Field of invention

The present invention relates to magnetic filtration apparatus configured to separate contaminant material from a working fluid and in particular, although not exclusively, to filtration apparatus comprising a primary and a secondary filtration device forming a transportable filtration unit.

Background art

Industrial applications that utilise a working fluid to provide cooling, lubrication or to remove wear debris from machine processing tools and products, employ fluid filtration devices to extract particulate matter from the fluid. The cleaned fluid may then be recirculated for further use or more readily disposed of due to the removal of the particulate matter. Without filtration devices, the working fluid would quickly become heavily contaminated resulting in machine wear and/or failure. Also, in most territories, the filtering and cleaning of industrial fluid waste is required prior to discarding. A number of magnetic based filtration devices have been proposed, configured to filter magnetic particles from fluids in particular, liquids. Such units may be employed in an online capacity, forming part of the fluid circuit during operation of the machinery or production line, or in an off-line state in which the working fluid is diverted or isolated from the production line when inoperative to provide the required filtration.

GB 1 192870, US 2007/0090055 and WO 2005/061390 disclose cartridge based magnetic separators. Fluid, flowing through the cartridge passes over a magnet which entraps the ferrous particles within its magnetic field. Clean, filtered liquid then flows out of the cartridge. GB 2459289 discloses magnetic filtration apparatus that utilises a carousel assembly mounting a plurality of filter cartridges between operative filtration positions and at least one cleaning position. An automated cleaning mechanism is provided to dislodge deposited ferrous material from entrapment by the magnetic field as part of the filtration cycle. The removal of deposited contaminant material is a necessity to avoid saturation of the filter and ultimately blockage of the fluid flow path and termination of the working fluid flow cycle which in turn would terminate the manufacturing process being reliant upon the working fluid. These cartridge based magnetic filtration devices are typically limited in their operation time between the necessary cleaning/purging operations to remove deposited contaminant materials entrapped within the magnetic field. Typically, a period length required to purge the filters is minimised as far as possible particularly where the filter is implemented inline as part of the working fluid cycle. The purging operation is commonly hydraulically actuated and results in a large volume of a waste slurry being deposited in a storage tank. The slurry containing the particulate contaminant and an appreciable volume of the working fluid is then discarded and is often transported off-site to a further processing or recycling station. Accordingly, there is a need for filtration apparatus that provides improved separation of magnetic contaminant material from a working fluid and/or apparatus that can provide a secondary filtration operation of a contaminant material slurry deposited by a primary filtration device.

Summary of the Invention

It is an objective of the present invention to provide a magnetic filter that provides an efficient and effective filtration of contaminant particulate material entrained within a working fluid. It is a specific objective to provide a magnetic filter that is reliable and that minimises maintenance and repair during use. It is a further specific objective to provide a filtration device that is compact and lightweight so as to be readily transportable between locations within a working environment.

It is a further specific objective to provide a transportable filtration unit that may be installed as part of a working fluid network to separate contaminant material from a working fluid. It is a further specific objective to provide a filtration unit that separates contaminant material from a working fluid under a primary filtration process and then to provide an energy and time efficient purging of the separated contaminant material within the filtration unit to minimise downtime of the apparatus when undertaking primary filtration. It is a further objective to provide a secondary filtration of the separated contaminant material so as to provide a 'cake' of filtered contaminant that contains minimal residual working fluid.

The objectives are achieved by providing a primary filtration device in which an elongate magnetic core may be actuated to shuttle back and forth at a filtration chamber when applying a differential fluid pressure to a piston mounted at the core. Such an arrangement provides a rapid extraction and withdrawal of the core at the filtration chamber to minimise a purge time. The pneumatic control and actuation of the core further minimises the complexity of the filtration apparatus that facilitates reliable working and minimises maintenance. Such an arrangement also provides a lightweight and compact configuration that provides a readily transportable filtration unit for example when the primary filter forms a component part of a unit having multiple filtration devices. The objectives are further achieved by providing a filtration unit that comprises a primary and a secondary filtration device capable of operating in-series and in parallel. In particular, in one aspect, the filtration unit comprises at least one conduit providing fluid flow communication between the primary and secondary filtration devices such that contaminant material may be purged from the primary filter to flow to the secondary filter where it is separated from the purge fluid prior to being deposited from the filtration unit as a dry 'cake '. According to first aspect of the present invention there is provided a magnetic filter to separate contaminant material from a fluid comprising: a filtration housing defining a filtration chamber through which a fluid to be filtered is capable of flowing, the housing having a fluid inlet and an outlet; a tube extending within the chamber; an elongate magnetic core movably mounted within the filter for positioning within the tube; a piston mounted at the core; a piston housing defining a piston chamber within which the piston is capable of moving axially in response to a fluid pressure acting on the piston, the piston chamber communicating with the tube to enable the core to move between positions within the tube and the piston chamber in coupled movable relationship with the piston. Preferably, the magnet filter comprises a single magnetic core. Optionally, the magnetic filter may comprise a plurality of magnet cores mounted on a common bracket or flange such that the cores are coupled as a single unit that may be extracted and withdrawn from the filtration chamber. Optionally, the filter comprises a plurality of tubes to correspond to the plurality of magnetic cores.

