AU709466B2 - A skimmer - Google Patents

Description

WO 97/07298 PCT/AU96/00502 A SKIMMER The present invention relates generally to a method and apparatus for separating two different materials, particularly a fluid and a solid material, and more particularly to a method and apparatus for separating solid material of relatively large size from a liquid. Even more particularly, the present invention relates to a pretreatment or preliminary step, such as a method and apparatus for separating debris, rubbish, leaves or the like from contaminated water which is to be treated. In particular, the present invention relates to a skimmer, particularly a skimmer used in an installation for separating oil from water, particularly water contaminated by petroleum products, including oils and the like. Even more particularly, the present invention relates to the use of a skimmer in the first step of an overall process of cleaning water, such as run-off water in an environment in which hydrocarbon oils such as motor-engine oils are used, sufficiently to enable the water to be discharged to the normal sewerage or drainage systems.

Although the present invention will be described with particular reference to a skimmer used to separate relatively large-sized trash, rubbish, debris or the like from contaminated water as the first step in an overall oil and water separation installation, it is to be noted that the skimmer of the present invention is not restricted in scope to the described embodiment or to the described use but rather the scope of the present invention is sufficiently broad to encompass other arrangements of the skimmer, and other uses, and application of the various forms of the skimmers.

In commercial or large scale cleaning and/or separating WO 97/07298 PCT/AU96/00502 2 installations, Particularly installations having one section open to the elements, rubbish and other debris such as packaging, paper cups, leaves, grass and the like settles onto the surface of a vat, tank, pit, pond or similar body of water which has been collected prior to being treated. Even in installations not open to the elements, rubbish can accumulate on the surface of the water in the collection area. In installations where the water is contaminated with a liquid having a lower density than that of water, such as for example an oil, particularly a petroleum-derived product such as engine oil, it is necessary to take the water from the top surface of the water layer at about the interface of the oil and water to ensure that the water is contaminated with sufficient oil for economic operation of the installation to ensure separation of the oil and water and to ensure that excessive amounts of oil are not admitted undiluted to the separation installation at concentrations of oil in excess of the operating parameters of the installation otherwise such installations will not properly separate the oil and water. The concentration of the oil in the water should be within a well defined range. Skimmers are used in such applications to admit the required amount of oil and water. However, skimmers hithertobefore available have suffered one or more serious disadvantages. One disadvantage is caused by the debris that falls into the pit, pond, tank or similar in that large size debris, such as packaging, twigs, leaves, grass and the like clogs the inlet to the skimmer, preventing the ingress of sufficient quantities of contaminated water for efficient, effective operation of the cleaning and/or separating installation.

One attempt to overcome this is to place small size open mesh or equivalent over the inlet to filter the debris from the water before the water is admitted to the skimmer.

However, due to the small size of the spacing in the mesh, the mesh quickly becomes clogged or blocked, particularly with vegetation such as leaves and the like, preventing the

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WO 97/07298 PCT/AU96/00502 3 further ingress of water.

Other arrangements of providing a filtering means to prevent the ingress of trash, rubbish, vegetation, leaves and the like have not been entirely satisfactory for much the same reason that the filtering means becomes clogged, requiring periodic maintenance and cleaning. In some cases, the filtering installation must be cleaned twice or more daily in order for it to be effective. Therefore, there is a need to provide an effective screening of rubbish, debris and the like from entering the skimmer, or more particularly from entering the separating/cleaning installation, which does not require excessive cleaning and maintenance.

Accordingly, it is an aim of the present invention to provide a skimmer arrangement having an effective and efficient filtering means which prevents the inlet from becoming blocked, clogged or the like due to trash, leaves, debris or similar, or when the filter does become blocked it may be easily cleaned, thus requiring much less maintenance.

According to the present invention there is provided an apparatus for separating a first material from a second material, such as for example a skimmer or barrier, said apparatus comprising an inlet means provided with at least one inlet port at least partially defined by a wall portion wherein at least a portion of the wall defining the inlet port is curved, said curved wall portion facilitating admission of a first fluid to the apparatus while substantially preventing or substantially orienting ingress of a second material to the apparatus, wherein said second material after contacting the curved wall portion is either prevented from entering the inlet port when the material is above a predetermined size or is directed or otherwise guided into a preselected orientation for admission to the WO 97/07298 PCT/AU96/00502 4 inlet port in the preselected orientation when below a predetermined size or of a preselected shape for collection at a remote location within the skimmer.

