TEMPERATURE-CONTROLLED CENTRIFUGE WITH CRASH PROTECTION

Abstract

A centrifuge and a method for preventing ignition of combustible temperature-control media in centrifuges after a crash of the centrifuge rotor are presented. It is monitored whether the pressure in the evaporator lies below a specified minimum pressure and/or above a specified maximum pressure. Measures to prevent ignition of the temperature-control medium can be taken in a targeted manner. In the event that the pressure lies below a minimum pressure, it must be assumed that either a leak or a crash is present, wherein a leak leads to a slow release of combustible temperature-control medium and a crash leads to an sudden release of combustible temperature-control medium. If the pressure lies above a maximum pressure, there is a risk that there is a large amount of combustible temperature-control medium in the evaporator which could be ignited in the event of a crash.

Claims

1.-13. (canceled)

14. A method for preventing ignition of combustible temperature-control media in centrifuges, comprising: providing a centrifuge (10) which 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 (24) with an evaporator (26), a compressor (28), and a combustible temperature-control medium which is guided in a temperature-control medium line (34) for the temperature control of the centrifuge rotor (20), and a housing (12), in which the centrifuge container (16), the centrifuge rotor (20), the temperature control (24) and the centrifuge motor (18) are accommodated; monitoring a pressure in the evaporator (26); and determining whether the pressure in the evaporator (26) lies below a specified minimum pressure or above a specified maximum pressure.

15. The method according to claim 14, wherein monitoring the pressure in the evaporator (26) is performed by a pressure sensor arranged at an outlet (42) of the evaporator (26).

16. The method according to claim 14, wherein the specified minimum pressure is at least 0.7 bar and/or wherein the specified maximum pressure is at most 5 bar.

17. The method according to claim 14, further comprising performing one or more of the following actions upon determining that the pressure in the evaporator (26) lies below a specified minimum pressure: a) interrupting a supply of temperature-control medium to the evaporator (26); b) switching off the compressor (28); c) stopping an 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; d) switching off the centrifuge motor (18); and e) directing residual electrical energy in a targeted manner to a fan (54) for its operation.

18. The method according to claim 14, further comprising reducing an amount of temperature-control medium in the evaporator (26) upon determining that the pressure in the evaporator (26) lies above the specified maximum pressure.

19. The method as in claim 18, further comprising one or more of the following steps: f) interrupting a supply of temperature-control medium to the evaporator (26); g) increasing a capacity of the compressor (28); and h) feeding the temperature-control medium into a temperature-control medium storage tank.

20. The method according to claim 14, further comprising starting a fan (54) of the centrifuge after switching on an electrical power supply (62) of the centrifuge (10).

21. A centrifuge (10), comprising: a centrifuge container (16) in which a centrifuge rotor (20) can be accommodated; a centrifuge motor (18) for driving the centrifuge rotor (20); temperature control (24) with an evaporator (26), a compressor (28), and a combustible temperature-control medium which is guided in a temperature-control medium line (34) for the temperature control of the centrifuge rotor (20); and a housing (12) in which the centrifuge container (16), the centrifuge rotor (20), the temperature control (24) and the centrifuge motor (18) are accommodated, wherein the centrifuge (10) is adapted to determine whether a pressure in the evaporator (26) lies below a specified minimum pressure and/or above a specified maximum pressure.

22. The centrifuge (10) according to claim 21, wherein at least one of the centrifuge motor (18), an electrical supply line (74, 82) to a component which is not explosion-proof nor designed to absorb less than 20 W of electrical power, a switch (76, 86) in an electrical supply line to a component which is not explosion-proof nor designed to absorb less than 20 W of electrical power, and a control unit (58) of the centrifuge (10) is arranged in a crash area of the centrifuge (10).

23. The centrifuge (10) according to claim 21, wherein i) a solenoid valve (38) is arranged in front of an inlet of the evaporator (26), wherein the solenoid valve (38) is preferentially arranged in front of a pressure relief element (32) and/or k) a non-return valve (40) is arranged after an outlet (42) of the evaporator (26) and/or l) at least one of a main electrical switch (64), a fan (54), a pressure monitoring control (48) and a pressure monitoring sensor (44) is designed to be explosion-proof and/or to absorb less than 20 W electrical power.

24. The centrifuge (10) according to claim 21, wherein the centrifuge (10) supplies a fan (54) with residual electrical energy present in the centrifuge (10) after a failure of an electrical power supply (62).

25. The centrifuge (10) according to claim 24, further comprising a relay which is fed by an electrical power supply (62) and, in the event of the failure of the electrical power supply (62), connects at least one capacitor or accumulator to the fan (54).

26. The centrifuge (10) according to claim 25, wherein the centrifuge (10) is configured to start a fan (54) of the centrifuge after switching on an electrical power supply (62) of the centrifuge (10).