Preferably, the piston is mounted at one end of the core. Preferably, the full axial length of the core in combination with the full axial thickness of the piston is contained within the piston housing. The piston is preferably formed as a disc in particular a cylindrical disc capable or sliding axially against the inside surface of the piston chamber housing.

Preferably, the piston comprises an axial thickness less than an axial length of the core. Such a configuration is advantageous to provide an axially compact filtration device to minimise the overall size of the filtration unit. Preferably, the piston and core assembly is devoid of any rod or shaft that extends axially beyond the piston. That is, the core extends from one side of the piston and a second side of the piston is devoid of any rod or extension such that the second side is capable of abutting against a cap that represents an axial end of the piston chamber housing. The piston housing is sealed and comprises a minimum internal volume to provide an efficient actuation mechanism for the

displacement of the piston and the core.

Preferably, the core comprises at least four columns of magnets, at least two columns having a north polarity extending substantially the length of the columns and at least two columns having a south polarity extending substantially the length of the columns wherein the at least four columns are arranged along a central longitudinal axis of the core and are distributed in a circumferential direction around the axis in alternating north and south polarity. Optionally, the core may comprise any configuration of magnets including in particular axially alternating north and south polarity magnets extending along the length of the core. However, the columns of magnets are advantageous to create a desired particulate entrapment within the filtration chamber that allows fluid flow even at saturation of the filter.

Preferably, the inlet is aligned axially adjacent one end of the tube. Preferably, the outlet is positioned at or towards an opposite lengthwise end of the filtration housing. Preferably, the outlet is orientated transverse or perpendicular to an orientation of the inlet. Such an arrangement is advantageous to create a desired fluid flow path through the chamber, to facilitate entrapment of the particulate around the tube and to facilitate purging of the particulate contaminants when the magnetic cores is withdrawn from the tube during a purge process.

Preferably, the tube comprises a domed or conical end positioned adjacent the inlet. The tube end is configured to direct the fluid flow through the chamber to create the desired flow path and to facilitate removal of the particulate by the fluid as it is directed from the inlet via the tube end over the axial extending surface of the tube. Preferably, the piston housing and the filtration housing are elongate, the piston housing mounted to extend axially at one end of the filtration housing. Optionally, the piston housing and the filtration housing are cylindrical with each housing having a respective cylindrical inward and outward facing surface. This provides the desired flow path of fluid within the filtration chamber and an arrangement that facilitates the axial displacement of the piston and magnetic core in response to the differential fluid pressure. Preferably, the actuation fluid is air such that the piston and core form a pneumatic actuation assembly configured to displace the magnets axially to and from the filtration chamber. Preferably, the piston housing comprises at least two fluid inlets/outlets to allow a piston actuation fluid to flow into/from the piston chamber at one of two sides of the piston so as to force the piston to slide axially within the piston chamber and insert and withdraw the core at the tube. The piston housing preferably comprises at least one inlet/outlet at or towards a first axial end and at least one inlet/outlet at or towards a second axial end.

Preferably, the piston is positioned in slidable sealed contact against an inside surface of the piston housing and wherein the piston actuation fluid is a gas and in particular air.

