Abstract:
A centrifugal separator ( 10 ) for an engine includes a rotor ( 30 ) mounted within a housing ( 12, 14 ) for rotation on hollow spindle ( 42 ) to the end of which oil is supplied at high pressure to enter the rotor. To prevent the rotor from flying from the base and oil spraying if the cover ( 14 ) is removed without shutting off the oil supply via optional valve ( 80 ), a rotor restraint ( 90 ) is provided in the form of a ring ( 91 ) which surrounds and overlies a flange of the rotor. The ring may be complete or discontinuous and may also include an interlock to prevent attachment of the cover and/or supply of oil if the ring is not in place.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]    This application is a continuation of international patent application no. PCT/GB00/02023, filed May 25, 2000 designating the United States of America, the entire disclosure of which is incorporated herein by reference. Priority is claimed based on United Kingdom patent application no. GB 9914610.9, filed Jun. 23, 1999. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    This invention relates to centrifugal separators for separating solid contaminants from a liquid supplied thereto at elevated pressure and in particular relates to operating and maintaining such a centrifugal separator with respect to a machine in which said liquid is contained and flows.  
           [0003]    United Kingdom patent specification no. GB-A-2311239 describes a self-powered centrifugal separator, that is, one having a separation rotor which is rotated by the pressure of the liquid supplied to and cleaned thereby, having such a separator rotor contained in a housing defined by separable base and cover parts and discusses the potential problems of inadvertent removal of the cover from the base. The patent specification proposes the inclusion of valve means to divert the elevated pressure supply within the separator to permit such removal without interrupting the supply per se and, also, the provision of a mechanical interlock between a manually operated handle of the valve means and the housing cover which impedes said removal until the valve means is operated to divert the liquid supply from the separation rotor.  
           [0004]    As discussed therein, it is a feature of that and other designs of centrifugal separator that the liquid is supplied at elevated pressure to the separation rotor through an axle on which the rotor is mounted for rotation and which axle is disposed between the base and usually also the cover.  
           [0005]    The supply is often arranged to exert an axial force on the rotor to overcome gravity so that the cover not only defines a housing to contain liquid discharged from the rotor but also serves to constrain/retain the rotor axially when supplied with liquid and subjected to such axial force.  
           [0006]    It has been found that inadvertent removal of the cover without shutting off the elevated pressure supply to the rotor risks having the rotor itself being lifted from the base by the applied pressure and detached, and indeed launched as a projectile, as well as uncontrolled discharge of the liquid.  
           [0007]    Whereas the construction of centrifugal separator described in the aforementioned patent specification, that is, the separator rotor being mounted on an elongate stationary spindle fixed to the base, makes it possible for the supply pressure per se to lift the rotor completely clear of the spindle the instant that the cover is separated from the base, it will be appreciated that there are many other configurations of axle means for mounting such separation rotor between base and cover which may be more susceptible to such detachment of the rotor by supply pressure. Particularly susceptible is the type of rotor mounting arrangement in which the rotor is located and mounted with respect to each of the base and cover parts by relatively short stub-axle engagement and in which, if the cover is inadvertently removed, there is little to keep the rotor, particularly if spinning, from instantaneously detaching completely from the base.  
           [0008]    In some centrifugal separator designs, it may not be possible to provide a valve arrangement in the separator itself to interrupt the liquid supply to the rotor or rotor mounting means, not only increasing the risk of inadvertent removal of the cover but also making it more difficult to provide a physical interlock against cover removal. Furthermore, even when such a valve for interrupting the liquid supply to the rotor mounting means is provided within the separator, it may be inappropriate to arrange for a manual interlock which prevents removal of the cover, or impracticable because of the necessity to manually overcome the interlock each time the valve means is operated, and even when it is intended to remove the cover.  
         SUMMARY OF THE INVENTION  
         [0009]    It is an object of the present invention to provide an improved centrifugal separator with an arrangement for hindering unintentional ejection of the separator rotor.  
           [0010]    Another object of the invention is to provide a centrifugal separator with a simple and unobtrusive means of guarding against inadvertent cover removal.  