27. The centrifuge (10) according to claim 25, wherein the fan (54) is configured such that its flow passed over a temperature-control medium line (34) at least in some areas and/or through at least one cavity in the centrifuge (10) in such a manner that a resulting exhaust air is conveyed out of the housing (12) of the centrifuge (10).

28. The centrifuge according to claim 21, further comprising a gas sensor arranged outside the temperature control, wherein the centrifuge is prevented from starting when temperature-control medium is detected by the gas sensor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0055] FIG. 1a shows a centrifuge in a perspective view.

[0056] FIG. 1b shows the centrifuge according to FIG. 1a in a sectional view.

[0057] FIG. 2 shows the centrifuge according to FIG. 1a in a simplified block diagram with regard to the temperature control means.

[0058] FIG. 3 shows the centrifuge according to FIG. 1a in a block diagram with regard to a highly simplified circuit diagram.

DETAILED DESCRIPTION

[0059] In FIGS. 1a to 3, the centrifuge 10 is shown purely schematically in various views.

[0060] The centrifuge 10 is designed as a laboratory centrifuge with 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 beakers 22.

[0061] FIG. 2 shows that the centrifuge has temperature-control means 24, comprising an evaporator 26, a compressor 28, a condenser 30 and a thermostatic injection valve 32, which are connected by a temperature-control media line 34.

[0062] The evaporator 26, for example, is designed as a temperature-control media line section that extends around the centrifuge vessel 16.

[0063] A solenoid valve 38 is arranged between the condenser 30 and the evaporator 26 in the temperature-control medium line 34 in the direction of flow 36 in front of the injection valve 32.

[0064] Between the evaporator 26 and the compressor 28, a non-return valve 40 blocking against the direction of flow 36 is arranged in the temperature-control medium line 34.

[0065] 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 preferentially has a processor (not shown) and controls by means of a control line 50 the compressor 28, by means of a control line 52 a fan 54, which is assigned to the condenser 30, and by means of a control line 56 the group 58 of the actual control unit including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10.

[0066] The group 60 of the components of pressure sensor 44, monitoring and control device 48 and fan 54 is designed to be explosion-proof and/or to consume less than 20 W electrical power, that is, such components cannot under any circumstances ignite the temperature-control medium in the temperature control means 24. R290 propane is preferentially used as the temperature-control medium.

[0067] FIG. 3 shows that the electrical power supply 62 of the centrifuge 10 has a conducting phase L and a neutral conductor N and is started by a main switch 64.

[0068] The main switch 64 connects the monitoring and control device 48 directly via line 66 to the electrical power supply 62.

[0069] There is also a line 68, which can be disconnected by a switch 70, which connects the fan 54 with the electrical power supply 62. The switch 70 is switched by the monitoring and control device 48 via the connection 72, in such a manner that, after the centrifuge has been started via the main switch 64, the fan 54 starts automatically at a low speed.

[0070] There is also a line 74, which can be disconnected via a switch 76, which connects the group 58 of the actual control unit including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10 with the electrical power supply 62. Such switch 76 can likewise be switched by the monitoring and control device 48 via the connection 78.

[0071] Following the line 74, there are lines 80, 82, which connect the compressor 28 and the solenoid valve 38 with the electrical power supply 62. Such lines also have switches 84, 86, which can also be switched by the monitoring and control device 48 via the connections 88 and 90.

[0072] The switch 86 for the solenoid valve 38 is also supplied with electrical energy 92 by the control unit 58 of the centrifuge 10, wherein it is closed if such electrical energy 92 is applied to the control unit 58.

[0073] It can be seen that the group 60 of the components designed to be explosion-proof and/or to consume less than 20 W electrical power not only includes pressure sensor 44, monitoring and control device 48 and fan 54, but also the main switch 64, switch 70 in line 68 and switch 76 in line 74.

[0074] The centrifuge 10 now functions as follows with regard to ignition protection:

[0075] As soon as the main switch 64 is actuated, the monitoring and control device 48 is activated, which on its part closes the switch 70, such that the fan 54 of the condenser 30 is supplied in such a manner that it operates at a low speed, preferentially at least 200 rpm. Even if temperature-control medium has already leaked out due to a leak, it will be dispersed such that the formation of an ignitable mixture is prevented.

[0076] If the monitoring and control device 48 detects 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, such that the group 58 of the actual control unit 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, such that both the compressor 28 is operated and the solenoid valve 38 is closed. The compressor can now be operated by the control unit 58 according to requirements.