According to a second aspect of the present invention there is provided a magnetic filtration assembly to separate contaminant material from a fluid, the assembly comprising: a primary magnetic filtration device comprising a filter as claimed in any preceding claim; a secondary magnetic filtration device comprising: a fluid inlet and outlet; a trough to receive a fluid to be filtered and output from the primary filtration device; a body rotatably mounted at a rotation mounting, the body having at least one magnet and mounted relative to the trough such that at least a part of the body is positioned within the trough to be capable of being submerged within the fluid supplied to the trough from the primary filtration device; and a scraper positioned immediately adjacent a region of the body, the scraper configured to dislodge contaminant material from the body; at least one fluid conduit connecting the primary and secondary filtration devices in fluid communication; wherein contaminant material entrapped by the primary filtration device may be transferred to the secondary filtration device via the at least one fluid conduit, the secondary filtration device configured to undertake a secondary magnetic filtration of the contaminant material received from the primary filtration device. Preferably, the scraper comprises a blade positioned adjacent an outward facing surface of the body. Preferably, the scraper is rigidly mounted at a frame or the chute of the filtration apparatus and is stationary relative to the rotatable body.

Preferably, the assembly comprises at least one valve positioned at the fluid conduit in a fluid flow path between the primary and secondary filtration devices, the conduit having at least one junction to allow fluid to flow to the secondary filtration device or a fluid outlet of the assembly. More preferably, the conduit comprises at least one junction and the assembly further comprises a first controllable valve positioned at the conduit at a first side of the junction in a fluid flow path between the primary and secondary filtration devices, and a second controllable valve positioned at the conduit at a second side of the junction in a fluid flow path between the primary filtration device and a fluid outlet of the assembly. Optionally, the first and second controllable valves are pneumatically controllable valves or electrically controllable valves.

Preferably, the assembly further comprises a reclaim vessel coupled to the outlet of the primary filtration device to contain a volume of the contaminant material received from the primary filtration device prior to delivery of the contaminant material to the secondary filtration device. Preferably, the reclaim vessel is coupled in the fluid flow path between the first controllable valve and the secondary filtration device.

Preferably, the junction is formed as a T-junction having a first end coupled in fluid communication with the outlet of the primary filtration device, a second end coupled to a port of the first controllable valve and a third end coupled to a port of the second controllable valve such that fluid is capable of flowing from the primary filtration device, into the junction and then either through the first or second controllable valves depending upon an 'open' or 'closed' state of each respective controllable valve. Accordingly, fluid flow from the primary filtration device is capable of being diverted either directly to the outlet of the filtration assembly (via the second controllable valve) or to be directed to the secondary filtration device via the first controllable valve. Advantageously, when the filtration unit is operating in a primary filtration mode, the fluid flow may be maintained at a positive pressure via the pump of the assembly. As will be appreciated, the first controllable valve may be regarded as a 'purge' valve whilst the second controllable valve may be regarded as a primary flow controllable valve. Such a configuration by the use of the valves provides a closed loop system to enable the filtration unit to be installed in non- horizontal configurations with the primary filtration process being unaffected accordingly.

Optionally and in a specific implementation, the filtration assembly comprises a flow diverter configured to direct a fluid flow from the outlet of the primary filtration device to i) a fluid outlet of the assembly or ii) an inlet of the secondary filtration device, the diverter acting on the conduit to displace the conduit between at least two different positions.

Preferably, the diverter comprises: a linear actuator; and a bracket coupled to the actuator and the conduit such that movement of the actuator provides lateral movement of the conduit in a direction transverse or perpendicular to a length of the conduit.

The diverter or the controllable valves are coupled to a control unit and may be actuated in response to certain conditions of the filtration assembly such as a saturation status of the primary filter, a saturation status of the secondary filter, a volume of fluid contained within regions of the assembly, a flow speed of fluid flowing through regions of the filtration assembly or a status of the fluid flowing into or from the filtration assembly or primary or secondary filtration devices. The diverter or the controllable valves may be actuated by the controller in response to sensor signals to divert the flow of fluid from the primary filter to one of a plurality of desired components, locations or vessels. In particular, the assembly may comprise a sensor provided at the reclaim vessel to provide an output signal that is used to actuate the first and/or second controllable valve if a fluid level in the reclaim vessel reaches a predetermined height.

Optionally and in a specific implementation, the filtration assembly comprises: a primary filter outlet vessel positioned in fluid communication with the outlet of the primary filtration device to receive fluid from the outlet of the primary filtration device prior to the fluid being output from the assembly via an assembly outlet; and a secondary filter inlet vessel positioned in fluid communication between the inlet of the secondary filtration device and the outlet of the primary filtration device to contain a volume of the

contaminant containing fluid delivered to the secondary flltration device from the primary flltration device. Optionally, the at least one conduit comprises a hose having a first end coupled to the outlet of the primary filter and a second end that is a free end so that fluid is capable of falling from the second end into the primary filter outlet vessel or the secondary filter inlet vessel. The hose is preferably a flexible hose such that the first end may be statically mounted at the primary filter whilst the second end is capable of being displaced between the two delivery positions by the flow diverter. Optionally, the linear actuator comprises a movable actuator rod coupled to the bracket, the actuator being electronically controlled to provide linear extension and retraction of the rod to move the conduit laterally between the two positions.

