TECHNICAL FIELD

The present invention relates to an apparatus for removing floating elements from a liquid surface. The apparatus is preferably applied, but not exclusively, to residential and industrial wastewater treatment plants, but also to fat separation tanks in the dairy industry, or to chemical/physical treatment tanks for the precipitation of elements in solution.

BACKGROUND OF THE INVENTION

In said plants there is always at least one apparatus used for removing floating elements from the surface of the liquid mass. Said materials are mainly composed of fat emulsions, foams, and generally solid elements that float on the free surface of the liquid mass. The apparatus of this type generally comprise a degreasing carriage provided with wheels being adapted to move along a dedicated pair of parallel guides. A swinging arm provided with a float and a floating knife is mounted on the carriage. The swinging arm is also equipped with command rollers which, in turn, roll along a set route back and forth so that the arm (with the float and the floating knife mounted thereof) is in the down position during the cleaning mode (working or front-running mode) while being in a raised position with respect to the free surface of the water when the floating knife is in the return mode (i.e., during non-working or reversing mode) .

All these measures are directed towards the fact that the free surface of the wastewater must always be swept in the same direction, while during the floating knife reversing mode, as mentioned, must be raised (with respect to the free surface of the water) , as if it remains lowered at least part of the debris might be swept up and down the degreasing channel without being expulsed towards an evacuation unit, as desired, to then be eventually directed towards a waste treatment plant . To this aim, therefore, during the carriage reversing mode, the floating knife, the float and the arm are raised in the above described mode .

However, one of the disadvantages that more frequently occur during the operation of said degreasing carriage is due to the fact that its wheels become blocked while rolling within the relative guides. In fact, due to the deformations that, for various reasons, are produced on the guides, said guides lose their parallelism along the floating knife channel so that the wheels of the carriage that are in these guides become blocked, with all the negative consequences of the case. Other wheel blocking factors along the tracks may be the presence of debris on the tracks themselves, or treatments to which the tracks have been submitted before use.

The present apparatus is designed, therefore, to overcome this and other disadvantages that will be later described.

SUMMARY

According to the present invention a device is provided for removing floating elements as claimed in claim 1 or any of the claims directly or indirectly dependent from claim 1.

BRIEF DESCRIPTION OF FIGURES

For a better understanding of the present invention, certain preferred embodiments will now be described, purely by way of non limitative example and with reference to the attached drawings, in which:

Figure 1 illustrates a side view of a compact type residential and/or industrial wastewater treatment plant comprising an apparatus object of the present invention; - Figure 2 shows a plan view of the plant of figure 1;

- Figure 3 shows a front view of the plant of figures 1, 2 ;

- Figure 4 illustrates a first configuration of a first embodiment of an apparatus for removing floating pollutant elements according to the present invention;

Figure 5 shows a three dimensional view of a second configuration of the apparatus of Figure 4;

- Figure 6 shows a side view of the first embodiment of the apparatus object of the invention while moving forward, i.e., in a "working mode";

- Figure 7 illustrates a side view of the first embodiment of the apparatus object of the invention while moving in reverse, i.e. when the apparatus is in a "non-working mode" ;

- Figure 8 shows a side view of the apparatus illustrated in Figures 6, 7, while sliding along an inclined plane to carry- out the discharge of floating pollutant elements in a discharge hopper;

- Figure 9 shows a second embodiment of the apparatus object of the invention;

- Figure 10 shows a side view of the second embodiment of the apparatus object of the invention while moving forward i.e., in a "working mode";

- Figure 11 shows a side view of the second embodiment of the apparatus object of the invention while is moving in reverse, i.e. when the apparatus is in a "non-working mode," and

- Figure 12 is a perspective view, with some details removed for clarity, of a variant of the treatment plant of figure 1.

EMBODIMENTS OF THE INVENTION

In Figures 1-3 with 100 is indicated as a whole a compact type residential and/or industrial wastewater treatment plant in which an apparatus 10 for removing floating pollutant elements according to the present invention has been used. In a known way, the wastewater treatment plant 100 comprises a tank 101, supported on the ground by a structure (STR) , in turn comprising, a tailings pond 102 separated from a degreasing area 103 by a fat-capturing bulkhead 104, whose shape and function will be described later. In the tailings pond 102 wastewater to be treated enters through an inlet mouth (INL) . The water flows into the tank 101 from the inlet mouth (INL) towards an outlet mouth (OTL) substantially in accordance with a direction and a way indicated by an arrow (Fl) (Figures 1, 2) .