           [0011]    According to the present invention a centrifugal separator of solid contaminants from a liquid supplied thereto at elevated pressure comprises a housing having a base part and a cover part releasably secured with respect to each other and containing a separation rotor, the separation rotor being contained between the base and cover being mounted with respect thereto by spindle means, rotatable about an axis extending between the base and cover and displaceable along the axis limited by said base and cover, the centrifugal separator being characterized by rotor restraining means comprising a restraining surface forming part of, or carried by, the rotor extending radially and circumferentially of the rotor and facing away from the base, and abutment means carried by the base, having an abutment surface overlying the restraining surface at or beyond said limit of axial displacement of the rotor from the base permitted by the cover, operable to prevent further axial displacement of the rotor away from the base in the absence of limitation by the cover. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]    The invention will be described in further detail hereinafter with reference to illustrative preferred embodiments shown in the accompanying drawings in which:  
         [0013]    [0013]FIG. 1( a ) is a sectional elevation through a centrifugal separator in accordance with the present invention including a first embodiment of rotor restraining means having an abutment constructed as a flanged, circumferentially complete tubular body;  
         [0014]    [0014]FIG. 1( b ) is a partly cut-away, perspective view of the rotor restraining means of FIG. 1( a ), and  
         [0015]    [0015]FIG. 2 is a perspective view of the abutment of a second embodiment of rotor retraining means, in which the abutment is constructed in the form of flanged, circumferentially discontinuous fingers. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0016]    Referring to FIG. 1( a ), a centrifugal separator  10  comprises a base part  12  and a cover part  14  releasably secured with respect thereto to define a housing enclosure for a separation rotor  16 .  
         [0017]    The base part  12  is a machined casting having a mounting region  18 , liquid supply duct  20 , of relatively small cross-section, and a drain duct  22 , of relatively large cross-section, which leads to an upwardly facing collection region  24 .  
         [0018]    The cover part  14  encloses the rotor and collection region, being supported on the base  12  by way of outwardly projecting sealing flanges  14   1  and  12   1  on each respectively and between which is disposed a sealing element  26 . The sealing flanges are tapered convergingly in a radial direction and surrounded by a correspondingly profiled, circumferentially discontinuous clamping ring arrangement  28  which is operable, by radial contraction, to provide significant axial force between the flanges and on the sealing element to secure the cover part with respect to the base part.  
         [0019]    The separation rotor  16  comprises an annular container  30  of two axially conjoined parts, somewhat similar to the housing. A first component part  32  is disposed adjacent the base  12  and a second component part  34  is disposed adjacent the cover, each being of generally tubular form closed at one end and open at the other, complementing and joined to each other at a peripheral seam  36  which defines a flange extending radially outwardly of, and circumferentially about, the peripheral wall of the rotor between its ends, the flange having an upper surface  36   1  discussed below.  
         [0020]    The separation rotor is substantially symmetrical about a longitudinal axis  38  thereof for rotation thereabout, and to this end, the separator  10  also includes, on said axis, rotor mounting spindle means  40  comprising a spindle  42  extending through, and fixed with respect to, the container  30 . The spindle extends axially beyond the ends the container in the form of relatively short, effective stub axles, to effect at the lower end a first stub axle  44  and at the upper end a second stub axle  46 . The first stub axle part locates in a bearing  48  in the base  12  and the second stub axle locates in a bearing  50  in the cover  14 , defining first stub axle means and second stub axle means respectively. The lower end of the spindle is stepped at  52  and with the bearing  48  effects a thrust bearing which inter alia limits axial displacement of the rotor in a downward direction towards the base. The upper end of the spindle carries a thrust bearing bush  54  which is able to bear against the cover and inter alia limit axial displacement of the rotor in an upward direction away from the base, that is, defines a rotor displacement limit. In normal circumstances there is a small amount of axial displacement, or end float, permitted.  
         [0021]    The bearing  48  is disposed in a recess  56  in the base  12  which forms a continuation of the supply duct  20 , and the spindle  42  has a supply feed passage  60 , extending part way therealong from an open lower end  62  in the recess  56 , which forms a further continuation of the supply duct  20 . The passage terminates at a cross-drilling  64  which communicates with an annular feed chamber  66  of the rotor leading into the container space  68 . A separate annular chamber  70  directs liquid from the container space to a plurality of discharge apertures  72  which in turn communicate with the discharge region  24  of the housing.  