Optionally, a sensor is provided at the reclaim vessel or the primary filter outlet vessel to provide an output signal that is used to actuate the flow diverter or the controllable valves. Preferably, the sensor comprises a float switch coupled to a control unit. Preferably, the sensor is coupled to the control unit so as to provide actuation of the flow diverter or the controllable valves in response to a signal output from the sensor.

Preferably, the rotation mounting comprises an indexing mechanism coupled to the rotatable body to provide substantially continuous indexed rotation of the body about a rotation axis. Preferably, the indexing mechanism comprises at least one sprag clutch. Optionally, the indexing mechanism may further comprise a linear actuator coupled to the sprag clutch. Preferably, the sprag clutch is pneumatically actuated via the linear actuator. The linear actuator is preferably controlled by a control unit and is responsive to a status of filtration of the primary and/or secondary filter. The control unit may be configured to control the time period of the indexed movements of the sprag clutch (and hence the rotatable body) to ensure a liquid volume within any one of the fluid containment vessels of the assembly does not exceed a predetermined amount so as to overflow from any one of the vessels and to ensure fluid is flowing through the filtration assembly at the desired rate. Accordingly, the indexing mechanism may be coupled to the control of the primary filter to achieve the desired fluid flow rate through and from the flltration assembly and the desired status of the filtered fluid and particulate contaminant that are separated as part of the filtration process.

Preferably, the filtration assembly comprises a pump to drive a fluid flow through the primary filtration device. Optionally, the assembly may comprise a single or a plurality of pumps positioned in series or in parallel and upstream and/or downstream in the fluid flow path relative to the primary filter and/or the secondary filter.

Preferably, the filtration assembly comprises a control unit to control operation of the primary and secondary filtration devices and the controllable valves (flow diverter arrangement). Optionally, the control unit may be a programmable logic circuit (PLC), a printed circuit board (PCB), a processing unit, a remote computer, network or server.

Optionally, the filtration assembly may comprise wired or wireless communication components to provide remote and automated control and status monitoring of the filtration assembly and in particular the status of the primary and/or secondary filters, the fluid flowing through the assembly at various regions and/or fluid and particulate contaminant entering and extracted from the filtration assembly.

Preferably, the filtration assembly comprises a base to mount and support the primary and secondary filtration devices such that the assembly is transportable on the base as a unitary structure. The base may comprise a suitable support structure that allows the mounting and demounting of components of the filtration assembly including in particular all or parts of the primary and secondary filter, motor, vessels and control units. Optionally, the base comprises legs to support the filtration assembly, optionally, the legs are extendable and retractable relative to the base.

According to a third aspect of the present invention there is provided a method of separating contaminant material from a fluid using magnetic filtration apparatus, the method comprising: providing a filtration housing defining a filtration chamber through which a fluid to be filtered is capable of flowing, the chamber containing an elongate tube; positioning a magnetic core within the tube; allowing the fluid to flow through the filtration chamber and around the tube such that a contaminant material within the fluid is entrapped at the tube; withdrawing axially the core from the tube by applying a fluid pressure to a piston mounted at the core; diverting a fluid flow path from the filtration chamber device to a secondary filtration device when the core is withdrawn axially from the tube; purging the contaminant material from the filtration chamber using a fluid flow; directing the fluid and contaminant material to the secondary filtration device comprising a body rotatably mounted within a trough; rotating the body within the trough about at least one magnet to entrap the contaminant material at an outward facing surface of the body; and scrapping contaminant material from the outward facing surface of the body. Brief description of drawings

A specific implementation of the present invention will now be described, by way of example only, and with reference to the accompanying drawings in which: Figure 1 is an external perspective view of a pneumatically operated primary magnetic filter according to a specific implementation of the present invention;

Figure 2 is a partial cross sectional perspective view of the filter of figure 1 ; Figure 3 is a further cross sectional perspective view of the filter of figure 2;

Figure 4 is an external front perspective view of a filtration unit comprising a primary and a secondary filtration device according to a specific implementation of the present invention with selected components removed for illustrative purposes;

Figure 5 is an external rear perspective view of the filtration unit of figure 4;

