EP3807011B1 - Temperature-controller centrifuge having crash protection - Google Patents

Description

The present invention relates to a centrifuge according to the preamble of claim 7 and a method for preventing ignition of combustible tempering media according to the preamble of claim 1.

Centrifuge rotors are used in centrifuges, especially laboratory centrifuges, to separate the components of samples centrifuged therein by utilizing mass inertia. Increasingly higher rotation speeds are used to achieve high demixing rates. Laboratory centrifuges are centrifuges whose rotors preferably operate at at least 3,000, preferably at least 10,000, in particular at least 15,000 revolutions per minute and are usually placed on tables. In order to be able to place them on a work table, they have a form factor of less than 1 m × 1 m × 1 m, so their installation space is limited. The device depth is preferably limited to a maximum of 70 cm.

Such centrifuges are used in the fields of medicine, pharmacy, biology and chemistry.

The samples to be centrifuged are stored in sample containers and these sample containers are rotated using a centrifuge rotor. The centrifuge rotors are usually set in rotation by a vertical drive shaft that is driven by an electric motor. There are various centrifuge rotors that are used depending on the application. The sample containers can contain the samples directly or the sample containers can have their own sample containers that contain the sample, so that a large number of samples can be centrifuged simultaneously in one sample container. In general, centrifuge rotors are known in the form of fixed-angle rotors and swing-out rotors and others.

In most cases, samples are centrifuged at certain temperatures. For example, samples containing proteins and similar organic substances must not be overheated, so the upper limit for the temperature of such samples is in the range of +40°C by default. On the other hand, certain samples are cooled by default in the range of +4°C (the anomaly of water starts at 3.98°C).

In addition to such predetermined maximum temperatures of, for example, approximately +40°C and standard test temperatures such as +4°C, other standard test temperatures are also provided, such as +11°C, in order to check at this temperature whether the centrifuge's refrigeration system is running at a regulated level below room temperature. On the other hand, for occupational health and safety reasons, it is necessary to prevent touching elements that have a temperature of greater than or equal to +60°C.

In principle, active and passive systems can be used for temperature control. Passive systems are based on air-assisted ventilation. This air is passed directly past the centrifuge rotor, which results in temperature control. The air is sucked into the centrifuge bowl through openings and the warmed air is discharged through further openings at another point in the centrifuge bowl, with the suction and discharge taking place automatically through the rotation of the centrifuge rotor.

Active cooling systems, on the other hand, have a coolant circuit that regulates the temperature of the centrifuge container, which indirectly cools the centrifuge rotor and the sample containers contained therein. Many different media are used as cooling or tempering media in compressor-operated cooling systems. Since in principle not only cooling, i.e. heat extraction, but also targeted heat supply can be desired during centrifugation, the present invention refers to tempering and tempering media. In addition to the tempering media commonly used for centrifuges, such as chlorodifluoromethane, tetrafluoroethane, pentafluoroethane or difluoromethane and many others, there are also flammable tempering media, such as butane or propane or various synthetic mixtures.

Although these flammable tempering media have very good heat transfer properties, they are generally not used for safety reasons, since the tempering medium can leak out and ignite in the event of a centrifuge rotor crash. In such a crash, fragments of the centrifuge rotor can at high speed and therefore with very high energy within the centrifuge and thereby also destroy the evaporator and the lines that carry the tempering medium. The escaping flammable tempering medium can then easily be ignited by the energy released during the crash and by electrical or electronic components inside the centrifuge or in its surroundings, which can cause very great damage, especially personal injury.

In order to prevent a crash of the centrifuge rotor from causing damage outside the centrifuge, stiffening and reinforcing means inside the centrifuge have been proposed. However, this would not prevent the escape of tempering media because the tempering medium lines that form the evaporator run around the centrifuge container, between the centrifuge rotor and the reinforcing means.