Typically, the first material is a fluid, more typically a liquid, most typically water contaminated with a hydrophobic or oleophilic material, such as for example an oil, particularly a petroleum-based product, especially a motor-engine oil or similar.

Typically, the second material is debris, rubbish, trash, leaves, grass, vegetation or similar large particle size solids material. More typically, the second material floats on the surface of the first material. Even more typically, the second material has a major axis which extends lengthwise along the material.

Typically, the material is acicular or other similar elongate shape. More typically, the material is oriented to flow in the same direction as its longitudinal or lengthwise extending axis after contacting the curved wall portion of the inlet means.

Typically, there are one, two, three, four or more inlet ports comprising the inlet means. More typically, each inlet port is provided with a curved wall portion defining at least a part of the port. Even more typically, there are up to eight or more inlet ports, each port having or being associated with its own curved wall portion. Even more typically, the inlet ports are spaced apart from each other, typically regularly spaced apart from each other around the circumference of a circle or other similar closed loop arrangement.

Typically, the inlet comprises an inflow weir, preferably having cut-outs or other flow control means. Typically, the base of the skimmer is fixed so as to be submerged and WO 97/07298 PCT/AU96/00502 5 the top floats at or about water level.

Typically, the skimmer of the present invention is provided with a flexible membrane. More typically, the flexible membrane is cylindrical in shape and impervious to the fluid in which the skimmer is partially submerged. Even more typically, the membrane is a sock or stocking material impregnated with a silicon.

Typically, the membrane is located intermediate the fixed stationary base of the skimmer and the floating top portion of the skimmer to accommodate fluctuations in the height of the top portion in accordance with variations of the water level.

Typically, the skimmer of the present invention is provided with a plurality of buoyancy tanks located at regular spaced apart intervals circumferentially around the periphery of the skimmer. Each buoyancy tank is substantially circular in shape having at least a curved wall portion. More typically, the inlet port is defined between the curved wall portions of adjacent buoyancy tanks.

Typically, the means for directing or otherwise guiding debris and rubbish into a preselected orientation is the curved walls of adjacent buoyancy tanks.

Typically, the skimmer of the present invention is provided with a removable receptacle for containing debris, rubbish and the like whilst allowing flow through of contaminated water.

Typically, the skimmer of the present invention is adapted to float at or near the water level by altering the buoyancy effect of the buoyancy chambers.

WO 97/07298 PCT/AU96/00502 6 The present invention will now be described by way of example with reference to the accompanying drawings in which: Figure 1 is a vertical cross-section of one form of the skimmer of the present invention; Figure 2 is a plan view of the inlet of the skimmer of Figure 1; Figure 3 is a vertical cross-section of a further form of the skimmer of the present invention; Figure 4 is a vertical cross-section of a still further form of the skimmer of the present invention; Figure 5 is a plan view of the skimmer of Figure 4.

In Figures 1 and 2, there is shown a first form of a skimmer in accordance with the present invention, generally denoted as 2. Skimmer 2 has a generally circular or annular inlet means 4 located at or towards the topmost surface of the top of the skimmer. Inlet 4 is defined by a cylindrical housing 6 made from a suitable material, such as for example plastics material, which is opened at the top to form the inlet 4 and open at the bottom 5 to form a throat or similar. An annular insert 8 is located within the top of housing 6 and is provided with an inflow weir portion 10 located around the upper end of housing 6. Weir 10 is optionally provided with a number of cut-outs (not shown) or other means to allow water to be admitted to skimmer 2 through inlet 4. Insert 8 is made from any suitable material, such as for example polyurethane foam or the like. Weir 10 is made with suitable dimensions, weight and buoyancy, along with housing 6, to float so that the top of weir 10 is just above the water level of the pond in which the skimmer 2 is located so that contaminated water may be admitted in controlled amounts through the cut-outs positioned at a lower level than the top of weir Housing 6 is provided with a circumferential flange portion WO 97/07298 PCT/AU96/00502 7 14 around its lower end in use. The outer surface of flange portion 14 is rebated inwards with respect to the outer surface of housing 6. A flexible sock, stocking, mesh 16 or other flexible impervious membrane is securely attached to the outer surface of flange 14 by a suitable fastening means, such as for example a circumferential strap 18, ring or similar. Therefore, sock 16 is securely attached around the lower in use edge of housing 6. Sock 16 is made from any suitable flexible material which is impervious to water. One particularly suitable material from which sock 16 is made is a heavy duty stocking material impregnated with a waterproof silicon material.