Figure 6 is a plan view of the filtration unit of figure 5 with selected components removed for illustrative purposes;

Figure 7 is a further perspective plan view of the filtration unit of figure 6; Figure 8 is a side elevation view of the filtration unit of figure 7;

Figure 9 is a magnified side elevation view of a secondary filter within the unit of figure 8; Figure 10 is a further perspective view of the secondary filter of the unit of figure 8;

Figure 1 1 is a further perspective view of the secondary filter of the unit of figure 8;

Figure 12 is a side elevation view of a filtration unit comprising a primary and a secondary filtration device according to a further specific implementation of the present invention with the selected components removed for illustrative purposes;

Figure 13 is a perspective view of the filtration unit of figure 12. Detailed description of preferred embodiment of the invention

Referring to figures 1 to 3 a primary magnetic filtration device 100 comprises a generally cylindrical filtration housing 101. Housing 101 comprises a fluid flow inlet 106 and fluid flow outlet 107. Inlet 106 is coupled in fluid communication with a conduit hose 103 and outlet 107 is coupled in fluid communication with an outlet conduit hose 104.

Accordingly, a fluid containing a particle contaminant may be introduced into housing 101 via inlet 106 and to flow from housing 101 via outlet 107. In particular, an inward facing surface 101a of housing 101 defines an internal filtration chamber 108. An elongate tube 109 extends axially within housing 101 being centred on an axis 115 that extends centrally through the elongate filtration device 100. Tube 109 comprises a first end 109a (secured to a disc-like annular flange 160 that provides a partial closure for one end of housing 101) and a second end 109b that comprises a conical end fitting 1 10 with fitting 1 10 positioned to be axially aligned with and separated by a short distance from inlet 106. Accordingly, fluid introduced into chamber 108 via hose 103 and inlet 106 is encouraged by fitting 1 10 and tube 109 to flow around tube 109 and along an axial length of chamber 108 from inlet 106 to outlet 107. Inlet and outlet 106, 107 each comprise a generally circular cross sectional profile with the inlet plane being perpendicular to the plane of outlet 107. Additionally, outlet 107 is positioned towards a second end of housing 101 relative to inlet 106. The configuration of the tube 109, end fitting 1 10 and the respective relative positions and orientations of inlet 106 and outlet 107 provide a desired fluid flow through chamber 108 that facilitates magnetic entrapment of the contaminant material within the flowing fluid and facilitate a 'purge operation' as detailed further below.

A generally cylindrical piston housing 102 is releasably mounted at and forms an axial extension of filtration housing 101. According to the specific implementation, an external diameter of piston housing 102 is approximately equal to an external diameter of filtration housing 101 with each respective housing 101 , 102 comprising an approximately equal axial length. Piston housing 102 comprises a first end 102b secured to filtration housing 101 via flange 160. A second end 102a of housing 102 is closed by an end cap 105 that seals piston housing 102 to define an internal piston chamber 161. A piston 1 13 is slidably mounted within piston chamber 161 in contact with an internal facing surface 102c of piston housing 102. A fluid tight seal between piston 1 13 and housing surface 102c is achieved via a quad ring seal 1 14 extending around piston 1 13. An elongate magnetic core 1 1 1 , (in the form of a rod) is rigidly attached to piston 1 13 and is capable of coupled movement axially with piston 1 13 (within piston housing chamber 161). Piston 1 13 is attached at one of core 1 1 1 such that the combined axial length of core 1 1 1 and piston 1 13 are contained within piston housing 102. Core 1 1 1 is centred on axis 1 15 and comprises an axial length that in combination with an axial thickness of piston 1 13 extend the full axial length of piston housing 102 between first and second ends 102a, 102b. Flange 160 comprises an aperture 162 at the region of coupling between piston housing 102 and filtration housing 101. Aperture 162 is dimensioned to allow axial passage of core 1 1 1 from piston housing 102 into filtration housing 101 and in particular insertion and withdrawal at tube 109. That is, aperture 162 is axially aligned with tube 109. A disc-like guide shoe 1 16 is mounted at one end of core 1 1 1 to ensure the smooth axial displacement of core 1 1 1 within tube 109. Piston 1 13 (and core 1 1 1) are capable of shuttling axially along axis 1 15 so as to insert and withdraw core 1 1 1 at tube 109 via a differential air pressure created within regions of piston chamber 161. Accordingly, piston housing 102 comprises a plurality of inlets/outlets (not shown) through which air may be delivered and extracted at piston chamber 161 to force movement of piston 1 13 axially. According to the specific implementation, four columns of magnets 1 12 are mounted at core 1 1 1. Magnets 1 12 comprise two columns of north polarity magnets 1 12a and south polarity magnets 1 12b arranged around axis 1 15 in alternating north and south polarity. Each column is aligned lengthways parallel to axis 1 15. With core 11 1 and magnets 1 12 positioned within tube 109, magnets 1 12 are positioned in close, near touching contact, with the inward facing surface of tube 109. Accordingly, particulate contaminant entrained within the fluid flowing within filtration chamber 108 between inlet 106 and outlet 107 is entrapped by the magnetic field circuit created by core 1 11 at an external facing surface of tube 109. According to further specific implementations, core 1 1 1 may comprise any suitable arrangement of magnets 1 12 to create a desired magnetic circuit for optimised entrapment of particulate contaminant.

