WO2000061923A1

WO2000061923A1 - Liquid cleaning arrangement

Info

Publication number: WO2000061923A1
Application number: PCT/GB2000/001278
Authority: WO
Inventors: Stephen Michael Harrison
Original assignee: Filterwerk Mann+Hummel Gmbh
Priority date: 1999-04-12
Filing date: 2000-04-05
Publication date: 2000-10-19
Also published as: GB9908252D0; AU3977500A; GB2348830A

Abstract

An oil cleaning arrangement (10) comprises a barrier, or full flow, filter (22) divided into two sections (221 and 222) within a housing chamber (16), and a centrifugal separator (60). The chamber has a liquid extraction port (18) and ports (401 and 402) which communicate with a valve (32) switchable between two operative states. In each state liquid at elevated pressure is passed through one section (221 or 222) to the extraction port and some of the filtered liquid passed in reverse direction to the centrifugal separator. The valve state is switched after relatively long intervals in each state, such switching causing contaminants collected on said one filter section to be back-flushed through the centrifugal separator and leaving the section clean for re-use upon next switching valve states.

Description

Liquid Cleaning Arrangement

This invention relates to liquid cleaning arrangements comprising in combination barrier, or full-flow, filter means and centrifugal separation means, and particularly, but not exclusively relates to such arrangements for cleaning oil pumped as a lubricant around internal combustion engines for vehicles and the like.

Lubrication arrangements for an internal combustion engine are well known comprising a sump or like reservoir of oil, a pump which takes oil from the sump and delivers it to working parts of the engine, such as bearings, from which it drains back to the sump, and between the pump and working parts an oil cleaning arrangement.

Universally such an oil cleaning arrangement has comprises a barrier type filter, also known as a full-flow filter, comprising a perforated screen, wire mesh or paper felt which is porous and traps contaminant particles exceeding the pore size of the barrier. Several compromises have to be made between having a pore size that is small and efficient at trapping particles, but also presents a pressure drop between pump and engine components and is susceptible to early blockage, and a coarser filler with larger pore size, which has less ability to trap small particles but also a lesser pressure drop and longer operating life.

Small particles, possibly being carbon deposits resulting from combustion, are not considered to cause immediate damage to engine parts but an accumulation thereof in the oil does with time significantly reduce its efficacy. Therefore it has frequently been the situation that the oil has been changed after a vehicle to which the engine is fitted has travelled for 6,000- 20,000 miles (10,000-30,000 km) and the filter pore size specified to trap particles down to a size which does not result in partial blockage thereof, introducing an unacceptable pressure drop in the pumped oil, in such oil change interval.

It is also well known to remove contaminant particles, particularly very small particles, by means of a centrifugal separator including a rotor canister to which oil is supplied at elevated pressure and which is spun at very high speed about an axis by ejection of the oil from the canister through tangentially directed jet nozzles. Because such rotor spinning arrangement results in ejected oil at low pressure fit only for draining back to the sump, such a centrifugal cleaner normally operates in a so-called by-pass mode, in effect tapping off a proportion of the circulated high pressure oil and effecting cumulative cleaning over a long period.

Patent specifications EP-A-0164882, EP-A-0606578 and GB-A-2160796 describe an oil cleaning arrangement of a vehicle internal combustion engine both a full-flow barrier filter and a self-powered centrifugal cleaner.

Whereas such a centrifugal separator, operating a by-pass mode, is efficient at removing very small particles from the oil for very long periods, and the removal of very small particulate contaminants, such as carbonaceous combustion products, has prevented their accumulation in the oil to prolong its useful working life, it has nevertheless been the case that the oil still needed changing at relatively short intervals (12,000-20,000 miles or 20,000-30,000 km vehicle travel) because of breakdown in its lubricating efficacy. Because such oil change operation presents an opportunity to replace or clean the barrier filter, such barrier filters have been changed in design to have a pore size consistent with trapping the smallest particles for the duration only of such oil-change intervals.

However, recent advancements in lubricant technology have resulted in such vehicle engine lubricating oils able to function for the order of 100,000 miles (160,000 km) vehicle travel which for most passenger and small commercial vehicles is the life of the vehicle.