Skimmer 2 further comprises skimmer body 22 having a circumferential flange 24 or collar extending outwardly therefrom in an in use upwards direction towards housing 6 and membrane 16. The lower end of sock 16 is received over flange 24 and securely attached thereto by strap 26, ring clamp or similar located around the outer surface of sock 16 and flange 24. Body 22 is provided with an inlet throat 54 or similar for admitting water from the inlet 4 after passing through the cavity formed by the membrane into body 22 and is provided with outlet 30 to discharge the contaminated water free of debris or the like to the next step in the overall cleaning process to separate the oil from the water. Outlet 30 is connected to suitable discharge conduits (not shown) for conveying contaminated water free of debris to a suitable cleaning installation for separating the oil from the water.

With particular reference to Figure 2, insert 8 is, in one embodiment, formed with three generally arcuate shaped inlet ports 32 separated by a generally Y-shaped web portion having three curved legs 33 generally arranged at 1200 to each other about a central portion 34. It is to be noted that inlet 10 is arranged so that each inlet port 32 is defined by a curved wall portion 38 of housing 6 around WO 97/07298 PCT/AU96/00502 8 one side and a curved wall portion 36 formed from two adjacent legs 33.

In operation of this form of the present invention, skimmer 2 is located at the bottom of a pit or other suitable container of water such as a tank, pond, weir or the like, such that the base of body 22 rests upon the bottom of the pit, pond or similar and the top edge of inlet 10 is located about the level of the water, denoted by reference numeral 39 in Figure 1, with the top of weir 10 just above water level 40. It is to be noted that in this embodiment that the base of body 22 is located on the floor or base of the pond or vat and that the housing 6 is free to float on or close to the surface of water 39 in accordance with variations in the water level 39 by means of flexible sock 16 interconnecting body 22 and housing 6 either expanding or contracting as the contaminated water is selectively collected and discharged. Thus, inlet 4 is always able to receive contaminated water from the pond or similar.

Any leaves, debris or other large size particles are prevented from entering inlet 4 by being too large to pass through one of ports 32. Any debris of a size which is smaller than the inlet port 32 is oriented or directed into the desired orientation by contact with the curved wall 36 of either weir 10 or curved wall 38 of housing 6. This form of the present invention finds particular application for use in connection with a small scale or small capacity tank or container in which there is little variation in the level of the water by being located at the bottom of the tank. Such a skimmer is generally known as a fixed skimmer since it is fixed or otherwise fastened to the base, bed, floor, of the tank or pond in which it is located even though inlet 4 is free to float on or about the water surface or level 39.

When cleaning of skimmer 2 is required, skimmer 2 can be WO 97/07298 PCT/AU96/00502 9 retrieved or otherwise exposed and strap 26 unfastened allowing housing 6 to be separated from body 22, such as by strap 18 being loosened thereby allowing easy cleaning of the device and its components.

One embodiment of this form of the skimmer (not shown) is provided with a two-part body in place of the one-piece body 22, the two-part body comprising a main body portion which has the discharge outlet 30 and a base cap threadingly connected to the base of main body portion. In addition, a cylindrical strainer is provided below inlet throat or aperture 54 inside the main body. When it is desired to clean this form of the skimmer, the base cap can be easily removed by threadingly disengaging it from the base of body 22 so that the strainer can be removed or cleaned while the skimmer remains in situ. This embodiment obviates the need to remove the sock 16 from the main body 22 by unfastening the strap 26 and thus maintenance can be performed more easily and efficiently.

With particular reference to Figure 3, a further embodiment of the present invention will now be described. In Figure 3 there is shown a further form of the skimmer of the present invention generally denoted as 40. Skimmer 40 has many parts in common with skimmer 2, and accordingly the same reference numerals will be used to describe similar parts in both Figures 1 and 3 with respect to skimmer 2 and respectively.

