Abstract:
A centrifuge for the purification of lubricating oil of an internal-combustion engine is provided which includes a housing with a removable cover, a housing-fixed shaft arranged in the housing and a centrifuge rotor which is rotatably mounted on the shaft and is replaceable. The shaft is hollow at least in its lower part and forms in its hollow inside a section of a lubricating oil supply canal, which canal is in flow connection with an inside of the centrifuge rotor mounted on the shaft over at least one orifice opening. The centrifuge also includes an adjustable valve plug arranged at the shaft and arranged to be held in an open position by the centrifuge rotor. The valve plug releases the orifice opening in the open position. The valve plug is also arranged to be transferred into a closing position and held in the closing position by a force created by at least one of a pressure of the lubricating oil and by a preloading component if the centrifuge rotor is missing. The valve plug plugs the orifice opening in the closing position.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention relates to a centrifuge for the purification of lubricating oil of an internal-combustion engine, with a housing with a removable cover, with a housing-fixed shaft arranged in the housing and with a centrifuge rotor, which is rotatably mounted on the shaft and is replaceable, whereby the shaft is hollow at least in its lower part and forms in its hollow inside a section of a lubricating oil supply canal, which is in flow connection with the inside of the centrifuge rotor mounted on the shaft over at least one orifice opening.  
         [0002]     Centrifuges of the type initially specified are usually used as partial flow filters beside a filter cartridge. Thereby usually only a partial oil volume stream flows over the centrifuge, which is approximately 10% of the entire oil flow, which flows through the filter cartridge. In order to keep flow resistances low, the lubricating oil supply canal to the centrifuge is usually designed with a large cross section. The throttling of the oil volume stream through the centrifuge takes place basically exclusively by recoil nozzles provided at the centrifuge rotor, which rotate the centrifuge rotor by means of the lubricating oil flowing through. If the centrifuge rotor is erroneously not assembled, which can inadvertently happen for example during careless work at a maintenance service, this throttling is omitted and a very large partial oil volume stream flows through the bypass flow path of the centrifuge. Thus this very large partial oil volume stream is removed from the oil circuit and is no longer available for the lubrication of the appropriate internal-combustion engine. The operational reliability of the appropriate internal-combustion engine is thereby seriously endangered because a sufficient lubrication is no longer ensured.  
         [0003]     It is therefore the task of the present invention to create a centrifuge of the type initially specified, with which it is ensured that even with the centrifuge rotor erroneously not assembled a sufficiently large oil volume stream is always available for the lubrication of the appropriate internal-combustion engine.  
       SUMMARY OF THE INVENTION  
       [0004]     The solution of this is achieved according to the invention with a centrifuge of the type initially specified, which is characterized by the fact, that a movable closing element is arranged in or on the shaft, that the closing element can be held in an open position by the centrifuge rotor arranged in the housing, in which the closing element releases the orifice opening, and that the closing element can be transferred into a closing position and can be held in this closing position by a force created by a pressure of the lubricating oil or by a preloading component if the centrifuge rotor is missing, in which the closing element blocks the orifice opening.  
         [0005]     It is achieved by the closing element in the centrifuge provided according to the invention, that the centrifuge releases the partial oil volume stream with the assembled centrifuge rotor and that the flow path for the lubricating oil is closed with the centrifuge rotor missing in the centrifuge. Thus no more lubricating oil can flow through the lateral branch of the oil circuit, in which the centrifuge is situated, with an erroneously missing centrifuge rotor, apart from small possible leakage amounts. Thus it is guaranteed that the entire lubricating oil amount is available for the lubrication of the appropriate internal-combustion engine. Filtering of the lubricating oil takes place further via the filter cartridge, which is usually present beside the centrifuge; only micro filtering through the centrifuge in the bypass flow is omitted. This missing micro filtering however does not pose an immediate danger of damage for the appropriate internal-combustion engine. Thus the operational reliability of the internal-combustion engine is ensured, even if the centrifuge rotor of the centrifuge is erroneously not assembled.  
         [0006]     Preferably a sleeve, which is movable in the longitudinal direction of the shaft, is arranged as a closing element in the hollow inside of the shaft or on the outer circumference of the shaft, whereby the orifice opening is a lateral opening from the hollow inside of the shaft outward. Opening and closing of the orifice opening then take place simply via axial shifting of the sleeve either away from the orifice opening or over the orifice opening. Thereby a particularly simple design is achieved, which requires only a low additional manufacturing expenditure compared to a conventional centrifuge.  
