This invention relates to a filter unit, and particularly although not exclusively, to a filter unit for fitment within a waste receptacle, for example, within an urinal bowl.

It is known to provide strainers, for example, strainers 2, 4 shown in Figure 1 of the accompanying diagrammatic drawings, at the entrance to an outflow pipe 6 of a urinal bowl having a lower part 8. Strainer 2 (Figure la) , made of plastics, has a body part 10 which has a plurality of slots 12 therein. Strainer 4 (Figure lb) , made of metal, has a body part 12 which has a plurality of slots 14 therein. The body part 12 is pivotal about a pivot point 16 so that the body part 12 may be pivoted away from its position shown in Figure lb, thereby to allow access to the pipe 6. Each of the respective strainers 2, 4 are provided to strain liquid in a urinal bowl before the liquid passes into the outflow pipe 6. However, strainers 2, 4 only very coarsely strain the liquid and in practice allow relatively large matter, for example, cigarette ends and paper to pass into the outflow pipe. In due course, the outflow pipe 6 becomes clogged and the urinal bowl overflows with liquid. Unclogging of outflow pipe 6 requires disassembly of parts associated with the outflow pipe.

Furthermore, the strainers 2,4 are liable to acts of vandalism. For example, the pivot point 16 of strainer 4 may be forced and broken and the strainer removed. This results in the pipe 8 being even more liable to clogging by extraneous matter.

It is an object of the present invention to improve upon the aforementioned situation.

According to one aspect of the present invention, there is provided a filtration unit for fitment upstream of a drainage outlet of a liquid container in order to filter liquid passing into the drainage outlet from the container, the device comprising a filtration member for filtering liquid and securement means for securing the filtration device upstream of the drainage outlet.

Preferably, the filtration unit is arranged to filter from the liquid passing into the drainage outlet particulate matter having a minimum dimension of about 6mm and above. Preferably, particulate matter having a minimum dimension of about 5mm, more preferably of about 4mm, will be filtered by the device. In the most preferred embodiment, particulate matter having a minimum dimension of about 3mm may be filtered from the liquid passing into the drainage outlet. The filtration member of the filter unit preferably includes a plurality of perforations. Preferably, said perforations are arranged to filter matter, having the aforementioned dimensions, from the liquid passing into the drainage outlet. Preferably, all of the perforations, or at least a majority thereof, have the same dimensions. Typically, the maximum dimension of the perforations in any direction does not exceed about 6mm. Preferably it does not exceed about 5mm. More preferably it does not exceed about 4mm. In the most preferred embodiment, the maximum dimension of the perforations in any direction does not exceed about 3mm. The perforations may be of any shape but preferably the perforations are substantially circular in shape. Thus, in the most preferred embodiment, circular perforations are provided having a diameter of about 3mm.

Preferably, the sum of the total surface area of the perforations in the filtration member is greater than the

cross-sectional area of the drainage outlet relative to which the device is fitted, in use. Typically, the sum of the total surface area is at least about twice, preferably at least about 5 times the cross-sectional area of the drainage outlet. In a preferred embodiment, the sum of the total surface area is at least about 7 times, more preferably at least about 10 times the cross-sectional area of the drainage outlet.

Preferably, the centre of each perforation is spaced from the centre of an adjacent perforation by a distance in the range 3 to 8mm, preferably by a distance of about 5mm.

Preferably, the filtration device is in the form of a hollow rigid body, which is preferably enclosed, at least to some extent, on all sides. The body is preferably cylindrical in shape. Preferably the axial length of the cylinder is greater than the diameter thereof. Thus, the body may have a first end wall (which is an upper wall in use) , a second end wall (which is a lower end wall in use) and an endless side wall disposed between the first and second walls and attached thereto. The endless side wall preferably includes a plurality of perforations as described above. The first end wall is suitably not perforated and preferably comprises a cap which is secured to the body. In this respect, cap securement means is preferably provided for releasably securing the cap to the body. The cap securement means may comprise a rod member which is fixed at one of its ends to the cap and at an opposite end is releasably securable to the second end wall. The rod member is preferably screw threaded at its lower end and, in this case, the rod member may be secured to the second end wall by a locking nut arrangement.

Preferably, the second end wall of the rigid body is perforated. Preferably these perforations are of greater area compared to perforations in the endless si e wall of the body, when provided.

Lower end wall securement means is preferably provided for securing the lower end wall relative to the endless side wall. Preferably, the aforementioned rod member is arranged, in addition to securing the cap in position, to provide said lower end wall securement means. Preferably, a restrictor means is provided for restricting lateral movement of the endless side wall relative to the lower end wall when the two walls are secured together. In this respect, a formation on the endless side wall may be arranged to cooperate with a formation on the lower end wall. For example, an annular shoulder may be provided by the lower end wall against which shoulder the endless side wall may abut in use for prevention of relative lateral movement.

Preferably, the filtration unit further comprises an outflow pipe. Suitably, when provided, this may be fixed to the lower end wall of the device. The outflow pipe is preferably arranged to be sealingly connected to downstream pipework of the liquid container. The outflow pipe is preferably a threaded pipe. Preferably, the sum of the total surface area of the perforations in the filtrator member is greater than the cross-sectional area of the outflow pipe. Typically, the sum of the total surface area is at least about twice, preferably at least about 5 times the cross-sectional area of the outflow pipe. In a preferred embodiment, the sum of the total surface area is at least about 7 times, more preferably, at least about 10 times the cross-sectional area of the outflow pipe.

