GB1605218A - Centrifuge and a method for the production of a rotor therefor - Google Patents

Abstract

The rotors, of ultracentrifuges for separating heterogeneous mixtures, are made, according to the invention, from composite materials reinforced with fibres in order to increase their strength. The case of the rotor 1 is manufactured by a filament-winding process, a central rotor body 10, possibly in several parts and made from refractory material (ceramic) serving as a mandrel which, during the winding of a coated reinforcing filament, is subjected to a galvanising process so that the reinforcing filaments are embedded in a metal matrix. <IMAGE>

Description

(54) A CENTRIFUGE AND A METHOD FOR THE PRODUCTION OF A ROTOR THEREFORE (71) We, MEssERscHMIrr-BoLKow BLOHM, Gesellschaft mit beschrankter Haftung, of 800 Munchen, German Federal Republic, a company organised and existing under the laws of the German Federal Republic, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an ultra-centrifuge and to a rotor therefor. Centrifuges of this kind are used as example, for the separation of heterogeneous mixtures using extremely high forces of inertia.

The casings of the rotors of known type of centrifuge are generally made of cold formed thin-walled steel or an alloy of high specific strength.

To increase the centrifugal forces and thus the separating performance of such centrifuges it has been suggested that the rotor be made to a dish-shape with containers for the material to be separated located in the rim.

The known rotors cannot withstand the centrifugal forces occurring in a case where rotational speeds of about 750()() r.p.m. are used. The structure of the material loosens and the rotors spread out. In certain cases centrifuges have disintegrated with explosive force. Loosening of the structure of the material of the rotor is made worse when the rotor, possibly as the result of a considerable frictional resistance caused by air in the gap between the rotor and housing heats up, or if the rotor is heated to increase the separating performance.

Extremely exact demands are therefore made on the material of the rotor of centrifuges of this kind and in addition to the high specific strength at room temperature (breaking length about 60 Km) it must also hav a high specific heat resistance at about 1500"C (breaking length about 50 Km). If the material to be separated is to be heated by induction then steps must be taken to ensure good conductivity in the casing of the rotor or other parts of the centrifuge.

According to this invention there is provided a centrifuge having a rotor constructed in part from carbon reinforced with carbon fibre.

Using a material of this kind in the event of overloading or concealed defects in the material it does not fly apart explosively under the effect of extreme centrifugal forces but will break-up into unravelled but still cohesive parts.

The rotor may include an outward extending rim with an increased proportion of carbon fibre reinforcement. The higher proportion of fibre in the edge zone increases the resistance of the rotor to the centrifugal forces occurring in this zone.

The volumetric proportion of the reinforcement threads in the composite material of the rotor preferably increases towards the outside as the winding progresses and is greater in the edge zones of the rotor casing than at the start of the winding.

The winding process for production of a rotor from fibre-reinforced composite material is preferably carried out intermittently, since because the winding and the electrolytic process are performed simultaneously the matrix will be built up in the form of a wedge between the layers of thread and this will increase during production and lead to a reduction in that volumetric proportion of the composite material which is formed by the reinforcement material.

A method for the production of the rotor for the centrifuge comprises using a reinforcement thread of carbon fibre wound onto a multi-part supporting core after which the winding undergoes an electrolytic process encasing the reinforcement thread and forming a matrix, the parts of the supporting core not susbequently required being then removed. This removal may be effected by dissolving the core parts out chemically or by extracting them for use again.

The multi-part supporting core is removable and can be replaced by a central rotor body which is preferably of a material having a thermal expansion coefficient substantially equal to that of the composite material.

After the supporting core or parts thereof have been dissolved out the central rotor body may be inserted into the wound casing part of the rotor.

The rotor and central body may be designed in various ways. Symmetrically arranged parts of the core can be left in the wound part of the rotor while other parts are dissolved out and replaced by the central rotor body.

The reinforcement thread may be pretreated before the winding process and for example be provided with a protective diffusion layer of silicon carbide. When the reinforcement thread is coated in this way it is thereby protected against undesirable reactions at high rotor operating temperatures.