         [0007]     The invention suggests further the fact that a lower end piece of the shaft itself or a shaft pedestal supporting the shaft exhibits an increased outside diameter in relation to the remaining shaft and that the sleeve sitting outside on the shaft exhibits fitting to this a stepped interior and outside diameter with a larger diameter in its lower part and with a smaller diameter in its upper part. A sleeve arranged in such a way adapts itself to given technical conditions and requires no complex modifications or adaptations on the side of the shaft or a shaft pedestal supporting said shaft.  
         [0008]     Preferably it is provided that the shaft exhibits further a lateral opening from its hollow inside outward at the height of the larger inside diameter of the sleeve and that the sleeve is sealed in its lower end area at its interior diameter against the outer circumference of the shaft or the shaft pedestal by means of a slide seal. With this arrangement of the centrifuge a hydraulic adjustment of the sleeve in its closing direction is achieved with the pressure of the lubricating oil with a missing rotor.  
         [0009]     Alternatively at least one pressure spring can be arranged as a preloading component between the sleeve and a pedestal part of the housing. In this design of the centrifuge a mechanical adjustment of the sleeve is caused by the pressure spring in a closing direction.  
         [0010]     The rotor provides in each case the maintenance of the open position of the sleeve, if it is assembled in the centrifuge.  
         [0011]     In order to secure the sleeve against torsion and to ensure thereby that only the parts of the bearings supporting the centrifuge rotor turn relative to each other, it is intended that the sleeve exhibits arms running radially from the outside inward if designed as an outer sleeve and running radially from the inside outward if designed as an inner sleeve, which are situated in longitudinal slots of the lower end area of the shaft and which guide the sleeve secured against torsion. The arms provide the desired protection against torsion, they however do not obstruct the axial adjustment of the sleeve. If necessary the arms can also be designed so long that they exceed radially over the longitudinal slots of the shaft. These exceeding areas of the arms can be used for further functions, for example for the support of a spring as a preloading component.  
         [0012]     A further embodiment of the centrifuge provides that a lower pivot bearing of the centrifuge rotor be designed as a shaft-fixed friction bearing or as a rotor-fixed friction bearing. In the design as a rotor-fixed friction bearing, the friction bearing is replaced each time the centrifuge rotor is replaced, which is to be preferred if during the use time of a centrifuge rotor a noticeable wear of the friction bearing is to be expected. The alternative design as a shaft-fixed friction bearing retains the friction bearing also during an exchange of the centrifuge rotor. This design is then suitable if over the use time of the centrifuge altogether no too large of a wear of the friction bearing is expected.  
         [0013]     Alternatively, a lower pivot bearing of the centrifuge rotor can be designed as a shaft-fixed antifriction bearing. Such an antifriction bearing is a more complex and thus more expensive bearing, however it is particularly wear resistant and particularly friction-less. For this reason, such a more complex antifriction bearing is suitably designed only shaft-fixed, so that it can be further used after an exchange of the centrifuge rotor.  
         [0014]     Regarding the antifriction bearing, it is further provided that it is preferably arranged at the interior circumference of the sleeve and that it is together with this axially movable on the shaft. With the assembled rotor then the sleeve turns together with the rotor, whose lower end sits on the sleeve.  
         [0015]     The invention suggests further that a pedestal part of the housing supporting the shaft serves for the limitation of the shift path of the sleeve in its opening direction. For this design no special component is required for the limitation of the shift path of the sleeve in its opening direction, which keeps production costs low.  
         [0016]     The shaft exhibits a stop for the limitation of the shift path of the sleeve in its closing direction. Thereby it is ensured that the sleeve can move only within the shift path required for its function. The stop on the shaft can be designed as one part with the shaft or also as a component, which is subsequently assembled at the shaft, for example a retainer ring.  
         [0017]     In order to provide during low lubricating oil pressure the lubricating oil in the full amount for the lubrication of an appropriate internal-combustion engine, it is further provided that a minimum pressure valve be integrated into the shaft, which releases a supply of lubricating oil to the centrifuge rotor only when achieving a preset minimum lubricating oil pressure. As long as the lubricating oil pressure is below this minimum pressure, the entire lubricating oil amount flows through the main flow and thus to the lubrication fittings of the internal-combustion engine. A direct flow of the centrifuge does not yet take place in this status. A partial stream of the lubricating oil flows only then through the centrifuge if the preset minimum lubricating oil pressure is reached or exceeded.  
