BACKGROUND TO THE INVENTION In a conventional filtration apparatus the filtration membrane is particularly prone to blocking with solid particles being filtered from a fluid stream. These solid particles may have adhered or lodged themselves against or within the membrane under the force or pressure of the incoming fluid stream. It is understood that"Residual Current Eddies"which develop in the housing of the filtration apparatus also contribute to fouling or blocking of the membrane."Residual Current Eddies"are in essence back-eddies which draw solid particles, having passed over the membrane, in a generally opposing direction to the main fluid flow back onto the membrane surface. Similarly, microscopic particles that have passed through the membrane are swept up by"Residual Current Eddies"back into the membrane. During operation of the conventional filtration apparatus there is a gradual deposition of solid particles on and within the membrane. This forms a"Boundary Layer" which reduces the flux rate of the membrane and will eventually block the membrane.

SUMMARY OF THE INVENTION An intention of the present invention is to provide a fluid flow housing that is relatively effective in reducing the formation of current eddies which drive particles back onto a filtration device.

According to one aspect of the present invention there is provided a fluid flow housing comprising: a fluid inlet port and a fluid outlet port disposed on one side of a filtration device adapted to be mounted within the housing; a filtrate outlet port located on an opposite side of the filtration device; and anti-current eddy means being arranged between the fluid inlet and the fluid outlet ports on said one side of the filtration device whereby, in use, whilst a fluid to be filtered is passed through the housing the anti-current eddy means is effective in reducing current eddies which develop within the housing and drive filtered particles back onto the filtration device and obstruct fluid flowing through the filtration device.

According to another aspect of the present invention there is provided a method of filtering particles from a fluid stream, said method comprising the steps of: providing a fluid flow housing including a fluid inlet port and a fluid outlet port disposed on one side of a filtration device mounted within the housing, the housing also having a filtrate outlet port located on an opposite side of the filtration device; and reducing current eddies in the filtration device by the provision of anti-current eddy means being arranged between the fluid inlet and the outlet ports on said one side of the filtration device whereby, in use, whilst the fluid stream is passed through the housing the anti-current eddy means is effective in reducing current eddies which develop within the housing and drive filtered particles back onto the filtration device and obstruct fluid flowing through the filtration device.

Generally, the fluid inlet, fluid outlet and filtrate outlet ports are defined by fluid inlet, fluid outlet and filtrate outlet passageways, respectively, being oriented relative to each other and a plane of the filtration device so that the current eddies which develop from the flow of fluid through the housing are less prevalent.

Typically, the anti-current eddy means includes an anti-current eddy flow channel arranged between the fluid inlet and the fluid outlet passageways, the anti-current eddy flow channel being configured so as to minimise the development of current eddies within the housing.

Preferably, the fluid flow housing is of a split construction having a first section including the fluid inlet, fluid outlet and anti-current eddy passageway, and a second section including the filtrate outlet passageway, the filtration device being located between the first and second housing sections. In one embodiment, the first and second housing sections are each shaped generally elliptical in profile.

In one example, the fluid inlet and the fluid outlet passageways are substantially cylindrical thereby defining an axial flow within said passageways. The fluid flow housing is configured so that an axial flow through the fluid inlet is at an angle of between 30 to 60° relative to the plane of the filtration device and an axial flow through the fluid outlet is at an angle of between 30 to 60° to the plane of the filtration device.

Typically, the anti-current eddy means also includes a filtrate channel arranged between the opposite side of the 12771

filtration device and the filtrate outlet passageway, the filtrate channel being configured to substantially balance the pressure drop measured across the filtration device so as to inhibit the onset of current eddies adjacent the opposite side of the filtration device. In one example, the filtrate channel is shaped in the form of a deformed cone being generally elliptical when sectioned parallel to the filtration device, the filtrate channel progressively tapering toward and being formed continuous with the filtrate outlet passageway.

Generally, the filtrate outlet passageway is substantially cylindrical thereby defining a filtrate axial flow within the passageway. The filtrate axial flow is at an angle of between 30 to 60° relative to the plane of the filtration device and is generally aligned with or at least parallel to the fluid inlet flow.