This is of limited advantage if the barrier filter still requires such periodic replacement or cleaning, as in respect of such vehicles, the costs of labour and vehicle unavailability associated with such replacement/cleaning often exceed those of materials and re-focuses attention on the divergent criteria of pore size and operating life.

It is known in heavy duty static and commercial vehicle engines to have a barrier filter of the so called back-flush type wherein the filter is of a generally cylindrical form divided circumferentially into sectors and each sector is isolated in turn so that a proportion of the oil passed by the remaining sectors can be passed in reverse direction through the isolated sector to flush contaminants from the surface thereof. Such a filter arrangement is described in EP-A-0136202. Oil cleaning arrangements capable of removing a large range of contaminants by combination of barrier filter and centrifugal separator and which are capable of operating for long intervals without intervention are described in WO96/23590 and WO96/12549.

There remains a problem in that such conventional back-flush barrier filters are complex and expensive and may not be cost-effective replacements to replaceable/cleanable barrier filters for small passenger vehicles.

Furthermore, in the aforementioned combination arrangements, the back-flush arrangement continually presents the centrifugal separator with oil from a newly selected sector of the barrier and therefore heavily contaminated. It does not provide, the centrifugal separator with the conditions conducive to its most efficient operation, that is, gradually extracting very small particles from multiple passes.

It is an object of the present invention to provide a liquid cleaning arrangement of simple design for removing solid contaminants, from a liquid pumped at elevated pressure over prolonged intervals with less attention and more cost effectively and efficiently than hitherto. The arrangement is particularly suited to cleaning lubricating oil circulating in vehicle internal combustion engines, but the invention is not intended to be limited with regard to the liquid.

According to the present invention a liquid cleaning arrangement comprises (i) a supply port arranged to receive liquid pumped into the arrangement at elevated pressure, (ii) housing means having chamber means including extraction port means and first and second chamber control port, (iii) barrier filter means, contained in said chamber means, divided into a first section, having a first filter surface thereof in communication with the first chamber control port, and a second section, having a first filter surface thereof in communication with the second chamber control port, said first and second sections each having a second filter surface in communication with the extraction port and with each other, (iv) a centrifugal separator having a contaminated liquid inlet arranged to received liquid passed through the barrier filter means, and (v) control means operable to control the flow of liquid through said first and second sections of the barrier filter means, the arrangement being characterised in that said first and second sections of the barrier filter means are permanently defined with respect to each other and by the control means comprising switchable valve means external to the chamber means, having an inlet port connected to the supply port, an outlet port connected to the contaminated liquid inlet of the centrifugal separator, a first valve port in communication with the first chamber control port and a second valve port in communication with the second chamber control port, the valve means being switchable alternately between a first operative state in which the inlet port is connected to the first valve port and the second valve port is connected to the outlet port, and a second operative state in which the inlet port is connected to the second valve port and the first valve port is connected to the outlet port.

Embodiments of the invention will now be described by way of example, in which

Figure 1 is a sectional elevation through a first embodiment of liquid cleaning arrangement in accordance with the present invention, having co-axial first and second barrier filter sections spaced apart axially,

Figure 2 is a sectional elevation through a modification of this embodiment wherein each barrier filter section comprises coarse and fine filters in tandem,

Figure 3(a) is a sectional elevation through a second embodiment of liquid cleaning arrangement, having co-axial barrier filter sectors in surrounding relationship,

Figure 3(b) is a sectional elevation modification of this second embodiment and generally similar to that of Figure 2(a) but wherein the inner filter section is longer axially to equalise surface area with the outer filter section,

Figure 4 is sectional elevation through a third embodiment of liquid cleaning arrangement corresponding functionally to that of Figure 3(a) but wherein the filter element are disposed alongside the centrifugal cleaner and both under separately removable covers,

Figure 5 is a sectional elevation through the housing part of a fourth embodiment of liquid cleaning arrangement, similar to that of Figure 1 but wherein the first and second sections of the barrier filter means comprise flat screens in side by side relationship, and

Figure 6 is a sectional elevation through a fifth embodiment of liquid cleaning arrangement, similar to that of Figure 1 but including heat exchange means proximate the barrier filter means.

