This invention relates to liquid cleaning arrangements of the centrifugal type including a separator of solid contaminants from a liquid passed through a container thereof rotated at high speed, and in particular relates to an arrangement including a centrifugal cleaner in which the chamber is rotated by a drive fluid separate from the liquid in the chamber.

It is well known to remove solid contaminants of all sizes from a fluid, frequently a liquid, by a centrifugal cleaner in which a substantially vertically-mounted, high speed rotor includes a contaminant-depositing container, (more conveniently referred to simply as a contaminant container) through which the fluid is passed and in which solid contaminants are separated from the fluid to deposit on the container wall from which they can be periodically removed or the container replaced. Such a centrifugal cleaner may have its rotor driven by external coupling to an engine or like rotary plant with which used, which results in a complex and expensive arrangement, or may, as is more usual, be driven by causing the fluid applied to the contaminant container under pressure to exit by way of tangentially directed nozzle means, the reaction to which spins the rotor at high speed essential for efficient centrifugal separation. Such a fluid- cleaner, in which the rotor is driven by the fluid being cleaned, is usually referred to as a self-powered centrifugal cleaner.

It is known to receive liquid which does not have a consistently

high enough pressure to maintain a continuous rotation of th rotor at a sufficiently high speed for centrifugal separation t occur. In s^ch circumstances the reaction nozzle means at th outlet to the contaminant container may become blocked by larg contaminant particles or pass small contaminant particles.

One instance in which such an inconsistent supply is found, i terms of supply of contaminant liquid at a minimal continuou pressure, is in so called self-cleaning barrier filler units whic employ a back-flush arrangement.

Self-cleaning barrier filter units are well known in the art i which a housing contains a plurality of filter elements o discrete surface regions each having an inlet surface exposed t a common inlet chamber of the pumped fluid and an opposite outlet, surface exposed to a common outlet chamber in which th filtrate, the cleaned fluid, is collected before leaving the uni still under pressure. In addition, the inlet chamber has a shiel or cover member which is operable periodically to isolate eac inlet surface in turn from the inlet chamber and connect i instead to a rejection conduit which leaves the housing, so tha as the shield member moves from element to element the temporaril shielded element is subject to reverse flow from the outle chamber which serves to lift contaminant debris from the inle surface of the element and flush it along the rejection conduit. Normally such contaminated liquid, despite the high concentratio of contaminants, is returned to the reservoir from where it i subsequently pumped around the system and the solid contaminant are again held by the barrier filter. Whereas such an arrangemen ensures the contaminants are contained in the system between th reservoir and barrier filter, the liquid in the reservoir doe become progressively more contaminated.

Such self cleaning barrier filter units may operate in a so-calle intermittent manner, in which the shield or cover member moves only occasionally between inlet surface regions, and possibl limiting flow through the inlet surface region for a predetermined interval less than the total time it serves that region and/or

whilst it is changing between inlet surface regions, or in a continuous manner so that the flow of back-flushed liquid is continuous but from a continuously varying, and frequently cleaned, region of inlet surface. It will be appreciated that when the liquid flows to the rejection conduit on a permanent or prolonged basis, the total quantity removed from the unit by way of the rejection conduit must be kept within limits and to this end, the product of the area of inlet surface exposed to back flushing and the time of exposure is minimal as far as is consistent with cleaning the inlet surface. Thus an intermittent back-flush system may flush at a high flow rate for short intervals whereas a continuous back flush arrangement would aim to produce a relatively small flow rate.

The use of such self-powered centrifugal cleaner in combination with a barrier type filter is disclosed in EP-A-0606578, the barrier type filter delivering a constant supply of liquid, some of which may be diverted through the centrifugal cleaner to by¬ pass the rest of the circulation system.