         [0022]    As an alternative to the more common arrangement of using reaction to emission of the liquid from the discharge apertures via flow constricting nozzles to drive the rotor in rotation, the rotor  16  may be driven by an external turbine arrangement  74  comprising an array of vanes or buckets  76 , carried by the spindle  42 , and a fixed jet  78  disposed to direct liquid tapped from the supply ducts  20 , or from some other source, against the vanes.  
         [0023]    The supply duct  20  also, optionally, contains valve means  80  comprising a valve body  82  rotatable about an axis  84 , normal to the duct, by operation of handle  86 . The valve body has a T-shape through passage and is operable upon rotation to redirect liquid flow along duct  20  by way of diversion passage  88  into the drain duct  22 .  
         [0024]    The centrifugal separator structure thus so far described, and its operation, is essentially conventional; liquid supplied at elevated pressure to duct  20  passes through valve means  80  and into the spindle passage  60 , passing therefrom via the container and discharge apertures  72  to the drain duct  22 . Some of the liquid is directed by way of nozzle  78  to impinge upon the spindle-mounted vanes  76  to spin the rotor and permit centrifugal separation of solid contaminants from the liquid that passes through the container space. It will be appreciated that the rotor, full of liquid has a significant weight and to minimise the downward thrust force on the lower bearing  48 , the liquid supply pressure is used to exert an axial lifting force on the spindle to compensate therefor.  
         [0025]    In normal operation, the valve means  80 , or an external equivalent (not shown), would be operated to prevent the supply liquid flow from reaching the rotor spindle before the clamping ring arrangement  28  is released and the cover is lifted from the base and the upper (stub axle) part of the spindle means. It will be understood that if the clamping ring arrangement were to be released without closing the valve, the axial force exerted by the supply pressure on the rotor and cover would lift them away from the base and, in addition to turning one or both into projectiles, would permit the liquid to discharge at high pressure and volume over surrounding machinery and/or personnel, and possibly starving the machinery of needed lubricant liquid with consequential damage thereto.  
         [0026]    Referring also to FIG. 1( b ), in accordance with the present invention the centrifugal separator  10  is provided with rotor restraining means indicated generally at  90 . The restraining means is in two parts. One part comprises a restraining surface forming part of, and extending circumferentially of, the rotor, and facing away from the base. This surface is provided by the aforementioned upper flange surface  361  of the rotor seam  36 . The other part comprises abutment  91 , carried by the base  12 , having an abutment surface  92  overlying the restraining surface  361  beyond the normal limit of axial displacement of the rotor from the base (end float) permitted by the cover. The abutment  91  comprises a tubular, that is, circumferentially continuous, body part  93  having, at a first end  94 , a radially outwardly directed mounting flange  95  for securing it with respect to the base  12  and, at a second end  96 , radially inwardly directed flange means  97  which provides the abutment surface  92 .  
         [0027]    The nature of the rotor restraining means is that the abutment, by its abutment surface, prevents removal of the rotor from the base without first removing the abutment. To this end, and having regard to the annular nature of the space available between rotor and housing, the abutment is arranged to engage with the base by approach thereto in an axial direction and be secured thereto by rotating the abutment about its axis so that it interlocks in the manner of a bayonet or similar type fitting. As shown, the mounting flange  95  comprises at least one mounting aperture  98  therethrough having a varying radial width circumferentially. Additionally, the base  12  carries a corresponding number of headed fasteners  99  each arranged to pass through a said mounting aperture at the point of greatest radial width but prevented from so doing at the point of least radial width.  
         [0028]    It will be appreciated that the precise structure of the abutment and the restraining surface may be open to variation, as desired and to accommodate different design features of the rotor housing. For example, if the rotor does not have a conveniently placed seam at some point on its peripheral wall, the abutment could be dimensioned to have its abutment surface overlying the upper end wall of the rotor (indicated at  30   1 ), or one or more flanges of arbitrary extent in the circumferential direction may be secured to the peripheral wall of the rotor or possibly, in the case of a rotating spindle, to the spindle means.  