Referring to Figure 1 , a first embodiment 10 of liquid cleaning arrangement in accordance with the invention is shown in sectional elevation, the structures of the components parts and their relationships being somewhat schematic, as will be evident to those skilled in the art, for the purpose of more clearly illustrating the invention.

The arrangement 10 has a supply port 12 for receiving liquid pumped into the arrangement at elevated pressure, which port is defined in housing means, indicated generally at 14, that also contains chamber means, in the form of a single chamber 16, having extraction port means 18 in the form of a single port in an end wall thereof and first and second chamber control ports 20., and 20₂ in a side wall thereof.

The arrangement 10 has barrier filter means, indicated generally at 22, contained in the chamber 16 and divided into a first section 22₁ and a second section 22₂ each in the form of a tubular body having a common longitude axis 24 and separated from each other along that axis.

The first section 22_! has a first filter surface 26_1A defined by the outer surface of the tubular body, which is in communication with the first chamber control 20.,, and a second filter 26_1B defined by the inner surface of the tubular body, adjacent the longitudinal axis 24, and in communication with the extraction port 18.

The second barrier filter section 22₂ similarly has a first filter surface 26_2A in communication with second chamber control port 20₂ and a second filter surface 26_2B in communication with both the extraction port and the second filter surface 26_1B in the first section. The first filter surfaces 26_1A and 26_2A are isolated from each other by a partition wall 28 extending radially into the chamber and permanently defining the sections 22- and 22₂ with respect to each other. The barrier filter sections 22, and 22₂ are also substantially identical in terms of dimensions and pore size.

The arrangement 10 has control means, indicated generally at 30 which comprises principally switchable valve means 32 external to the chamber.

In this embodiment the valve means 32 comprises a shuttle, or spool, valve comprising a valve chamber 33 containing a shuttle 34, supported by side walls 36 of the chamber, reciprocable therealong between longitudinal positions defining first and second operative states. Figure 1 shows the valve means in the first operative state. The side walls 36 have apertures therein defining ports for the valve chamber. Apertures 38, and 38₂ comprise an inlet port 38 in communication with the supply port 12. Apertures 40, and 40₂ comprise first and second valve ports which extend through the housing wall and in communication with the first and second chamber control ports 20, and 20₂ respectively. An aperture 42 comprises a valve outlet port discussed further below. The shuttle is provided in conventional manner with lands separating regions of smaller cross section which isolate the first and second control ports from each other and the inlet and outlet ports from each other at all longitudinal positions of the shuttle. The lands are also positioned such that with the valve in the first operative state shown, the inlet port 38 is connected to the first valve port 40, (and first chamber port 20,) and outlet port 42 is connected to the second valve port 40₂ (and second chamber port 20₂).

In the second operative state of the valve (not shown) the shuttle is displaced to the opposite end of the valve chamber and the inlet port is connected to the second valve port 40₂ and the first valve port 40, is connected to the outlet port 42.

The shuttle valve is switchable, that is, the shuttle displaceable between two positions to place it in either said first or second operative state. It may be of a type wherein the shuttle is displaced by manual, hydraulic of pneumatic effort but conveniently comprises solenoid valve driven by electrical signals applied to a solenoid 44 which contains an armature 46 connected to the shuttle. The solenoid receives signals that determine shuttle position from a controller 50, as will be discussed below in relation to operation of the cleaning arrangement.

The cleaning arrangement 10 also comprises a centrifugal separator 60 of the self-powered type generally known is the art and from the aforementioned patent specifications, but essentially comprising an upstanding shaft 62 supporting a rotor canister 64 for rotation thereabout and containing a duct 66 for communicating to the rotor oil received at a contamination liquid inlet 68 thereof in communication with the aforementioned outlet port 42.

A housing 70 contains the rotor and shaft and the rotor canister has tangentially directed reaction nozzles 72 by which the centrifuged oil is ejected from the rotor (causing it to spin) into the housing. A drainage duct (not shown) drains the ejected oil to a sump (not shown) in conventional manner.

As it is the intention that the cleaning arrangement that the cleaning arrangement should be operated with a vehicle engine for a prolonged period, possible the life of the engine, the housing means 14 is designed not to be opened for access to the barrier filter means 22 nor the centrifugal separator.