With a centrifuge thus constructed, alloying and doping problems can be overcome particularly when the rim of the rotor is additionally heated. By removal of undesirable impurities and deposits, as well as by compacting, very pure substances and elements can be produced from numerous mixtures of substances in a liquid state. This is of importance for the semi-conductor and industrial diamond industries. Furthermore production of hard substances such as silicates, boron nitride and diamond is simplified. The process of re-cycling used metals and the separation of slags and melts is rendered possible. The invention also enables problems in diffusion kinetics to be solved more satisfactorily.

For example, experiments with highpressure synthetics without recourse to hydraulic or other means are possible.

The invention is further described by reference to a number of examples shown in the accompanying drawings.

Figure 1 shows a section of a rotor of a centrifuge, Figure 2 is a plan view of the rotor shown in Figure 1 but without the cover, Figure 3 is a plan view of another version of a rotor, Figure 4 shows a rotor in section, and produced by a winding process, Figure 5 is a section on V-V of the rotor shown in Figure 4, and Figure 6 shows a diagram of a winding apparatus.

A rotor 1 with a cover 2, as shown in Figures 1 and 2, is mounted so as to be rotatable about an axis 3 and is driven by a shaft 4 from a motor (not shown) through dogs 5 and 6 which engage recesses 7 and 8 in a metal insert 9 provided in the lower part of the rotor 1. The rotational drive can also be transmitted through a magnetic clutch or other device, instead of the dogs 5 and 6.

The rotor 1 has a central body 10 with a base which is slightly dished and an edge part or rim 11 extending approximately parallel to the rotor axis 3. The rim is made of highstrength carbon-fibre reinforced carbon (carbon-carbon) or carbon-fibre reinforced graphite which is both mechanically and thermally resistant.

Specimen containers 12 are arranged in the body 10 and are evenly distributed around the periphery of the rotor 1. They extend into the edge part or rim 11 and are embedded in silicon nitride or graphite 13. In the present example cylindrical containers 14 of platinum foil or other non-reactive material having a high melting point to accommodate the extract from the centrifugal materials are located in the specimen containers 12.

The connection between the central body 10 and the rim 11 can be produced by the winding of the composite material of the rim 11.

It is advisable for the central body 10 and the specimen containers 12 with the containers 14 to be made from materials having approximately the same thermal expansion coefficients as the fibre-reinforced composite material used for the rim 11.

The specimen containers may be constructed in various ways. Figure 3 for example shows four specimen-containers 15 in the central body of the rotor 1 and having a large capacity and a wide base surface.

Figure 4 shows a rotor 1 produced by a winding process, and is driven by shaft 4 from a driving motor (not shown) through dogs 5, 6 which engage recesses 7, 8 in a metal insert 9 provided in the lower part of the rotor 1. The rotational drive can also be transmitted through a magnetic clutch or similar device, instead of the dogs 5 and 6.

The rotor 1 has a multi-part central body 20 of ceramic or similar material and a rim 11 of carbon fibre-reinforced composite material with a carbon matrix.

Figure 5 shows a plan view of the rotor 1 with the cental body 20 in the form of a supporting core and comprising a number of parts 21, 22, 23, etc, of materials which are such that after the fibre-reinforced rim 11 has been wound they can be wholly or partly extracted or dissolved out chemically and replaced by a similar multi-part body which remains in the rotor.

As shown in Figures 4 and 5 the specimen containers 12 are evenly spread around the periphery of the rotor 1. The containers 12 extend into the rim 11 and are lined with cylindrical inserts 14 of platinum foil or other non-reactive material having a high melting point. They serve to accommodate the subsequently extracted centrifuged materials.

It is advisable for the central body 20 and the containers 12 with inserts 14 to be made of materials having approximately the same thermal expansion coefficients as the fibrereinforced composite material used for the construction of the rim 11.

For the production of the rim 11, use is made of the winding apparatus shown schematically in Fig. 6 and in which the multi-part supporting core 2() is mounted on the end of a pivoted arm 24. The arm 24 also carries the driving unit (not shown) serving to rotate the winding mandrel supporting core 20. The arm can be lowered, by means of a worm gearing 25 driven by a motor 32, into a vessel 26 containing electrolyte. Connected with the pivot arm 24 is a known layer-winding apparatus 27 having a reel 28, slide 29 and a tensioning device 30 serving as a feed for a thread 31 from the reel 28 and enabling the distance to be varied between individual turns of the thread deposited on the core 20. The thread brake of the layer winding apparatus may, for example be Type F 9 M2 supplied by the firm of Etabs. PARVEX, of DIJON, France, described in U.S.Patents 3,090,880 and 3,144,574. The layer winding apparatus 27 is mounted on a base 33 in such a way that it can be adjusted to different heights.

