Flow-through centrifuge for centrifuging biological fluids

Details Flow-through centrifuge for centrifuging biological fluids Flow-through centrifuge for centrifuging biological fluids

1999-01-19

2001-08-28

Walker, W. L. (Department: 1723)

Imperforate bowl: centrifugal separators

Including specific device or structure for driving or...

C494S045000

Reexamination Certificate

active

06280375

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a centrifuge, in particular a flow-through centrifuge for centrifuging biological fluids, such as blood, and capable of being free of rotating seals.
RELATED TECHNOLOGY
With such a centrifuge, the biological fluid is centrifuged in a flow-through process, with the fluid flowing through a line into and out of the rotating centrifuge chamber. The line routing proves to be problematical because of the relative movement between the centrifuge chamber and the stationary connection point of the line. Traditional flow-through centrifuges use rotating joints to prevent the line from twisting. German Patent Application No. 3,242,541 A discloses a blood centrifuge free of rotating seals, with the line being guided in a loop around the centrifuge chamber at half the rotational speed of the centrifuge chamber. To do so, the line is connected to a rotating frame which rotates at half speed in comparison with the centrifuge chamber. To drive the centrifuge chamber and the rotating frame, it is proposed that the rotating frame be connected to a hollow shaft, and that the centrifuge chamber be driven with a drive shaft extending through the hollow shaft. A belt drive is used to transmit the torque from the drive shaft to the centrifuge chamber. A blood centrifuge with a belt drive is also disclosed in U.S. Pat. No. 4,425,112.
International Patent Application No. WO 96/40322 discloses a blood centrifuge characterized by a very compact design. The centrifuge chamber and the line pusher are driven at half the rotational speed in the same direction of rotation as the chamber by a toothed gear. One disadvantage is the relatively loud running noises of the gearwheels, which noises are perceived as unpleasant by both the donor and the personnel. Furthermore, using gearwheels requires a high-precision manufacturing process for the centrifuge, which is therefore very expensive. Furthermore, the gearwheels must be lubricated, which not only increases the maintenance cost of the centrifuge but also leads to a buildup of dust and dirt. Therefore, the gear should be completely closed. However, arranging the gear in a closed casing in turn leads to problems in dissipating the resulting heat loss. In addition, the gearwheels are subjected to constant wear.
International Patent Application No. WO 96/04996 discloses a centrifuge in which the centrifuge chamber is designed as the rotor of an electric motor. However, this known centrifuge is not a flow-through centrifuge where there is the problem of twisting of the line.
SUMMARY OF THE INVENTION
An object of the present invention is to create a centrifuge capable of being free of rotating seals that will have low running noise and a drive that is largely maintenance-free while permitting operation at high rpms and relatively low driving power.
The present invention provides a centrifuge having:
a stand (
21
) on which a frame (
1
) is rotatably mounted,
a separation unit (
3
) rotatably mounted on the rotating frame (
1
),
a first drive train for transmitting the torque to the separation unit (
3
),
a line (
7
) for supplying and/or removing at least one fluid, leading from a stationary connection point (
6
) around the separation unit (
3
) and connected to the separation unit (
3
) on a side of the separation unit (
3
) facing away from the stationary connection point, and
a second drive train for transmitting a second torque to the rotating frame (
1
), with the separation unit (
3
) and the rotating frame (
1
) being driven so that the separation unit (
3
) rotates in the same direction as the rotating frame (
1
) but at twice the speed.
The centrifuge of the present invention is characterized in that the first and/or second drive train has coupling elements (
17
to
20
) arranged with a distance between them and designed so that the torques can be transmitted using magnetic forces.
The present invention also provides a centrifuge characterized in that the first and/or second drive train has at least one stator (
143
) with a first and/or second coil arrangement (
142
) and a mechanism (
145
/
136
) for magnetic coupling, designed so that the torques can be transmitted by magnetic forces.
The centrifuge according to the present invention has two drive trains, with the first drive train serving to transmit the torque to the centrifuge chamber and the second drive train serving to transmit the torque to the rotating frame. The centrifuge chamber and the rotating frame can be driven by a common motor or by separate motors.
The first and/or second drive train has coupling elements arranged with a spacing between them for transmitting the torque; said coupling elements are designed so that the torque can be transmitted by magnetic forces. Force is transmitted in a non-contact and wear-free manner. Lubrication is not necessary, which therefore also reduces the accumulation of dust and dirt. In addition, little noise is generated. It is also advantageous that the line for supplying and/or removing the fluid can be passed through the gap between coupling elements, thereby simplifying the spatial arrangement of drive elements. The coupling elements may be in one piece with the centrifuge chamber or the rotating frame. However, they may also be spatially separated from the centrifuge chamber and the rotating frame, with the torque being transmitted from the respective coupling element to the centrifuge chamber or the rotating frame by way of additional coupling elements which are magnetically engaged, or additional gear elements of a wide variety of designs. The magnets may be attached to the top or bottom side of the clutch disks. However, they may also be integrated into the clutch disks or they may be of one piece with the centrifuge chamber. For example, the gaps between the magnets may be filled with a casting compound to produce smooth surfaces.
It has been found in experiments that a relatively great torque can be transmitted in particular when the coupling elements have magnets arranged on a circumference such that the magnetic poles of adjacent magnets of a coupling element are arranged in opposition to one another. The magnets are preferably permanent magnets. In principle, however, electromagnets can also be used for transmission of torque.
The coupling elements may be designed in the manner of a clutch disk. In a preferred embodiment of the centrifuge, two coupling elements designed in the manner of a clutch disk mounted to rotate about a common axis may be provided in the first and/or second drive train(s), with the magnets being arranged in opposition to one another along the circumference on the top or bottom side of the coupling elements. Such an arrangement serves to transmit torques with the shafts of the drive train aligned.
It has surprisingly been found that a relatively high torque can be transmitted even when the clutch disks are mounted rotatably about two parallel axes, with the magnets being arranged in opposition to one another only along part of the circumference on the top or bottom side of the coupling elements. Such an arrangement serves to transmit torques when the shafts are not aligned.
However, the coupling elements may also be designed in the manner of a gearwheel. In a preferred embodiment, two coupling elements mounted rotatably about perpendicular axes are provided in the first and/or second drive train of the centrifuge. The coupling elements may be designed as bodies in the form of truncated cones with the magnets arranged on the conical faces, or the coupling elements may be designed as disk-shaped bodies, with the magnets arranged on the top or bottom side thereof.
In an especially preferred embodiment, the magnets have a rectangular cross section with one narrow side and one long side. The magnets preferably are arranged on the circular disk-shaped coupling elements in such a way that their longitudinal axes run radially. This arrangement allows an especially large torque to be transmitted at a low angle offset. The lateral spacing between the magnets of a coupling

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