EP2335830B1 - Laboratory centrifuge with compressor cooler - Google Patents

Description

The present invention relates to a laboratory centrifuge according to the preamble of claim 1.

Such laboratory centrifuges are used in biological, chemical and medical laboratories for the separation of various constituents in a liquid or for the separation of solids from a liquid. For this purpose, the centrifugal force acting differently on different masses is used.

In currently used laboratory centrifuges, rotational speeds of up to 16,000 revolutions per minute are usually generated, whereby forces of up to approximately 21 x 9.81 m / s ^{2 are} achieved. However, it has been found that in such centrifuges no complete or satisfactory demixing of the sample liquid can be achieved. Centrifuges are currently being planned in which demixing is to be improved by higher rotational speeds of up to 25,000 revolutions per minute.

However, this is associated with a strong increase in warming, since on the one hand the motor of the rotor of the centrifuge gives off heat. This heat can be largely kept away from the samples treated in the centrifuge by thermal insulation. However, on the other hand, heat is also generated by rapid rotation under the effect of air resistance. The consequent sample heating can not be easily prevented because laboratory centrifuges for cost reasons, a rotation in a vacuum is not possible.

The heat thus generated causes a strong heating of the centrifuged samples without appropriate countermeasures, which can easily lead to their destruction or uselessness. Usually, the samples must be kept at defined temperatures, for example, depending on the application to temperatures of 4 ° C, 22 ° C or 37 ° C.

In order to prevent the sample temperature from rising above these values, usually passive or active cooling devices are provided in the laboratory centrifuge, with compressors, namely reciprocating compressors, usually being used for the active cooling. Such Kühlunriechtungen for laboratory centrifuges are out EP 1 196 247 B1 . DE 28 16 449 A1 . JP 56 017956 U known.

The object of the present invention is to provide laboratory centrifuges that allow better separation, ie a higher rate of separation of the centrifuged samples.

This object is achieved with a laboratory centrifuge according to claim 1. Advantageous developments of this laboratory centrifuge are specified in the dependent claims.

The inventors have surprisingly discovered that the rates of segregation of the centrifuged samples can be increased by using rotary compressors for active cooling within the laboratory centrifuge.

This finding is based on the fact that it is not the centrifuge performance that is decisive for the rate of demixing, but the rate of re-mixing caused by the laboratory centrifuge.

So far, only centrifugal compressors are used in the centrifugal compressor in laboratory centrifuges due to their relatively low compared to the performance design. In such reciprocating compressors, a purely linear movement of the compressor body takes place in the compressor chamber. Compressors that operate on such a compression principle are therefore also called linear compressors. Linear compressors have in the movement of the compressor dead points, which lead to a strong swinging of the compressor when starting and stopping the compressor. These oscillations can not be completely kept away from the rotator of the centrifuge, since in a laboratory centrifuge the compressor with the rotator are housed in a single housing.

The inventors have now recognized that these vibrations lead significantly to the high backmixing rates of such laboratory centrifuges.

With the inventively provided rotary compressors, ie compressors in which the compressor is constructed so that the compressor body at least performs a rotational movement in the compressor chamber, such vibrations can be significantly reduced, because here is always carried out a rotational movement in the interior of the compressor, so not in the the same extent as with linear compressors to be overcome dead points arise.

Compressors are preferably used as rotary compressors for the laboratory centrifuge according to the invention, in which the compressor is a rotary compressor, scroll compressor, vane compressor, swash plate compressor, screw compressor, scroll compressor, rotary compressor or the like. However, scroll and scroll compressors are preferred.

Although such compressors are already known from the refrigerator, but these devices have completely different specifications than laboratory centrifuges. First, laboratory centrifuges are very small compared to refrigerators, which means that all components must be housed in a very limited space: In addition, have laboratory centrifuges with the very fast moving rotor on a moving part, which must be operated as possible uninfluenced by other components despite this limited space , Secondly, laboratory centrifuges must cover a very wide temperature range, with frequent temperature changes having to be realized at high lowering speeds.

In addition, rotary compressors are now available which, with the same dimensions with respect to a reciprocating compressor, provide at least the same compression performance so that the dimensions of the laboratory centrifuge do not increase when used.

