EP3171982B2 - Centrifuge - Google Patents

Description

The invention relates to a centrifuge according to the type specified in the preamble of patent claim 1.

During the operation of a centrifuge, undesirable heat is generated which is harmful to the material to be centrifuged. A particular problem here is that the centrifuge rotor, the rotation of which and the resulting air friction causes a large part of the heat, is usually arranged for safety reasons in a safety chamber that is tightly closed by a lid. This makes it difficult for the heat to escape from it. Biological samples often require a temperature of 4°C to be maintained during centrifugation. Active cooling is therefore indispensable, especially with longer operating times, high speeds and sample temperatures below ambient temperature.

A large number of generic centrifuges in which a compression refrigeration unit is provided is known from the prior art. A refrigerant flows in a refrigeration circuit, which is separated into a high-pressure and a low-pressure area by a throttle and a compressor. After heat has been removed from the refrigerant in the high-pressure area in a condenser, it flows in the low-pressure area in, for example, spirally arranged lines around a safety tank in which the rotor of the centrifuge is arranged, and in the process extracts heat from the safety tank.

While this type of cooling is proven and reliable, it also has disadvantages. In the case of centrifuges in particular, high safety standards must be observed because of the high kinetic energy that occurs during operation. Although flammable refrigerants ensure a high efficiency of the cooling system. Due to the risk of a rotor crash and the wall of the safety chamber penetrating, which can also lead to sparks, their use is fundamentally not possible from a safety point of view in centrifuges. As a rule, refrigerants containing fluorine, so-called F-gases, are used instead. used because they are non-flammable. However, these F-gases have a high global warming potential, and for this reason their use is gradually being restricted or prohibited by the legislature.

the JP H07 144 155 A aims to provide a centrifugal separator equipped with a water cooler capable of precisely controlling the temperature by controlling the air temperature in the bowl of the centrifuge by controlling the operation of a pump. A water cooler 20 is connected to a connecting pipe. A chilled cooling liquid is sent to the centrifugal separator to cool the air in the bowl. When the air in the bowl is regulated to a set temperature, a bowl air temperature regulator opens the contact of a relay and the supply of cooling liquid is stopped. When the temperature of the air in the bowl is raised again by the frictional heat due to the rotation of a rotor 1, the contact of the relay is closed, when the air temperature in the bowl is raised to the temperature set by the controller, the pump motor becomes operated and coolant is supplied to cool the air in the bowl. This keeps the rotor at a suitable temperature.

the DE 10 2012 002 593 A1 relates to a centrifuge with a compressor cooling device and a method for controlling a compressor cooling device of the centrifuge. The centrifuge includes a centrifuge bowl and a compressor cooling device, which has a refrigeration circuit, an evaporator, a condenser and a compressor. A controllable throttle device for regulating the refrigerant flow is provided in the refrigeration circuit of the compressor cooling device.
It is the object of the invention, while avoiding the disadvantages mentioned, to create a centrifuge whose cooling is efficient and, at the same time, harmless both from the point of view of safety and from the point of view of environmental protection.

This object is achieved by the characterizing features of patent claim 1 in conjunction with its preamble features.

The invention is based on the finding that by dividing the cooling circuit into a safety-critical area and a separate safety-related non-critical area, this task can be solved in a simple manner, particularly if different heat transfer mediums—refrigerants—are used in the two areas.

According to the invention, the centrifuge has a centrifuge housing, a safety tank arranged in the centrifuge housing, an inner space delimited by the safety tank, a rotor arranged in the inner space, and a cooling system arranged in the centrifuge housing for cooling the inner space. The refrigeration system comprises a compressor, a condenser and an evaporator, which are connected to one another via duct means. The cooling system has a primary circuit with primary line means and a secondary circuit with secondary line means, the primary circuit comprising the compressor, the condenser and the evaporator, which is part of a heat exchanger, and the secondary circuit flowing through the heat exchanger and cooling the safety boiler. A pump is provided in the secondary circuit to ensure a constant flow of the heat transfer medium and thus efficient cooling of the safety boiler. It is therefore possible to use different heat transfer media in the two circuits, depending on the safety requirements, which result in further design options and targeted safety measures to take for the corresponding circuit.

A conventional combustible refrigerant flows in the primary circuit, which has a large specific enthalpy of vaporization at comparatively low procurement costs.