Skimmer 40 is provided with circular or annular housing 6 having a lower in-use flange portion 14 as previously described. An insert 8 is located within the upper end in use of housing 6 and is provided with an upstanding inflow weir portion 10 forming an inlet 4 to skimmer 40. Weir is provided with a number of cut-outs (not shown) or similar depressions in its surface thus allowing water to flow over or through the depressions for admission WO 97/07298 PCTAU96/00502 10 internally into skimmer 40. Alternatively, or additionally, insert 8, and optionally housing 6, may be provided with ports to admit water into skimmer 40 through the ports located in the side wall of the upper portion of skimmer A flexible impervious membrane in the form of a sock 16 is securely fastened to the outer surface of flange 14 by strap 18 or similar ring clamp. Thus, in one embodiment of this form of the invention the upper portion of skimmer is the same as or similar to the upper portion of skimmer 2.

Skimmer 40 is provided with a modified body portion 42 which is a modified form of body portion 22. Body portion 42 is essentially bowl-shaped having a cylindrical side wall 44 in which is located an outlet 46 for discharging contaminated water via a suitable discharge conduit not shown and at a lower portion of wall 44 there is provided a drain 48, located remote from outlet 46, such as on the diagonally opposite side of body 42 to where outlet 46 is located. The upper circular edge of wall 44 defines a circular opening in which in use is received a lid 50 which is sealingly engageable with a flange 52 located circumferentially around the open upper end in use of body 42. Lid 50 is sealingly connected to body 42. Lid 50 is provided with an upstanding flange or collar 24 forming a circular opening inside the annular wall of collar 24 to which the lower end in use of sock 16 is securely fastened by means of a circumferential strap 26 or ring clamp or similar as described previously.

Collar or flange 24 may be integrally formed with lid 50 or may be securely fastened to lid 50 in the area around or forming the circumference of aperture 54. Lid 50, in one form, is made from a flexible or resilient material, such as rubber or plastics material. The peripheral edge of lid WO 97/07298 PCT/AU96/00502 11 is elastically deformable so as to be snugly receivable between flange 52 and securely held in place. A circular support ring 53 forming the top edge of wall 44 is provided around the circumference of the open end of body 42 and is located relatively in-board of flange 52.

The lower surface in use of lid 50 is provided with a circular or annular groove 56 formed by downwardly depending circular projection 58. Groove 56 has an outboardly directed semi-circular or similar curved profile for receiving a rubber O-ring 60 therein to provide a seal between lid 50 and a trash basket 61 downwardly depending from the underside of lid 50. Lid 50 is provided with a centrally located aperture 54 which in use is located in alignment with the opening formed by circular collar or flange 24 to allow contaminated water to flow freely into the body 42 of skimmer 40 in use.

Trash basket 61 is made from an open mesh material or similar apertured material for retaining relatively large size material whilst allowing the through flow of contaminated water is sealingly interconnected to the underside of lid 50 by means of rubber O-ring 60 or similar. Trash basket 61 may be easily removed from lid for cleaning of basket 61 and replaced due to the sealing press fit of the upper circumferential edge of trash basket 61 contacting O-ring An elongate handle 62 extends from the base of the trash basket 61 through aperture 54, through circular collar 24, through opening 5 and inlet 4 to extend substantially vertically outwardly above the top of skimmer 40 to enable trash basket 61 and associated components such as lid 50 to be removed from body 42 while the skimmer 40 is retained in situ in the pond or similar. One end of handle 62 is securely fastened to the base of trash basket 61 and handle 62 is provided at the other end with an eye 64 to which a WO 97/07298 PCT/AU96/00502 12 suitable rope, lanyard or the like (not shown) may be attached to assist in retrieval of the skimmer 40 from the pond and the trash basket 61 from the skimmer Operation of skimmer 40 is similar to that of skimmer 2 except that skimmer 40 can be either fixed in place as in the case of skimmer 2 or may float in a suitable container such as a tank, pit, pond or the like in which it is located. The discharge pipe or conduit connected to outlet 46 may be either fixed or flexible, depending on whether body 42 is fixed in place or whether skimmer 40 is free to float. If skimmer 40 is fixed in place, housing 6 floats at a level so that weir 10 is slightly above water level 39 and any variation in the water level 39 is accommodated by movement of housing 6 and sock 16 to maintain housing 6 in fluid communication with body 42. If skimmer 40 is free to float in its entirety, it adopts a position in which weir is located above water level 39.

