Abstract:
A separator comprising a centrifugal drum driven by a centric spindle mounted with at least one axial bearing on a machine frame and a barrier chamber for hydrohermetic sealing an oil layer inside the barrier chamber. The barrier chamber has an immersion plate therein and is disposed in the axial region between the at least one bearing and the centrifugal drum around the spindle.

Description:
PRIORITY INFORMATION 
   This application is a continuation of International Patent Application PCT/EP03/02752, filed on Mar. 17, 2003, which claims priority to German Patent Application DE10212808.1, filed on Mar. 22, 2002 both of which are included herein by reference in their entirety. 

   BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   This invention relates to a separator in which the vessel with the centrifugal drum forms the hood region of the centrifuge. The centrifugal drum with its vertical rotational axis is set on a spindle, which is supported on a machine frame, for example with an upper bearing and a lower bearing axially offset thereto. The region of the bearings is to be construed as belonging to the gearing region of the separator. A problem is posed by the sealing between the gearing region and the hood region, because the spindle extends continuously from the centrifugal drum in the hood region into the gearing region. In the prior art, the required sealing on the spindle is implemented for example with contact seals. 
   2. Description of Prior Art 
   DE 1 285 412 shows an ultracentrifuge whose rotor runs on a vacuum chamber. Two plain bearings serve for support, accommodating the radial forces of the structure, a disk is located between the plain bearings as a thrust bearing. Lubricating oil is delivered under pressure via a line. The support is formed by the totality of the housing with the spindle, the disk, and the upper bearing point. 
   According to DE 1 286 785, a stuffing box system in a vacuum centrifuge is supplied with lubricating oil from an overhead reservoir and, via a chamber, conveyed by gravity in the reservoir and line. 
   U.S. Pat. No. 3,765,688 shows a fluid seal for a high-speed shaft of a centrifuge. 
   DE 825 575 shows a spindle support with two roller bearings, which are supplied with lubricating oil from a sump with a self-priming system. 
   In WO 9857752 and WO 9857751, lubricating oil is admitted below the bearing of the spindle. This design does not include a separation between drive system, in particular between the bearing compartment and the drum compartment. 
   SUMMARY OF THE INVENTION 
   The goal of the invention is to implement, in a fashion, simple in terms of design, sealing that is reliable and not subject to wear problems between the gearing region and the hood region. 
   The invention achieves this goal through a separator having a centrifugal drum arranged in a vessel whose rotational axis is oriented vertically and which is drivable by a central spindle that is supported on a machine frame with two bearings, wherein a barrier chamber for hydrohermetic sealing by an oil layer is fashioned around the spindle, at least segmentally, in the axial region between the upper bearing and below the centrifugal drum, an immersion plate is arranged in the barrier chamber. The barrier chamber has a connection to a passage in which the two bearings are axially arranged so that the oil is led on out of the barrier chamber to the bearings for lubrication. 
   The oil delivered to the bearings—for external lubrication—is preferably used as a barrier medium, which oil is initially led through the barrier chamber and there forms a sealing oil layer before it is led out of the barrier chamber to the bearings for lubrication. An additional barrier medium such as water is not necessary. The oil layer that forms in the barrier chamber when the centrifugal drum revolves takes care of reliable sealing in a manner simple in terms of design, without any wear problems. Lubrication of the roller bearing is effected at the same time. 
   An immersion plate dipping into the oil layer is arranged in the barrier chamber. This immersion plate is preferably equipped with fins on its axial walls. This feature is attractive in particular if the immersion plate rotates along with the spindle in operation and the outer wall or end wall and the two axial walls of the barrier chamber are fashioned so as to be stationary in operation. This design can be implemented with particularly little design effort. 
   Alternatively, it is also conceivable that the outer wall and the two axial walls of the barrier chamber are fashioned so as to co-rotate with the spindle in operation and the immersion plate is fashioned so as to remain stationary. In this case it is expedient if the axial walls of the barrier chamber are equipped with fins. The immersion plate can then be molded onto a cylindrical machine frame part enclosing the spindle and remaining stationary in operation, and the barrier chamber can be connected to the spindle in the region of its lower axial wall. This embodiment can also be implemented in simple fashion and offers all the other aforementioned advantages. 
   The barrier chamber especially has a connection to a passage in which the bearings are arranged, so that the bearings (in particular roller bearings) are lubricated in extremely simple fashion via the passage. Two of the bearings—in particular a collar and a step bearing—are arranged axially offset relative to one another in the passage, so that oil is jointly fed to the two bearings and the barrier chamber via a single system in extremely simple fashion. 
   Further advantageous developments of the invention can be inferred from the remaining dependent claims. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In what follows, the invention is described in greater detail on the basis of an exemplary embodiment with reference to the drawings, in which: 
       FIG. 1  is a sectional view of a separator in simplified schematic depiction; 
       FIG. 2  is a detail of the separator of  FIG. 1 ; 
       FIG. 3  is a detail of a second separator in simplified schematic depiction; and 
       FIG. 4  is a detail of a third separator in simplified schematic depiction. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a separator  2  with a vessel  4 , which is arranged on a machine frame  6 . In vessel  4 , separator  2  has a centrifugal drum  8  with rotational axis oriented perpendicularly to the floor. Vessel  4  with centrifugal drum  8  forms the hood region of the centrifuge. 