The EN 10 2012 002 593 A1 relates to an invention that deals with the use of electronic injection valves. In this context, Fig.1 reference is made to a solution according to the state of the art in which a thermostatic injection valve is used that reacts to a pressure sensor after the evaporator outlet. According to section [0047], the thermostatic injection valve should open when superheating is reached. This document does show a pressure determination at the evaporator outlet, whereby a maximum pressure (superheating pressure) is determined and the thermostatic injection valve is then switched, but this document does not deal with flammable refrigerants or with preventing the ignition of these refrigerants.

It is therefore an object of the present invention to propose a centrifuge with which flammable temperature control media can also be used without these representing an increased safety risk in the event of a crash of the centrifuge rotor.

This object is achieved with the centrifuge according to the invention according to claim 7 and the method according to the invention for preventing ignition of combustible tempering media according to claim 1. Advantageous further developments are specified in the subclaims and in the following description together with the figures. The inventors realized that this problem can be solved in a surprising and particularly simple way if the pressure in the evaporator is monitored to determine whether it is below a predetermined minimum value or above a predetermined maximum value. Targeted measures can then be taken to prevent a possible ignition of the tempering medium. If the pressure is below a minimum pressure, it can be assumed that there is either a leak or a crash, although a leak in the evaporator is very unlikely but could still lead to a gradual release of flammable tempering medium and a crash to a sudden release of flammable tempering medium. If the pressure is above a maximum pressure, there is a risk that there is a lot of flammable tempering medium in the evaporator, which could leak out and be ignited in the event of a crash.

The method according to the invention for preventing ignition of flammable tempering media in centrifuges, in particular after a crash of the centrifuge rotor, wherein the centrifuge, which is designed in particular as a laboratory centrifuge, has a centrifuge container in which a centrifuge rotor can be accommodated, a centrifuge motor for driving the centrifuge rotor, tempering means with an evaporator and a compressor for tempering the centrifuge rotor and a housing in which the centrifuge container, the centrifuge rotor, the tempering means and the centrifuge motor are accommodated, wherein the tempering means have a flammable tempering medium which is guided in a tempering medium line, wherein the pressure in the evaporator is monitored to determine whether it is below a predetermined minimum pressure and/or above a predetermined maximum pressure, is characterized in that a fan of the centrifuge is started after an electrical power supply to the centrifuge is switched on and the fan has a The temperature control medium line is at least partially overflowed and/or at least one cavity in the centrifuge is flowed through in such a way that the resulting exhaust air is transported out of the housing of the centrifuge.

In an advantageous development, the pressure at the outlet of the evaporator is determined, preferably using a pressure sensor, in particular in the form of a pressure transmitter. This makes it particularly easy to monitor the pressure and to take control measures directly.

In an advantageous development, it is provided that the predetermined minimum pressure is at least 0.7 bar, preferably at least 1 bar and in particular at least 1.3 bar.

In an advantageous further development, it is provided that the predetermined maximum pressure is at most 5 bar, preferably at most 3 bar, in particular at most 2 bar.

In an advantageous further development, R290 propane is used as the temperature control medium. Alternatively, isobutane, propene, butene, etc. can also be used. However, R290 propane is preferred due to its advantageous parameters (pressure ranges, temperature profiles, boiling point, enthalpies and volumetric efficiency).

Ultimately, the pressure range depends directly on the temperature control medium used and the intended use (e.g. deep freezing or normal cooling); it has been shown with R290 propane that the above-mentioned pressure range is advantageous.

• die Zuleitung von Temperierungsmedium zum Verdampfer wird unterbrochen;
• der Verdichter wird abgeschaltet;
• die elektrische Energieversorgung der elektrischen Elemente der Zentrifuge, die eine Explosion verursachen könnten und nicht Ex-geschützt oder unter 20 W elektrische Leistung aufnehmend ausgebildet sind, wird gestoppt;
• der Zentrifugenmotor wird gestoppt;
• elektrische Restenergie wird gezielt an einen Lüfter der Zentrifuge zu dessen Betrieb geleitet.