A further form of the skimmer of the present invention which is shown in Figures 4 and 5 will now be described.

The skimmer of Figures 4 and 5, generally denoted as 80, is similar to skimmer 40 apart from skimmer 80 additionally having a plurality of buoyancy chambers 82, 83 located circumferentially at spaced apart locations around the circumference of body 42. Similar reference numerals to those used in the description of the embodiment of Figure 3 will be used to describe the embodiment of Figures 4 and In this embodiment there are eight separate buoyancy chambers 82, 83 located at regularly spaced apart intervals circumferentially around the perimeter of the skimmer surrounding housing 6 and sock 16 of the skimmer. with particular reference to Figure 4, it can be seen that one form of the buoyancy chamber, denoted as 82, is formed with the inner cylindrical wall 84 formed as a continuation of flange 52 of the embodiment shown in Figure 3. Inner wall WO 97/07298 PCT/AU96/00502 13 84 extends from outlet 46 at the lower end in use to above the level of inflow weir 10. Buoyancy chamber 82 is formed with circular base 86 and top circular disc 88 provided with aperture 90 which is provided with a suitable closure means (not shown) for maintaining a desired air space in buoyancy chamber 82. Upper surface 88 is provided with upstanding circular flange 92 which surrounds the upper portion of the skimmer.

Another form of the buoyancy chamber useful with skimmer is denoted as 83 in Figure 4. Buoyancy chamber 83 has an inner cylindrical wall 84 formed as a continuation of flange 52 and is provided with a base 85 having a centrally circular opening 87 for allowing ingress of water into the interior of the chamber 83. A small air release hole 89 is provided in the outboard side of wall 84 to determine the level to which water rises inside chamber 83. In this manner the air hole can be located at a preselected position to control the height at which the skimmer floats in water. It is to be noted that the one skimmer 80 can have all the same types of chambers or a mixture of chambers.

With particular reference to Figure 5, there can be seen an inlet port 94 located between two adjacent buoyancy chambers 82. Inlet port 94 may extend to any desirable or suitable depth between the top and base of the buoyancy chambers. In one example, inlet port 94 is open over the entire height of buoyancy chamber 82.

In operation of skimmer 80, the skimmer is located on the surface of a suitable tank or the like such that the water level 39 is just below inflow weir 10. The position of skimmer 80 may be accurately determined by altering the amount of lift from the buoyancy chambers 82.

Any debris or rubbish in the vicinity of skimmer 80 is WO 97/07298 PCT/AU96/00502 14 forced to flow towards skimmer 80 whereupon it contacts the curved walls 84 of buoyancy chambers 82. Any rubbish larger than the spacing between adjacent buoyancy tanks 82, that is, larger than inlet port 94, is prevented from entering into the interior of skimmer 80. Any material small enough to pass through port 94 is oriented in its lengthwise extending direction so as to flow between adjacent buoyancy chambers 82 with its lengthwise extending direction aligned in the direction of flow. Thus, the curved walls 84 act as a guiding or directing means to orient and direct rubbish of a preselected size and shape to flow in a preferred orientation into inlet 4 of skimmer Rubbish in this orientation flows through inlet 4, opening 5, and through aperture 54 into trash basket 61 where it is collected. Due to the orientation of the rubbish, it does not span inlet 94 nor inlet 4 to cause blockage or clogging of the inlet, but rather flows directly into trash basket 61 without hindering or adversely affecting the flow of contaminated water through the skimmer. Thus, using the skimmer of the present invention, the rubbish collects in the trash basket which can be emptied periodically.

It is to be noted that the base of trash basket 61 is located below the level of discharge outlet 46 so that, as the rubbish accumulates at the bottom of trash basket 61, contaminated water can flow through the skimmer for discharge through outlet 46. The accumulating rubbish does not block or clog discharge outlet 46 or interrupt the flow of contaminated water through the skimmer.

One modification of the buoyancy tanks of this form of the skimmer is to provide different sized buoyancy tanks around the outside of the skimmer which allows the skimmer to be selectively adjusted in position in use. The modified buoyancy tanks may be sealed or partially sealed and may be filled with any suitable material assisting in flotation, WO 97/07298 PCT/AU96/00502 15 such as for example filled with a gas or filled with buoyancy aids such as flotation spheres like polystyrene beads or the like.