         [0018]     In order to protect the centrifuge and its centrifuge rotor from damage by a too high lubricating oil pressure, the invention suggests a design that with the centrifuge rotor inserted into the housing, the closing element is movable in a closing direction against a preloading force working in its opening direction by a force which is created by a lubricating oil pressure above a preset upper lubricating oil limiting pressure. Hereby it is achieved that with a reaching or exceeding of an upper lubricating oil limiting pressure, the closing element is transferred by the lubricating oil into its closing position, whereby a further inflow from lubricating oil to the centrifuge is prevented. Thus it is safely eliminated that too large and harmful lubricating oil pressures can occur within the area of the centrifuge.  
         [0019]     In a further embodiment of the design of the centrifuge described before, it is intended that at least one spring is provided between the bottom of the centrifuge rotor and the closing element, that the spring preloads the closing element with a force aiming in its opening direction and that the closing element is movable in the closing direction against the force of this spring which is created by the force of the upper lubricating oil limiting pressure. The generation of the preloading force by a spring is technically simple and reliable. Additionally a desired lubricating oil limiting pressure can be defined trouble-free by selection of suitable spring characteristic values, at which the closing element shuts off the oil flow through the centrifuge.  
         [0020]     Finally, the invention furthermore suggests that a guide sleeve, which is movable coaxially to the shaft, is arranged between the bottom of the centrifuge rotor and the spring, which is, if the centrifuge rotor is inserted, held in a lower final shift position by said centrifuge rotor and which assumes an upper final shift position, if the centrifuge rotor is not present, due to a lubricating oil pressure force or a spring force. With this design a technically simple solution is achieved to ensure a closing of the oil flow path to the centrifuge if the centrifuge rotor is missing and to cause at the same time the blocking of the oil flow path through the centrifuge during an excessively high lubricating oil pressure. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0021]     Following design examples of the invention are described using a drawing. The figures of the drawing show:  
         [0022]      FIG. 1   a - FIG. 7   a  illustrate in each case in cross-section different versions of a centrifuge in each case with the assembled centrifuge rotor,  
         [0023]      FIG. 1   b - FIG. 7   b  illustrate in each case in the same representation the centrifuges from  FIGS. 1   a - 7   a,  now however in each case without the centrifuge rotor,  
         [0024]      FIG. 7   c  illustrates the centrifuge from  FIGS. 7   a  and  7   b  in a status with a lubricating oil pressure above an upper pressure limiting value,  
         [0025]      FIG. 8  illustrates a centrifuge without centrifuge rotor in a further design, likewise in cross-section, and  
         [0026]      FIG. 9  illustrates a further centrifuge in the same representation, in a status without centrifuge rotor. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0027]      FIG. 1   a  of the drawing shows a first centrifuge  1 , which is a part of a purification setting for the lubricating oil of an internal-combustion engine. Besides the centrifuge  1  the purification setting comprises an oil filter with a filter cartridge here not represented, which is located beneath the centrifuge  1 . The filter cartridge is located in the main flow of the oil system; a partial flow of it, in the order of magnitude of approximately 10%, is usually branched off after the filtering by the filter cartridge and piped for the separation of finest dirt particles through the centrifuge  1 . The lubricating oil coming from the filter cartridge flows during the operation of the internal-combustion engine through the hollow inside  30  of a shaft  3 , which is arranged housing-fixed underneath a removable cover  11 . The cover  11  is a part of the centrifuge housing, which is in all other respects not represented. A centrifuge rotor  2  is rotatably mounted on the shaft  3  by means of two friction bearings  24 ,  25 ; the centrifuge rotor consists as usual of a center tube  23 , a globe  21  and a base  22 . The lubricating oil can flow over at least one orifice opening  32  out of the hollow inside  30  of the shaft  3  into the inside  20  of the centrifuge rotor  2 . From there the lubricating oil exits through here not visible recoil nozzles and thereby brings the rotor  2  into a fast rotation, which causes the dirt particle separation through centrifugal forces. The lubricating oil drains pressure-free from the housing area underneath the centrifuge rotor  2 , usually into the sump pan of the appropriate internal-combustion engine.  