Typically, the filtration device includes a substantially planar filtration membrane. In one embodiment the filtration membrane is sandwiched between the first and second housing sections.

According to yet another aspect of the present invention there is provided a housing comprising: a fluid inlet port and a first and second fluid outlet port being in fluid flow communication with each other; and one or more flow restrictor plates each having a flow opening of a predetermined size, the plates each being designed to locate over at least one of the fluid inlet or first and second fluid outlet ports whereby, in use, the fluid flowrate through the housing can be controlled by the

incorporation of said one or more flow restrictor plates within the housing.

Typically, said one or more flow restrictors are each ring members with the flow opening being shaped substantially circular. Generally, the ring members are each located coaxially across the fluid inlet and/or outlet ports which are also shaped circular.

Generally, the housing is designed and incorporated within a flow system as a fluid flow valve. In one example, the housing is used as a replacement valve in a circulatory system of a human organism, such as the heart.

Advantageously, the housing in this application when used with a filtration device, such as that disclosed in the preceding paragraphs, assists in the reduction of introduced genetic and viral contaminants.

Typically, the housing is a fluid flow housing such as that disclosed in the preceding paragraphs. However, it should be appreciated that the housing may be used without a filtration device.

BRIEF DESCRIPTION OF THE DRAWINGS In order to facilitate a better understanding of the nature of the present invention several preferred embodiments of a fluid flow housing will now be described, by way of example only, with reference to the accompanying drawings in which: Figure 1 is a side elevational view of a first embodiment of a fluid flow housing together with a clamping member shown in section; Figure 2 is an end elevational view of the housing of Figure 1 with the clamping member shown in section;

Figure 3 is a side sectional view of the housing of Figure 1; Figure 4 is an end sectional view taken obliquely along the line GG-HH through the housing of Figure 1; Figure 5 is another end sectional view taken obliquely along the line EE-FF through the housing of Figure 1; Figure 6 is a plan and end sectional view of one of the clamp members depicted in Figure 1; Figure 7 shows in various detailed views interconnection of the clamp members of Figure 6.

Figure 8 is a sectional view of the housing illustrated in the preceding drawings together with a schematic representation of flow lines; Figure 9 is a crude schematic depicting fluid flow through an embodiment of the invention; Figure 10 is in plan and elevational view two (2) restrictor plates suitable for use with a housing of one embodiment of the invention; Figure 11 is a side sectional view of a modified form of the fluid flow housing of Figures 1 to 5; Figure 12 is a plan view of the housing of Figure 11; and, Figure 13 is a plan view of a filtration device incorporated in the housing of Figure 11.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Figures 1 to 5 illustrate in various views a fluid flow housing or in this embodiment a filtration device housing 10. The housing 10 includes a fluid inlet port 12 and a fluid outlet port 14 located on one side of a filtration membrane 16 which is designed to be mounted within the housing 10. The housing 10 also comprises a filtration

outlet port 18 positioned on an opposite side of the filtration membrane 16.

The housing 10 of this embodiment is of a split construction having a first housing section 20 and a second housing section 22 located on either side of and sandwiching the filtration membrane 16 therebetween. The fluid inlet and outlets 12 and 14 are formed within the first housing section 20 whereas the filtrate outlet 18 is formed in the second housing section 22.

The fluid inlet and outlets 12 and 14 are defined by fluid inlet and outlet passageways 24 and 26, respectively, being formed in the first housing section 20. The filtrate 30 outlet 18 is defined by a filtrate passageway 28 formed in the second housing section 22. In this particular construction of the filtration device housing 10, the passageways 24,26 and 28 are each tubular spigots being threaded externally for ease of connection to associated plumbing. The first and second housing sections 20 and 22 each have opposing annular flanges 30A and 30B between which the filtration membrane 16 is sandwiched. In this embodiment, the flanges 30A and 30B, filtration membrane 16, and first and second housing sections 20 and 22 when viewed in profile are shaped generally elliptical.