In an advantageous further development, it is provided that if the evaporator pressure is below the specified minimum pressure, one or more of the following measures are carried out:

• the supply of tempering medium to the evaporator is interrupted;
• the compressor is switched off;
• the electrical power supply to the electrical elements of the centrifuge which could cause an explosion and are not explosion-proof or designed to consume less than 20 W of electrical power is stopped;
• the centrifuge motor is stopped;
• Residual electrical energy is directed to a fan in the centrifuge to operate it.

If the supply of tempering medium to the evaporator is interrupted, only the tempering medium already in the evaporator can be ignited, which effectively limits the ignitable quantity.

When the compressor is switched off, no air is sucked into the remaining circuit containing the temperature control medium, thus improving safety.

If the electrical power supply is stopped, the centrifuge itself cannot cause an ignition. Explosion-proof components are those according to the ATEX Directive of the European Union (ATEX Product Directive 2014/34/EU and the ATEX Operating Directive 1999/92/EC), or elements that have a power consumption of less than 20 W.

Preferably, the centrifuge motor is designed to be explosion-proof in order to fundamentally prevent ignitions caused by the centrifuge motor.

In an advantageous development, it is provided that the tempering medium circuit contains a quantity of tempering medium of less than 150 g, preferably less than 140 g, particularly preferably less than 130 g, in particular less than 120 g.

In an advantageous further development, it is provided that the tempering medium circuit contains a quantity of tempering medium of more than 30 g, preferably more than 40 g, particularly preferably more than 50 g. The quantity is advantageously in the range 60 g to 110 g, but the other specified quantities can also be used for this range.

If the centrifuge motor is stopped, a crash that has not yet occurred is prevented or the extent of a crash that has already occurred is reduced. It is also advantageous to switch off the centrifuge motor if the centrifuge motor is explosion-proof, because this provides mechanical crash protection.

If the residual electrical energy is fed to a fan of the centrifuge, the tempering medium is dispersed to such an extent that ignition is made more difficult. Such an electrical fallback level could be implemented, for example, by means of at least one relay that is constantly energized during normal operation. If, in the event of a crash, the If there is no power to pull in or if a deliberate changeover occurs, the relay then establishes a contact between the residual electrical energy (for example from capacitors and the like) and the fan. Such capacitors could be capacitors provided as standard in the electronics of the laboratory centrifuge. Special capacitors or accumulators could also be used that only exist to be charged during normal operation and to supply energy to the fan on request. For example, the request in the event of a crash could be made by the aforementioned relay or the like.

In an advantageous further development, the amount of tempering medium in the evaporator is reduced if the evaporator pressure exceeds the specified maximum pressure. This provides for a possible crash by keeping the ignitable amount as low as possible from the outset.

• die Zuleitung von Temperierungsmedium zum Verdampfer wird unterbrochen;
• die Leistung des Verdichters wird erhöht;
• das Temperierungsmedium wird in einen Temperierungsmedienspeicher geleitet.

In an advantageous further development, it is provided that if the evaporator pressure exceeds the specified maximum pressure, one or more of the following measures are carried out:

• the supply of tempering medium to the evaporator is interrupted;
• the performance of the compressor is increased;
• The tempering medium is fed into a tempering medium storage tank.

If the supply of tempering medium to the evaporator is interrupted, the ignitable quantity is kept as low as possible.

When the compressor capacity is increased, tempering medium is sucked out of the evaporator so that the flammable amount is kept as low as possible.

If tempering medium is fed into a tempering medium reservoir, the amount of flammable tempering medium in the evaporator is also reduced. This can be done, for example, by closing a valve in the tempering medium circuit so that no tempering medium can flow into the evaporator. The compressor then pumps the tempering medium down to the minimum pressure and automatically feeds it into the opened tempering medium reservoir. The tempering medium is then removed again from the tempering medium reservoir. simply by opening the valve in the line. During normal operation the valve remains open.

Before increasing the performance of the compressor or introducing the tempering medium into the tempering medium storage tank, the supply of tempering medium to the evaporator is preferably interrupted.

According to the invention, a fan of the centrifuge is started after the electrical power supply of the centrifuge is switched on. This disperses any temperature control medium that may leak out in advance in such a way that a possible ignition is prevented. This method requires independent protection regardless of whether the pressure in the evaporator is monitored or not.