With regard to the risk of a rotor crash and a breakdown of the safety boiler, however, it is advantageous in the secondary circuit that a non-flammable heat transfer medium is used. The use of cooling water with additives that lower the freezing point, such as salt or alcohol, is cost-effective and environmentally friendly.

According to one aspect of the invention, the primary circuit is located below the secondary circuit and the safety tank. This significantly reduces the risk of the primary circuit being damaged in the event of a rotor crash and a blowout of the safety tank.

If, on the other hand, the primary circuit is offset laterally to the secondary circuit in the centrifuge housing, a significantly more compact design of the centrifuge can be realized, especially with regard to the vertical expansion.

In an advantageous development of the invention, a safety wall spatially separating the two circuits is provided between the primary circuit and the secondary circuit. The risk of damage to the primary circuit in the event of a rotor crash and a breakdown of the safety boiler is further reduced if the primary circuit is offset to the side of the secondary circuit.

It is favorable if the safety tank is fixed in the centrifuge housing via a clamp connection, which allows the safety tank to move relative to the centrifuge housing in the event of a rotor crash. In the event of a crash, a movement, in particular a rotary movement, of the safety boiler is initiated by the rotor impacting the safety boiler or by the rotor parts impacting the safety boiler and the resulting angular momentum, which is braked by the clamp connection. The energy of the crash acting on the centrifuge housing is significantly weakened or completely eliminated, which improves the protection of the primary circuit from damage.

According to a further aspect of the invention, at least one additional mass element is arranged in the centrifuge housing in order to stabilize the centrifuge housing. This stabilization also serves to protect the primary circuit from the effects of the angular momentum that occurs in the event of a rotor crash.

The protection of the primary circuit can also be improved in that the primary line means are made of a mechanically stronger material than the secondary line means.

In an alternative embodiment, predetermined breaking points are provided on the secondary line means. In the event of a particularly large impulse, which was caused by a rotor crash and cannot be sufficiently compensated for by a relative movement of the safety chamber in relation to the centrifuge housing, the mechanical connection between the secondary circuit and the primary circuit is separated and this prevents the impulse from being transmitted via the secondary Line means is directed into the area of the primary circuit and causes damage there.

The safety tank is preferably surrounded by a separate, in particular cylindrical, protective wall that is concentric with the safety tank. This further reduces the risk of damage to the primary circuit or the centrifuge housing in the event of a rotor crash.

It is also advantageous if the predetermined breaking points mentioned above are provided at the points at which the secondary line means reach through the cylindrical protective wall. With this arrangement, the secondary line means are easily sheared off by the protective wall during a relative movement, in particular a rotary movement, of the safety chamber with respect to the centrifuge housing.

As stated, a predetermined breaking point can be formed in the secondary line means, for example by weakening an area of the line means. As an alternative to forming a predetermined breaking point in the conduit, the predetermined breaking point can also be formed solely by assigning a shearing device to an area of the conduit. The shearing device is activated during a relative movement, in particular a rotary movement, of the safety tank by the line means being moved towards the shearing device and/or the shearing device towards the line means. The shearing device cuts through the conduit in the area assigned to it. This solution is associated with little effort and has the advantage, among other things, that less expensive line means can be used in the secondary circuit, since there is no need to incorporate weakened areas into the power means. The installation of the conduit is also easier, since the position of the predetermined breaking point is determined by the arrangement of the shearing device and not by a specific area of the conduit.

In a further preferred embodiment, insulating and/or insulating materials are provided in the primary circuit, in particular between the compressor, the condenser and the evaporator. Insulation materials ensure greater stability, especially when the primary circuit is subjected to a large external impulse. In particular, it is prevented that the compressor, which is mounted on elastic damping elements, can be torn from its anchorage and the pipelines rupture. Another positive property of insulating materials is that they increase the efficiency of the refrigeration components. For example, rigid foam moldings are well suited to fulfill these two tasks and as insulation and to serve as an insulator. It is particularly advantageous if the molded parts have integrated channels that are used on the one hand for laying cables and on the other hand for a defined air flow.

A positive secondary aspect of this invention is that the demands on the line means that are provided in the secondary circuit are significantly lower than the demands on the line means that are provided in the low-pressure area of a conventional cooling device with a cooling circuit. On the one hand, the operating pressure in the secondary circuit of a cooling device according to the invention is still significantly lower than in the low-pressure area of a conventional cooling device. On the other hand, due to the separation of the two circuits, damage to the line means in the secondary circuit does not pose any safety risks. Consequently, instead of rigid, massive and expensive line means such as copper pipes, flexible hoses can be used here, for example. This reduces the construction effort and lowers the cost of the centrifuge.