Owing to the requirement that the volumetric proportion of the reinforcement thread 31 in the composite material should increase in the outer zones of the rotor, the winding process and the electrolytic deposit of the carbon or graphite matrix must be simultaneous. This is possible but only when extremely low current densities ((1.1 A/dm2) are used.

WHAT WE CLAIM IS: 1. A centrifuge having a rotor constructed in part from carbon reinforced with carbon fibre.

2. A centrifuge in accordance with Claim 1, wherein the rotor includes an outwardly extending rim with an increased proportion of carbon fibre reinforcement.

3. A centrifuge in accordance with Claim 1 or 2, wherein the rotor is formed as a coiled body.

4. A centrifuge in accordance with any preceding claim, wherein the volumetric proportion of reinforcement fibres in the rotor increases towards the outside and is greatest towards the outside of the rotor.

5. A centrifuge in accordance with any preceding claim, wherein the inner parts of the rotor form a central body of a material having a thermal expansion coefficient substantially equal to that of the carbon fibre-reinforced material.

6. A centrifuge in accordance with any preceding claim, wherein a central rotor body is inserted into a wound outer part of the rotor.

7. A centrifuge in accordance with Claim 6 wherein symmetrically located parts are provided in the central body to serve as containers.

8. A centrifuge or a rotor therefor constructed substantially as herein described with reference to or as shown in Figures 1 and 2, Figure 3, or Figures 4 and 5 of the accompanying drawings.

9. A method for the production of a rotor for a centrifuge substantially as herein described with reference to Figures 4, 5 and 6 of the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (9)

**WARNING** start of CLMS field may overlap end of DESC **. schematically in Fig. 6 and in which the multi-part supporting core 2() is mounted on the end of a pivoted arm 24. The arm 24 also carries the driving unit (not shown) serving to rotate the winding mandrel supporting core 20. The arm can be lowered, by means of a worm gearing 25 driven by a motor 32, into a vessel 26 containing electrolyte. Connected with the pivot arm 24 is a known layer-winding apparatus 27 having a reel 28, slide 29 and a tensioning device 30 serving as a feed for a thread 31 from the reel 28 and enabling the distance to be varied between individual turns of the thread deposited on the core 20. The thread brake of the layer winding apparatus may, for example be Type F 9 M2 supplied by the firm of Etabs. PARVEX, of DIJON, France, described in U.S.Patents 3,090,880 and 3,144,574. The layer winding apparatus 27 is mounted on a base 33 in such a way that it can be adjusted to different heights. Owing to the requirement that the volumetric proportion of the reinforcement thread 31 in the composite material should increase in the outer zones of the rotor, the winding process and the electrolytic deposit of the carbon or graphite matrix must be simultaneous. This is possible but only when extremely low current densities ((1.1 A/dm2) are used. WHAT WE CLAIM IS:

1. A centrifuge having a rotor constructed in part from carbon reinforced with carbon fibre.

2. A centrifuge in accordance with Claim 1, wherein the rotor includes an outwardly extending rim with an increased proportion of carbon fibre reinforcement.

3. A centrifuge in accordance with Claim 1 or 2, wherein the rotor is formed as a coiled body.

4. A centrifuge in accordance with any preceding claim, wherein the volumetric proportion of reinforcement fibres in the rotor increases towards the outside and is greatest towards the outside of the rotor.

5. A centrifuge in accordance with any preceding claim, wherein the inner parts of the rotor form a central body of a material having a thermal expansion coefficient substantially equal to that of the carbon fibre-reinforced material.

6. A centrifuge in accordance with any preceding claim, wherein a central rotor body is inserted into a wound outer part of the rotor.

7. A centrifuge in accordance with Claim 6 wherein symmetrically located parts are provided in the central body to serve as containers.

8. A centrifuge or a rotor therefor constructed substantially as herein described with reference to or as shown in Figures 1 and 2, Figure 3, or Figures 4 and 5 of the accompanying drawings.

9. A method for the production of a rotor for a centrifuge substantially as herein described with reference to Figures 4, 5 and 6 of the accompanying drawings.