APPARATUS FOR SKIMMING A LIQUID SURFACE

Abstract: An apparatus for skimming a liquid surface comprises a weir (9) having an adjustable level, a pump (12) or the like to permit the level of the liquid which has passed over the weir to be lowered, a float (3) for detecting the level of the liquid which passed over the weir, a drive (4, 5, 6, 7) for adjusting the level of the weir in dependence upon the detected level, and a filter (11) arranged to filter liquid which has passed over the weir. The float and weir are mounted for pivotal movement about generally-horizontal spaced-apart axes, and the drive causes contra-rotation of the float and weir.

Description: TITLE Apparatus for Skimming a Liquid Surface DESCRIPTION This invention relates to apparatus for skimming a liquid surface. The apparatus is intended to be used to maintain the surface of, for example, ornamental or display ponds (or "water features"), fishponds and swimming pools by removing, for example, leaves, litter and scum. In accordance with the present invention, there is provided an apparatus for skimming a liquid surface, comprising a weir having an adjustable level, means to permit the level of the liquid which has passed over the weir to be lowered (e.g. by a pump, siphon or drainage to a lower level), means for detecting the level of the liquid which passed over the weir, and means for adjusting the level of the weir in dependence upon the detected level. The adjustment means can therefore be arranged so that there is automatically a fairly consistent flow of liquid over the weir, regardless (within limits) of the level of the liquid on the upstream side of the weir. Preferably the apparatus includes a filter arranged to filter liquid which has passed over the weir. In this case, the detecting means is preferably arranged to detect the level of the liquid which has been filtered. If this is done, the filter not only filters the liquid, but also damps the movement of the float and weir so that they do not oscillate greatly or resonate in response to waves in the liquid. Preferably, the detecting means comprises a float. In this case, the float is preferably mounted for pivotal movement about a generally-horizontal float axis. Preferably, the weir is mounted for pivotal movement about generally-horizontal weir axis. The float axis and weir axis may be coaxial, but preferably the float axis and weir axis are spaced apart and generally mutually parallel. Preferably, they are generally at the same height. Preferably, the weir axis is disposed generally between the float and the float axis. The adjusting means preferably comprises a proportional drive between the angular position of the float and the angular position of the weir. This all provides for a very compact arrangement. Preferably, the angular velocity ratio of angular movement of the float to angular movement of the weir is less than unity. The drive preferably causes contra-rotation between the float and the weir. The drive preferably simply comprises a pair of meshing gears fixed relative to the float and the weir, respectively. The apparatus is preferably arranged so that the liquid can leak between the two sides of the weir without passing over the weir. A small amount of leakage does not have any significant detrimental effect on the operation of the apparatus, but obviates the need for good seals between the moving parts, which would add to the cost of the apparatus and also produce friction. Especially when used in water containing fish, the weir is preferably provided by a portion of an apertured member below the aperture therein so that the size of the aperture limits the size of the matter which can pass over the weir. In this case, a portion of the apertured member above the aperture is preferably movable relative to, or removable from, the remainder of the apertured member to provide cleaning access to the downstream side of the weir, and in particular to the filter, if provided. Especially when used in water on which is floating undesirable living matter such as mosquito eggs, pupae and larvae, the apparatus preferably includes an ultraviolet light source arranged to irradiate matter which has passed over the weir. The weir, filter if provided, detecting means and adjusting means may be contained in a housing, which may be fixed or arranged to float in the liquid. Alternatively, they may be fitted into some larger apparatus or into the natural surroundings. A specific embodiment of the invention and a modification thereto will now be described, being a fixed, boxed skimmer operating in water, by way of example, with reference to the accompanying drawings in which: Figure 1 is a plan view of a skimmer forming an embodiment of the invention; Figures 2 to 5 are sectioned side views of the skimmer of Figure 1 at differing operational states; namely: Figure 2 not in operation and the external fluid level at its upper limit. Figure 3 in operation and the external fluid level at its upper limit. Figure 4 not in operation and the external fluid level at its lower limit. Figure 5 in operation and the external fluid level is at its lower limit. Figure 6 is a schematic sectioned side view of the skimmer of Figure 1 to illustrate the operation of a geared float arm and drum gear thereof. Figure 7 is a sectioned side view of a modified skimmer. Referring to Figures 1 to 6, the whole skimmer is contained within a box 1 , which has a rimmed aperture 8 in the front face. The box is drawn without any lid, but may be provided with one. The rimmed aperture is shaped to the diameter of a drum 2, which houses the skimming aperture and skimming edge 9. The ends of the skimming aperture 10 are rimmed to maintain a sufficient seal against the box rimmed aperture 8 as the drum 2 rotates about its axis. The drum 2 is removable for cleaning of a filter element 11 , being located at each end to a slide out socket arrangement 7. The drum 2 is linked to a float 3 by float arms 4 and gears 5, 6. The gears 5 are fast with the float arms 4, and the gears 6 are fast with the drum 2. The float arms 4 are mounted for pivotal movement in the box 1 about the axis of the gears 5. In the embodiment shown in the drawings, the gear ratio produces an angular velocity ratio of about 1:2 float:drum. The range of rotation of the float, ergo that of the drum, is limited within design limits by the gear ratio and the geometry of the slots 15 in the arms 4. This is to ensure alignment of the drum sockets 7 for drum 2 removal, and to maintain a narrow gap between the drum 2 and the top and bottom edges of the box rimmed aperture 8. Both pins 16 17, about which the drum 2 and the arms 4 rotate, are securely fixed to the box ends. The amount of buoyancy turning moment provided by the float 3 is arranged to be half that of the weight turning moment of the float 3 and float arms 4. In this way the rotational forces applied to the drum 2 are approximately equal in each direction of rotation. The drum 2 is preferably balanced on completion, by the addition of weights at appropriate locations, to prevent it contributing any turning moment to the mechanical system during skimmer operation. The skimmer operates over a range of water levels, between high water 13 (Figures 2 and 3) and low water 14 (Figures 4 and 5). At all water levels between high and low water the skimming edge 9 of the drum 2 is maintained a short distance above the water level when the box is not being drained (Figures 2 and 4). Operation of a remote means 12, such as a pump, to drain the water level at the float 3, causes the drum 2 to rotate until the rate of flow of water over the skimming edge 9 balances with the flow leaving the box (Figures 3 and 5). Upon stopping water removal, the float 3 immediately starts to rise in response to continued ingress of water over the skimming edge 9. Once the skimming edge 9 is raised clear of the water, water continues to seep past the imperfect seal between the drum rim 10 and the box skimming aperture 8, until the internal water level has returned to that outside the box. The filter element 11 is provided by perforations in the drum 2 generally opposite the skimming aperture 10. The perforation diameter may be sufficiently small, e.g. 0.5 mm, as to prevent all unwanted matter passing through the filter element 11. Alternatively, the perforation diameter may be sufficiently small, e.g. 6 mm, as to filter out matter which would damage the pump 12, and then a secondary filter may be provided to remove other unwanted matter. The skimming aperture is arranged to be large enough for at least human hand access to remove debris without removing the drum, which, for some designs, would be too heavy. In these cases, or for any other reason, the drum need not be made removable. A drum aperture that is large enough to access for cleaning could be too large for the skimming application. Therefore, as shown in Figure 7, an optional hinged or removable skimmer guard 18 provides a means to govern the size of the skimming aperture to the particular requirements. This might be to prevent larger items of debris or marine life from interrupting the skimming process or being trapped within the skimmer. The addition of an ultraviolet lamp 19, within the skimmer guard, provides a means to irradiate floating mosquito eggs, pupae and larvae trapped during the skimming action. Power supply to the lamp would be arranged from a suitable box lid, controlled in any way desirable, whether manually or automatically outside the box 1, or automatically within the box 1 by a position switch or similar. It should be noted that the embodiment of the invention and modification thereto have been described above purely by way of example and that many other modifications and developments may be made thereto within the scope of the present invention.

