WO2011016067A1

WO2011016067A1 - Apparatus for treating liquids

Info

Publication number: WO2011016067A1
Application number: PCT/IT2009/000368
Authority: WO
Inventors: Isodoro Daneluz; Michele Rigo; Andrea Di Prampero
Original assignee: Friulana Costruzioni S.R.L.
Priority date: 2009-08-05
Filing date: 2009-08-05
Publication date: 2011-02-10

Abstract

An apparatus comprises a cleaning device (7) for cleaning a tank (2), the tank (2) being suitable for containing a liquid to be treated, a motion transmitting device (17) for moving the cleaning device (7), the motion transmitting device (17) comprising a plurality of units (18), a unit (18) of the motion transmitting device (17) being connected to two adjacent units (18) respectively by a first hinge element (19) and by a second hinge element (20), each unit (18) comprising at least one roller (21) interposed between the first hinge element (19) and the second hinge element (20).

Description

"Apparatus for treating liquids"

The invention relates to an apparatus for treating liquids. In more detail, the invention relates to a circular sedimentation tank which can be used in a purification plant, or in a water potabilisation plant. Apparatus are known comprising a tank delimited by a cylindrical side wall and by a bottom wall having the shape of a frustum of cone, the bottom wall having a central zone that converges in a downwards direction in the manner of a funnel. The tank is filled with a liquid to be purified such that by effect of gravity the solid particles contained in the liquid deposit on the bottom of the tank in the form of sludge.

A scraper bridge is located internally of the tank, the scraper bridge supporting a plurality of scraper blades. A motion transmitting device rotates the scraper bridge about an axis of the tank, such that the scraper blades scrape up the sludge on the bottom of the tank and convey it towards a central collection zone therefor. Known motion transmitting devices can comprise a chain formed by a plurality of links hinged one to another, the chain being moved by a pinion along a looped path in a peripheral region of the bottom of the tank.

The above-described motion transmitting devices however have the drawback of generating quite high stress on the components of the apparatus. In particular, the chain link engaging with the pinion applies a high degree of force on the links which are yet to engage with the pinion, in order to draw them towards the pinion and thus move the scraper bridge. This force considerably stresses the chain, which can even reach breaking point in the case of .large-diameter tanks.

A plurality of support elements is mounted on the side wall of the tank, for supporting the chain. The portion of chain interposed between two consecutive support elements is arranged along a straight line. During working, the chain exerts a force on the support elements which is directed towards the centre of the tank. This force can lead the support elements to deform or, in more serious cases, to detach from the side wall of the tank.

An object of the invention is to improve the apparatus for the treatment of liquids.

A further object is to reduce the stresses that are generated when a cleaning device, in particular a scraper bridge, is moved in an apparatus for treatment of a liquid.

A further object is to reduce the risk of breakage of the components of an apparatus for treatment of a liquid.

According to the invention, there is provided an apparatus comprising a cleaning device for cleaning a tank, the tank being suitable for containing a liquid to be treated, the apparatus further comprising a motion transmitting device for moving the cleaning device, the motion transmitting device comprising a plurality of units, a unit being connected to two adjacent units respectively by a first and a second hinge element, characterised in that each unit comprises at least one roller interposed between the first and the second hinge element.

The units of the apparatus according to the invention enable a reduction in the stresses generated when the cleaning device is moved. Each unit exerts both a traction action on the units that follow and a thrusting action on the units preceding it. In particular, while the roller of a predetermined unit engages with a driving element, for example a wheel, the unit in question applies a traction force on the following unit, through the first hinge element, and a thrust force on the preceding unit, through the second hinge element. This enables a better distribution of the force required in order to drive the motion transmitting device and also enables a reduction in the traction force applied on the following unit with respect to known-type chains. Consequently the components of the apparatus according to the invention are less intensely stressed.

In an embodiment, each unit can extend along a curved line, in particular an arc of circumference.

This form of the unit enables, when the units are supported on a curved wall of the tank via a plurality of support elements, a reduction in the force applied on the support elements. The curved units apply on the support elements a force which is directed towards the centre of the tank, which force is less than the force applied by traditional chains, which are arranged along a straight line between two consecutive support elements.

The invention can be better understood and carried out with reference to the accompanying figures of the drawings, which illustrate a non-limiting embodiment of the invention, in which:

Figure 1 is a partly-sectioned perspective view showing an apparatus for treatment of liquids;

Figure 2 is a view from above of the apparatus of Figure

1;

Figure 3 is a partly-sectioned front view of the apparatus of Figure 1;

Figure 4 is an enlarged and interrupted perspective view of a unit of the apparatus of Figure 1;

Figure 5 is an enlarged perspective view from below showing a driving device of the apparatus of Figure 1; Figure 6 is an enlarged perspective view illustrating a support element of the apparatus of Figure 1;

Figure 7 is a lateral view of the support element of Figure 6, taken in the direction of arrow A of Figure 6; Figure 8 is an enlarged perspective view of a portion of the apparatus of Figure 1, including the driving device of Figure 5.