This or the previously mentioned fan, which serves to disperse any escaping temperature control medium, can be a specially designed fan, but it can also be a fan for cooling the centrifuge's electronics or a fan for operating the centrifuge's condenser. The fan should preferably be designed so that it flows over the temperature control medium line at least in some areas and/or flows through at least one, in particular several cavities in the centrifuge in such a way that the resulting exhaust air is transported out of the centrifuge housing. These are preferably cavities that can fill up with escaping temperature control medium.

In an advantageous further development, it is provided that the fan is operated in such a way that no explosion-critical tempering medium-air mixture is formed, preferably no tempering medium-air mixture with a tempering medium content of 2 to 9 vol.% is formed.

Independent protection is claimed for the centrifuge according to the invention, in particular a laboratory centrifuge, with a centrifuge container in which a centrifuge rotor can be accommodated, a centrifuge motor for driving the centrifuge rotor, tempering means with an evaporator and a compressor for tempering the centrifuge rotor and a housing in which the centrifuge container, the centrifuge rotor, the tempering means and the centrifuge motor are accommodated, wherein the tempering means comprise a combustible tempering medium which is guided in a tempering medium line, wherein the centrifuge is adapted to determine whether the pressure in the evaporator is below a predetermined minimum pressure and/or above a predetermined maximum pressure, which is characterized in that the centrifuge is designed to start a fan of the centrifuge after an electrical power supply to the centrifuge is switched on, wherein the fan is set up such that it flows over a tempering medium line at least in regions and/or flows through at least one, in particular several cavities in the centrifuge such that the resulting exhaust air is conveyed out of the housing of the centrifuge.

In an advantageous further development, it is provided that the centrifuge is adapted to carry out the method according to the invention.

In an advantageous further development, at least one of the elements - electrical supply line to a non-Ex-protected component, switch in the electrical supply line to a non-Ex-protected component and control of the centrifuge - is arranged in the crash area of the centrifuge. In the event of a crash, the power supply to the non-Ex-protected components is then deliberately interrupted, thus preventing ignition. "Crash area" in this context means the area around the centrifuge container. If crash protection in the form of one or more stiffening elements or crash energy absorber elements is present in the centrifuge, then these elements should be arranged between the centrifuge container and the stiffening elements or crash energy absorber elements. For this design of the centrifuge, independent protection is claimed regardless of whether or not a sensor for monitoring the pressure in the evaporator is present.

In an advantageous development, it is provided that a solenoid valve is arranged in front of the inlet of the evaporator, whereby the solenoid valve is preferably arranged in front of the pressure relief element. A solenoid valve, which is always kept open by the electrical supply of the centrifuge, closes automatically under spring force if the electrical supply is interrupted, as is to be expected in the event of a crash. For safety reasons, the pressure monitoring can be switched off in the event of a pressure below the The solenoid valve closes automatically when the minimum pressure is reached. This prevents the tempering medium from flowing in and possibly igniting in the event of a crash. As an alternative to a solenoid valve, electronic injection valves (NC) (normally closed) or pressure switching valves can be used.

In an advantageous further development, a check valve is arranged after the outlet of the evaporator. This prevents the tempering medium from flowing back into the evaporator from the condenser via the compressor, which becomes leaky over time, in the event of a crash. As an alternative to a check valve, another solenoid valve could also be used.

In an advantageous further development, it is provided that at least one of the elements centrifuge motor, electrical main switch, fan, pressure monitoring control and pressure monitoring sensor is explosion-proof and/or designed to consume less than 20 W of electrical power. This means that these elements can be operated continuously and carry out the monitoring or ignition protection measures without being able to contribute to an ignition.

In an advantageous further development, it is provided that the centrifuge has a gas sensor outside the temperature control medium, whereby leaks can be detected independently of a pressure drop below the minimum pressure in order to prevent the centrifuge from starting.