Further advantages, features and application possibilities of the present invention result from the following description in connection with the exemplary embodiments illustrated in the drawings.

Fig. 1

eine schematische Perspektivansicht einer erfindungsgemäßen Zentrifuge;

Fig. 2

eine schematische graphische Darstellung der beiden Kühlkreisläufe;

Fig. 3

eine seitliche Schnittansicht des Primärkreislaufs einer erfindungsgemäßen Zentrifuge mit Dämm- und Isolationselementen, und

Fig. 4

eine schematische Perspektivansicht einer erfindungsgemäßen Zentrifuge mit einem unterhalb des Sekundärkreislaufs angeordneten Primärkreislauf.

In the description, in the claims and in the drawing, the terms used in the list of reference numbers given below and associated reference numbers are used. In the drawing means:

1

a schematic perspective view of a centrifuge according to the invention;

2

a schematic graphic representation of the two cooling circuits;

3

a side sectional view of the primary circuit of a centrifuge according to the invention with damping and insulating elements, and

4

a schematic perspective view of a centrifuge according to the invention with a primary circuit arranged below the secondary circuit.

In 1 a schematic perspective view of a centrifuge 10 according to the invention is shown. For the sake of clarity, the housing is not shown; the arrangement of the housing cover 13a and the side walls 13b can of 3 be removed. A safety tank 14 of the centrifuge 10 is arranged on a base plate 12 together with a compression refrigeration unit 20 . The compression refrigeration unit 20 essentially comprises a compressor 22, a condenser 24, a fan 25, a filter drier 28 and an evaporator 26, which is part of a heat exchanger 30, which are connected to one another via primary pipes 29 and a primary circuit 52 (see Fig 2 ) form. A combustible refrigerant 54 flows in the primary pipelines 29.

The safety boiler 14 is surrounded by secondary pipelines 34, which can only be partially seen in this figure, which essentially form a secondary circuit 62 (see 2 ) form. A non-combustible heat transfer medium 64 flows in the secondary pipelines 34.

The structure of the primary circuit 52 and the secondary circuit 62 is shown in 2 again illustrated by a schematic representation.

A protective cylinder 18 is arranged concentrically around the safety tank 14 and is fixed, in particular horizontally, by four clamping elements 38 which are fixed at equal distances from one another on the outer circumference of the protective cylinder 18 on the base plate 12 . From this perspective, however, only one clamping element 38 can be seen. In the event of a rotor crash, the protective cylinder 18 prevents rotor parts flying around from spreading over a wide area, which could penetrate the centrifuge wall and cause major damage. For additional protection of the primary circuit 52 from penetrating rotor parts in the event of a crash, which could possibly even penetrate the protective cylinder 18 , a safety wall 36 is arranged on the base plate 12 between the safety tank 14 and the compression refrigeration unit 20 .

The secondary circuit 62 flows through the heat exchanger 30. For this purpose, two recesses 34a and 34b are provided in the safety wall 36, through which the pipelines 34 of the secondary circuit 62 each pass. The pipe 34 runs from the safety tank 14 through the recess 34b to the heat exchanger 30 by the secondary circuit 62 heat is extracted. A pump 32 for conveying the non-combustible heat transfer medium 64 is arranged between the heat exchanger 30 and the recess 34a, through which the pipeline 34 runs back to the safety boiler 14.

In 2 the principle of the two-circuit cooling of a centrifuge 10 according to the invention is shown schematically. On the cold side 60 is the secondary circuit 62, in which a non-combustible heat transfer medium 64 circulates. The heat transfer medium 64 is guided in secondary pipelines 34 around a safety tank 14, as a result of which the safety tank 14 heat is withdrawn. Furthermore, the pump 32 is provided, which conveys the heat transfer medium 64 .

On the hot side 50 is the primary circuit 52, in which a flammable refrigerant 54 flows, with the compression refrigeration unit 20, which comprises the compressor 22, the condenser 24, the fan 25, the throttle 28 and the evaporator 26, which are connected via primary pipes 29 are connected to each other.