However, it should be said that before entering the tank 101 the wastewater undergoes other well known treatments, such as the separation of solid pollutants (e.g. mechanical filtration and grit removal), by means of appropriate apparatus not shown.

The fat-capturing bulkhead 104, along with a wall 101A of the tank 101 parallel thereto, defines the abovementioned degreasing area 103 that extends in a direction parallel to (Fl) . Within the degreasing area 103 is operated the abovementioned apparatus 10 for removing floating pollutant elements (see below) .

To allow the unidirectional passage of floating pollutant elements from the tailings pond 102 to the degreasing area 103 the fat-capturing bulkhead 104 is provided with a plurality of windows 104A. In addition, in the tailings pond 102 there is an insufflation device 130 of compressed air, immersed in the liquid mass (ML) , which pushes the floating pollutant elements towards the free surface (PL) of the wastewater in the tank 101 and in particular towards the free surface (PL) of water which is in the degreasing area 103 from which, as will be seen, is evacuated from the apparatus 10 made according to the dictates of the present invention.

As shown in particular in Figure 3, the floating pollutant elements are routed from the tailings pond 102 to the degreasing area 103 through the plurality of openings 104A made in the bulkhead 104 by the action exerted upon them by jets of compressed air exiting the tubes of the insufflation device 130.

As will be better seen in the following when the operation of the apparatus 10 will be described in more detail, at the end of the degreasing area 103 there is an exhaust system 140 of floating pollutant elements dragged by the floating knife of the apparatus 10 and by a traction unit 145, for example a geared motor that, as will be seen, acts upon on said floating knife (see below) . The operation of the treatment plant 100 where the apparatus 10 object of the present invention is integrated is as follows :

(a) the wastewater is introduced into the treatment plant 100 through the inlet mouth (INL) and flows toward the outlet mouth (OTL) in a direction and a way indicated by the arrow (Fl) ;

(b) the wastewater goes through a mechanical filtration device (not shown) in which more bulky residues are retained;

(c) entering the tailings pond 102, however, the water is still full of sand and floating pollutant elements; the sand falls by gravity towards the bottom of the tailings pond 102 and is separated from it by a grit removal device (not shown) ; and in addition, always in the tailings pond 102, the water is cleaned by jets of compressed air delivered by the insufflation device 130, jets of compressed air that, agitating the liquid mass, facilitate the separation and ascent of the floating pollutant elements; and

(d) as far as possible, the floating pollutant elements by way of the plurality of openings 104A made in the fat-capturing bulkhead 104 and are sent towards the free surface (PL) of the water in the degreasing area 103, from which is then evacuated by the action of the apparatus 10 by means of the exhaust system 140.

In Figures 4-7 with 10 is indicated as a whole, as has been said, a first embodiment of the apparatus for removing floating pollutant elements according to the present invention.

The device 10 comprises a floating raft 20 whereon is mounted a floating knife 21 provided in this case with a hydraulic double-effect pendulum 22.

The hydraulic double-effect pendulum 22 in reality is merely a balance scale activated by liquid flows (FF) created by the relative motion between the floating raft 20 and the liquid mass (ML) (Figures 6, 7).

Furthermore, as explained in greater detail in Figures 4, 5, the floating raft 20 comprises two pontoons 23, 24 substantially parallel to each other and joined to each other, on the one hand by a cross member 25 and on the other hand by the floating knife 21, which is also transversal to the lying directions of the two pontoons 23, 24. In addition, the floating knife 21 is constrained to a rotation having an axis (X) (Figure 5) by means of hinges 26, 27 placed at the front ends 23A, 24A (Figure 5) of the respective floating pontoons 23, 24.

The hydraulic double-effect pendulum 22 is adapted for rotating the floating knife 21 around the axis (X) .

The floating knife 21 has an inner face 21A (Figure 5) and an outer face 21B (Figure 4) with respect to the direction of progress in working mode indicated by an arrow (F2) parallel, but of opposite direction, to the arrow (Fl) (Figure 2) . When the floating knife 21 is in the working position shown in Figures 4, 6 its inner face 21A is supported at the front ends 23A, 24A, slightly sloping, of the two pontoons 23, 24. Obviously, the front ends 23A, 24A, can be perpendicular with respect to a longitudinal axis (not shown) of the pontoons 23, 24.