Primary filter 100 according to the specific implementation forms one of two filtration devices incorporated within a filtration unit 120. Referring to figures 4 and 5, unit 120 further comprises a secondary filtration device 127 in a form of a magnetic filtration wheel or drum. Unit 120 further comprises a PLC control unit 128; a feed pump 129; a base 122; an external housing 121 ; a unit fluid inlet 123; a unit primary flow outlet 124 and a unit purge outlet 125. Unit 120 further comprises a particulate contaminant output chute 126 forming a part of the secondary filtration device 127.

Referring to figures 6 and 7, unit inlet 123 is coupled to pump 129 via conduit hose 152. Primary filter 100 is coupled to pump 129 in fluid communication via hose 103 that provides fluid supply from unit inlet 123 to primary filter inlet 106. Processed fluid is output from filter 100 via hose 104 having a first end 134 secured to primary filter 100 and a second free end 133 that is suspended in uncoupled position within unit 120. Unit 120 further comprises a pair of side-by-side located discharge vessels 131 , 132. Each vessel 131 , 132 is formed as a tank having an internal volume defined by vessel walls. In particular, each vessel 131 , 132 is partitioned from one another by an intermediate partition wall 138 that includes a recess 139 within an uppermost edge to enable a lateral sideways travel of hose end 133 between vessels 131 , 132. First vessel 131 represents a primary filter outlet vessel to contain the fluid processed by primary filter 100 during primary filtering operation of unit 120. The filtered fluid output from primary filter 100 falls under gravity from the hose free end 133 into vessel 131. The filtered fluid then drains from vessel 131 via a drain port 170 coupled in fluid communication with unit main flow outlet 124 via a conduit hose 154.

Unit 120 further comprises a diverter mechanism indicated generally by reference 130 referring to figures 6 and 7. Diverter mechanism 130 comprises an electronically controlled actuator 135 in which an elongate rod 136 is capable of reciprocating linear movement to and from actuator 135. Rod 136, at one end comprises a bracket 137 that is secured to hose 104. Accordingly, linear actuation of rod 136 provides a lateral sideways displacement of hose 104 and in particular free end 133 between a first position at (or above/within) primary filter outlet vessel 131 and a second position (not illustrated) at (or above/within) second vessel 132. Accordingly, hose 104 comprises a suitable flexible hose capable of bending to provide the lateral displacement of hose end 133 via diverter mechanism 130 whilst hose first end 134 is secured to primary filter 100.

Vessel 132 represents a secondary filtration inlet vessel for the secondary filter 127.

Secondary filter 127 comprises a drum 145 rotatably mounted on a central axis 141. Drum 145 is dimensioned to accommodate an array of magnets 146 mounted internally within drum 145. The magnets 146 are distributed in the circumferential direction around axis 141 opposed to a radially inward facing surface of drum 145 that is capable of free rotation over magnets 146. A non-magnetic region 171 (extending an angular distance in the range 70 to 1 10 degrees) is located internally within drum 145 and is devoid of magnets 146. Accordingly, the magnetic circuit created by magnets 146 extends to an external facing surface 142 of drum 145 (over an angular distance of 250 to 290 degrees) except for the section of drum 145 that is located over non-magnetic region 171. Magnets 146 are mounted on a magnet support drum 140 centred around axis 141. Referring to figures 8 to 1 1 a scraper blade 172 is positioned in near touching contact with drum outer surface 142. Blade 172 represents an upper region of contaminant discharge chute 126 that is supported in a declined position extending from an upper region of drum 145. Rotatable drum 145 is at least partially mounted within a trough indicated generally by reference 143. Trough 143 is configured to contain a contaminated slurry supplied from second filter inlet vessel 132. An elongate slot-like aperture 147 provides fluid communication between inlet vessel 132 and trough 143. Rotatable drum 145 is suspended such that approximately a lower quarter of the drum 145 is positioned vertically below slot 147. Trough 143 is divided by a curved plate 144 that sits a distance below a lower region of drum 145 opposed to outward facing surface 142. Plate 144 defines a slurry reservoir 149 immediately below drum 145 with reservoir 149 positioned below slot 147.