         [0028]     As  FIG. 1   a  shows further, additionally a valve  33  is provided in the hollow inside  30  of the shaft  3 , which ensures as a minimum pressure valve that the lubricating oil arrives in the orifice opening or orifice openings  32  and therefore into the centrifuge rotor  2  from the hollow inside  30  of the shaft  3  only after reaching a certain minimum lubricating oil pressure. In the status shown in  FIG. 1   a,  the valve  33  is in its closed position, which means that a sufficiently high pressure is not yet present to open the valve  33 .  
         [0029]     On the lower end area  31  of the shaft  3 , which is located in a pedestal part  12  of the centrifuge, a closing element  4  is arranged outside. A stepped sleeve  40  forms the closing element  4 , which is movable in an axial direction of the shaft  3 . The sleeve  40  is sealed close to its lower end by a sealing ring  45  against the outer circumference of a shaft pedestal  13  containing the lower end of the shaft  3 . In the area of the larger diameter, thus within the area of the lower part of the sleeve  40 , a further opening  35  is provided in the shaft  3 , which connects the hollow inside  30  of the shaft  3  with the inside of the sleeve  40 .  
         [0030]     As mentioned, the sleeve  40  exhibits a stepped design, whereby it exhibits on the outside a step  41  pointing upward. On this step  41  the centrifuge rotor  2  with its here rotor-fixed lower friction bearing  24  mounts in its assembled status. The centrifuge rotor  2  for its part is held in its position by the cover  11 , which forms a part of the housing. Thus the centrifuge rotor  2  ensures that with assembled rotor  2  the sleeve  40  takes and retains its lower final shift position.  
         [0031]     If the appropriate internal-combustion engine operates, an appropriate oil pump creates a lubricating oil pressure. The valve  33  remains still closed at an oil pressure below a minimum pressure, e.g. 2 bars. Pressure acts upon the sleeve  4  however via an opening  35  in the shaft  3  on an annulus area, which is pointing downwards and is situated radially inside and below the external level  44 . The hydraulic force resulting from this shifts the sleeve  4  and the rotor  2  upward, until the cover  11  or a bearing application located in said cover prevents a further upward shift. As soon as the lubricating oil pressure exceeds the minimum pressure, the lubricating oil is able to shift the valve  33  into its open position. Thereby then the centrifuge  1  releases a bypass flow of the lubricating oil, the rotor  2  fills with lubricating oil and is at operating pressure. Now also an upward pointing annulus area of the sleeve  4 , which is larger than the first acted upon, downwards pointing annulus area of the sleeve  4 , is acted upon with pressure. Thus the sleeve  4  is pressed downwards again and the rotor  2  can turn freely and friction-less without an axial clamping or braking by the sleeve  4 .  
         [0032]      FIG. 1   b  shows the centrifuge  1  from  FIG. 1   a,  now however in a status with a missing centrifuge rotor  2 , which can erroneously occur for example during improper or careless maintenance. From  FIG. 1   b  it is evident that now the sleeve  40  forming the closing element  4  assumed a position shifted upward. The sleeve  40  gets into this position by a lubricating oil pressure of the lubricating oil present in the hollow inside  30  of the shaft  3 . This lubricating oil enters the inside of the sleeve  4  through the opening  35  and causes there an axial transverse force upward. This shift of the sleeve  40  leads to the fact that the top of the sleeve  40  covers and therefore closes the orifice openings  32 . In this position then the sleeve  40  rests with its upper end at a stop  36 , which is designed as one piece with the shaft  3 . This way it is ensured that no oil flow flows through the bypass flow path with a missing centrifuge rotor  2 . The lubricating oil is thus not removed from the internal-combustion engine. By automatically closing the bypass flow path through the centrifuge  1 , the entire lubricating oil amount of the internal-combustion engine is made available for its lubrication. At the most, small leakage amounts, which are not relevant, can still flow through the bypass flow through the centrifuge  1 . This closing of the bypass flow path through the centrifuge  1  also does not change, if the lubricating oil pressure continues to rise and the valve  33  reaches its open position. The sleeve  40  still ensures a closing of the orifice openings  32  even with an open valve  33 .  
