Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04B—CENTRIFUGES
  • B04B5/00—Other centrifuges
  • B04B5/04—Radial chamber apparatus for separating predominantly liquid mixtures, e.g. butyrometers
  • B04B5/0442—Radial chamber apparatus for separating predominantly liquid mixtures, e.g. butyrometers with means for adding or withdrawing liquid substances during the centrifugation, e.g. continuous centrifugation
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04B—CENTRIFUGES
  • B04B9/00—Drives specially designed for centrifuges; Arrangement or disposition of transmission gearing; Suspending or balancing rotary bowls
  • B04B9/12—Suspending rotary bowls ; Bearings; Packings for bearings
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B04—CENTRIFUGAL APPARATUS OR MACHINES FOR CARRYING-OUT PHYSICAL OR CHEMICAL PROCESSES
  • B04B—CENTRIFUGES
  • B04B9/00—Drives specially designed for centrifuges; Arrangement or disposition of transmission gearing; Suspending or balancing rotary bowls
  • B04B9/08—Arrangement or disposition of transmission gearing ; Couplings; Brakes

Definitions

• the present invention relates to a centrifuge for continuous flow centrifugation according to the general part of claim 1.
• Centrifuges for continuous flow centrifugation and in particular centrifuges for fluidized bed centrifugation, which are of particular interest here, are used for a range of applications in biotechnology, including cell therapy, vaccine production and cell cultivation for recombinant protein production like antibody production.
• the type of continuous centrifuge in focus here comprises a rotor with chambers which are usually single-use chambers that can be fed with media while rotating.
• a force equilibrium between the centrifugal force and a fluid flow in the opposite direction suspends particles of different sizes at different locations in the chambers.
• applications of fluidized bed centrifuges comprise for example cell separation.
• an anti-twisting mechanism is implemented for the tubes leading to the chambers.
• This anti-twisting mechanism is based on the known principle that the chambers may rotate with double the velocity of the tubes without the tubes twisting. Implementing this principle puts a number of constructional restraints on the centrifuge, leading to complex mechanics.
• the known prior art ( EP 4 321 255 A1 ) that builds the basis of the invention is related to a centrifuge according to the general part of claim 1.
• This document also summarizes the general working principle of fluidized bed centrifuges.
• the centrifuge comprises a drum, a rotor and a motor for driving the drum and the rotor, wherein the drum, driven by the motor, rotates around a common rotation axis with a rotational frequency during use of the centrifuge, wherein the rotor is coupled to the drum, wherein due to being coupled to the drum, the rotor, driven by the motor, rotates around the common rotation axis with the double of the rotational frequency, wherein the centrifuge comprises a drive bearing arrangement, wherein the drive bearing arrangement comprises at least two drive ball bearings, wherein the drive ball bearings each comprise an inner race, an outer race and a bearing axis, wherein one of said races is connected to the drum and one of said races is
• the invention is based on the problem of improving the known centrifuge such that a further optimization regarding the named challenge is reached.
• the main realization of the present invention is that a centrifuge with rotating drive ball bearings in which the bearing axes are parallel to the common rotation axis has the problem that the balls of the bearings at two points in the rotation around the bearing axis move towards or away from the common rotation axis and therefore in, respectively against, the direction of centrifugal force. At these points, the balls tend to slip and hit against a cage of the drive ball bearing.
• the centrifuge may be able to turn the drum at a rotational frequency at which the forces acting on the drive ball bearing, e.g. a preload towards the common rotation axis and the centrifugal force, are balanced. At this rotational frequency, the drive ball bearings may have no load or almost no load acting on them. The drive ball bearings then fail quickly as the lubricant between races and balls is pushed by the slipping balls, breaking the film of lubricant and excessively increasing the friction and therefore wear.
• angular ball bearings with an axial preload are used to withstand axial load (i.e. load in the direction of the bearing axis).
• angular ball bearings with an axial preload are used to generate axial load on the balls of the bearings. This constant load reduces the tendency of the balls to slip, increasing the live time of the drive ball bearings.
• the drive ball bearings are angular drive ball bearings which are preloaded along their bearing axes.