Preferably, an outer surface more preferably a major part of the whole outer surface, of the filter unit is highly polished an/or has a mirror finish. The outer surface may be coated with a material which is resistant to build up of chemical deposits such as alkaline or acidic deposits, for example, deposits of uric acid, or may be made of such resistant material, for example a said plastics material.

The invention extends to a filter unit as described in any statement herein in combination with a liquid container, the filter unit being fixed upstream of a drainage outlet of the container for filtering liquid prior to its passage into the drainage outlet of the container.

The invention further extends to a method of filtering liquid contained in a container, for example, in a urinal basin, sink or mortuary table, the method comprising securing a filter unit as described in any statement herein upstream of a drainage outlet of the container.

Specific embodiments of the invention will now be described, by way of example, with reference to the accompanying diagrammatic drawings, in which:

Figure 2 is a perspective view showing a filter unit in an urinal bowl;

Figure 3 is a perspective, partly cut away, view of a filter unit;

Figure 4a shows the filter unit of Figure 3 in cross- section in situ;

Figure 4b is an enlarged view of a region B in Figure 4a; and

Figure 5 is a cross-section along line A-A of Figure 4a.

A filter body 30 (Figure 2) of a filter unit 32 is fixed within an outflow passageway of a urinal bowl 34, the passageway being disposed in a lowermost region of the bowl 34 into which region fluid in the bowl is channelled. In use, liquid in the urinal bowl 34 is channelled towards the filter unit 32. In order to flow to an outflow pipe 36, disposed downstream of the outflow passageway, liquid passes into the filter body 30 and solid matter is removed thereby. Thus, solid matter does not pass into the pipe 36 and the tendency for pipe 76 to become blocked is reduced.

In more detail, referring to Figure 3, the filter unit 32 comprises the aforementioned filter body 30 which is fixed to a threaded pipe 38 having a locking nut 40, thereon. The locking nut 40 includes an annular flanged region 42. The filter body 32 is a rigid hollow structure which includes a perforated cylindrical region 44 which is closed by means of an end cap 46.

The end cap 46 includes a short annular skirt 50 (Figure 4) which has a diameter which is slightly greater than the diameter of the cylindrical region 44 so that the cap may engage sealingly around an upper part 52 of the cylindrical region. The body 30, furthermore, includes a perforated lower plate 54 having apertures 60 therein (Figure 5) . The plate 54 includes an annular seat 56 (Figure 4b) for engagement with a lower part 58 of the cylindrical region 44. The seat 56 is defined by means of

a tapering annular shoulder 90 which is disposed at an angle of about 110° to the main plane of the lower plate 54. The lower plate 54, furthermore, includes a central aperture 62 through which a fixing rod 48 passes. The fixing rod 48 is welded, at its upper end, to the end cap 46 and towards a lower end carries a nut 66 disposed on one side of the plate 54 and a nut 70 disposed on the other side thereof. A lower surface 72 of the plate 54 includes an annular seat 74. The lower surface 72 is sealingly fixed to the threaded pipe 38.

Assembly of the filter unit 32 is as follows. Threaded pipe 38 is sealingly welded to lower surface 72 of the perforated lower plate 54. The cylindrical region 44 is then fitted into the lower plate 54, outside the annular shoulder 90. Then, the end cap 46, with fixing rod 48 welded thereto and nut 66 located on the rod 48, is fitted on to the upper part 52 of the cylindrical region 44. As the end cap is fitted in place, threaded lower end 64 of the rod 48 enters the aperture 62 in the lower plate 54. The nut 66 acts as a stop member as it engages plate 54. Nut 70 is then threaded onto the threaded lower end 64 of the rod 48 and tightened against the plate 54. The provision of nut 66 stops the nut 70 from being over tightened which might cause the cap 46 to collapse inwardly.

When the filter unit 32 has been assembled, as described, the cap 46, cylindrical region 44, plate 54 and threaded pipe 38 are effectively secured in fixed positions relative to one another.

The filter unit 32 may be secured into an outflow passageway 80 in a lowermost region 82 of a urinal bowl, as follows. The filter unit 32 shown in Figure 3,

excluding the locking nut 40, is pushed into the outflow passageway 80 from above until the seat 74 of the plate 54 engages an annular seat 84 defined in the lowermost region 82 at the entrance to the outflow passageway 80. A rubber washer 84 and the locking nut 45 are then engaged around the threaded pipe 38. The locking nut is tightened against the lowermost region 82 of the urinal bowl to secure the filter unit in the urinal bowl.

It should be noted there when the unit is fixed in position, the plate 54 sealingly abuts the lowermost region 82 of the urinal bowl which, in turn, abuts the rubber washer 84 which, in turn, abuts the locking nut 40. With this arrangement, it is not possible to remove the filter unit 32 without removing the locking nut 40. If a person, for example, a vandal, attempts to dismantle the unit 32 by attempting to turn the cylindrical region 44 of the unit, this will, in general, not be possible due to the presence of nut 70. However, it may be possible to rotate the cylindrical region, for example a 1/4 turn. Nevertheless, the provision of angled annular shoulder 90 makes it generally impossible to move the cylindrical region laterally relative to the lower plate 54 and therefore, for a vandal to lever the cylindrical region away from the plate 54.

It is preferred that the filter unit 32 is made substantially of highly polished stainless steel material. The externally facing parts of the unit are highly polished, and preferably of a mirror finish. The mirror finish may prevent build up of alkaline substances and/or uric acid in the filter.

The reader\'s attention is directed to all papers and documents which are filed concurrently with or previous to

this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification

(including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings) , may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment(s) . The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.