Trough 143 comprises a drainage port 148 positioned vertically below plate 144 that is coupled in fluid communication with unit purge outlet 125 via conduit hose 153.

Secondary filtration device 127 further comprises an indexing mechanism indicated generally by reference 173 that is responsible to actuate rotational movement of drum 145 within trough 143 and about the array of magnets 146. Indexing mechanism 173 comprises a 'Sprag' clutch indicated generally by reference 150 coupled at one end of a linear actuator 151 that is in turn mounted to base 122 of unit 120. As will be appreciated Sprag clutch 150 provides a single rotational indexing motion of drum 145 and is capable of continuous operation when powered.

In use, filtration unit 120 represents a self-contained primary and secondary filtration processing apparatus configured to separate magnetically susceptible contaminant particulate from a working fluid. Contaminated fluid flows into unit 120 via inlet 123 under the force of pump 129. The fluid then flows into primary filter 100 via hose 103 where it is filtered. In particular, air is introduced into the axially upper region of piston chamber 161 so as to displace piston 1 13 axially downward from piston housing first end 102a to piston housing second end 102b. Accordingly, core 1 1 1 and magnets 112 are displaced axially downward from piston housing 102 into tube 109 (and filtration chamber 108). Fluid flowing through chamber 108 passes through the magnetic circuit created by magnets 1 12 such that the contaminant material collects at the external surface of tube 109 with filtered fluid flowing from chamber 108 via outlet 107 and hose 104. The primary outlet flow of primary filter 100 is discharge via hose end 133 into outlet vessel 131 where it drains from unit 120 via drain port 170, hose 154 and main flow outlet 124. When primary filter 100 reaches saturation, diverter mechanism 130 is actuated by controller 128 to displace hose end 133 laterally from vessel 131 to vessel 132. During this diversion, fiuid flow into primary filter 100 is temporarily terminated. Controller 128 simultaneously actuates piston 1 13 via a suitable air circuit to force piston 1 13 and core 1 1 1 axially within piston housing 102 and in particular, to extract core 1 1 1 from tube 109. A 'purge volume ' of fluid is then allowed to flow through primary filter 100 and is discharged via hose end 133 into secondary filter inlet vessel 132 where it flows subsequently into trough 143 and reservoir 149 via elongate slot 147. The heavily saturated contaminant slurry deposited within reservoir 149 is maintained in the magnetic field circuit created by magnets 146 such that particulate contaminant adheres to the outward facing surface 142 of drum 145 as it rotates clockwise (according to the orientation of figures 8 to 10). Contaminant is drawn steadily from the slurry (within reservoir 149) as the drum 145 rotates via the action of Sprag clutch 150. The contaminant is retained at surface 142 within the region of magnets 146 until the rotation position aligned with non-magnetic region 171 where scraper blade 172 is positioned. Material is then dislodged from surface 142 by blade 172 to fall under gravity down chute 126. The residual decontaminated slurry fluid then flows from trough 143 via outlet port 148 to the purge outlet 125 via hose 153. Controller 128, immediately after the purge operation, returns hose end 133 to the primary filter outlet vessel 131 to allow the continued primary filtration of the working fluid through primary filter 100. As will be appreciated, the purge operation is actuated by controller 128 at desired time intervals and in response to a predetermined prior-saturation point of filter 100. Secondary filter 127 works independently of primary filter 100 so as to continually filter the purge slurry output from the primary filter 100.