• the drive ball bearings therefore do not reach a no-load state during use and are protected against the problem described above resulting from the use with a high centrifugal force.
• a preferred embodiment according to claim 2 relates to a feeding pipe for the rotor in which tubes may be placed.
• the feeding pipe of this embodiment helps provide an anti-twisting mechanism, however, because the feeding pipe rotates around the rotor, driving the rotor via the motor is mechanically challenging.
• An end of the feeding pipe may define a front side of the centrifuge.
• the centrifuge may comprise a rotor drive train between the motor and the rotor with a drive shaft connected to the drive ball bearings (claim 4).
• the drive shaft extends through the drum such that motor and rotor may be located on different sides of the drum functionally.
• the bearing housing may be mounted onto the drum and the rotor drive shaft may extend completely through the bearing housing (claim 5). The drive bearing arrangement then may rotate with the feeding pipe, providing a solution to drive the rotor without interference with the feeding pipe.
• the inner or outer races may be angled with a one-sided groove while the respective other races may comprise a two-sided groove. An angle in one direction may be sufficient to achieve the proposed effect.
• a tandem arrangement of drive ball bearings is proposed.
• the drive bearing arrangement is preloaded towards the common rotation axis with a certain force (center preload). This force however can be overcome or even (approximately) nullified by the centrifugal force during normal use of the centrifuge (claim 8).
• the proposed solution prevents quick failing of the drive ball bearings.
• the rotational frequency may be set arbitrarily by a user, making it problematic to impossible to prevent no load / very low load states by a software (claim 9).
• Claim 10 relates to the preload being generated by one or two preload elements, in particular tooth belts.
• the preload elements may be oriented orthogonally to the bearing axes and/or may be drive elements of the rotor drive train (claim 11).
• the proposed solution is used in an arrangement in which no axial load is applied to the drive bearing arrangement (not including tolerances from slightly different preloads from the tooth belts or the like). Such an arrangement further underlines the use of angular ball bearings to protect the bearings.
• Claim 13 refers to preferred arrangements of the drive ball bearings in relation to the common rotation axis.
• the drive bearing arrangement may comprise one or two rings screwed into the bearing housing for exerting an axial preload on the drive ball bearings.
• the axial preload may be changeable by adjusting the tightening torque of the ring or rings. Thereby, the axial preload can be precisely set and holds for a long time. Further, the axial preload is transmitted to the balls, protecting the cage as proposed.
• the lifetime of the drive ball bearings can be further increased by using balls with less weight and/or a cage from fiber reinforced phenolic resin which gives the balls less space to slip (claim 15).
• Fig. 1 shows as a preferred embodiment a centrifuge 1 for continuous flow centrifugation.
• the centrifuge 1 is here and preferably usable for fluidized bed centrifugation.
• the outer view of Fig. 1 shows a front side of the centrifuge 1 with a closed door 2.
• the centrifuge 1 may comprise an outer housing not shown in Fig. 1 .
• Fig. 2 shows a longitudinal cut through the centrifuge 1 in Fig. 1 along the line marked with II.
• the centrifuge 1 comprises a drum 3, a rotor 4 and a motor 5 for driving the drum 3 and the rotor 4.
• the drum 3, driven by the motor 5, rotates around a common rotation axis A with a rotational frequency during use of the centrifuge 1.
• the rotational frequency here and preferably can be set arbitrarily by the user in a range leading up to for example a g-force of 2000g applied to a medium in the rotor 4.
• the rotor 4 is, preferably mechanically, coupled to the drum 3. Due to being coupled to the drum 3, the rotor 4, driven by the motor 5, rotates around the common rotation axis A with the double of the rotational frequency. It is a known principle that providing a ratio of 1:2 leads to an anti-twisting mechanism for tubes 6 feeding the rotor 4.
• the rotor 4 is preferably coupled mechanically to the drum 3, though a software coupling is conceivable. The mechanical coupling ensures that the rotational frequencies of the drum 3 and the rotor 4 keep the ratio of 1:2 without high precision sensors and software, such that the anti-twisting mechanism works.
• the centrifuge 1 comprises a drive bearing arrangement 7.
• the drive bearing arrangement 7 comprises at least two drive ball bearings 8, here and preferably four drive ball bearings 8.
• the drive ball bearings 8 each comprise an inner race 9, an outer race 10 and a bearing axis B.
• the races 9, 10 of the outer drive ball bearings 8 are visible in more detail in Fig. 4 .
