined time span from the smaller opening position into the larger opening position.

3. Centrifuge (19) of one of the preceding claims, characterized in that the relaxing device (6) is a passive thermostatic injection valve (7).

4. Centrifuge (19) of one of the preceding claims, characterized in that the compressor (4) is a rotary piston compressor (31).

5. Centrifuge (19) of one the claims 1, 3 and 4, characterized in that the valve comprises a plurality of different opening cross sections and the control unit comprises control logic which in the case that a difference - of the desired temperature in the centrifuge vessel (3) and - of the temperature sensed by the temperature sensor (23) exceeds a threshold value induces a larger opening cross section depended on the amount of the difference, on a changing velocity of the difference and / or the time span during which the difference exceeds the threshold value.

6. Centrifuge (19) of one of the preceding claims, characterized in that the compressor (4) is permanently operated during the operation of the centrifuge (19), wherein during the operation the number revolutions at least corresponds to a minimum number of revolutions.

7. Method for operating a centrifuge (19), in particular a flow-through centrifuge, a biotechnical centrifuge or a blood centrifuge, comprising a centrifuge vessel (3), a cooling medium circuit (1) with a circulating cooling medium and a temperature sensor (23) which senses a temperature which at least correlates with the temperature in the centrifuge vessel (3), the cooling medium circuit (1) comprising a controllable compressor (4), a liquefier (5), a relaxing device (6) and an evaporator (2) delivering cooling energy to the centrifuge vessel (3), a connecting line (17) of the compressor (4) to the liquefier (5) being connected by a bypass line (15) to the connecting line (16) between the relaxing device (6) and the evaporator (2) and an electronically controlled valve (20) controlling the flow being arranged in the bypass line (15), the method comprising the following method steps: a) execution of an analysis if a difference of the desired temperature in the centrifuge vessel (3) and of the temperature sensed by the temperature sensor (23) exceeds a threshold, characterized in that b) in the case that the analysis leads to the result that the difference exceeds the threshold, increasing the flow through the bypass line (15), c) wherein an analysis is performed if the absolute value of the difference of the desired temperature in the centrifuge vessel (3) and of the temperature sensed by the temperature sensor (23) is smaller than the threshold or a second threshold and ca) if this is the case, the centrifuge (19) is operated in a normal operation mode (21) wherein a control is provided by means of the relaxing device (6) and / or by means of the compressor (4) whereas the valve (20) is in a first position and cb) if this is not the case, the centrifuge (19) is operated in an extraordinary operation mode (26) wherein the valve (20) is controlled from the first position into a different second position, wherein in the extraordinary operation mode (26) there is no control by the compressor (4), wherein preferably in the extraordinary operation mode (26) there is also no control by means of the relaxing device (6), wherein in the first position of the valve (20) the opening cross section of the valve (20) is smaller than the opening cross section of the valve (20) in the second position.

8. Method of claim 7, characterized in that the flow of the cooling medium through the evaporator (2) is controlled (open loop or closed loop) by a passive thermostatic injection valve (7).

9. Method of claim 7 or 8, characterized in that in the cooling medium circuit (1) the cooling medium is delivered by a rotary piston compressor (31).

10. Method of one of claims 7 to 9, characterized in that a) the valve (20) is controlled in a plurality of different cross sections and b) it is analysed if a difference of the desired temperature in the centrifuge vessel (3) of the temperature sensed by the temperature sensor (23) exceeds a threshold value and, if this is a case, an increase of the opening cross section of the valve (20) is induced depended on the absolute value of the difference, on a changing velocity of the difference and / or on the time span during which the difference exceeds the threshold value.

11. Method of one of claims 7 to 10, characterized in that the compressor (4) is permanently operated during the operation of the centrifuge (19) wherein during the operation the number of revolutions at least corresponds to a minimum number of revolutions.

12. Computer-readable medium comprising control logic for executing a method for operating a centrifuge (19) configured according to one of claims 1 to 6, characterized in that the steps f), g), ga), gb) and gc) are part of the control logic of the electronic control unit.