As shown in Figure 6, the inner face 21A of the floating knife 21 abuts against the front ends 23A, 24A due to the pressure exerted upon the outer face 2IB of the water when the floating raft 20 moves in the direction and way indicated by the arrow (F2) .

As shown in particular in Figure 4, the inner face 21A of the floating knife 21 is integral to the hydraulic double-effect pendulum 22 comprising, in turn, an arm 31 to which a fin 32 at its free end is fixed. The fin 32 has, in turn, an inner face 32A and an outer face 32B. As illustrated in more detail in Figure 6, during the work stroke the floating knife 21, provided with the hydraulic double-effect pendulum 22, is affected by the liquid flows (FF) and given the suitable arrangement of the rotation axis (X) , said floating knife 21 rotates around the axis (X) reaching an almost vertical plane with respect to the free surface (PL) of wastewater to be purified.

At the same time also the outside face 32B of the fin 32 is affected by the liquid flows (FF) . Said action of the liquid flows (FF) on the outer face 32B helps to press the inner face 21A of the floating knife 21 on the ends 23A, 24A of the pontoons, 23, 24 respectively.

As shown particularly in Figures 2, 8 to the floating knife 21 a harness 160 is attached pulled by a first branch 161A of a cable 161 which, in turn, is wound around a pulley system 162 placed in rotation by the traction unit 145. A second branch 161b of the cable 161 is deflected by an idler pulley 165 (Figures 1, 2). The second branch 161 is hooked to the crossbar 25 by means of a harness 166 (Figure 2) .

During the working stroke (arrow (F2); Figures 6, 8), the floating raft 20 moves from a first end position (posl) to a second end position (pos2) . In this case, the floating elements 300 (Figure 8) that float on the free surface (PL) of the water which is in the degreasing area 103 are pushed by the outer face 2IB of the floating knife 21 towards the exhaust system 120.

To facilitate the discharge of pollutant elements 300 (Figure 8) in the exhaust system 120 in the final part of the work stroke (second end position (pos2 ) ) a slide 170 is arranged whereon slides the floating raft 20 due to the traction exerted on it by the first branch 161A of the cable 161. In reality, the pulling action of the traction unit 145 on the floating raft 20 is exerted on the whole work stroke of the floating knife 21 along the degreasing area 103. The traction force of the branch 161A of the cable 161 on the floating raft 20 has a point of application of the traction force (Ftl) at or above the axis (X) (Figures 6, 8).

As shown particularly in Figures 4, 5, to improve the stability of the floating raft 20 it has been verified that on each side edge 21C, 21D of the floating knife 21 it is advantageous to apply a driving and sealing elastic element respectively, 33, 34, such as a brush. The free tips of the elastic elements 33, 34 are supported on the wall 101A of the tank 101, at one part, and on the fat-capturing bulkhead 104, at the other (Figure 3) and sweep said elements both in the work stroke and in the return stroke (see below) .

The floating raft 20 of the apparatus 10, therefore, is self- sustaining and self-leveling at the varying of height of the free surface (PL) of wastewater to be purified.

A suitable shape, with suitable bevels 20 of the floating raft, or so called "catamaran", creates a "hydrodynamic skate" effect on the sides of the floating raft 20 itself, which fluidizes its motion, both during work and return modes.

In order to guarantee a correct sliding of the floating raft 20 in the degreasing area 103 it is important that there is a proper proportion between the width (La) (substantially equal to the width of the degreasing area 103) of the floating raft 20 and its length (Lu) (Figure 2) . It has been verified by way of calculation and experimentation that the following relation holds true:

(Lu)> (1.25 ÷ 1.5) * (La) Furthermore, in a further embodiment not shown, the position of the cross member 25 along the two pontoons 23, 24 can be adjusted to change the weight distribution between the front and rear part of the floating raft 20, avoiding possible overturning of the floating raft 20 itself.

During the return stroke according to an arrow (F3) (Figure 7), instead, the floating raft 20 proceeds in reverse having appropriately reversed the direction of the traction force which has now been designated as (Ft2) . Therefore, during the return stroke the floating raft 20 moves from the second end position (POS2) to the first end position (POS1) .