• one of said races 9, 10 is connected to the drum 3 and one of said races 9, 10 is connected to the rotor 4.
• the drive bearing arrangement 7 therefore provides a connection between the drum 3 and the rotor 4 that allows for relative rotation between both.
• the bearing axes B of the drive ball bearings 8 are each located spaced apart from, and parallel to, the common rotation axis A, such that the drive ball bearings 8 rotate around the common rotation axis A.
• the drive ball bearings 8 may be significantly spaced apart from the common rotation axis A, leading to a strong centrifugal force Fc acting on the drive ball bearings 8 as a whole. That is usually not the case for common uses of ball bearings.
• the centrifugal force Fc acts on the drive bearing arrangement 7 in a direction pointing downwards.
• Fig. 5 shows in a rather schematic manner the forces acting on a drive ball bearing 8 in an arrangement where the bearing axis B and the common rotation axis A are parallel.
• a preload element 11 acts on the drive bearing arrangement 7 and preferably each drive ball bearing 8.
• a tooth belt acts on the drive ball bearings 8 preloading the drive ball bearings 8 towards the common rotation axis A.
• Fig. 5 shows that the centrifugal force Fc resulting from the rotation of the drive ball bearing 8 around the common rotation axis A acts in the opposite direction of the preload force Fp.
• the centrifugal force Fc and the preload force Fp may be such that the resulting force on the drive ball bearing 8 is very small.
• the bearing balls 12 of the drive ball bearing 8 rotate around the bearing axis B and at two points P on their movement path, the bearing balls 12 move parallel to the centrifugal force Fc and the preload force Fp.
• the bearing balls 12 can easily slip as, for "normal" (non-angular) ball bearings, almost no force acts on the bearing balls 12 towards the bearing axis B at these two points P.
• Any tolerances between the bearing balls 12 and a cage 13 of the drive ball bearings 8 lead to the bearing balls 12 bouncing back and forth at the two points P and damaging the cage 13, increasing the tolerances and subsequently the damage.
• the sliding also leads to abrasion and therefore particles, further damaging the drive ball bearings 8.
• the drive ball bearings 8 are angular drive ball bearings 8 which are preloaded along their bearing axes B. Angular ball bearings with an axial preload make sure that there is always a load acting on the bearing balls 12. The tendency of the bearing balls 12 to slip is therefore greatly reduced.
• the drive bearing arrangement 7 may comprise an axial-preload element for generating the axial preload.
• the preload per bearing may be at least 5 N, preferably at least 15 N, more preferably at least 25 N, for example 33 N, and/or at most 100 N, preferably at most 75 N, more preferably at most 50 N.
• the centrifuge 1 comprises a feeding pipe 14 for continuously feeding the rotor 4 with a medium for centrifugation, which can be seen in Fig. 2 .
• the feeding pipe 14 may be connected to the drum 3.
• the feeding pipe 14 preferably rotates around the common rotation axis A with the rotational frequency.
• the feeding pipe 14 leads along a back direction 15 of the centrifuge 1 around the rotor 4 and is connected to the drum 3 along a front direction 16 of the centrifuge 1, such that the feeding pipe 14 rotates around the rotor 4 around the common rotation axis A.
• the rotation of the feeding pipe 14 completely envelopes the rotor 4.
• to contact the rotor 4 only elements rotating synchronously with the feeding pipe 14 can be used.
• the drive bearing arrangement 7 for driving the rotor 4 is connected to the drum 3.
• the feeding pipe 14 takes in tubes 6 of a single-use tube set 17 connected to chambers 18 of the single-use tube set 17 and the rotor 4 takes in the chambers 18.
• the anti-twister mechanism aims at not intertwining these tubes 6.
• the chambers 18 may comprise a volume of at least 25 ml, preferably at least 50 ml, and/or, at most 200 ml, preferably at most 100 ml, more preferably exactly 50 ml, per chamber 18.
• the tube 6 set may comprise two or four or six chambers 18.
• the chambers 18 may also have a greater volume for example of 100 ml or 1000 ml.
• the drive bearing arrangement 7 comprises a bearing housing 19.
• the bearing housing 19 comprises an outer wall 20 rotationally fixed to the outer races 10 of the drive roller bearings.
• the connection between the outer races 10 and the outer wall 20 may be based on friction as the rotational forces on the outer races 10 will usually be rather low.
• the centrifuge 1 may comprise a main shaft 21 defining the common rotation axis A.
• the main shaft 21 is mounted to a centrifuge housing 22, in particular at a side located in the back direction 15 from the drum 3 and the rotor 4, here at a back side 23, though it could also be mounted to a top side at the back of the centrifuge 1 or the like.
• the drum 3 and the rotor 4 are mounted onto the main shaft 21.