In an advantageous development, it is provided that the centrifuge is designed to supply a fan with residual electrical energy present in the centrifuge after the electrical power supply fails, wherein there is preferably a relay that is fed by the electrical power supply and connects at least one element with residual electrical energy to the fan in the event of a failure of the electrical power supply, wherein the at least one element is in particular a capacitor. This ensures that the tempering agent is dispersed for as long as possible even in the event of a crash and when the electrical power supply fails.

Fig. 1a

die erfindungsgemäße Zentrifuge in einer perspektivischen Ansicht,

Fig. 1b

die erfindungsgemäße Zentrifuge nach Fig. 1a in einer Schnittansicht,

Fig. 2

die erfindungsgemäße Zentrifuge nach Fig. 1a in einer vereinfachten Blockbilddarstellung hinsichtlich der Temperierungsmittel und

Fig. 3

die erfindungsgemäße Zentrifuge nach Fig. 1a in einer Blockbilddarstellung hinsichtlich eines stark vereinfachten Stromlaufplanes.

The features and further advantages of the present invention will become clear below from the description of a preferred embodiment in conjunction with the figures. These show purely schematically:

Fig. 1a

the centrifuge according to the invention in a perspective view,

Fig. 1b

the centrifuge according to the invention Fig. 1a in a sectional view,

Fig.2

the centrifuge according to the invention Fig. 1a in a simplified block diagram representation with regard to the tempering means and

Fig.3

the centrifuge according to the invention Fig. 1a in a block diagram representation with regard to a highly simplified circuit diagram.

In the Fig. 1a to 3 the centrifuge 10 according to the invention is shown purely schematically in various views.

It can be seen that the centrifuge 10 is designed as a laboratory centrifuge, which has a housing 12 with a lid 14 and an operating front 15. In the centrifuge container 16 of the centrifuge 10, a centrifuge rotor 20 is arranged on a drive shaft 17 of a centrifuge motor 18, which is designed as a swing-out rotor with centrifuge cups 22.

In Fig. 2 It can be seen that the centrifuge has tempering means 24 which comprise an evaporator 26, a compressor 28, a condenser 30 and a thermostatic injection valve 32, which are connected by a tempering media line 34.

The evaporator 26 is designed, for example, as a temperature control media line section that extends around the centrifuge container 16.

A solenoid valve 38 is arranged in the temperature control media line 34 between the condenser 30 and the evaporator 26 in the flow direction 36 upstream of the injection valve 32.

Between the evaporator 26 and the compressor 28, a check valve 40 blocking against the flow direction 36 is arranged in the temperature control media line 34.

A pressure sensor 44 in the form of a pressure transmitter is arranged at the outlet 42 of the evaporator 26, the signal 46 of which feeds a monitoring and control device 48. The monitoring and control device 48 preferably has a processor (not shown) and controls the compressor 28 by means of a control line 50, a fan 54 associated with the condenser 30 by means of a control line 52, and the group 58 of the actual control system including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10 by means of a control line 56.

Group 60 of the components pressure sensor 44, monitoring and control device 48 and fan 54 is explosion-proof and/or designed to consume less than 20 W of electrical power, i.e. these components cannot under any circumstances ignite the temperature control medium in the temperature control medium 24. R290 propane is preferably used as the temperature control medium.

In Fig.3 It can be seen that the electrical power supply 62 of the centrifuge 10 has a conductive phase L and a neutral conductor N and is started by a main switch 64.

The main switch 64 connects the monitoring and control device 48 directly to the electrical power supply 62 via the line 66.

There is also a line 68 that can be disconnected via a switch 70, which connects the fan 54 to the electrical power supply 62. The switch 70 is switched by the monitoring and control device 48 via the connection 72, in such a way that after the centrifuge is started via the main switch 64, the fan 54 starts automatically at a low speed.

In addition, there is a line 74 which can be disconnected via a switch 76 and which connects the group 58 of the actual control, including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10, to the electrical power supply 62. This switch 76 can also be switched by the monitoring and control device 48 via the connection 78.

Following the line 74 there are lines 80, 82 which connect the compressor 28 and the solenoid valve 38 to the electrical power supply 62. These lines also have switches 84, 86 which can also be switched by the monitoring and control device 48 via the connections 88 and 90.