Considering operation of the arrangement 10, assuming that the valve in the first operative state as shown, pumped oil at elevated pressure is received at the supply port and thus inlet port 38. It enters the valve chambers by apertures 38, and 38₂. The latter is isolated but the oil flows from the former to valve port 40, and thus by way of first chamber control port 20, to the first filter surface 26_1A of the first section 22, of the barrier filter means. The oil flows through the body of the first section 22, exiting from the second filter surface 26_1B and thence along the chamber to the extraction port 18.

With the valve in this operative state the second chamber control port 20₂ is in communication with the outlet port 42 and thus the inlet 68 for the centrifugal separator. Thus a proportion of the oil passing from the first filter section to the extraction port passes through the second section 22₂ of the barrier filter, from its second filter surface 26_2B to its first filter surface 26^, and thence through the valve chamber to the centrifugal separator.

After a period of operation the first section 22, of the barrier filter becomes partly occluded with contaminants collected at the first filter surface 26_1A, resulting in an increased pressure difference between its surface and a reduction in pressure and/ or flow rate of oil at the extraction port.

In response to specified conditions, which may comprise a time-related computation or determination of pressure conditions as discussed more fully below, the controller 50 causes the valve means 32 to switch to the second operative state, displacing the shuttle 34, which results in the supply port 12 and inlet port 38 communicating with the chamber control port 20₂ so that the oil flows by way of barrier filter section 22₂ (from the first filter surface 26_2A to second filter surface 26_2B ) to the extraction port restoring barrier filter efficiency.

At this time the contaminated first filter surface 26_1A of the first filter section 22, is connected by way of the valve to the inlet port 68 of the centrifugal separator and the extraction port oil pressure in the chamber causes a proportion of the oil to flow through the first section 22, in the direction from the second filter surface to the first filter surface, thus dislodging, or back- flushing, the contaminants from the first filter surface of the section and passing them through the centrifugal separator. It will be appreciated that the removal of the concentrated contaminants from the surface of the first section occupies only a relatively small period of time after which the centrifugal separator operates for a prolonged period with oil that, having passed through both the second and first sections of the barrier filter, contains only the small contaminated particles which such centrifuge excels at removing efficiently.

When conditions determine that the second filter section is becoming too contaminated on the first filter surface thereof, the control means 30 operates to switch the valve into its first operative state so that the oil from supply port at elevated pressure is fed again to the clean first filter surface 22_1A of the first section and passes from the second filter surface 22,_B of the section to the extraction port.

In a manner corresponding to the previous change in valve states, the extraction port pressure directs a proportion of the oil through the second section 22₂ of the filter to the centrifugal separator, initially serving to back-flush the accumulated contaminants from the first filter surface 22^ and then passing oil cleaned by the first section of the barrier filter for the remainder of the time that the valve means remains in this state, so that the centrifugal separator can continue to remove the contaminants too small to be stopped by the barrier filter.

It will be appreciated that if such a cleaning arrangement utilises a barrier filer pore size that would, in a conventional road vehicle engine, require cleaning or replacing say every 10,000 miles (16,000 Km) and the vehicle is expected to cover about 120,000 miles (200,000 Km) in its lifetime, then the barrier filter would require cleaning only about 12 times throughout the vehicle life, and in the above described embodiment, the valve means would require to switch states only 12 times. Clearly with the convenience of being able to effect cleaning of the barrier filter by merely switching between valve states it is possible to have barrier filter means with a smaller pore size and/or smaller filter surface area and to effect such switching of valve state more frequently.

It will be seen that the operation differs from the arrangements described in the aforementioned patent specifications, notwithstanding that back-flushing is effected when the valve means changes states, as described therein the centrifugal separator receives continually, or at least frequently, the oil heavily contaminated with particles large enough to be stopped by the barrier filter means from consecutive sections of the barrier filter newly isolated and back-flushed in sequence, and spends relatively little time receiving oil clean of the contaminants large enough to be stopped by the barrier filter means, whereas the arrangement according to the present invention does for most of the time provide such oil cleaned of 'large' contaminants to the centrifugal separator.

As mentioned above, the conditions leading to, and manner of, changing the operating state of the valve means are open to variation.