• the motor 5 may be mounted onto the centrifuge housing 22, too, here from the outside. A further outer housing is not shown. It can be seen that between the main shaft 21 and the rotor 4 and the drum 3, several main bearings 24 are located.
• the back direction 15 and front direction 16 are defined along the common rotation axis A. In principle, the directions are arbitrary and defined only by their functions.
• the front side may also be an upper side, for example.
• the drive ball bearings 8 may comprise sealings 25 connected to the outer races 10 and the bearing housing 19 may in addition to the sealings 25 comprise a ridge 26.
• the ridge 26 gathers lubricant leaving the drive ball bearings 8 through the connections of the outer races 10 and the sealings 25 due to the high centrifugal forces Fc.
• the centrifuge 1 may comprise a rotor drive train 27 between the motor 5 and the rotor 4.
• the rotor drive train 27 comprises a rotor drive shaft 28 connected to one of the races 9, 10 of each drive roller bearing.
• the rotor drive shaft 28 is connected, in particular directly, to the inner races 9 of the drive roller bearings and the drum 3 is connected to the outer races 10 of the drive roller bearings via the bearing housing 19. Further elements of the drive train will be explained in the following.
• the rotor drive shaft 28 is visible in a) and b).
• the bearing housing 19 is cut with the components of the rotor drive train 27 and the drive roller bearings removed to allow a view inside the bearing housing 19 and in particular to show one embodiment of the ridge 26.
• the rotor drive train 27 extends through the drum 3 via the rotor drive shaft 28.
• the mechanical coupling of the rotor 4 and the drum 3 is realized here by driving the rotor drive train 27 and the drum 3, via a drum drive train 29, by the same motor 5. It is then a question of gearing to synchronize the speeds with a factor of 1:2.
• the rotor drive train 27 and the drum drive train 29 may comprise gearwheels 30, here belt wheels, in particular toothed belt wheels 31, with different sizes.
• the rotor drive train 27 here and preferably leads to the rotor 4 from the back direction 15 of the centrifuge 1. Further, it is conceivable to connect the races 9, 10 the other way around, the inner races 9 being connected to the drum 3 and the outer races 10 to the rotor 4.
• the rotor drive shaft 28 may be a counter shaft with regard to the main shaft 21.
• the or a connection between the housing and the drum 3 may be achieved by mounting the bearing housing 19 onto the drum 3.
• the bearing housing 19 is screwed to the drum 3.
• the rotor drive shaft 28 extends completely through the bearing housing 19 from one longitudinal side 32 to another longitudinal side 32 of the bearing housing 19 along at least one of the bearing axes B and that the rotor drive train 27 comprises drive elements 33 connected to the rotor drive shaft 28 at both longitudinal sides 32 of the bearing housing 19.
• the drive elements 33 on both sides are belts, in particular tooth belts.
• the rotor drive train 27 here and preferably comprises toothed belt wheels 31 on both longitudinal sides 32 of the bearing housing 19, one of them leading towards the motor 5 and one leading towards the rotor 4, here driving the rotor 4 directly. It can be seen that parts of the rotor drive train 27 rotate together with the feeding tube 6, enabling the rotation of the rotor 4 in spite of the feeding tube 6 enveloping the rotor 4.
• the belts may comprise mechanisms for adjusting the belt tension 34.
• the inner races 9 of the drive ball bearings 8 may comprise one-sided grooves 35 and an inner race 9 of one of the drive ball bearings 8 may comprise a one-sided groove 35 angled in the opposite direction than the one-sided groove 35 of an inner race 9 of another of the drive ball bearings 8 (not shown).
• the outer races 10 of the drive ball bearings 8 may comprise one-sided grooves 35 and an outer race 10 of one of the drive ball bearings 8 may comprise a one-sided groove 35 angled in the opposite direction than the one-sided groove 35 of an outer race 10 of another of the drive ball bearings 8.
• the outer races 10 comprise one-sided grooves 35 and the inner races 9 comprise two-sided grooves 36.
• a contact angle of the drive ball bearings 8 between the balls and the angled race 9, 10 is preferably between 5° and 45°, here and preferably 15°.
• the drive bearing arrangement 7 may comprise at least two drive ball bearings 8 in a tandem arrangement.
• the drive bearing arrangement 7 comprises at least three drive ball bearings 8.
• the drive bearing arrangement 7 comprises four drive ball bearings 8 arranged in a TOT arrangement as can be seen in Fig. 4 .
• the balls may have a diameter of 5 mm or less.
• a drive ball bearing 8 may comprise at least 10, preferably at least 14, balls.