         [0033]      FIG. 2   a  shows a centrifuge  1 , in which the axial shift of the valve blocks  4  also formed here by a sleeve  40  does not take place via the lubricating oil pressure but via the force of a spring  46 . In the status shown in  FIG. 2   a,  in which the centrifuge rotor  2  is located in the centrifuge  1 , the centrifuge rotor  2  with its rotor-fixed lower friction bearing  24  presses the axially movable sleeve  4  downwards against the force of the spring  46 .  
         [0034]     The sleeve  40  is now in a position, in which it unblocks the orifice openings  32 . As soon as the oil pressure is sufficiently large to open the minimum pressure valve  33 , the lubricating oil flows through the centrifuge with its centrifuge rotor  2  in a usual manner.  FIG. 2   b  shows the centrifuge from  FIG. 2   a  with a missing centrifuge rotor. Since now the centrifuge rotor  2  does not act upon the sleeve  40  anymore, the pressure spring  46  is now in a position to shift the sleeve  40  in the axial direction of the shaft  3  upward until it is laying against the stop  36  at the shaft  3 . In this upper final shift position of the sleeve  40 , this sleeve again closes the orifice openings  32 , so that a lubricating oil stream through the bypass flow path through the centrifuge  1  is prevented. The blocking of the bypass flow path is also here independent of the fact of whether the minimum pressure valve  33  is in its closed position, as shown in  FIG. 2   b , or in its open position with a somewhat higher lubricating oil pressure.  FIGS. 3   a  and  3   b  show a centrifuge  1 , which differs from the centrifuge  1  in accordance with  FIGS. 1   a  and  1   b  in the fact that it exhibits a shaft-fixed friction bearing  34  as a lower bearing for the centrifuge rotor  2 . The closing element  4  is also here again designed as a sleeve  40 , which is axially movable on the outer circumference of the lower part of the shaft  3 . In the status in accordance with  FIG. 3   a,  the rotor  2  assembled in the centrifuge  1  ensures that the sleeve  40  is pressed into its lower final shift position and held in this position. In this position of the sleeve  40 , the sleeve  40  does not cover the orifice openings  32  from the hollow inside  30  to the centrifuge rotor  2 . If the lubricating oil pressure reaches a minimum pressure during operation of the internal-combustion engine, the lubricating oil provides an opening of the minimum pressure valve  33  and the oil flow flows in the desired way as bypass flow partially through the centrifuge rotor  2 .  
         [0035]     In  FIG. 3   b  the status of the centrifuge from  FIG. 3   a  is represented with a missing centrifuge rotor. Here now the lubricating oil pressure ensures during operation of the internal-combustion engine that through the opening  35  an oil pressure acts upon the sleeve  40  from below upward seen in the axial direction. This force caused by the oil pressure shifts the sleeve  40  upward against the stop  36  designed at the shaft  3 . The sleeve  40  covers the orifice openings  32  in this upper final shift position, so that the bypass flow for the lubricating oil through the centrifuge  1  is blocked. This blocked status is maintained, independently of whether the minimum pressure valve  33  is in its open position or in its closed position. At the same time the sleeve  40  forms the shaft-fixed lower friction bearing for the rotatable support of the centrifuge rotor  2  in this design of the centrifuge  1 .  
         [0036]      FIGS. 4   a  and  4   b  of the drawing show a design of the centrifuge  1 , in which it is substantial that the lower bearing of the centrifuge rotor  2  is formed by a shaft-fixed antifriction bearing  34 ′. This antifriction bearing  34 ′ is located in the interior circumference of the closing element  4 , which is also here designed as a sleeve  40 , and is movable on the shaft  3  together with the sleeve  40  in the axial direction of the shaft  3 . The shifting of the sleeve  40  is here again caused by the lubricating oil pressure, which disseminates through the opening  35  on the inside of the sleeve  40 .  
         [0037]     In the status in accordance with  FIG. 4   a,  thus with assembled centrifuge rotor  2 , said centrifuge rotor ensures that the sleeve  40  assumes its lower final shift position. The sleeve  40  rotates with the operating centrifuge  1  together with the centrifuge rotor  2  around the shaft  3  with the antifriction bearing  34 ′ in-between. Also here the minimum pressure valve  33  is additionally provided, which still assumes in the status in accordance with  FIG. 4  its closed position. The valve  33  changes into its open position when reaching a minimum lubricating oil pressure and a partial oil flow can flow through the centrifuge  1 .  