The control means 30 may be operated manually on the basis of human judgement of the passage of time, vehicle distance covered or other, separately measured criteria. Insofar as the control means is fitted within a vehicle, it may automatically monitor the passage of time, duration of engine operation and/or distance covered by the vehicle to effect such change of valve operating state by means of the aforementioned controller 50. Alternatively, and as shown in Figure 1 , pressure sensors 52 and 54 may be provided at the supply port 12 (or inlet port communicating therewith) and at the extraction port 18 (or chamber communicating therewith) to determine the pressure drop across the barrier filter section providing the cleaning and the signals thereof fed to the controller 50 which is arranged to respond to a predetermined level of pressure drop to effect switching of the valve means between operative states.

Clearly pressures could be sensed elsewhere in the arrangement to provide such controller signals and the liquid at such pressure may be applied in a fluid liquid arrangement to effect controlled displacement of the valve shuttle directly rather than by way of electrical signals. The control means may more accurately determine which part of the pressure difference is due to occlusion by contaminants by determining the pressure difference between the first and second filter surfaces of both sections in order to eliminate any pressure drop across a 'clean' section, that is, to determine the pressure difference of one element section relative to the other.

Alternatively, instead of determining a pressure drop across a filter section as being indicative of occlusion, the control means may determine flow rate by means of a suitable transducer (not shown) although such flow rate may have to be related to other criteria such as engine speed and/or supply pressure. It will be appreciated that the shuttle valve arrangement is conveniently bistable in that it remains in either operative state until actively changed. If appropriate, it may take a monostable form in which it naturally reverts to one operative state except when actively maintained in the other state. This may be particularly appropriate in a shuttle valve as shown operated by an electrical solenoid where there is risk of power failure or where the shuttle is positioned by the supplied liquid pressure, to avoid it assuming an intermediate and indeterminate disposition, possibly one blocking the valve ports 40, and 40₂. A simple bias spring 35 may be associated with the shuttle body to bias it into, say, the first operative state unless overridden by the controller.

Although the above embodiment has been described with a rectilinearly reciprocable shuttle valve, it will be appreciated that any valve configuration having the ability to connect the parts as specified may be used.

In the embodiment 10, the sections 22, and 22₂ of the barrier filter means are essentially identical in respect of pore size and dimensions. It will be understood that a close match between pore sizes is important as when a screen section of small pore size is in the path to the centrifugal separator, contaminants large enough to pass through the other section may accumulate on the second filter surface and agglomerate thereon such that when flows reverse, such agglomerations will be detached and flushed from the chamber by way of the extraction port. Whereas the individual contaminants may be considered unharmful to the engine (or such large pore size for one filter section would not be used) it may not be the case where each contaminants have formed agglomerations.

The screen sections are conveniently of the same dimensions and filter surface area to simplify and cheapen manufacture when disposed as shown, but this need not be the case, provided that different rates at which contaminants accumulate thereon, and possible differences in extraction port pressure, are accommodated in determination of switching the valve means between operative states.

As illustrated in the embodiment 10, each barrier filter section comprises a tubular body having a simple tubular wall which comprises the porous filter element through which the liquid flows in a generally radial direction inwardly or outwardly. It will be appreciated that such tubular bodies may take a more complex shape that increases the first and second filter surface areas, for example pleated. Additionally or alternatively each section may comprise a number of tubular bodies of different porosity in tandem, as illustrated in a modification of the embodiment shown at 10¹ in Figure 2, only the housing means being shown for simplicity.

The barrier filter means 22¹ comprises identical, axially separated tubular sections 22¹, and 22 ₂. The section 22¹, comprises an outer tubular body 23, of relatively large pore size, the surface 23,_Aof which lying adjacent the chamber control port 20, comprises first filter surface of the section, and the section 22¹, comprises an inner tubular body 23 , of relatively small pore size, the surface 23¹,_A lies adjacent the body 23, and the surface of which lying adjacent the longitudinal axis 24 comprises the second filter surface 23¹,_B of the section.

Such arrangement may be considered to give an effective increase in the first filter surface area of each section in trapping contaminants against the radially outer surfaces 23_1A and 23¹ _1A of both bodies.