         [0029]    It will be appreciated that provided at least one of the restraining and abutment surfaces is circumferentially continuous, the other one need not be. Therefore, if the restraining surface is circumferentially complete the abutment surface, and indeed other parts of the surface, and indeed the abutment itself, may be circumferentially discontinuous.  
         [0030]    Referring now to FIG. 2 a second form of rotor restraining means ( 190 ) comprises the aforementioned rotor restraining surface  36   1  and abutment  191 . The abutment  191  differs from abutment  90  described above in that the abutment surface and axially extending body is discontinuous circumferentially and comprises one or more discrete axially extending fingers  193   1 .  193   2 .  193   3  each topped by respective flanges  197   1 .  197   2  . . . that define circumferentially limited components  192   1 .  192   2  . . . of abutment surface  193 . Mounting flange means  195  maybe discontinuous as a flange  195   1 ,  195   2  . . . associated with each finger or may be circumferentially continuous, as shown in broken lines, in the manner of flange  95  for easier manipulation.  
         [0031]    It will be appreciated that when the rotor restraining surface  36   1  is tapered, any force it exerts on the abutment surface components has a radial component and the fingers  192   1 ,  192   2  . . . should be capable of resisting deflection thereby. However, if the rotor restraining surface does not exert a component of force radially on the abutment, then the fingers may be manually deflectable to permit engaging the rotor with, and removing it from, the base  12 . Notwithstanding the form taken by the abutment, it may be secured with respect to the base by other forms of attachment.  
         [0032]    It will be appreciated that there is a possibility of the abutment being inadvertently omitted when the cover is secured to the base and for the operator to be unaware that the safety factor of the restraining means is not present and about which, at the very least, the operator should not be complacent. This is particularly so if the optional valve  80  is omitted.  
         [0033]    Simple warning means may be included, such as a window in the cover which makes the present or absence of the abutment apparent or a resilient tongue which extends radially inwardly from the peripheral wall of the cover or base to scrape audibly against the rotor unless deflected away therefrom by the abutment, that is, remain silent when the abutment means is in place.  
         [0034]    Alternatively, more complex interlock may by provided that inhibits operation of the centrifugal separator without the abutment. Such an interlock may take the form of a valve (not shown) which is linked to the presence of the abutment adjacent the body to permit liquid to be supplied to the spindle passage, or if the valve  80  is included, such interlock may require the presence of the abutment adjacent the body to permit the valve to be moved from diversion to through-flow status. The interlock may alternatively or additionally take a form that inhibits attachment of the cover to the base in the absence of the abutment. For example, the base may carry a resilient member extending at least in part radially outwardly so that it prevents the cover from moving into engagement with the base, which member has a radially inwardly directed component upon which force is exerted by installation of the abutment to deflect member out of the path of the cover. These should be considered as exemplary only and may be used alone or in conjunction with each other or other methods within the knowledge of the skilled practitioner.  
         [0035]    It will be appreciated that the centrifugal separator of the invention is not confined to having the rotor mounting means or rotor drive arrangements described above. The rotor may be driven by more conventional reaction nozzles at container outlet  72  and/or be driven by fluid other than the liquid being cleaned within the rotor container. The rotor mounting means may comprise a stationary spindle fixed with respect to the base, or stationary stub axles fixed with respect to the base and cover.  
         [0036]    Although a centrifugal separator in accordance with the invention may benefit particularly from having rotor restraining means when the supply liquid pressure exerts an axial force on the rotor tending to separate it from the base, the provision of such restraining means is beneficial even when the rotor is not susceptible to such forces, in avoiding the liquid spillage consequences of inadvertent normal removal of the rotor.  
         [0037]    The foregoing description and examples have been set forth merely to illustrate the invention and are not intended to be limiting. Since modifications of the described embodiments incorporating the spirit and substance of the invention may occur to persons skilled in the art, the invention should be construed broadly to include all variations falling within the scope of the appended claims and equivalents thereof.