         [0038]      FIG. 4   b  shows again the status of the centrifuge  1  with a missing centrifuge rotor. When an oil pressure is present in the hollow inside  30  of the shaft  3 , this oil pressure disseminates through the opening  35  into the inside of the sleeve  40 . There the oil pressure causes a force on the sleeve  40 , directed upward in the axial direction of the shaft  3 , whereby said sleeve is shifted together with the antifriction bearing  34 ′ on the lower part of the shaft  3  upward to a stop  36  provided at the shaft  3 . In this upper final shift position the sleeve  40  again covers the orifice openings  32 , so that even with an open minimum pressure valve  33 , no oil flow from the hollow inside  30  of the shaft  3  can reach the inside of the cover  3 , thus into a pressure-free area. Thus it is also ensured with this design of the centrifuge  1  that with a missing centrifuge rotor, the bypass flow through the centrifuge  1  is blocked and therefore the entire lubricating oil amount is made available for the internal-combustion engine.  
         [0039]      FIGS. 5   a  and  5   b  of the drawing show a design of the centrifuge  1 , for which it is typical that the lower bearing of the centrifuge rotor  2  is a shaft-fixed friction bearing  34 . The shifting of the sleeve  40 , which also forms here the closing element  4 , takes place in this design by means of a pressure spring  46 , which is arranged between the sleeve  40  and a pedestal part  12  of the centrifuge  1 .  
         [0040]     With the centrifuge rotor  2  arranged in the centrifuge  1  it ensures with its lower end that the sleeve  40  is held downwards against the pedestal part  12  against the force of the spring  46 . The top of the sleeve  40  in this position opens the orifice openings  32  in the shaft  3 . After reaching a minimum lubricating oil pressure the valve  33  also provided here moves into its open position and opens the flow path through the centrifuge  1 .  
         [0041]     If the centrifuge rotor  2  is missing, as is represented in  FIG. 5   b,  the pressure spring  46  is able to lift the sleeve  4  off the pedestal part  12  upward until the sleeve  40  pushes with its upper front end against a stop  36 , which is designed here as a retainer ring located on the shaft  3 . In this position the sleeve  40  blocks the orifice openings  32  and therefore shuts off the bypass flow path for the lubricating oil. This blockage of the bypass flow is also maintained if the minimum pressure valve  33  changes into the open position.  
         [0042]      FIGS. 6   a  and  6   b  of the drawing show a design of the centrifuge  1 , for which it is typical that the lower bearing of the centrifuge rotor  2  is a shaft-fixed antifriction bearing  34 ′ and that the shifting of the sleeve  40  forming the closing element  4  in a closing direction can be caused by the force of a spring  46 . In the status in accordance with  FIG. 6   a  with assembled centrifuge rotor  2 , said centrifuge rotor presses the sleeve  40  by compressing the pressure spring  46  downwards into its lower final shift position, in which the sleeve  40  rests with its lower front end upon the pedestal part  12 . The top of the sleeve  40  now opens the orifice openings  32 . With open minimum pressure valve  33 , the bypass flow path for the lubricating oil for the centrifuge  1  is opened.  
         [0043]      FIG. 6   b  shows the status of the centrifuge  1  from  FIG. 6   a  now again with a missing centrifuge rotor. In this status the pressure spring  46  lifts the sleeve  40  upward up to a stop  36  on the shaft  3 . In this position the sleeve  40  again blocks the orifice openings  32 , independently of whether the minimum pressure valve  33  is in the open position or in the closed position.  
         [0044]     The shaft-fixed antifriction bearing  34 ′ is located here again in the interior circumference of the sleeve  40  and shifts together with said sleeve in the axial direction of the shaft  3 .  
         [0045]      FIGS. 7   a ,  7   b  and  7   c  of the drawing show a design of the centrifuge  1 , which exhibits in contrast to the designs previously described still another additional function, which is described as follows.  
         [0046]      FIG. 7   a  shows first the centrifuge  1  with an assembled centrifuge rotor  2 , which is also here mounted rotatable on the central housing-fixed shaft  3 , here by means of rotor-fixed friction bearings  24 . The shaft  3  is also here designed with a hollow inside  30 . A closing element  4  in the form of an axially movable sleeve  40  is arranged in the lower part of the hollow inside  30  of the shaft  3 . The lower end area of the shaft  3  is equipped with longitudinal slots  37 . Through these longitudinal slots  37  extend one-pieced arms  47  in a radial direction outward from the sleeve  40 . The shaft  3  is held with its lower end in a pedestal part  12  of the centrifuge  1 , here by bolting.  