Obviously, to make the direction change of the floating raft 20 from the arrow (F2) to the arrow (F3) the traction unit 145 causes the change of rotation to a system of pulleys 162. The floating knife 21, due to the hydraulic double-effect pendulum 22, now affected by the liquid flows (FF) with motion contrary to the arrow (F3), it now maintains an approximately horizontal position, lying on a plane that does not allow the floating knife 21 itself to interfere with the free surface (PL) of wastewater.

In this case, as shown in Figure 7, the relative motion between the floating raft 20 and the wastewater generates forces that act upon the inner face 32A of the fin 32. A torque is therefore also generated, substantially due to the resultant of hydraulic forces exerted on the inner face 32A for the length of arm 31. Said torque causes the arm 31, the fin 32 and the floating knife 21 to rotate clockwise around the axis (X) .

As long as the floating raft 20 moves along the degreasing area 103 according to the arrow (F3), the hydraulic forces acting on the fin 32 keep the floating knife 21 raised preventing in the returning movement that the floating knife 21 itself may drag any possible floating elements in the degreasing area 103 towards the first end position (POS1) .

Therefore, by cyclically reversing the rotation direction of the pulley system 162 by way of the traction unit 145, programmed accordingly, the desired working-returning movement cycle is obtained of the floating raft 20 from the first end position (POS1) to the second end position (POS2), and vice- versa .

In the working mode (Figure 6) the floating knife 21 is lowered and therefore sweeps the floating elements 300 pushing them towards the mouth of the exhaust system 140, while in the return step (Figure 7 ) ; due to the actuation of the hydraulic double-effect pendulum 22, the floating knife 21 is lifted and therefore, said floating knife 21 does not contact the free surface (PL) of the wastewater upon which the raft 20 floats, thus avoiding the risk of bringing back floating pollutant elements during the return route. In embodiments not represented the floating knife 21 has a saw-toothed lower edge and/or the slide 170 has a rough surface for improving the drainage of liquid parts .

Take note that the apparatus 10 does not necessarily move along a straight path. In fact, according to some embodiments, the degreasing area 103 may be nonlinear and, consequently, the apparatus 10 moves along a curved path.

In this regard, particular reference is made to the embodiment of Figure 12. This embodiment is related to a wastewater treatment plant 100', which is very similar to the wastewater treatment plant 100 and whose parts are marked with the same reference numbers that distinguish the corresponding parts of the wastewater treatment plant 100.

The wastewater treatment plant 100' differs from the wastewater treatment plant 100 for the fact that the degreasing area 103 is curved (in particular, substantially having the form of a circumference arc); and the traction unit 145 is connected to a rotating shaft 190, from which branch off two support arms 195A and 195B connected, respectively, to the branches 161A and 16IB. The support arms 195A and 195B extend radially from a longitudinal axis 200 of the shaft 190. In use, the traction unit 145 rotates the shaft 190 around the longitudinal axis 200. In this way, the apparatus 10 is moved along the degreasing area 103. To reverse the direction of progress from that indicated by the arrow (Fl) to that indicated by the arrow (F2) (or vice-versa), the direction of rotation of the shaft 190 it reversed from counterclockwise to clockwise (or vice-versa) . In the embodiment illustrated in Figure 12, the tailings pond 102 has a substantially cylindrical shape (circular section) , the shaft 195 is substantially vertical and the degreasing area 103 extends horizontally along an outer perimeter of the tailings pond 102.

As mentioned, the wastewater treatment plant 100' and its relative operation differ from the wastewater treatment plant 100 and its relative operation only as stated above. In particular, note that the apparatus 10 of the wastewater treatment plant 100' is substantially identical to that described with reference to Figures 4 to 7. In Figures 9, 10, 11 has been illustrated a second embodiment of an apparatus 10* for removing floating pollutant elements object of the present invention.

In this case, the apparatus 10* comprises a floating raft 20* whereon a floating knife 21* is mounted equipped with a hydraulic double-effect pendulum 22*.

The hydraulic double-effect pendulum 22* is actually a balance scale that is activated by said liquid flows (FF) .

The floating raft 20* comprises two pontoons 23*, 24* substantially parallel to each other and joined to each other, on the one hand by the floating knife 21* and, on the other hand by the support and connection system 25*, 26*, 27* of the hydraulic double-effect pendulum 22*, also transversal to the lying planes of the two pontoons 23*, 24*. More specifically, each pontoon, 23*, 24* is divided into a front portion 23 *a, respectively, 24*a, and a rear portion 23*b, respectively, 24*b.