The first housing section 20 includes an anti-current eddy flow channel 32 being disposed alongside the filtration membrane 16 and providing fluid communication between the fluid inlet and outlet passageways 24 and 26.-The anti- current eddy flow channel 32 as illustrated in figure 4 generally resembles a flattened"U"shaped channel when viewed in a section taken transverse to the plane of the

filtration membrane 16. The second housing section 22 includes a filtrate channel 34 which is formed continuous with and provides filtrate flow to the filtrate passageway 28. The filtrate channel 34 is shaped in the form of a deformed cone being generally elliptical when sectioned in a plane lying parallel to that of the filtration membrane 16.

As depicted in figure 4, the filtrate channel 34 when sectioned transverse to the plane of the filtration membrane 16 is generally dome-shaped.

The housing 10 includes a pair of generally C-shaped (in section) clamp members 36A and 36B configured to sealably clamp the filtration membrane 16 between the first and second housing sections 20 and 22. Figure 6 shows one of the clamp members 36 having an inner facing channel 38 being shaped complementary to and designed to locate about the annular flanges 30A and 30B of the first and second housing sections 20 and 22. As best shown in Figure 3 an outer seal 40 is provided within the clamp member channel 38 so as to prevent the egress of fluid from between the first and second housing sections 20 and 22. An inner seal 42 locates circumferentially about the filtration membrane 16 whereby the membrane 16 is sealably sandwiched between the first and second housing sections 20 and 22.

The clamp members 36 of Figure 6 include coupling holes 44A and 44B formed on opposing legs thereof. As best illustrated in Figure 7 a coupling pin 46 is designed to pass through one of the corresponding coupling holes 44 so as to couple the clamp members 36 together. In this example, a taper pin 47 locks the coupling pin 46 in place and is concealed whilst the clamp members 36 are locked together. Compression of the clamp members 36 is provided by a compression screw

49 as depicted in Figure 7. A locking mechanism, such as a padlock (not shown), can be installed in the hole 44 opposing the coupling pin 46 so as to securely lock the clamp members 36 about the housing sections 20 and 22. The padlock may for ease of operation be replaced with a flush-mounted"push-in twist lock". The essence of this embodiment of the invention resides in the internal configuration of the housing 10. The housing is configured so that fluid passing through the housing is less susceptible to current eddies which may develop in a conventional filtration device housing, the current eddies driving particles filtered from the fluid stream back onto the filtration device. In this particular housing 10, the eddy flow channel 32 and filtrate channel 34 together with the orientation of the fluid inlet and outlet passageways 24 and 26 and filtrate passageway 28 combine to reduce eddy currents within the housing 10. For the purposes of this embodiment of the invention these features in combination are deemed to be anti-current eddy means.

Figure 8 schematically illustrates both the main currents and residual current eddies depicted by the solid and lighter lines, respectively, of fluid flowing through the housing 10. It is believed that the lighter residual current eddies work in a complementary fashion with the main currents to produce a"reverse wave"of fluid thereby reducing the deleterious effect of current eddies wherein filtered particles are driven back onto the filtration membrane. Thus, it will be appreciated that blocking or fouling of the filtration membrane is reduced whereby flux rates through the housing 10 and across the filtration membrane 16 are maintained at a relatively high flow rate.

Computer simulations of the fluid dynamics present in the housing of Figures 1 to 5 have demonstrated the effect of the"reverse wave"of fluid in the housing. The results also suggest that in some flow conditions the upstream flow dynamics provided by the housing dissipate in the direction of flow, (along the corrugations in the filtration device), if the upstream flow is not controlled within a specified manner. The dissipation occurring in the upstream flow dynamics is in direct proportion to the loss of fluid passing through the spaces within the filtration device. In order to improve the upstream flow dynamics, a degree of rotation or tapering of the anti-current eddy flow channel 32 as illustrated in Figure 11 may be applied. As shown in Figure 11 the first housing section 20 of a modified housing is tapered towards the waste outlet passageway 26 and in the direction of fluid flow indicated by arrow A. It is thought that the tapering helps to equalise the fluid pressures and velocities applied across the surface of the filtration device 16, thus equalising the dynamic wave front, (in passage), flowing through the channels provided in the filtration device 16.