The evaporator 26 is part of a heat exchanger 30, through which the pipes 34 of the secondary circuit 62 also flow. The primary circuit 52 and the secondary circuit 62 are thus thermally coupled via the heat exchanger 30 . The heat extracted from the safety boiler 14 is transferred from the non-flammable heat transfer medium 64 from the secondary circuit 62 in the heat exchanger 30 to the flammable refrigerant 54 in the primary circuit 52 . The transferred heat is released from the combustible refrigerant 54 to the ambient air 56 via the condenser 24 . The use of the fan 25 improves the heat dissipation. Compression refrigeration units are known in principle, so that further explanations are unnecessary.

In 3 is a side view, partially in section, of the 1 illustrated primary circuit 52 of the centrifuge 10 from the perspective of the secondary circuit 62 is shown. As already in 1 described, the compressor 22, the condenser 24 with the associated fan 25, the filter dryer 28 and the evaporator 26, not shown here, are connected to one another via primary pipelines 29. The primary circuit 52, like the one in 3 secondary circuit 62, not shown, surrounded by a cuboid housing 13, which has a base plate 12 on the underside, a housing cover 13a on the upper side and side walls 13b, 13c between the base plate 12 and the housing cover 13a. Ventilation slots 24a are provided in the area of the side wall 13c adjacent to the condenser 24 .

In the space between the housing 13 and the elements of the primary circuit 52 with the greatest spatial extent, i.e. in particular the compressor 22, condenser 24, fan 25 and - the evaporator 26 - not shown here - there is a rigid foam molded part for the purpose of insulation and damping of vibrations 40 arranged. The shape of the rigid foam molded part 40 is adapted to the housing 13 and in some areas to the profile of the elements of the primary circuit 52 mentioned. The rigid foam molded part 40 extends horizontally between the side walls 13b and 13c along the housing cover 13a and vertically in some areas along the side walls 13b and 13c and in some areas along the profile of the aforementioned elements of the primary circuit 52. The vertical extent of the rigid foam molded part 40 is adapted to the structural conditions of the Adjusted primary circuit and chosen so that it is easy to introduce and surrounds about the upper third of the compressor 22 and at the same time at least on the top of said elements of the primary circuit 52 is present. For example, the rigid foam molding 40 surrounds the compressor 22 approximately in the upper third of its vertical extent. Furthermore, 40 channels 42 are provided in the rigid foam molded part, in which primary pipes 29 run.

The centrifuge 10 stands on four feet 46 attached to the underside of the base plate 12 on a base, two of which feet 46 are located below the primary circuit. To increase stability, a rectangular mass element 44 is also attached approximately centrally to the underside of the base plate 12 .

In 4 An alternative embodiment of a centrifuge 10 according to the invention is shown in which a secondary circuit 62 is arranged above a primary circuit 52 . For the sake of clarity, no housing is shown here.

The primary circuit 52 is arranged on a rectangular base plate 70 with two end faces 72 and two longitudinal sides 74 . Structure and function are identical to those in Figures 1 to 3 described primary circuit 52 and therefore require no further explanation. A frame 76 is fastened to the edges of the base plate 70 by means of screws 88, which is used on the one hand to attach side walls of the housing (not shown here) and on the other hand to stably fasten an intermediate base 90 with two end faces 92 and two long sides 94, on which the secondary circuit 62 is arranged. The framework 76 comprises two rectangular frame parts 78 each with two end faces 80 and two longitudinal sides 82a and 82b, which are arranged between the two end faces 72 of the base plate 70 and the two end faces 92 of the intermediate floor 90 . The longitudinal sides 82a are firmly connected to the base plate 70 by screws 88 and the longitudinal sides 82b are firmly connected to the intermediate base 90 by means of screws 88 . The frame structure 76 also includes two horizontally extending frame elements 84, which are firmly connected to the base plate 70 on both of its longitudinal sides 74 by means of screws 88, and four vertical frame elements 86. The vertically extending frame elements 86 extend from the four corners of the base plate 70 to the four corners of the intermediate floor 90. To improve the stability, the frame elements 86 have two legs 87a and 87b which are perpendicular to one another and are designed in one piece and of the same material. The legs 87a are each arranged between the end face 72 of the base plate 70 and the end face 92 of the intermediate floor 90 , and the legs 87b are each arranged between the longitudinal side 74 of the base plate 70 and the longitudinal side 94 of the intermediate floor 90 . Horizontal frame elements 96 are fastened to both end faces 92 and horizontal frame elements 98 to both long sides 94 by means of screws 88--among other things for fastening side walls of the housing not shown here.