The two front portions 23*a and 24*a are joined to each other by the floating knife 21*, while the two rear portions 23*b 24*b are integral to the hydraulic double-effect pendulum 22*. In addition, the floating knife 21* and the hydraulic double- effect pendulum 22* are integral to each other and are correspondingly united to a cross member 25*, in turn supported by two uprights 26*, 27*, each of which is integral to a respective rear portion 23b*, 24*b.

Incidentally, the elements 22*, 23*b, 24*b, 25*, 26*, 27*, form an assembly of elements integral to each other and each to the apparatus 10*. In this context the connection and/or joining method of the various elements 22*, 23*b, 24*b, 25*, 26*, 27* with each other becomes irrelevant; the important factor is that none of said elements 22*, 23*b, 24*b, 25*, 26*, 27* have any relative movement with respect to one or more elements of the apparatus 10* itself.

In the area where the floating knife 21* and the hydraulic double-effect pendulum 22* are joined, there are two rings 28*, 29* (of center (C) ) on which, as we shall see, the traction force on the floating raft 20* is exerted. The apparatus 10* subject to the actions of forces Ftl*, Ft2* (applied practically in the center (C) ) rotates around an axis of instantaneous rotation (X*) as shown particularly in Figures 10, 11.

The axis of instantaneous rotation (X*), in turn, passes from the center of gravity of the shaded areas (Al), respectively, (A2) shown in Figure 10, respectively, in Figure 11.

The perimeter of each shaded area (Al) , (A2) (which actually changes from moment to moment) is indicated in summation by a broken line of the free surface outline, of the outline of the element 23*a (or 24*a) , and of the outline of the floating knife 21*, or with the terminal surface of the elements 23*b, 24*b. As shown in Figure 10, when to the rings 28* and 29* a force (Ftl *) is applied, and therefore the apparatus 10* is in active mode, the front portions 23*a, 24*a are submerged and therefore the floating knife 21 sweeps the free surface (PL) pushing solid debris towards the discharge system 140 (Figures 1, 8) . In this case, the rear portions 23*b, 24*b are raised.

On the contrary, when a force (Ft2*) (Figure 11), is applied to the rings 28* and 29 * being opposite to the force (Ftl*) , the rear portions 23*b, 24*b and the hydraulic double-effect pendulum 22* are submerged, at least partially, while the front portions 23 *a, 24*a and the floating knife 21*a are raised, and, therefore, in the returning stroke, said floating knife 21* does not sweep the free surface (PL) .

As shown in Figure 10, when the apparatus is in an active mode, therefore a torque is exerted to the floating raft 20* given by the product of the force (Ftl*) multiplied by the arm (bl), given by the distance between said center (C) of application of the force (Ftl*) and the axis of instantaneous rotation (X*) .

Similarly, as shown in Figure 10, when the apparatus is in passive mode (returning) , a torque is exerted to the floating raft 20*, given by the product of the force (Ft2*) multiplied by the arm (b2), always given by the distance between the center (C) of application of the force (Ft2*) and the axis of instantaneous rotation (X*).

What has been previously said in relation to the floating knife 21 and to the hydraulic double-effect pendulum 22 can be applied to the floating knife 21* and to the hydraulic double- effect pendulum 22*.

In particular, as shown in Figure 9, it is possible to provide the floating knife 21* with driving and sealing elastic elements 33*, respectively, 34*, as, for example, brushes.

Also in the second embodiment relating to figures 9-11 a slide 170 of the type shown in Figure 8 can be combined. Obviously, with the foresight to properly shape the lower part of each half-raft and moving as far as possible the center of gravity of the whole apparatus 10* downwards; in these conditions the shifting of apparatus 10* on the water will be comparable to the sliding of the same apparatus 10* on the slide 170.

In a further embodiment not shown, the floating knife is moved to and from the free surface of the water by a guillotine type mechanism activated, also in this case, by the dynamic hydraulic thrust generated by the liquid flows created by the relative motion between the raft and liquid mass.

The main advantage of the apparatus for removing floating pollutant elements object of the invention is that, by way of the use of a simple movement device, the lowering/lifting of the floating knife is obtained, also avoiding the use of guide rails, the deformation of which could hinder, also drastically, the sliding of the carriage whereon is mounted the floating knife itself.