This tapering of the fluid flow housing may also involve a lateral tapering of the housing section 20 as illustrated in Figure 12, which is a plan view of the modified housing shown in Figure 11. This lateral tapering is visible as a narrowing of the elliptical shaped section 20 in the region of the channel 32 towards the waste outlet passageway 26, in the direction of fluid flow indicated by arrow A. One effect of this tapering is that the feed water becomes further concentrated due to the reduced flow volume while flowing through the housing towards the waste outlet. Key

factors are equalisation of pressure and velocity of fluid flows occurring within the housing achieved when the upstream distribution of flows are balanced and stabilised.

The filtration device 16 may itself also benefit from a degree of tapering, similar to that applied to the housing.

As illustrated in Figure 13, a filtration device 16 of generally elliptical shape is tapered both laterally and longitudinally in the direction of fluid flow as indicated by arrow A.

It will be appreciated from the filtration device housing 10 described that the relative disposition and orientation of the fluid inlet, outlet and filtrate passageways 12,14, and 18 are critical factors in reducing the detrimental effects of current eddies as described above. In both embodiments, fluid streams flowing through the inlet and outlet passageways 24 and 26 are substantially perpendicular to each other and each of these streams is disposed at an angle of approximately 45° to the filtration membrane 16.

Furthermore, the filtrate passageways 28 are generally aligned although it is believed that offsetting of the filtrate outlet 28 of the housing 10 balances the pressure drop across the filtration membrane 16. This is understood to avoid any residual current eddies on a downstream surface of the membrane 16 which drive relatively fine particles back into the membrane 16.

Figure 9 depicts in an over-simplified manner the beneficial effects of internally designing the housing so that "damaging"residual current eddies are largely eliminated.

In the schematic, the points of"critical velocity"are

located at the fluid inlet and outlet passageways. The broken lines depict compression of the various"laminar" layers of fluid as they are affected by the filtration membranes.

Figure 10 illustrates a pair of restrictor plates 100 having a fluid flow opening 102 of a predetermined size. The flow restrictors 100 of this example are ring-shaped and adapted to locate over a fluid inlet, outlet or filtrate outlet so as to control the flowrate of fluid passing through a housing such as the housings 10 described above. Thus, the fluid inlet to fluid and filtrate outlet ratios can be adjusted for applications where pressure and flowrates may vary. This will also accommodate variations in plumbing associated with the fluid inlet, outlet and the filtrate outlet. The purpose of adjusting or varying the fluid inlet to outlet ratio may be to automatically balance the flow of fluid passing through the housing without the need for valving.

The following table provides examples of various fluid inlet to outlet ratios using the flow restrictors 100 described.

FLOW RESTRICTORS/REGULATORS INLET/OUTLET RELATIVE FLOW DIAMETERS FLUID INLET/OUTLET RATIO INLET WASTE FILTRATE 0.254:1:11.000.25 0.504:1:21.000.25 1: 3 1: 4 2: 3 2: 4 2: 5 3: 4 3: 5 1.256:4:51.501.00 0.508:1:22.000.25 1: 3 1: 4 1.258:1:52.000.25 1.508:1:62.000.25 1: 7 2: 3 2: 5 1.758:2:72.000.50 1.008:3:42.000.75 3: 5 3: 6 1.758:3:72.000.75 1.258:4:52.001.00 4: 6 4: 7

The housing 10 when used in conjunction with the restrictor plates 100 is particularly well suited to application as a replacement valve in a circulatory system of a human organism. The housing 10 may depending on the application include a filtration device such as that described above.

Now that several possible embodiments of the present invention have been described it will be apparent to those skilled in the relevant arts that the filtration device housing has at least the following advantages: 1. The housing is configured to at least reduce residual eddy currents and thus blocking or obstruction of filter membranes; 2. The filtration device housing and in particular the anti-current eddy means is relatively simple in construction; and 3. The housing can be readily adapted to existing installations with relative ease.

It will be apparent to those skilled in the relevant arts that the invention is susceptible to variations and modifications other than those specifically described. For example, the relative orientation of the fluid inlet, outlet and filtrate outlet passageways together with the eddy flow and filtrate channels may vary provided the detrimental effects of residual eddy currents are reduced. Furthermore, the specific construction of the housing may vary from the split construction described wherein the housing may for example be formed as a single casting or moulding.

All such variations and modifications are to be considered within the scope of the present invention the nature of which is to be determined from the foregoing description.