Advantageously, the starting currents can also be reduced with the specified rotary compressors. So far, certain laboratory centrifuges have not been sold in some countries, such as the USA, because of the 110V AC power grid used there, as current spikes generated by powerful reciprocating compressors would jeopardize the stability of the power grids commonly used in these countries. Alternatively, certain controls had to be provided in the laboratory centrifuges, which ensure that the compressor is only controlled in such a way that the starting currents do not exceed the legally required values. With the present invention provided rotary compressors can be dispensed with such controls, so that the laboratory centrifuges are simple and thus more robust and cheaper and their sale is also permitted in these countries.

In a further preferred embodiment, the rotary compressor is an electrically driven compressor (direct and / or alternating current). Such compressors can be very compact and high-torque build and their control is independent of the mains voltage via a regulated switching power supply or frequency converter possible. In addition, smaller compressions can be made easier with such compressors.

It is particularly useful if at least two compressors are arranged in parallel. Thus, the compressors can be made smaller overall and with less power, so that the usable space in a laboratory centrifuge space can be better used, whereby a total of the required construction volume of such a laboratory centrifuge drops.

The laboratory centrifuge according to the invention can be carried out particularly advantageously as a laboratory bench centrifuge and microliter centrifuge and the like, since it is particularly important for these types of centrifuge to have a very compact design.

It is particularly advantageous if the laboratory centrifuge has a backmixing rate of less than or equal to 20%, preferably less than or equal to 17%, in particular less than or equal to 14%. Then the segregation rate is particularly high.

Fig. 1

die erfindungsgemäße Laborzentrifuge und

Fig. 2

eine Laborzentrifuge des Standes der Technik.

The characteristics and further advantages of the present invention will now be described with reference to a preferred embodiment. Showing:

Fig. 1

the laboratory centrifuge according to the invention and

Fig. 2

a laboratory centrifuge of the prior art.

In Fig. 1 is purely schematically illustrated the laboratory centrifuge 1 according to the invention in a preferred embodiment. This laboratory centrifuge 1 has a housing 2 and a centrifuge lid 3. The centrifuge lid 3 is designed to close a centrifuge container 4, in which a rotor 5 is arranged. The rotor 5 is drivable by a motor (not shown), whereby samples (not shown) arranged on the rotor 5 can be centrifuged to separate them.

For cooling the samples, the laboratory centrifuge 1 has an active cooling device which comprises a compressor 6. The compressor 6 is designed as a rotary compressor and has a rotary piston compressor. In the area of the compressor 6, the top of the housing 2 is not shown.

This compressor 6 is very compact and high-torque and its control is possible via a regulated switching power supply regardless of the mains voltage. With the help of this compressor 6, smaller power gradations of the cooling capacity can be easily.

In FIG. 2 is shown purely schematically a laboratory centrifuge 10, as is prior art. This laboratory centrifuge 10 differs from the laboratory centrifuge 1 according to the invention in that a compressor 11 with a reciprocating compressor is used as the compressor 11. All other parts are therefore provided with the same reference numerals as in the laboratory centrifuge according to the invention.

From the comparison of the laboratory centrifuge 1 according to the invention with the known laboratory centrifuge it is clear that with modern rotary compressors 6 with the same power less space in the housing 2 is needed. In this way, either the housing 2 can be made smaller, or the cooling capacity can be increased by parallel installation of multiple compressors 6.

In the following, a comparative investigation of the backmixing rates of the laboratory centrifuge 1 according to the invention in comparison with the ordinary laboratory centrifuge 10 with a reciprocating compressor will now be described. A laboratory centrifuge 1 with the rotary piston compressor XB357 from Mitsubishi was used and rotor 5 was the rotor F-45-24-11 from Eppendorf. For the comparative study, the centrifuge 5415 R from Eppendorf (model SN 5426 0023218) was used as the laboratory centrifuge 10, which had a reciprocating compressor PL50 from Danfoss and wherein the rotor 5 was the same rotor F-45-24-11 was used. The pipette Eppendorf Reference 500 - 2500 μl was used for pipetting

(Model SN 475116) and the pipette Eppendorf Research pro 5 - 100 μl (model SN 022760). In addition, an Eppendorf biophotometer (model SN 6131 00197) was used.