It is found that such a self-powered conventionally sized and mounted centrifugal cleaner is not satisfactory when obliged to operate with back-flushed liquid from such a barrier filter type due to the intermittent flow and variable pressure thereof, which requires at least part of each flow to pass through the contaminant container before that passage can accelerate the rotor to a speed at which centrifugal separation is effected, or continually low flow rate which is incapable of effecting rotation of the rotor. There is the possibility also that if such highly contaminated liquid is supplied to the centrifugal cleaner in circumstances when rotation efficiency, and thus separation efficiency, is low there is a risk that contaminants not separated and retained may accumulate and the relatively small reaction nozzles as they leave the container and result in blockage thereof this blockage of the back-flush path for the liquid.

It is known to rotate such a contaminant container by means of a fluid which is separate from the contaminant fluid, as in

US-A-3,791,576. The centrifugal separation arrangement describe therein is primarily concerned with separating liquids o different densities, although the separation may also compris separating some solid contaminants from the liquids within th rotor container. Where the contaminated liquid is contaminate only with solids, and such solids are in relatively hig proportion in the liquid supplied, the rotor container will ten to fill more quickly and require removal more frequently, exacerbated if the contaminated liquid is itself the contaminan loaded residue of an earlier filter process. Furthermore, it ma not be convenient to interrupt the supply of contaminated liqui to the centrifugal separator arrangement to attend to the rotor.

It is an object of the present invention to provide centrifuga liquid cleaning arrangement for cleaning solid contaminants fro a liquid that instigates disadvantages of known arrangements.

According to the present invention a fluid-powered centrifugal cleaner for a supply of liquid containing solid contaminants, comprises a housing having a base defining a discharge region at ambient pressure, spindle means extending from the base along an operably vertical axis through the housing and containing an axially extending main inlet passage to receive said contaminated liquid, a rotor, supported on the spindle means for rotation thereabout, comprising an annular contaminant chamber in communication with the discharge region and the main inlet passage, fluid operated rotor drive means, comprising a first part fixed with respect to the housing to receive therein a consistent supply of drive fluid at super-ambient pressure and a second part coupled to the rotor in respect of rotation about the axis, operable to cause flow of drive fluid, separate from said liquid, to said discharge region by way of the first and second parts to cause rotation of the rotor at at least a minimum speed required to effect centrifugal separation of solid contaminants from said liquid passing through the contaminant container, and control valve means operable to permit removal of the rotor contemporaneously with supply of said contaminated liquid to the housing.

An embodiment of the present invention will now be described by way of example with reference to the accompanying drawings, in which:-

Figure 1 is a schematic representation of a liquid cleaning system including pump means and barrier filter having an intermittent back-flush arrangement and including in accordance with the present invention a fluid driven centrifugal cleaner for the back- flushed liquid, driven by system liquid provided by the pump means,

Figure 2 is a sectional elevation through the fluid driven centrifugal cleaner of Figure 1, and

Figures 3(a) and 3(b) are cross sections through the base of the cleaner of Figure 1 taken in the direction A-A and illustrating operation of the control valve thereof, in first and second positions which direct the back-flushed liquid through the cleaner or to by-pass it respectively.

Referring to Figure 1, a liquid cleaning system 10 comprises a reservoir 11 of the liquid, pump means 12, a barrier or full-flow type filter 13, utilisation means 14 for the liquid, and a return

15 for utilised liquid to the reservoir.

The filter 13 is of a type having an intermittent back-flush arrangement substantially as outlined above, comprising a housing

16 containing inlet and outlet chambers 17 and 18 respectively and a plurality of filter elements 20 each comprising screens of metal mesh having what may be termed an inlet surface 21, exposed to the inlet chamber 17, and an opposite or outlet surface 22 exposed to the outlet chamber 18. Thus pumped liquid enters the inlet chamber, passes through each filter element from inlet surface to outlet surface and collects in the outlet chamber before exiting to the utilisation means. The housing also includes and intermittent back-flush arrangement 23 represented by a shield or cover 23' which is caused to move by an indexing mechanism (not shown) to close off each filter element 20, or its inlet surface

21, in turn from the inlet chamber whilst leaving outlet surface 18 exposed to the outlet chamber pressure. The shield 23 includes a rejection conduit 24 by which liquid from the close off element is removed from the housing by liquid from the outlet chamber as pressure being flushed through the filter element in the reverse direction from outlet to inlet surface and, in doing so, entraining contaminants previously deposited on the inlet surface. It is known in the art that it is desirable for the pressure difference across the filter element during back-flushing to be as large as possible.