Advantages of the present invention include the following: The skimmer of the present invention is cheap to manufacture and inexpensive to operate.

The guiding means for directing or orienting rubbish allows the rubbish to be oriented in a preselected orientation allowing accumulation of rubbish in a trash basket without affecting the through flow of contaminated water. This results in less maintenance and more efficient operation of the skimmer.

The described arrangement has been advanced by explanation and many modifications may be made without departing from the spirit and scope of the invention which includes every novel feature and novel combination of features hereindisclosed.

Those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described. It is understood that the invention includes all such variations and modifications which fall within the spirit and scope.

Claims (1)

1. 05-96..doc 16/06/99 17 petroleum product is a motor-engine oil. 7) An apparatus according to any one of claims 3 to 6 in which the second material is debris, rubbish, trash, leaves, grass or vegetation which floats on the surface of the water. 8) An apparatus according to any preceding claim in which the second material has a major axis which extends lengthwise along the material in that the material is substantially acicular or elongate in shape. 9) An apparatus according to claim 8 in which the second material is oriented to flow in the same direction as its longitudinal or lengthwise extending axis after contacting the curved wall portion or the inlet means. An apparatus according to any preceding claim in which the inlet means comprises one, two, three, four or more inlet ports, wherein each inlet port is provided with one or more curved wall portions defining at least a part of the inlet port. 2 5 11) An apparatus according to claim 10 in which there are up to eight or more inlet ports, each port having or being associated with one or more curved wall portions. 12) An apparatus according to claim 10 or 11 in which the inlet ports are spaced part from each other. 13) An apparatus according to claim 12 in which the inlet ports are regularly spaced apart from each other S around the perimeter of the apparatus. 14) An apparatus according to any preceding claim in which the inlet means comprises an inflow weir having cut- outs or other flow control means located at spaced apart H:\Sirid\keep\patents\66505-96.doc 16/06/99 18 locations around the top edge of the inflow weir. An apparatus according to any preceding claim further comprising a flexible membrane means interconnecting the base portion and the top portion of the apparatus. 16) An apparatus according to claim 15 in which the flexible membrane is cylindrical in shape in use and impervious to the fluid in which the apparatus is located. 17) An apparatus according to claim 15 or 16 in which the flexible membrane is a sock or stocking material impregnated with a silicone or silicone rubber or similar material. 18) An apparatus according to any one of claims 2 to 17 further comprising a plurality of buoyancy tanks to enable at least the top portion of the apparatus to adopt a predetermined or preselected location within the fluid in which it is located. 19) An apparatus according to claim 18 in which the buoyancy tanks are located at regularly spaced apart intervals circumferentially around the periphery of the apparatus. An apparatus according to claim 18 or 19 in which the buoyancy tank is substantially circular in shape having e. ,30 at least a curved wall portion. 21) An apparatus according to any one of claims 18 to in which the inlet port is defined between the curved wall portions of two adjacent buoyancy tanks. 22) An apparatus according to any preceding claim further comprising a removable receptacle for containing H:\Sigrid\keep\patents\66505-96.doc 16/06/99 19 debris, rubbish or vegetation whilst allowing flow through of contaminated water. 23) An apparatus according to any one of claims 18 to 22 in which at least the top portion of the apparatus or the apparatus itself is adapted to float at or near the water level in which it is located under the buoyancy effect of the buoyancy tanks. 24) An apparatus according to any one of claims 2 to 23 in which the apparatus is adapted to be fixed at or towards the base of a vessel, pond, vat, tank or container for holding the contaminated water. 25) An apparatus according to any preceding claim further comprising an outlet port or discharge means for discharging contaminated water substantially free of debris, rubbish, trash, vegetation or leaves. 26) An apparatus according to any preceding claim which is a skimmer for separating debris from contaminated water. 27) A method of separating a first material from a second material using an apparatus according to any :preceding claim. S28) An apparatus for separating a first material from a second material substantially as hereinbefore defined 30 with reference to the accompany drawings. Dated this 16th day of June, 1999 INTERNATIONAL FLUID SEPARATION PTY LTD By their Patent Attorneys GRIFFITH HACK Fellows Institute of Patent and Trade Mark Attorneys of Australia H:\Sigrid\keep\patents\ 6 6 5 0 5 9 6 .doc 16/06/99