The switch 86 for the solenoid valve 38 is also supplied with electrical energy 92 by the controller 58 of the centrifuge 10, and is closed when such electrical energy 92 is applied to the controller 58.

It can be seen that group 60 of the components designed to be explosion-proof and/or consume less than 20 W of electrical power includes not only the pressure sensor 44, the monitoring and control device 48 and the fan 54, but also the main switch 64, the switch 70 in line 68 and the switch 76 in line 74.

The centrifuge 10 now functions as follows with regard to ignition protection:
As soon as the main switch 64 is actuated, the monitoring and control device 48 is activated, which in turn closes the switch 70 so that the fan 54 of the condenser 30 is supplied so that it operates at a low speed of preferably at least 200 rpm. Even if tempering medium has already escaped due to a leak, this disperses it so that the formation of an ignitable mixture is prevented.

If the monitoring and control device 48 determines via the pressure sensor 44 that the pressure in the evaporator 26 is above a minimum pressure of 1.3 bar, the switch 76 is closed so that the group 58 of the actual control, including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10, is supplied with electrical energy. Furthermore, the switches 84 and 86 are closed so that both the compressor 28 is operated and the solenoid valve 38 is closed. The compressor can now be operated by the control 58 as required.

If the pressure sensor 44 detects a pressure in the evaporator 26 that is greater than the specified maximum pressure of 2 bar, there is a risk that there will be too much flammable tempering medium in the event of a crash. The monitoring and control device 48 will then open the switch 86, causing the solenoid valve 38 to interrupt the supply of tempering medium to the evaporator 26. In addition, the monitoring and control device 48 will increase the output of the compressor 28 (the corresponding direct control of the compressor 28 by the monitoring and control device 48 is not shown). In addition, it can be provided that tempering medium is fed into a tempering medium reservoir (not shown). For this purpose, a valve (not shown) arranged between the reservoir and the tempering medium line 34 is opened. This reduces the amount of tempering medium in the evaporator 26 so that the pressure in the evaporator 26 is again between the minimum pressure and the maximum pressure. Subsequently, the switch 86 is closed again by the monitoring and control device 48 in order to reopen the solenoid valve 38, the compressor control is again taken over by the controller 58 and the temperature control medium is removed from the storage tank again if necessary.

If the pressure sensor 44 detects a pressure in the evaporator 26 that is less than the specified minimum pressure of 1.3 bar, there is a risk of a crash in which the tempering medium could be ignited. To prevent this, the monitoring and control device 48 opens the switch 86, whereby the solenoid valve 38 interrupts the supply of tempering medium to the evaporator 26. In addition, the monitoring and control device 48 will open the switch 76, whereby all non-Ex-protected components of the centrifuge 10, such as the compressor 28 and the controller 58, are switched off, making ignition impossible. The switch 70 is deliberately left open and residual electrical energy from capacitors in particular is delivered to the fan 54 in order to operate it to disperse the tempering medium. Such an electrical fallback level could be implemented, for example, by means of at least one relay (not shown) that is constantly energized during normal operation. This relay is switched in a targeted manner by the monitoring and control device 48 so that contact is made between the residual electrical energy (for example from capacitors and the like) and the fan 54.

The centrifuge 10 can only be put into operation again after the main switch 64 has been opened and the monitoring and control device 48 determines that the pressure in the evaporator 28 is at least as high as the minimum pressure of 1.3 bar.

In the event of a crash, the control unit 58 and the lines 74, 82 are destroyed, so that all non-explosion-proof components, in particular the compressor 28, the control unit 58 and the centrifuge motor 18, are no longer supplied with energy and at the same time the solenoid valve 38 is closed, which prevents ignition. The lines 74, 82 and in particular the switches 76, 86 and the control unit 58 are arranged in the crash zone for this purpose, i.e. preferably between the centrifuge container 16 and any crash protection in the form of one or more stiffening elements or crash energy absorber elements.