Normally such heavily contaminated back-flushed liquid is returned to the reservoir or further full-flow filter but in accordance with the present invention it is supplied to a fluid-powered centrifugal cleaner 25 which forms part of the system and effects separation of solid contaminants from the entraining liquid, permitting the latter to be returned to the system by way of duct 26 and reservoir 11.

Referring now to Figure 2, the centrifugal cleaner 25 comprises a housing, indicated generally at 27, having a base 28 defining a discharge region 29 coupled to the reservoir 11 by way of passage 26 the latter being of such cross-sectional area and slope as to facilitate drainage by gravity when the ambient pressure within the drainage region is normal atmospheric pressure. The base supports spindle means 30 extending from the base along an operably vertical axis 31 through the housing, the spindle means supporting at its other end a relatively thin cover 32 which extends axially to abut the base at joint 33 and is removable from the base.

The spindle means contains a main inlet passage 34 extending part way therealong connected, by way of inlet duct 35 (Figure 3(a)) in the base, to rejection conduit 24 to receive back-flushed liquid.

The housing further includes a rotor 40, supported on the spindle means for rotation thereabout, comprising an annular contaminant

chamber 41 apertured and in communication with the discharge region 29 by way of a lower part 42 _L of a stand tube 42 apertured at 43, and nozzle means 44 comprising a plurality of substantially tangentially directed nozzles (also indicated as 44) arrayed about the axis 31. The stand tube 42 comprises a radially inner wall of the contaminant container 41 and an upper part 42-j of the tube separated from the base part by septum 45 is apertured at 46 and in communication, in a manner to be described more fully hereafter, with the main inlet passage 34 by way of a main rotatable fluid coupling shown generally at 47.

The centrifugal cleaner as thus far described is conventional except insofar as the nozzle 44 may be dimensioned to offer a relatively small pressure drop for liquid passing therethrough, as opposed to a relatively large pressure drop conventionally required to effect high speed rotation of the rotor by reaction to liquid ejection from the nozzles. The nozzle dimensions may create some pressure drop in the ejected liquid that exerts force on the rotor by reaction to liquid ejection, although it may not be sufficient on its own and in response to the inconsistent supply of liquid to effect high speed rotation, and in that sense the nozzle means (and nozzles) 44 may be referred to as liquid reaction nozzle means and nozzles respectively.

In accordance with the invention the centrifugal cleaner also includes fluid operated drive means, indicated generally at 50. This drive means comprises a first part fixed with respect to the housing, in the form of an auxiliary inlet passage 51 associated with the spindle means and extending at least part way along the spindle means and through the base and connected to receive a supply conduit 52 to receive drive fluid at super-ambient pressure, (the ambient pressure of the discharge region being considered as ambient) , being system liquid from the pump means 12. The drive means also comprises a second part comprising fluid reaction nozzle drive means 53 comprising a plurality of substantially tangentially directed drive nozzles (also indicated as 53) carried by the rotor and opening to the discharge region 29, a plurality of drive conduits 54 individually connecting the

drive nozzles 53 to the auxiliary inlet passage 51 by way of a auxiliary rotatable fluid coupling 55. The drive nozzles 53 ar conveniently contained in a lower wall of the contaminan container adjacent the liquid reaction nozzles 44, the associate drive conduits extending through the contaminant chamber thereto