As described with reference to Figure 2, and notwithstanding the axial separation of the barrier filter sections therein, barrier filter elements in the form of tubular bodies may be disposed in a surrounding relationship and Figure 3 shows at 110, in comparable sectional elevation, a second embodiment of liquid cleaning arrangement in accordance with the present invention. As with Figure 2, the centrifugal separator, valve means and controller have been omitted for clarity. The housing 114 defines a single chamber 116 and along which chamber extends, between opposite ends thereof, first and second barrier filter sections 122, and 122₂. The sections are formed as tubular bodies and disposed substantially co-axially with respect to a common longitudinal axis 124 with the second section 122₂ surrounding the first section 122, and an annular space 125 therebetween, the second filter surface 122,_B and 122_2B respectively of each section forming a radial boundary of the annular space. Extraction port 118 opens into said annular space. The second chamber control port 120₂ opens into the annular space surrounding the second section, whose first filter surface 122_2A faces it, and the first chamber control port 120, opens into the centre of the chamber 116 surrounded by the first section and with the first filter surface 122_1Aof the section adjacent thereto.

It will be appreciated that whichever chamber control port admits the liquid it will pass through a section of the barrier filter means from the first filter surface thereof to the second filter surface and the annular space 125 and therefrom to the extraction port. Such an arrangement may be made axially more compact but it will be appreciated that the filter surface areas of the sections are no longer equal. This may not matter when control means functions to switch the valve means between operative states for appropriately unequal durations. Alternatively, and as illustrated in Figure 3(b) which shows a modification of a position of the arrangement 110 of Figure 3(a), the housing 116 may provide an elongated chamber 116 for the inner tubular filter section 122, so that the surface area thereof is equal, or more nearly equal, to that of the outer filter section 122₂.

As indicated above, the configuration and functioning of a liquid cleaning arrangement in accordance with the present invention lends itself a completely closed system in which the barrier filter sections and centrifugal separator rotor are not removable for cleaning or replacement. However, such accessibility is not inconsistent with the invention and Figure 4 shows in sectional elevation a third embodiment 210 of the invention in which the barrier filter means and centrifugal separator are disposed in a side-by-side relationship that permits such access.

Switchable valve means 232, supply port 217, and centrifugal separator 260 correspond essentially to items 31, 12 and 60 described above for arrangement 10 except that the centrifugal separator has a removable cover 270.

The barrier filter means 222 is contained in a removable housing 214 which defines chamber 216 and is secured to, and has one wall containing, chamber control ports 220, and 220₂ and extraction port 218 fixed with respect to the valve means. The barrier filter means 222 comprises sections 222, and 222₂ disposed in the coaxial, surrounding relationship described above for embodiment 110.

Although the housing 214 and centrifuge cover 270 are each shown to be removable, either or both may be permanently closed.

In all of the above described embodiments the barrier filter means has comprised first and second sections of tubular form, not necessarily cylindrical, wherein the liquid flows between first and second filter surfaces in a generally radial direction.

Referring now to Figure 5 which shows a sectional elevation through a fourth embodiment of liquid cleaning arrangement 310 in accordance with the present invention, the structure is similar to the embodiment 10 of Figure 1 and like parts are given the same reference numbers. It differs in that the extraction port 318 is not defined at the end of housing chamber 314 but centrally whereof where the partition wall, now superfluous, was disposed. Barrier filter means 322 is formed by two sections 322, and 322₂ of flat, rather than tubular, shape extending transversely to the longitudinal axis 324 and disposed axially one each side of the extraction port but both between the first and second chamber control ports 20, and 20₂. Operation will be evident from the above descriptions.

Referring now to Figure 6, this shows in sectional elevation a fifth embodiment of liquid cleaning arrangement 10¹¹ corresponding to the embodiment 10 of Figure 1 modified by the inclusion of a heat exchanger 80 in the housing 14. The heat exchanger comprises an array of heat exchange elements 82,, 82₂... disposed adjacent the second filter surfaces 26_1B and 26_2B of the barrier filter sections. Conveniently the heat exchange elements comprise pipes 84,, 84₂ coupled to a split manifold 86 which in turn has inflow and outflow ducts 87, 88 for a temperature regulating fluid, liquid or gas. The fluid may be kept (by means not shown) at constant temperature whereby the liquid in the chamber 16 is heated or cooled towards such temperature.