According to the specific implementation, a float switch (not shown) or other sensor is positioned at outlet vessel 131 such that should vessel 131 become blocked or otherwise contain a maximum volume of fluid, diverter mechanism 130 may be actuated by controller 128 so as to divert further fluid into secondary filter inlet vessel 132. Controller 128 under such conditions may be configured to prevent further purge operations until suitable further conditions are satisfied. As will be appreciated, the filtration unit 120 may comprise fluid flow sensors, particulate sensors (to detect levels of contaminant material), fluid flow sensors, temperature sensors and the like at various regions within the unit 120 including primary filter 100, secondary filter 127, vessels 131 , 132, trough 143, chute 126, drum 145, inlet 123 and outlets 124, 125. A further implementation of the filtration unit described with reference to figures 1 to 1 1 is illustrated in figures 12 to 13. The second embodiment comprises the majority of components and functionality of the first embodiment including in particular the primary and secondary filtration devices 100, 127, pump 129, base 122, control unit 128 and all associated components. The function of the unit of figures 12 to 13 corresponds generally to the function of the first embodiment of figures 1 to 1 1 in which fluid is initially introduced into the primary filtration device 100 via inlets 123, 106. Filtered fluid during primary filtering then exits the unit via outlets 124, 106. The unit of the second embodiment is configured for a secondary filtration under a ' purge' operation with the purged slurry from the primary filtration device 100 being routed to the secondary filtration device 127. The fluid output from the secondary filtration device 127 is returned to a machine tank (with which the filtration unit is coupled) via outlet 125. The collected solid contaminant is discharged from the secondary filtration device 127 via a chute 126 and collected within container 201. As with the first embodiment, the second embodiment is mounted on a common base or sled 122 to allow convenient transportation and installation of the filtration unit as a single assembly.

In place of the displaceable hose 124 and actuator assembly 135, 136, 137 of the first embodiment, the second embodiment comprises a pair of valves to control directing of the fluid from the primary filtration device outlet 107 to either the unit outlet 124 (during primary filtration) or to direct the fluid to the secondary filtration device 127 (during a purge operation). In particular, a hose 200a is coupled to primary filtration device outlet 107. Hose 200a is formed as a T-junction hose with a first end coupled to primary filtration device outlet 107, a second end coupled to a purge valve 205 and a third end coupled to a primary process valve 203. Purge valve 205 is further coupled to a downstream hose 200b that is in turn coupled to reclaim vessel 202. Primary process valve 203 is further coupled to unit outlet 124 via hose 204. According to the specific implementation, valves 205, 203 comprise 'pinch' valves having an internal rubber sleeve that lines the inside of the valve. Compressed air supplied to the valves 205, 203 is configured to compress radially the rubber sleeve to close respectively each valve independently. According to further implementations, valves 205, 203 may comprise any electrically controllable valves such as solenoid valves, ball valves, logic valves, servo valves, etc as will be appreciated. In operation, and when the filtration unit is operating in a primary filtration mode, the filtered fluid from primary filtration device 100 flows from device outlet 107 into hose 200a. The primary process valve 205 is in an 'open' state whilst purge valve 205 is in a 'closed ^' ' state. Accordingly, the output fluid flows through hose 200a, valve 203, hose 204 and outlet 124. Prior to saturation of the primary filtration device 100, the electronic control 128 actuates valves 205, 203 by switching their status such that purge valve 205 is opened whilst primary process valve 203 is closed. Accordingly, the output fluid is directed through hose 200a, valve 205 and hose 200b into reclaim tank 202. Tank 202 comprises a slot-like aperture (not shown) corresponding to the aperture 147 of the first embodiment referring to figure 10. The heavily contaminated fluid within tank 202 is fed into the trough 143 of the secondary filtration device 127 for filtration by the magnetic array support drum 140 as described previously.

Accordingly, the second embodiment of figures 12 and 13 is configured as a ' closed-loop ^' ' system, such that at least when the unit is operating in the primary filtration mode, the fluid is maintained under a positive pressure by pump 129. In particular, and in contrast to the first embodiment, the fluid flow from the primary filtration device outlet 107 to the unit outlet 124 is continuously pumped and is not controlled under gravity. Accordingly, the second embodiment may be advantageous to provide enhanced control of fluid flow rates through the unit and a possible enhanced synclironisation of the switching between primary filtration processing and purging via the synchronised control of valves 205, 203 and the positive pressure applied by pump 129. Additionally, the second embodiment is advantageous for installation and operation in a non-horizontal or inclined configuration. This is facilitated by the 'closed-loop' configuration and the positive pressure applied by pump 129 during primary filtration.

As will be appreciated, the specific magnetic array of the primary and secondary filtration devices 100, 127 may be selected so as to achieve the desired magnitude of filtration. Optionally, the primary and secondary filtration devices 100, 127 are configured with interchangeable magnet packs (and associated mounting components) so as to allow variation of the magnetic configuration and hence filtration magnitude within devices 100, 127.