The secondary circuit 62 arranged on the intermediate floor 90 essentially corresponds to that in FIGS Figures 1 to 3 described, therefore further explanations are superfluous. Only the routing of the secondary pipelines 34 is changed accordingly due to the arrangement of the primary circuit 52 and the secondary circuit 62 lying vertically one above the other. The safety tank 14 and the protective cylinder 18 surrounding it are mounted on a holding device 100 which is firmly connected to the intermediate floor 90 and to the horizontal frame elements 98 and the horizontal frame elements 96 . For additional stabilization, support struts 102 are provided below the intermediate floor 90, which run parallel to the end faces 92 and are firmly connected to the intermediate floor 90 and to the horizontal frame elements 98 by means of screws 88.

Reference List

10

centrifuge

12

bottom plate

13

casing

13a

housing cover

13b, 13c

side walls

14

safety boiler

16

inner space

18

protective cylinder

20

compression refrigeration unit

22

compressor

24

capacitor

25

fan

26

Evaporator

28

filter dryer

29

primary plumbing

30

heat exchanger

32

pump

34

secondary piping

34a

recess

34b

recess

36

safety wall

38

clamping elements

40

rigid foam molding

42

channels

44

mass element

50

warm side

52

primary circuit

54

flammable refrigerant

56

ambient air (UL)

60

cold side

62

secondary circuit

64

non-flammable heat transfer medium

70

bottom plate

72

end faces

74

long sides

76

frame

78

frame parts

80

end faces

82a, 82b

long sides

84

horizontally extending frame member

86

vertically extending frame member

88

screws

90

intermediate floor

92

end faces

94

long sides

96

horizontal frame elements

98

horizontal frame elements

100

holding device

102

carrier struts

Q1

heat flow on the cold side

Q2

heat flow warm side

Claims (10)

1. Centrifuge (10) having a centrifuge housing (13), a safety vessel (14) arranged in the centrifuge housing (13), an interior space (16) at least partially delimited by said safety vessel (14), a rotor arranged in the interior space (16), and a cooling system arranged in the centrifuge housing (13) for cooling the interior space (16), having a compressor (22), a condenser (24) and an evaporator (26), which are connected to one another via conduit means, characterized in that the cooling system has a primary circuit (52) with primary conduit means (29) and a secondary circuit (62) with secondary conduit means (34), wherein said primary circuit (52) comprises the compressor (22), the condenser (24) and the evaporator (26), which is part of a heat exchanger (30), wherein said secondary circuit (62) flows through the heat exchanger (30), cools the safety boiler (14) and includes a pump (32), and wherein a combustible refrigerant (54) flows in the primary circuit (52) and a noncombustible heat transfer medium (64) flows in the secondary circuit (62).
2. Centrifuge according to claim 1, characterized in that the primary circuit (52) is arranged below the secondary circuit (62) and the safety vessel (14).
3. Centrifuge according to claim 1 or claim 2, characterized in that within the centrifuge housing (13), the primary circuit (52) is arranged laterally offset with respect to the secondary circuit (62).
4. Centrifuge according to claim 3, characterized in that a safety wall (36) is provided between the primary circuit (52) and the safety vessel (14) for spatially separating them from one another.
5. Centrifuge according to any one of the preceding claims, characterized in that the safety vessel (14) is fixed in the centrifuge housing (13) via a clamping connection which, in the event of a crash, permits relative movement of the safety vessel (14) with respect to the centrifuge housing (13).
6. Centrifuge according to any one of the preceding claims, characterized in that at least one additional mass element (44) is arranged in the centrifuge housing (13) in order to stabilize the centrifuge housing (13).
7. Centrifuge according to any one of the preceding claims, characterized in that the primary conduit means (29) are made of a material that is mechanically stronger than the material of the secondary conduit means (34).
8. Centrifuge according to claim 7, characterized in that predetermined breaking points are provided on the secondary conduit means (34).
9. Centrifuge according to any one of the preceding claims, characterized in that the safety vessel (14) is surrounded by a protective wall (18) that is separate from the safety vessel (14).
10. Centrifuge according to any one of the preceding claims, characterized in that damping and/or insulating materials (40) are provided in the primary circuit (52), in particular between the compressor (22), the condenser (24) and the evaporator (26).

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