Samples were placed in 2.0 ml Safe-Lock tubes (Model U123342P 2243) and samples were prepared using a 10 mM Tris solution and a salt concentrate color solution at a density of 1.2 g / ml. In each case, 1450 μl of Tris solution were pipetted into a 2.0 ml Safe-Lock vessel with the Eppendorf Reference pipette. The pipette Eppendorf Research pro was then underlaid with 50 μl of the salt concentrate dye solution with the pipette set to the lowest aspiration and dilution level.

In this way, four samples each were produced for the laboratory centrifuge 1 and the laboratory centrifuge 10, which were then centrifuged at 13,200 revolutions per minute and 4 ° C. for 5 minutes.

In addition, four 2.0 ml Safe-Lock tubes were filled in the same way for positive control and immediately mixed vigorously. For the negative control another four 2.0 ml Safe-Lock tubes were filled in the same way, but these samples were not centrifuged or mixed, but incubated for 5 minutes at room temperature.

After 5 minutes of centrifugation or diffusion in the positive and negative control tubes, the underlaid 50 μl salt concentrate color solution was removed from the tubes with the Eppendorf Research pro pipette. Thereafter, the vessels were closed again and mixed vigorously. The liquid contained in the vessels was then in each case transferred to a cuvette and measured photometrically at an extinction of 562 nm.
The values obtained with the positive control tubes serve as maximum values (100% value) and the values obtained in the negative control as background (diffusion).

The backmixing rate was then calculated from the formula: $$\mathrm{Remixing\; rate}\mathrm{=}\left(\mathrm{zentrifugierteWert}\mathrm{-}\mathrm{diffusion\; value}\right)\mathrm{x}\mathrm{100}\mathrm{/}\mathrm{100}\mathrm{\%}\mathrm{-}\mathrm{value}\mathrm{,}$$

In the table below, the results obtained are shown, the right column shows the averages calculated from the four samples used. With respect to diffusion, the value in brackets was not used because it was considered as an outlier. Based on the determined mean values, a backmixing rate of 13.44% was determined for the laboratory centrifuge 1 according to the invention, while the backmixing rate of the conventional laboratory centrifuge 10 was 28.26%. With the laboratory centrifuge 1 according to the invention, therefore, the backmixing rate could be reduced by about 15% absolute or even by more than 55% relatively.

Table: Laboratory centrifuge 1 Laboratory centrifuge 10 means diffusion (0.179%) 0.064% 0.092% 0.046% 0.055% centrifuged value 0.145% 0.141% 0.121% 0.138% 0.161% centrifuged value 0,248 0,228% 0.244 0.197 0.222 100% value 0.570% 0.573% 0.584% 0.576% 0.560%

From the present description it has become clear that with the laboratory centrifuge 1 according to the invention, significantly better separation rates of centrifuged samples can be ensured, since significantly fewer vibrations are introduced into the laboratory centrifuge 1 by the provision of at least one rotary compressor 6 according to the invention, resulting in substantially lower backmixing rates.

Claims (6)

1. A laboratory centrifuge (1) comprising a rotor (5) driven by a centrifuge motor; and a cooling device including a compressor (6), wherein the compressor is a rotary compressor (6).
2. The laboratory centrifuge (1) according to claim 1, wherein the compressor (6) that is used as the rotary compressor includes a compression device from the group including: rotating piston compressor, scroll compressor, vane type compressor, wobble plate compressor, screw compressor, spiral compressor, rotary piston compressor and similar.
3. The laboratory centrifuge (1) according to one of the preceding claims, wherein the rotary compressor is a compressor (6) that is electrically driven, in particular by direct voltage and/or alternating voltage.
4. The laboratory centrifuge (1) according to one of the preceding claims, wherein at least two compressors are arranged in parallel.
5. The laboratory centrifuge (1) according to one of the preceding claims, wherein the laboratory centrifuge is a laboratory table centrifuge (1), a micro liter centrifuge or similar.
6. The laboratory centrifuge (1) according to one of the preceding claims, wherein a remix rate is less than or equal to 20%, preferably less than or equal to 17%, particularly preferably less than or equal to 14%.

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