From the above description it has become clear that the present invention provides a centrifuge 10 with which even flammable tempering media can be used in the context of tempering without safety concerns, without these representing a safety risk in the event of a crash of the centrifuge rotor.

Unless otherwise stated, all features of the present invention can be freely combined with one another. The features described in the description of the figures can also be freely combined with the other features as features of the invention, unless otherwise stated. In this case, actual features of the centrifuge can also be used in the context of a process, reformulated as process features, and process features in the context of the centrifuge can be reformulated as features of the centrifuge.

List of reference symbols

10

centrifuge according to the invention, laboratory centrifuge

12

Housing

14

Lid

15

Control panel

16

Centrifuge container

17

Drive shaft

18

Centrifuge motor

20

Centrifuge rotor, swing-out rotor

22

Centrifuge cup

24

Tempering agents

26

Evaporator

28

compressor

30

Condenser

32

Thermostatic injection valve

34

Tempering media line

36

Flow direction

38

Solenoid valve

40

Check valve

42

Evaporator outlet 26

44

Pressure sensor, pressure transmitter

46

Signal of pressure sensor 44

48

Monitoring and control device

50

Control line of the monitoring and control device 48 to the compressor 28

52

Control line of the monitoring and control device 48 to the fan 54

54

fan

56

Control line of the monitoring and control device 48 to group 58

58

Group of the actual control system including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10

60

Group of explosion-proof components such as pressure sensor 44, monitoring and control device 48 and fan 54

62

electrical power supply of the centrifuge 10

64

Main switch of the electrical power supply 62

66

Line

68

Line

70

Switch in line 68

72

Connection, control of the switch 70 by the monitoring and control device 48

74

Cable, electrical supply line

76

Switch in line 74

78

Connection, control of the switch 76 by the monitoring and control device 48

80, 82

Cables, electrical supply lines

84, 86

Switches in lines 80, 82

88, 90

Connections, controls of the switches 84, 86 by the monitoring and control device 48

92

Supply of the switch 86 with electrical energy by the control 58

L

conductive phase of the electrical power supply 62

N

Neutral conductor N of the electrical power supply 62

Claims (12)

1. Method for preventing ignition of combustible temperature-control media in centrifuges (10), wherein the centrifuge (10), which is configured in particular as a laboratory centrifuge, comprises a centrifuge container (16) in which a centrifuge rotor (20) can be accommodated, a centrifuge motor (18) for driving the centrifuge rotor (20), a temperature-control means (24) with an evaporator (26) and a compressor (28) for controlling the temperature of the centrifuge rotor (20), and a housing (12), in which the centrifuge container (16), the centrifuge rotor (20), the temperature-control means (24) and the centrifuge motor (18) are accommodated, wherein the temperature-control means (24) comprise a combustible temperature-control medium which is guided in a temperature-control media line (34), wherein the pressure in the evaporator (26) is monitored in order to determine whether it lies below a specified minimum pressure and/or above a specified maximum pressure, characterised in that a fan (54) of the centrifuge (10) is started once an electrical power supply (62) of the centrifuge (10) has been switched on and the flow from the fan (54) passes over a temperature-control medium line (34) at least in some regions and/or through at least one cavity in the centrifuge (10) such that the resulting exhaust air is conveyed out of the housing (12) of the centrifuge (10).
2. Method according to claim 1, characterised in that the pressure at the outlet (42) of the evaporator (26) is determined, wherein preferably a pressure sensor, in particular in the form of a pressure transmitter (44), is used.
3. Method according to claim 1 or 2, characterised

   in that the specified minimum pressure is at least 0.7 bar, preferably at least 1 bar, and in particular at least 1.3 bar, and/or

   in that the specified maximum pressure is at most 5 bar, preferably at most 3 bar, in particular at most 2 bar.
4. Method according to any one of the preceding claims, characterised in that
   when the evaporator pressure lies below a specified minimum pressure

   a) the supply line of temperature-control medium to the evaporator (26) is interrupted and/or