The fluid drive means thus receives a consistent, and convenientl constant, supply of relatively uncontaminated liquid from the pum means at a rate and pressure regulated by the pump means and/o the dimensions of any of conduit 52, inlet passage 51, condui means 54 or drive nozzle means 53, and is response to ejection o the pumped liquid by way of the drive nozzle means 53 to rotat the rotor at at least the minimum speed to effect centrifuga separation of solid containments from the back-flushed liqui passing through the contaminant container 41. The back-flushe liquid, insofar as it periodically has a super-ambient pressure, may react against the nozzle means 44 on ejection therefore t supplement the reaction on the rotor from drive nozzle means 5 and provide supplementary reaction nozzle means which serves t increase the rotation rate and thus efficiency of contaminan separation.

Although a proportion of the pumped liquid is used by the driv means after which it is returned from the discharge means to th reservoir (or further cleaning operation) with the centrifugall cleaned, back-flushed liquid, the drive nozzle means i dimensioned such that only a relatively small proportion of th pumped liquid used as the drive fluid is prevented from reaching the utilisation means 14 and readily compensated for, if necessary, by slightly increasing the output pressure and/o delivery rate of the pumping means.

It will be appreciated that the conceptually simple provision of the fluid drive means may be implemented in the centrifugal cleaner in many ways, of which that shown in Figure 2 is only one, but the manner in which the drive fluid (pumped liquid) is supplied from the stationary auxiliary inlet passage 51 to the rotating conduit means 54 in addition to the supplying back-

flushed liquid to the contaminant container is of practicable significance.

Considering the spindle means 30 more closely, it comprises, static spindle 60. The rotor 40 includes a bearing tube 61 joumalled to the spindle at 62 and 63 towards each end thereof and defining between the journals an annular tube space 64. The spindle has formed therein said main and auxiliary inlet passages which communicate with the annular tube space by way of main and auxiliary radial aperture means 65 and 66 respectively separated from each other in the axial direction. Each aperture means may comprise one or more apertures arrayed around the spindle. Tube seal means 67 extends between the bearing tube and the spindle at an axial position between the main and auxiliary radial aperture means to separate the tube space into discrete main (upper) and auxiliary (lower) regions respectively. The bearing tube is apertured in the main region at 68 to communicate with the contaminant chamber 41, by way of stand tube upper region 42,; and aperture 46, and is apertured in the auxiliary region at 69 to communicate with individual drive conduits 54, thereby providing said main and auxiliary rotatable fluid couplings 47 and 55 respectively.

The main and auxiliary inlet passages conveniently are formed in a blind recess 70, extending from the end of the spindle supported on the base 28, in which the passages are defined coaxially one within the other.

The recess extends at least as far as the main radial aperture means 65 furthest from the base and contains a pipe 71 of smaller cross-sectional area which extends axially to a position between the main and auxiliary radial aperture means at which it is sealed at 72 to the spindle to define the main inlet passage within the pipe and recess (communicating with the radial aperture means 65) and the auxiliary inlet passage surrounding the pipe (communicating with the other radial aperture means 66) .

It will be appreciated that by adopting such a structure for the

(hollow tube or drilled) spindle means, a spindle within conventionally joumalled bearing tube that provides contaminated liquid inlet for the rotor of a conventional self powered centrifugal cleaner may be readily adapted to provide a auxiliary inlet passage whilst avoiding any orientation problem in aligning the passage within the spindle with continuation thereof in the base, permitting the spindle to be simply secure to the base by a screw thread 73.

It will be appreciated that a principal reason for employing suc a barrier filter having a back-flush capability is to operate th system for a prolonged interval without the necessity to stop i for removing contaminants from the surfaces of the filter elemen screens. In accordance with the present invention the centrifuga cleaner has associated therewith control valve means which i operable to facilitate removal of the rotor with its contaminan container during continued operation of the system and barrie filter, that is, contemporaneously with the supply of liquid an drive fluid to the centrifugal cleaner.