A variation to the form of heat exchanger 80 is shown ghosted at 80¹ and wherein the heat exchange elements 81 - pass through, that is longitudinally, the barrier filter sections.

The heat exchanger may be employed particularly to pre-heat cold liquid to reach working temperature more rapidly. The heat exchanger may also be divided into separately functioning sections, associated one each with each section of the barrier filter means, whereby different temperature criteria may be applied to each in dependence upon which direction the oil is flowing in the filter section.

It will be appreciated that the valve means may be operated to change operative states at any time but that depending upon the valve construction and function such change may result in a temporary change in liquid flow to the extraction port. If it is important to prevent such a fluctuation whilst the engine is in operation, and the engine is stopped frequently and thus all supply suspended, the control means may be arranged to record the conditions that dictate that a change in valve operative state is required but delay effecting such a change until the supply pressure is below a level indicative of the engine being stopped, so that when the supply is resumed the valve is in the alternate operative state.

The liquid cleaning arrangement has been described above, in what represents a most cost effective implementation, with a centrifugal separator of the self-powered type wherein the liquid applied to the contaminated liquid inlet 68 also provides the energy for rotation of the rotor canister. It will be appreciated that if desired the centrifugal separator may be powered by a separately supplied liquid, conveniently from the supply port. Referring again to Figure 1 , it is a simple modification to provide the rotor spindle 62 with a drive liquid inlet, shown ghosted at 39, and connected to the inlet port 38, the rotor canister taking the form shown and described in the aforementioned WO96/23590.

It will be appreciated that although the chamber means has been described in the above embodiments as a single chamber within a housing the chamber means may comprise discrete chambers in discrete housing without change of functionality.

Also, although the above embodiments have related to arrangements for cleaning lubricating oil of an internal combustion engine, it will be appreciated that a cleaning arrangement in accordance with the invention may be used for cleaning solid contaminants from any other liquid that is pumped at elevated pressure.

Claims

1. A liquid cleaning arrangement (10, 10¹, 110, 210, 310, 10¹¹) comprising

(i) a supply port (12) arranged to receive liquid pumped into the arrangement at elevated pressure,

(ii) housing means (14) having chamber means (16) including extraction port means

(18) and first and second chamber control port (20,, 20₂),

(iii) barrier filter means (22), contained in said chamber means, divided into a first section (22,), having a first filter surface (26,_A) thereof in communication with the first chamber control port, and a second section (22₂), having a first filter surface (26_2A) thereof in communication with the second chamber control port, said first and second sections each having a second filter surface (26,_B), 26_2B) in communication with the extraction port and with each other,

(iv) a centrifugal separator (60) having a contaminated liquid inlet (68) arranged to received liquid passed through the barrier filter means, and

(v) control means (30) operable to control the flow of liquid through said first and second sections of the barrier filter means, the arrangement being characterised in that said first and second sections of the barrier filter means are permanently defined with respect to each other and by the control means comprising switchable valve means (32) external to the chamber means, having an inlet port (38) connected to the supply port, an outlet port (42) connected to the contaminated liquid inlet of the centrifugal separator, a first valve port (40,) in communication with the first chamber control port and a second valve port (40₂) in communication with the second chamber control port, the valve means being switchable alternately between a first operative state in which the inlet port is connected to the first valve port and the second valve port is connected to the outlet port, and a second operative state in which the inlet port is connected to the second valve port and the first valve port is connected to the outlet port.

2. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in claim 1 in which the chamber means (16) comprises a single chamber containing both first and second sections (22,, 22₂) of the barrier filter means.

3. A liquid cleaning arrangement as claimed in claim 2 in which each section (22,, 22₂) of the barrier filter means comprises a tubular body having a longitudinal axis (24) and said first and second surfaces (26,_A, 26_2A, 26,_B, 26_2B) separated radially with respect to said axis.

4. A liquid cleaning arrangement (10, 10¹, 310, 10¹¹) as claimed in claim 3 in which the first and second sections (26,, 26₂) are separated axially.