• the centrifuge 1 is arranged to be operated with a first rotational frequency that leads to a centrifugal force Fc on the drive bearing arrangement 7 greater than the center preload and with a second rotational frequency that leads to a centrifugal force Fc on the drive bearing arrangement 7 smaller than the center preload. Switching between the first and the second frequency then means that at least for a moment the center preload and the centrifugal force Fc are equal.
• the centrifuge 1 is arranged to be operated with a third rotational frequency that leads to a centrifugal force Fc on the drive bearing arrangement 7 equal to the center preload. It is preferred to allow for a broad range of rotational frequencies to cover many use cases.
• the rotational frequency can be set by a user.
• the user can set the rotational frequency to the first, the second and preferably the third rotational frequency. If the user sets the rotational frequency to the third rotational frequency, a drive bearing arrangement 7 without angular bearings would fail quickly.
• the center preload on the drive bearing arrangement 7 is generated by a preload element 11, in particular by two preload elements 11.
• the preload element 11 is a belt, in particular tooth belt, and/or, the two preload elements 11 are belts, in particular tooth belts.
• the preload elements 11 are located at two opposite sides of the drive bearing arrangement 7.
• the preload elements 11 here and preferably act on the rotor drive shaft 28 and via the rotor drive shaft 28 on the drive ball bearings 8.
• the preload elements 11 are oriented orthogonally to the bearing axes B, and/or, that the preload elements 11 are drive elements 33 of the rotor drive train 27.
• axial load means such loads that act in addition to loads from tolerances or other sources that cannot reasonably be removed.
• the bearing axes B may be identical.
• the common rotation axis A does not pass through the drive ball bearings 8 and/or does not pass through the bearing housing 19.
• the drive bearing arrangement 7 comprises a ring 37 screwed into the bearing housing 19 exerting an axial preload along at least one of the bearing axis B onto the drive ball bearings 8 ( Fig. 3 b) and Fig. 4 ).
• the ring 37 may be the axial-preload element.
• the drive bearing arrangement 7 comprises a further ring 38 screwed onto the rotor drive shaft 28 exerting an axial preload along at least one of the bearing axes B onto the drive ball bearings 8.
• the further ring 38 may be a further axial-preload element.
• the axial preload can be adjusted by adjusting a tightening torque of the ring 37 and/or the further ring 38.
• One of the ring 37 and the further ring 38 may preload only the outer races 10 and the other only the inner races 9.
• the outer races 10 may contact each other and/or be pressed against an outer race ridge 39 of the bearing housing 19.
• the inner races 9 may contact each other and/or be pressed against an inner race ridge 40 of the rotor drive shaft 28.
• the bearing housing 19 may comprise a screw thread 41.
• the rotor drive shaft 28 may comprise a screw thread 41.
• the ridge 26 is formed integral with the outer wall 20, or, the ridge 26 is formed by the ring 37.
• the drive bearing arrangement 7 comprises a further ridge 26 and the further ridge 26 is also formed integral with the outer wall 20 or by the ring 37.
• one ridge 26 is formed integral with the outer wall 20 ( Fig. 4 on the left) and one ridge 26 is formed by the ring 37 ( Fig. 4 on the right). Which of those is seen as the ridge 26 and which as the further ridge 26 is arbitrary.
• the ridge 26 and the further ridge 26 are located at opposite longitudinal sides 32 of the bearing housing 19. If the ridge 26 is formed by the ring 37, the threaded connection may have the sealing-function simply by a tight fit between the ring 37 and the screw thread 41.
• connection formed between the bearing housing 19 and the ring 37 by screwing the ring 37 is sealed.
• the ring 37 may be screwed into a sealing-material.
• the sealing 25 may be clipped onto the outer race 10 of the drive ball bearing 8 comprising the sealing 25.
• each drive ball bearing 8 comprises a sealing 25, in particular two sealings 25.
• At least one of the drive ball bearings 8, in particular all drive ball bearings 8, comprise a cage 13 comprising, in particular made of, a fiber reinforced phenolic resin.
• a resin allows encasing the bearing balls 12 with less tolerances, reducing the possible space for sliding for the bearing balls 12.
• At least one of the drive ball bearings 8, in particular all drive ball bearings 8, comprise bearing balls 12 comprising, in particular made of, ceramic.
• the ceramic is a Trisilicon tetranitride ceramic.

Landscapes

• Centrifugal Separators (AREA)

Priority Applications (2)

Applications Claiming Priority (1)

Publications (1)

Family

ID=91375242

Family Applications (1)

Country Status (2)

Citations (4)

• 2024
  • 2024-05-31 EP EP24179381.9A patent/EP4656293A1/de active Pending
• 2025
  • 2025-05-30 WO PCT/EP2025/065013 patent/WO2025248103A1/en active Pending

Patent Citations (4)

Also Published As

Similar Documents

Legal Events