The housing 27 contains within the base 28 thereof control valv means 80 comprising a drive fluid part 81, operable to pass o impede the passage of drive fluid to the auxiliary input passag 51 and a 'back-flushed liquid' part 82, operable in conjunctio with the part 81 to divert the flow of back-flushed fluid receive in duct 35 from the main inlet passage 34 to the discharge regio 29 by way of passage 26 leading from discharge passage 83.

The parts 81 and 82 of the control valve means are defined by single valve body 84 extending through an aperture 85 in th housing base to which supply conduit 52 is coupled. One end 86 o the valve body protrudes from the aperture, permitting it to b rotated about its longitudinal axis, whereas the other end 8 extends to a part of the aperture which comprises an extension o the aforementioned supply conduit 52 for receipt of drive flui and beyond the junction of the aperture with inlets passage 51.

The valve body end 86 has a recess 88 extending axially from th

end to receive drive fluid from supply conduit 36 and a lateral aperture 89 to pass it to inlet passage 51 or block its passage, depending upon the orientation of the valve body about its axis, defining thereby a drive fluid part of the control valve means. The valve body also includes a cut-off valve 90 comprising a piston 91 extending along the recess and biased by spring 92 towards the recess end 86 to isolate the lateral aperture 89 from received drive fluid irrespective of the orientation of the valve body. The cut-off valve is responsive to drive fluid pressure in excess of the predetermined minimum acting thereon to be displaced against the bias to permit the drive fluid to exit lateral aperture 89 to the auxiliary input passage, that is, the centrifugal cleaner only takes drive fluid from the system when pump delivery pressure is sufficient to sustain its loss.

Referring also to Figures 3(a) and 3(b) the valve body 84 also has a groove 95 extending part way about its periphery that defines a recess between the body and the aperture wall such that in a first rotational position of the valve body, wherein the lateral aperture 89 is aligned with inlet passage 51, the groove 95 is disposed to connect back-flushed liquid receiving ducts 35 and main inlet passage 34 whilst blocking drain passage 83. When the valve body is rotated to close the ducts 34 and 35 from each other, isolating the auxiliary inlet passage from the drive fluid, the groove 95 directs back-flushed liquid to the discharge region by way of drain passage 86 and isolates the main inlet passage, thereby permitting the housing to be opened and the rotor 41 to be removed without stopping liquid flow through the system. It will be appreciated that whilst the centrifugal cleaner is isolated, any heavily contaminated back-flushed liquid is discharged directly to the discharged region and may find itself returned to the reservoir. Although such contaminants will eventually be trapped by the barrier filter and removed by the centrifugal cleaner when it is subsequently operating, even such occasionally presented contaminants, and the back-flushed liquid bearing them, may be eliminated from the system by the discharge duct 83 discharging outside of the system, to waste, rather than the drainage region 26 which feeds to the reservoir.

It will be appreciated that numerous variations may be made in respect of the structural details of the above described fluid- powered centrifugal cleaner without departing from the scope of the invention.

The first and second parts of the drive means may also take the form other than described above in detail. For example, the first part may comprise an auxiliary inlet passage other than extending coaxially surrounding the main inlet passage defined by a central recess in a static spindle.

A unitary static spindle extending from the base and/or housing cover opposite thereto may have main and auxiliary inlet passages extending side by side from the same end, or from opposite ends, or may be a pair of stub spindles extending one each from the base and housing cover. Although it is convenient to define the auxiliary passage within a spindle, it may additionally be defined within the base and an annular passage space surrounding the spindle that comprises rotatable coupling means of the second part. Depending upon how the inlet passages are defined, the main radial aperture means may be the lower, rather than upper, aperture if liquid is to enter the contaminant container towards the lower end thereof, possibly if the exit is by way of reaction nozzles at the upper end of the rotor.