5. A liquid cleaning arrangement (10, 10\ 10¹¹) as claimed in claim 4 in which the second filter surface (26,_B, 26_2B) of each tubular body is adjacent the longitudinal axis.

6. A liquid cleaning arrangement (110, 210) as claimed in claim 3 in which one section (122₂) of the barrier filter means surrounds said other section (122,) with an annular space (125) therebetween, and the second filter surface (122,_B, 122_2B) of each section forms a radial boundary of said annular space.

7. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of claims 3 to 6 in which said first and second sections are disposed with respect to each other substantially co-axially.

8. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of the preceding claims in which said first and second sections of the barrier filter means have substantially the same pore size as each other.

9. A liquid cleaning arrangement (10, 10\ 110, 310, 10¹¹) as claimed in claim 8 in which said first and second section of the barrier filter means have substantially the same filter surface area as each other.

10. A liquid cleaning arrangement (10¹) as claimed in any one of the preceding claims in which each said section (22¹,, 22¹ ₂) of the barrier filter means comprises a primary filter element (23,) of relatively large pore size and a secondary filter element (23¹,) of relatively small pore size connected in tandem in respect of liquid flow therethrough, said secondary filter element providing the second filter surface (23¹,_B) of ^tne section and said primary filter element providing the first filter surface (23,_A) of the section.

11. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of the preceding claims in which the control means includes liquid pressure sensing means (52, 54), operable to derive a signal related to the pressure difference across at least one section of the filter barrier means, and is responsive to a predetermined level of pressure difference across the section in communication with the supply port to effect a change in valve state.

12. A liquid cleaning arrangement (10, 10¹, 110, 210, 310, 10¹¹) as claimed in claim 11 in which said control means (50) is arranged to determine said predetermined level of pressure difference relative to the pressure difference across the other section.

13. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of the preceding claims in which the valve means (32) is arranged to change state and divert flow between supply and extraction ports from one section of the barrier filter means to the other without significant change in pressure at the extraction port.

14. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of the preceding claims in which the control means (50) is arranged to effect a change in operative state of the valve means (32) only when the supply pressure is below a predetermined pressure.

15. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of the preceding claims in which the control means (50) is responsive to passage of a predetermined time interval to effect a change in valve operative state.

16. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in claim 15 in which said predetermined time interval is measured in terms of time for which liquid is flowing through the arrangement.

17. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of the preceding claims in which the switchable valve means (32) comprises a bistable valve operable to remain in each state upon switching.

18. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10¹¹) as claimed in any one of claims 1 to 16 in which the switchable valve means (32) comprises a monostable valve operable to return to a predetermined state in the absence of an applied force maintaining it in the other of said two states.

19. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in any one of the preceding claims in which the switchable valve means (32) comprises an electrically operated valve.

20. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in any one of claims 1 to 18 in which the switchable valve means (32) comprises an hydraulically actuated valve.

21. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in any one of the preceding claims in which the switchable valve means (32) comprises a valve chamber (33) containing a shuttle (34) reciprocable therealong supported by side walls (36) of the chamber between longitudinal positions defining said first and second operative states.

22. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in claim 21 in which the valve chamber has apertures (38, , 38₂, 40,, 40₂) in the side walls for the inlet and outlet ports and first and second control ports, and the shuttle (34) is provided with lands to isolate said first and second control ports from each other and said inlet and outlet ports from each other at all longitudinal positions of the shuttle.

23. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in any one of the preceding claims in which the centrifugal separator (60) is a self powered centrifugal separator including a contaminant rotor (64) powered by ejection of the liquid received at said contaminated liquid inlet.

24. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in any one of claims 1 to 22 in which the centrifugal separator includes a contaminant rotor (64) powered by a drive liquid applied to a drive inlet, (39) separate from said liquid applied to the contaminated liquid inlet from said outlet port of the valve means.

25. A liquid cleaning arrangement (10, 10\ 110, 210, 310, 10") as claimed in claim 24 in which said drive liquid inlet (39) is in communication with the supply port (12).

26. A liquid cleaning arrangement (10") as claimed in any one of the preceding claims including heat exchanger means (80, 80¹) having at least one heat exchanger element (82,, 82¹,) disposed proximate the barrier filter sections within the chamber means.