   b) the compressor (28) is switched off and/or

   c) the electrical power supply (62) of electrical elements (58) of the centrifuge (10) which could cause an explosion and are not explosion-proof nor designed to absorb less than 20 W electrical power is stopped and/or

   d) the centrifuge motor (18) is switched off and/or

   e) residual electrical energy is conducted in a targeted manner to a fan (54) for its operation.
5. Method according to any one of the preceding claims, characterised in that when the evaporator pressure lies above the specified maximum pressure the amount of temperature-control medium in the evaporator (26) is reduced, wherein preferably

   f) the supply line of temperature-control medium to the evaporator (26) is interrupted and/or

   g) the capacity of the compressor (28) is increased and/or

   h) the temperature-control medium is conducted into a temperature-control medium store.
6. Method according to any one of the preceding claims, characterised in that a fan (54) of the centrifuge is started once an electrical power supply (62) of the centrifuge (10) has been switched on.
7. Centrifuge (10), in particular laboratory centrifuge, comprising a centrifuge container (16), in which a centrifuge rotor (20) can be accommodated, a centrifuge motor (18) for driving the centrifuge rotor (20), a temperature-control means (24) with an evaporator (26) and a compressor (28) for controlling the temperature of the centrifuge rotor (20), and a housing (12), in which the centrifuge container (16), the centrifuge rotor (20), the temperature-control means (24) and the centrifuge motor (18) are accommodated, wherein the temperature-control means (24) comprise a combustible temperature-control medium which is guided in a temperature-control media line (34), wherein the centrifuge (10) is adapted to determine whether the pressure in the evaporator (26) lies below a specified minimum pressure and/or above a specified maximum pressure, characterised in that the centrifuge (10) is configured to start a fan (54) of the centrifuge once an electrical power supply (62) of the centrifuge (10) has been switched on, wherein the fan (54) is set up such that its flow passes over a temperature-control medium line (34) at least in some regions and/or through at least one cavity, in particular a plurality of cavities, in the centrifuge (10) such that the resulting exhaust air is conveyed out of the housing (12) of the centrifuge (10).
8. Centrifuge (10) according to claim 7, characterised

   in that the centrifuge (10) is adapted to carry out the method according to any one of claims 1 to 6 and/or

   in that at least one of the elements constituted by the centrifuge motor (18), electrical supply line (74, 82) to a component that is not explosion-proof nor is designed to absorb less than 20 W electrical power, switches (76, 86) in the electrical supply line to a component that is not explosion-proof nor is designed to absorb less than 20 W electrical power, and control unit (62) of the centrifuge (10) is arranged in the crash region of the centrifuge (10).
9. Centrifuge (10) according to any one of claims 7 or 8, characterised in that

   i) a solenoid valve (38) is arranged in front of the inlet of the evaporator (26), wherein the solenoid valve (38) is preferably arranged in front of the pressure relief element (32), and/or in that

   k) a non-return valve (40) is arranged after the outlet (42) of the evaporator (26), and/or in that

   l) at least one of the elements constituted by a main electrical switch (64), fan (54), pressure-monitoring control unit (48) and a pressure-monitoring sensor (44) is designed to be explosion-proof and/or to absorb less than 20 W electrical power.
10. Centrifuge (10) according to any one of claims 7 to 9, characterised in that the centrifuge (10) is configured to supply a fan (54) with residual electrical energy present in the centrifuge (10) after a failure of the electrical power supply (62), wherein there is preferably a relay which is fed by the electrical power supply (62) and, in the event of the failure of the electrical power supply (62), connects at least one element having electrical residual energy to the fan (54), wherein the at least one element in particular is a capacitor or accumulator.
11. Centrifuge (10) according to any one of claims 7 to 10, characterised in that the fan (54) is set up such that its flow passes through a plurality of cavities in the centrifuge (10) such that the resulting exhaust air is conveyed out of the housing (12) of the centrifuge (10).
12. Centrifuge according to any one of claims 7 to 11, characterised in that the centrifuge comprises a gas sensor arranged outside the temperature-control means and is preferably set up to prevent the centrifuge from starting when temperature-control medium is detected by the gas sensor.

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