         [0047]     A guide sleeve  50  is furthermore guided concentrically to the shaft  3  and axially movable in the upper central area of the pedestal part  12 . This sleeve  50  is closed on its upper side. A helical compression spring  51  is supported at the bottom of this sleeve  50 , which is closed on top, and at the top of the arms  47 , which preloads the guide sleeve  50  and the arms  47  of the sleeve  40  with a force, which acts downwards on the sleeve  40  and upwards on the sleeve  50 .  
         [0048]     In the status with an assembled centrifuge rotor  2 , shown in  FIG. 7   a , said centrifuge rotor presses with its lower friction bearing  24  on the top of the guide sleeve  50 . Thereby the spring  51  is compressed and it presses in return, over the arms  47 , the sleeve  40  downwards to its lower final shift position. The upper end area of the sleeve  40  is then situated in a position, in which it opens the orifice openings  32  from the hollow inside  30  of the shaft  3  into the inside of the centrifuge rotor  2 .  
         [0049]     As in the previously described design examples, a minimum pressure valve  33  is also provided in the area of the orifice opening  32 , which is still in a closed position in the representation in accordance with  FIG. 7   a . As soon as a minimum lubricating oil pressure is reached in the hollow inside  30 , the minimum pressure valve  33  moves into the open position and opens the flow path for the lubricating oil through the centrifuge  1  and its centrifuge rotor  2 .  
         [0050]      FIG. 7   b  shows the centrifuge  1  from  FIG. 7   a  now in a status with a missing centrifuge rotor. Since now the centrifuge rotor  2  does not act upon the guide sleeve  50  anymore, a lubricating oil pressure present in the hollow inside  30  of the shaft  3  ensures now that the sleeve  40  is shifted together with the spring  51  and the guide sleeve  50  upward, until the sleeve  40  reaches its upper final shift position, as is shown in  FIG. 7   b . In this position the sleeve  40  blocks the orifice openings  32  with its top and prevents this way oil flow through the centrifuge  1 . The minimum pressure valve  33  is shifted upward into its open position by the present lubricating oil pressure and by the sleeve  40 ; the sleeve  40  however blocks the orifice openings  32 .  
         [0051]      FIG. 7   c  shows now the previously mentioned additional function, which is provided with the centrifuge  1  in accordance with  FIGS. 7   a - 7   c . This additional function consists of the fact that with the centrifuge rotor  2  assembled in the centrifuge  1 , the closing element  4  in the form of the movable sleeve  40  blocks the orifice openings  32 , if a preset maximum lubricating oil pressure is reached or exceeded. In this case of a too high lubricating oil pressure, the hydraulic force of the lubricating oil acting upon the sleeve  4  ensures that the sleeve  40  is shifted upward against the force of the spring  51  into an upper final shift position, in which the sleeve  40  blocks the orifice openings  32 . The movable guide sleeve  50  with this process retains its position unchanged, since it is inevitably localized in this position by the centrifuge rotor  2 . The pressure spring  51  is compressed upward during the shifting of the sleeve  40 . The upper limiting pressure, at which the sleeve  40  blocks the orifice openings  32 , can be defined by the selection of the spring strength.  
         [0052]     If the lubricating oil pressure drops again below the upper pressure limiting value, the force of the spring  51  exceeds the hydraulic force caused by the lubricating oil and working on the sleeve  40 , so that the sleeve  40  is then moved again downwards and opens the orifice openings  32 .  
         [0053]      FIG. 8  shows an example of a centrifuge  1 , in which the closing element  4  is again designed as an axially movable sleeve  40  on the inside  30  of the shaft  3 . The sleeve  40  also exhibits in its lower area several radially outward protruding arms  47 , which are guided in longitudinal slots  37  of the shaft  3 . The shaft  3  is here held again in the pedestal part  12 . An intermediate sleeve  13 , which surrounds for its part the lower end of the shaft  3 , is guided adjustably in the axial direction of the shaft  3 .  