   The centrifugal drum is set on a spindle  10 , which is supported on machine frame  6  in two bearings  12 ,  14  axially offset relative to one another and drivable with a (flat) drive belt  15 , which passes around spindle  10  on the one hand and a driven part of a drive unit  16  on the other hand. The region of the two bearings  12 ,  14  is associated with the gearing region of the separator. Spindle  10 , in its upper region, engages into centrifugal drum  8  with a portion narrowing in wedge fashion. 
   Because spindle  10  extends from the hood region into the gearing region, reliable sealing of simple design is necessary between these regions. This is effected here by hydrohermetic sealing. 
   This sealing is effected in that, above upper bearing  12  and below centrifugal drum  8 , spindle  10  is enclosed by an annular barrier chamber  18  with a cylindrical outer wall  18   a , a disklike upper axial wall  18   b , and a disklike lower axial wall  18   c . Arranged in barrier chamber  18  is a circular disk-shaped immersion plate  20 , which is attached to the outer circumference of spindle  10  and has an outer radius smaller than the radius on the inner side of end wall or outer wall  18   a  at the larger circumference of barrier chamber  18 . In this way, fluid, for example a lubricant, is enabled to flow around immersion plate  20  in the barrier chamber. The immersion plate is equipped with fins  34  running, for example, radially on its two axial walls. 
   Because immersion plate  20  in  FIG. 1 ,  FIG. 2 , and  FIG. 3  is connected to spindle  10 , it rotates along with spindle  10  when the separator is in operation. Walls  18   a, b , and  18   c , on the other hand, are connected to or molded onto machine frame  6 , so that they are stationary when the centrifuge is in operation. 
   Spindle  10 , which is equipped with a central hole  22 , has its lower end, which faces away from centrifugal drum  8  and is reduced in diameter—here stepped twice—dipping into an oil sump  24  in a reservoir  26 . Hole  22  extends centrally axially through spindle  10  as far as radial distributor ducts  28 ,  30 , which open radially into barrier chamber  18  in the region above immersion plate  20 . 
   At its lower end, barrier chamber  18  opens inwardly toward spindle  10  into a passage—here in the shape of an annular duct  32  around spindle  10 —which extends from barrier chamber  18  to a return flow region  33  into reservoir  26  for oil sump  24  and in which the two bearings, axially offset relative to one another, are so arranged that they are lubricated by the oil in the passage. 
   The function of this arrangement according to  FIG. 1  is as follows. 
   When centrifugal drum  8  revolves, oil from oil sump  24  is conveyed through hole  22  into distributor ducts  28 ,  30  and from there into barrier chamber  18 . There, by the rotation of spindle  10  and by fins  34  on immersion plate  20 , which is rotating along with spindle  10 , it is accelerated into the radially outer region of barrier chamber  18  and there forms an oil layer with a radius r—as viewed inwardly from outer wall  18   a —into which the outer rim of immersion plate  20  dips. 
   From barrier chamber  18 , the overflowing oil flows into annular duct  32 , where it lubricates bearings  12  and  14  before flowing back into return flow region  33  of reservoir  26  and from there into oil sump  24 . 
   Thus the lubrication required for bearings  12 ,  14  is advantageously also utilized for hydrohermetic sealing on the spindle above bearing  12 . 
   A first alternative embodiment is shown in  FIG. 3 . Here the oil is led radially from outside into the barrier chamber through a hole  35  in outer wall  18   a  of barrier chamber  18 , for example by a pump apparatus. In other respects the design and function correspond to the exemplary embodiment of  FIG. 1 . 
   Alternatively—not depicted here—it is also conceivable to deliver the oil to hole  35  by an external oiling system and recycle the draining oil into a reservoir of the oiling system. 
   A second alternative embodiment is shown in  FIG. 4 . Here the oil is led not through spindle  10  but radially from outside into a short annular duct  36  above the barrier chamber around spindle  10 , which annular duct opens below into the radially inner region of barrier chamber  18 , which is equipped with fins  38 , running radially for example, in the region of its axial walls  18   b, c . Immersion plate  20  is here fashioned so as to be stationary and is molded onto a cylindrical machine frame part  40  that encloses the spindle but is stationary in operation. Barrier chamber  18 , in contrast, is connected to spindle  10  in the region of its lower axial wall  18   c , so that the two axial walls  18   b  and  c  and outer wall  18   b  co-rotate with spindle  10  in operation. Passages  42  in lower axial wall  18   c  of barrier chamber  18  permit the penetration of oil into annular duct  32 . At its outer circumference, barrier chamber  18  is enclosed by an annular compartment  44  through which oil can likewise flow into annular duct  32  with bearings  12  and  14 . 
   When centrifugal drum  8  revolves, oil from oil sump  24  is conveyed into barrier chamber  18 . There, by the rotation of the barrier chamber walls  18   a–c  and of fins  38  on the axial walls, it is accelerated into the radially outer region of barrier chamber  18  and there once again forms an annular oil layer with a radius “r” into which the outer rim of immersion plate  20 ′ dips. In this way, hydrohermetic sealing is once again implemented.