The second part of the drive means may therefore have conduit means 54 receiving drive fluid from the spindle means at any axial position and extend to drive nozzle means at any axial and radial position with respect to the rotor. Such drive nozzle means need not comprise a vertically disposed arrangement in a section of the base of the rotor, that is, extending through the wall of the contaminant container from a conduit within, but may comprise a simple nozzle defining the end of drive conduit means that extends outside of the contaminant container.

The fluid reaction drive nozzle means need not be fixed with respect to the rotor, provided it is coupled in respect of rotation about the axis to cause the rotor to rotate with it.

As an alternative to supplying fluid to drive nozzle means outside of the contaminant container by way of conduit means and a rotatable coupling means which defines an annular chamber surrounding the axis, such an annular chamber may extend radially, to a distance from the axis at which the reaction nozzle means may be defined in the walls thereof, for efficient rotation of the rotor contaminant container coupled thereto; that is, the rotatable coupling means may comprise a container for the fluid similar to the contaminant container and disposed in line with, or possibly inside of, the latter.

Notwithstanding the structure of the drive reaction nozzles 53 they need not be disposed at the same rotational positions as nozzles (44) for the cleaned back-flushed liquid, nor in vertical alignment therewith, provided the tangential direction which produces rotation is maintained.

The drive means, as described hereinbefore functions by ejecting fluid from nozzles means which is free to rotate about the axis as a reaction to ejecting the fluid. It will be appreciated that in an alternative form the rotor may be associated with, and coupled thereto for rotation, a set of impeller blades which are disposed within the discharge region to receive drive fluid from static nozzle means arranged to eject the fluid from the base or housing cover to impinge directly on them and generate a rotation force.

Notwithstanding the mechanism by which the fluid drives the rotor and its contaminant container at high speed, the back-flushed liquid which is passed through the contaminant chamber may exit the chamber and the rotor by other than the reaction nozzle means of the type conventionally used for centrifugally cleaned fluid to self-power the rotation, as the drive fluid provides sufficient reaction to maintain rotor speed; the liquid may for instance exit via slots or large diameter holes anywhere in the base of the rotor, possibly in line with the lower end of the stand tube 42 or where the reaction nozzle means 44 would normally be sited. Such nozzles, or their alternatives, may be dimensioned to provide

a maximum pressure difference thereacross so that maximum pressure difference is available across the back-flushed filter region for optimum flushing of contaminants therefrom.

It will also be appreciated that whereas it is convenient for the drive fluid to comprise the liquid pumped through the system, and thus miscible with the cleaned liquid in the discharge region 29, it may comprise a fluid, liquid or gas, from a separate source.

The supply of fluid is required to be consistent to maintain the rotation momentum of the rotor such that any back-flushed liquid it receives is subjected to centrifugal separation of contaminants. To this end the supply of fluid need not be constant, but could vary in supply rate or pressure cyclically, possibly, pulse, such that it effects and maintains rotation of the rotor above a predetermined minimum speed to effect centrifugal cleaning.

If it is necessary to maintain segregation between the drive fluid and the back-flushed liquid, individual, radially separated, annular drainage regions may be defined in the base of the housing and the base of the rotor for the fluid and liquid and the reaction nozzle means arranged such that the cleaned, back-flushed liquid and the drive fluid exits into the different discharge regions.

Alternatively, a drive fluid immiscible with the back-flushed liquid may be discharged into a common discharge region but separated therefrom later, possibly by a further centrifugal device which separates fluids on the basis of their densities. The ambient pressure defined by the drainage region may be other than atmospheric pressure provided appropriate steps are taken to facilitate drainage.

The above description has been based on the supply of contaminated liquid being from a barrier filter including a back-flush arrangement which operates to discharge such liquid from the filter irrespective of whether the centrifugal cleaning

arrangement is operable and ready to receive it, the control valve means taking care of its passage.

It will be appreciated that it functions similarly with other forms of back-flush arrangements or indeed any source of supply, whether non-interceptable or not.