The known bearing assembly comprises at least three bearing rollers, each of which is rotatably supported on a bearing journal, and which are arranged rotationally symmetrical and lying in one plane, and which guide and support a bearing race between them. The bearing journals are arranged on a carrier device that is in turn rotatably supported on a central axle aligned with the axis of rotation of the bearing race. The bearing race is driven by a drive apparatus in such a fashion that the carrier device and the bearing race rotate with different angular velocities relative to a stationary housing.
The centrifuge has a disposable separation chamber with a bearing race and a line attached in a fixed manner. The chamber is supported between the bearing rollers, whereby a free floating tube segment or line section is carried around by means of a keeper at half the angular velocity of the rotating separation chamber, so that any twisting around its longitudinal axis is prevented. In the centrifuge art the carrier device is also known as a rotor.
A centrifuge with a conventional bearing assembly for supporting the separation chamber is described, for example, in German patent application 42 20 232.9, assigned to the same assignee as the present invention. A similar bearing assembly is known from JP 56/76260A. In the latter bearing assembly, a hollow, cylindrical axle segment is guided between a total of six bearing rollers arranged one above the other in two planes, whereby in each plane three bearing rollers in the form of ball bearings are arranged in a rotationally symmetrical fashion. In connection with this, a separation chamber is arranged on the top end of the essentially vertical hollow axle segment, and a discharge line is connected to its bottom end. In this regard, a free floating segment of the line is guided within the rotor and runs at half the RPMs compared to the RPMs of the separation chamber, in order to prevent any twisting together of the tube segment or of the entire discharge line. The basic principle of guiding the free floating tube segment around a rotating separation chamber at half angular velocity is known from German Patent 32 42 541, also assigned to the same assignee as the present invention.
In the case of the known centrifuge from the Japanese reference, have a conventional bearing assembly, two bearings are provided arranged one above the other and are displacable in a radial direction, in order to thus make possible the removal of the axle segment and the separation chamber and discharge line connected to it. In the case of a bearing assembly, likewise known from the Japanese reference, in which a total of eight bearings are arranged in two planes, four bearings are arranged rotationally symmetrical to one another in each plane. At a total of two bearing locations, that is two sets of bearings arranged one above the other, the bearings are displacable in a radial direction in order to create an opening through which the axle segment, and with it the separation chamber and the discharge line, can be removed in a radial direction.
The bearing assembly known in the art is thus very difficult to handle during an exchange of the guided bearing race or axle segment or a separation chamber joined with it, which is particularly problematic when the bearing assembly is part of a centrifuge used in a hospital. Centrifuges with a conventional bearing assembly of this type are used in particular for the separation of cells in internal body fluids, such as blood in particular, whereby the separation chamber and the line fixedly connected to it are often configured as a disposable part made of plastic. In day-to-day hospital operations a number of centrifuge procedures for cell separation are carried out on one centrifuge, whereby each time--for reasons of incompatibility--the disposable separation chamber has to be exchanged. When such use is made of a centrifuge with a conventional bearing assembly, the bearing assembly known from the art leads to a significant loss of time.