Claims: CLAIMS I. An apparatus for skimming a liquid surface, comprising a weir (9) having an adjustable level, means (12) to permit the level of the liquid which has passed over the weir to be lowered, means (3) for detecting the level of the liquid which passed over the weir, and means (4,5,6,7) for adjusting the level of the weir in dependence upon the detected level. 2. An apparatus as claimed in claim 1, further including a filter (11) arranged to filter liquid which has passed over the weir. 3. An apparatus as claimed in claim 2, wherein the detecting means is arranged to detect the level of the liquid which has been filtered. 4. An apparatus as claimed in any preceding claim, wherein the detecting means comprises a float (3). 5. An apparatus as claimed in claim 4, wherein the float is mounted for pivotal movement about a generally-horizontal float axis. 6. An apparatus as claimed in any preceding claim, wherein the weir is mounted for pivotal movement about a generally-horizontal weir axis. 7. An apparatus as claimed in claim 6 when dependent on claim 5, wherein the float axis and weir axis are spaced apart and generally mutually parallel. 8. An apparatus as claimed in claim 7, wherein the float axis and weir axis are generally at the same height. 9. An apparatus as claimed in claim 7 or 8, wherein the weir axis is disposed generally between the float and the float axis. 10. An apparatus as claimed in any of claims 6 to 9 when dependent directly or indirectly on claim 5, wherein the adjusting means comprises a proportional drive (5,6) between the angular position of the float and the angular position of the weir. II. An apparatus as claimed in claim 10, wherein the angular velocity ratio of angular movement of the float to angular movement of the weir is less than unity. 12. An apparatus as claimed in claim 10 or 11, wherein the drive causes contra-rotation between the float and the weir. 13. An apparatus as claimed in claim 12, wherein the drive comprises a pair of meshing gears (5,6) fixed relative to the float and the weir, respectively. 14. An apparatus as claimed in any preceding claim, and arranged so that the liquid can leak between the two sides of the weir without passing over the weir. 15. An apparatus as claimed in any preceding claim, wherein the weir is provided by a portion of an apertured member (2;2,18) below the aperture therein so that the size of the aperture limits the size of matter which can pass over the weir. 16. An apparatus as claimed in claim 15, wherein a portion (18) of the apertured member above the aperture is movable relative to, or removable from, the remainder of the apertured member to provided cleaning access to the downstream side of the weir. 17. An apparatus as claimed in any preceding claim, and including an ultraviolet light source (19) arranged to irradiate matter which has passed over the weir. 18. An apparatus as claimed in any preceding claim, wherein the weir, detecting means and adjusting means are contained in a housing (1). 19. An apparatus as claimed in any preceding claim, wherein the means to permit the level of the liquid which has passed over the weir to be lowered is provided by a pump.

Inventors: MILES JOHN ARTHUR, MILES, JOHN, ARTHUR
Applicants: MILES JOHN ARTHUR, MILES, JOHN, ARTHUR
Application year: 2000
Main classification: E04H4
IPC codes: E04H4