         [0054]     At the bottom of the arms  47  a helical compression spring  46  supports itself, whose lower end is supported at a fixed area of the pedestal part  12 , which is represented here only in a section. If the centrifuge rotor is missing, as represented in  FIG. 8 , the helical compression spring  46  is able to shift, via the arms  47 , the sleeve  40  upward together with the intermediate sleeve  13  to their upper final shift position. In this final shift position the sleeve  40  blocks the orifice openings  32 , so that an oil flow through the centrifuge  1  is prevented if the centrifuge rotor is missing.  
         [0055]     Also here the minimum pressure valve  33  is shifted at the same time into its open position; this however has no effect, since the orifice openings  32  are blocked by the sleeve  40 .  
         [0056]     If a centrifuge rotor is assembled into the centrifuge  1  in accordance with  FIG. 8 , the centrifuge rotor presses the intermediate sleeve  13  downwards with its lower end, which is the reason why said sleeve is axially movable in the pedestal part  12  and on the outer circumference of the shaft  3  in a suitable guide. The lower end of the intermediate sleeve  13  presses on the arms  47  and thus moves the sleeve  40  downwards by compression of the pressure spring  46 . In this status the sleeve  40  then opens the orifice openings  32  again. After reaching a minimum lubricating oil pressure and the opening of the minimum pressure valve  33  caused thereby, the oil flow path through the centrifuge is then free.  
         [0057]      FIG. 9  of the drawing finally shows a design example of the centrifuge  1 , which provides the same functions as the centrifuge  1  in accordance with  FIGS. 7   a  to  7   c . The representation of  FIG. 9  corresponds thereby to the representation of  FIG. 7   b , thus shows the centrifuge  1  without an assembled centrifuge rotor.  
         [0058]     The shaft  3  for the rotatable support of the centrifuge rotor is also here again firmly held in the pedestal part  12 . A sleeve  40 , which is axially movable in the hollow inside  30  of the lower part of the shaft  3 , serves here again as a closing element  4 . Also here the lower end area of the shaft  3  exhibits longitudinal slots  37 , through which arms  47  of the sleeve  40  extend outward. A guide sleeve  50  is mounted on the outer circumference of the shaft  3  axially movable in its lower part, which is closed on its upper side and rests there tightly against the outer circumference of the shaft  3 . Between the sleeve  50  and the top of the arms  47  of the sleeve  40  a helical compression spring  51  is arranged, which acts upon the guide sleeve  50  with a force pointing upward and upon the sleeve  40  with a force pointing downward. At the bottom of the arms  47  a second, weaker helical compression spring  46  supports itself, which rests with its other end against the pedestal part  12  of the centrifuge  1 . In the status without a centrifuge rotor, shown in  FIG. 9 , the lower helical compression spring  46  presses the sleeve  4  as well as thereby together the spring  51  and the guide sleeve  50  upward, until the sleeve  40  reaches its upper final shift position, in which it, as represented in  FIG. 9 , blocks the orifice openings  32 . The minimum pressure valve  33  also provided here is then in its open position, however the blocking of the orifice openings  32  takes place independently of that via the sleeve  40  as the closing element  4 .  
         [0059]     If the centrifuge rotor is assembled into the centrifuge  1  in accordance with  FIG. 9 , the lower end of the rotor presses the guide sleeve  50  downwards. The stronger helical compression spring  51  thereby shifts the sleeve  40  over the arms  47  likewise downwards, whereby the weaker helical compression spring  46  is compressed. In this status the sleeve  40  opens the orifice openings  32 . An oil flow through the centrifuge  1  is then opened, as soon as a minimum lubricating oil pressure is present to open the minimum pressure valve  33 . If the lubricating oil pressure in the hollow inside  30  of the shaft  3  rises above a preset upper pressure limiting value with assembled rotor, a hydraulic force acting upon the sleeve  40  results, which is directed upward. Since with assembled centrifuge rotor the guide sleeve  50  is defined in its lower position, the pressure spring  51  is compressed upward with the shift of the sleeve  40  by the hydraulic force of the lubricating oil if the lubricating oil pressure is accordingly high. If the sleeve  40  reaches its upper position, it blocks the orifice openings  32  and thus prevents the creation of a harmful excess pressure inside the centrifuge  1 . If the lubricating oil pressure drops again below the preset upper limiting value, the coil spring  51  is able to shift the sleeve  40  again downwards against the now diminishing pressure of the lubricating oil and against the hydraulic force caused thereby. Thus the oil flow through the orifice openings  32  is opened again.  
         [0060]     As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.