[0077] 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 is too much combustible temperature-control medium in the event of a crash. The monitoring and control device 48 will then open the switch 86, by which the solenoid valve 38 interrupts the supply of temperature-control medium to the evaporator 26. Furthermore, the monitoring and control device 48 will increase the capacity of compressor 28 (the corresponding direct control of compressor 28 by the monitoring and control device 48 is not shown). In addition, it may be provided that temperature-control medium is routed into a temperature-control medium storage tank (not shown). For this purpose, a valve (not shown) arranged between the storage tank and the temperature-control medium line 34 is opened. This reduces the amount of temperature-control medium in the evaporator 26 such that the pressure in the evaporator 26 returns to between minimum pressure and maximum pressure. Subsequently, the switch 86 is closed again by the monitoring and control device 48 in order to open solenoid valve 38 again, the compressor control unit is taken over again by the control unit 58 and the temperature-control medium is removed from the storage tank again if necessary.

[0078] If the pressure sensor 44 detects a pressure in the evaporator 26 that is lower than the specified minimum pressure of 1.3 bar, there is a risk of a crash in which temperature-control medium could be ignited. In order to prevent this, the monitoring and control device 48 opens the switch 86, which causes the solenoid valve 38 to interrupt the supply of the temperature-control medium to the evaporator 26. In addition, the monitoring and control device 48 will open the switch 76, which will shut down all non-explosion-proof components of the centrifuge 10, such as the compressor 28 and the control unit 58, making ignition impossible. The switch 70 is left open in a targeted manner and residual electrical energy from capacitors in particular is transferred to the fan 54 in order to operate it to disperse the temperature-control medium. Such an electrical fall-back level could be realized, for example, by means of at least one relay (not shown), which is constantly energized during normal operation. Such relay is switched over in a targeted manner by the monitoring and control device 48, such that contact is established between the residual electrical energy (for example, from capacitors and the like) and the fan 54.

[0079] Only after opening the main switch 64 can the centrifuge 10 be restarted if 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.

[0080] In the event of a crash itself, the control unit 58 and the lines 74, 82 are destroyed, such 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, by which ignition is prevented. The lines 74, 82 and in particular also the switches 76, 86 and the control unit 58 are arranged for this purpose in the crash zone, that is, preferentially between the centrifuge container 16 and a crash protection device, if present, in the form of one or more stiffening elements or crash energy absorber elements.

[0081] It is clear from the preceding description that the present invention provides a centrifuge 10 with which combustible temperature-control media can also be used without safety concerns within the framework of a temperature control without posing a safety risk in the event of a crash of the centrifuge rotor.

[0082] Unless otherwise indicated, all features of the present disclosure may be freely combined. Moreover, the features described in the description of figures may, unless otherwise indicated, be freely combined with the other features. Thereby, substantive features of the centrifuge can also be used within the framework of a method reformulated as method features and method features within the framework of the centrifuge reformulated as features of the centrifuge.

LIST OF REFERENCE SIGNS

[0083] 10 Centrifuge, laboratory centrifuge [0084] 12 Housing [0085] 14 Lid [0086] 15 Operating front [0087] 16 Centrifuge container [0088] 17 Drive shaft [0089] 18 Centrifuge motor [0090] 20 Centrifuge rotor, swing-out rotor [0091] 22 Centrifuge beaker [0092] 24 Temperature control means [0093] 26 Evaporator [0094] 28 Compressor [0095] 30 Condenser [0096] 32 Thermostatic injection valve [0097] 34 Temperature-control medium line [0098] 36 Direction of flow [0099] 38 Solenoid valve [0100] 40 Non-return valve [0101] 42 Outlet of evaporator 26 [0102] 44 Pressure sensor, pressure transmitter [0103] 46 Signal of the pressure sensor 44 [0104] 48 Monitoring and control device [0105] 50 Control line of monitoring and control device 48 to compressor 28 [0106] 52 Control line of monitoring and control device 48 to fan 54 [0107] 54 Fan [0108] 56 Control line of monitoring and control device 48 to group 58 [0109] 58 Group of the actual control unit including the electrical and electronic components and the centrifuge motor 18 of the centrifuge 10 [0110] 60 Group of explosion-proof components, such as pressure sensor 44, monitoring and control device 48 and fan 54 [0111] 62 Electrical power supply of the centrifuge 10 [0112] 64 Main switch of electrical power supply 62 [0113] 66 Line [0114] 68 Line [0115] 70 Switch in line 68 [0116] 72 Connection, control unit of switch 70 by the monitoring and control device 48 [0117] 74 Line, electrical supply line [0118] 76 Switch in line 74 [0119] 78 Connection, control unit of switch 76 by the monitoring and control device 48 [0120] 80, 82 Lines, electrical supply lines [0121] 84, 86 Switches in the lines 80, 82 [0122] 88, 90 Connections, control units of switches 84, 86 by the monitoring and control device 48 [0123] 92 Supply of the switch 86 with electrical energy through the control unit 58 [0124] L Conducting phase of the electrical power supply 62 [0125] N Neutral conductor N of the electrical power supply 62