Figures 1 to 3 show an apparatus 1 for treatment of a liquid to be purified, in particular dirty water, for example coming from civil or industrial installations. The apparatus 1 can be included in a purification plant and/or a water potabilisation plant.

The apparatus 1 comprises a tank 2 which can be filled with the liquid to be purified, which usually contains solid particles in suspension. The tank 2 functions as a sedimentation or decanting tank, since the solid particles, by effect of gravity, are deposited on the bottom of the tank 2, thereby forming a sludge which is then removed from the tank 2. In this way the liquid is purified.

Only a half of the tank 2 is represented in Figure 1. In the illustrated example, the tank 2 has a substantially circular plan shape.

The tank 2 is delimited by a side wall 3 and a bottom wall 4. In the illustrated example, the side wall 3 has an internal surface 5 which is substantially cylindrical. A channel 6 is provided in the thickness of the side wall 3, internally of which the purified liquid can be sent. The bottom wall 4 can be inclined towards the centre of the tank 2, like a funnel, such as to convey the sludge towards a central collection zone.

A cleaning device is movable inside the tank 2, the cleaning device being arranged to remove the sludge deposited on the bottom wall 4 and to convey the sludge towards a predetermined zone, for example at the centre of .the tank 2. The cleaning device can comprise a scraper device 7, also called a scraper bridge, which can include a support frame 8 supporting a plurality of scraper elements 9, for example blades. In the illustrated example, the support frame 8 has an elongate structure which extends in a radial direction near the bottom wall 4. The support frame 8 can however also be of another geometrical shape, for example curved. The support frame 8 is made as a lattice truss, comprising a plurality of metal rods connected to one another such as to guarantee high resistance.

The support frame 8 is fixed, through a plurality of arms 10, to an annular frame 11 which surrounds a central body 12 of the tank 2. The central body 12 is arranged in a central zone of the tank 2 and extends about an axis Z, shown in Figure 3, of the tank 2. The axis Z extends vertically.

The annular frame 11 is rotatably coupled to the central body 12, for example via a plurality of guide wheels 14 which roll on an external surface 13 of the central body 12. The guide wheels 14 are freely rotatable about respective rotation axes which can be substantially parallel to the axis Z of the tank 2, i.e. vertical. In the illustrated example, the annular frame 11 has a substantially octagonal shape. The annular frame 11 can support eight guide wheels 14, mounted such that a pair of guide wheels 14 is supported by a side of the annular frame 11 interposed between two sides of the annular frame 11 which do not support guide wheels. Several rows of guide wheels 14 can be provided.

The annular frame 11 further supports, through respective vertical bars 15, a plurality of support wheels 16 mounted such as to roll in contact with the bottom wall 4. The support wheels 16 are freely rotatable about approximately-horizontal respective rotation axes. The support wheels 16 enable the weight of the annular frame 11 to be discharged onto the bottom wall 4. The support wheels 16 can be fixed to the same sides of the annular frame 11 which support the guide wheels 14, for example in an intermediate position between two guide wheels 14.

Both the support wheels 16 and the guide wheels 14 can be replaced after the scraper device 7 has been stopped. The scraper device 7 is rotated by a motion transmitting device 17 conformed as a flexible element which can be closed as a loop. The motion transmitting device 17 can be of the same shape as the perimeter of the tank 2. For example, in the illustrated case, in which the tank 2 is delimited by a substantially circular perimeter zone, the motion transmitting device 17 is also circular. The motion transmitting device 17 has however a smaller diameter than the internal diameter of the tank 2, such as to be containable internally of the tank 2.

The motion transmitting device 17 comprises a plurality of transmission units 18, one of which is illustrated in detail in Figure 4. Each unit 18 is connected to two adjacent units, respectively by means of a first hinge pin 19 and a second hinge pin 20. In this way, the units 18 can oscillate with respect to one another about the respective hinge pins, which makes the motion transmitting device 17 flexible within certain limits. Each unit 18 further comprises a plurality of rollers 21 interposed between the first hinge pin 19 and the second hinge pin 20. The rollers 21 are freely rotatable about respective internal supports, each of which can comprise a bushing (not illustrated), mounted on a pin 22.

The pin 22 can have a greater length than the roller 21, such as to pass through the whole roller 21 and exit from the two ends of the roller 21. In an alternative embodiment, for each roller 21 two shorter pins can be used, each of which projects from an end of the roller 21.

The rollers 21 rotate about reciprocally parallel axes, which can be substantially vertical.

The first hinge pin 19 and the second hinge pin 20 also support respective rollers 21, which are in common between two adjacent units 18.

Each unit 18 further comprises a first support structure, or lower support structure 23, and possibly a second support structure, or upper support structure 24. The lower support structure 23 supports respective lower ends of the pins 22, while the upper support structure 24 supports respective upper ends of the pins 22.

The lower support structure 23 and the upper support structure 24 can each be conformed as a flat element and be made, for example, by cutting a sheet of a metal material. The lower support structure 23 and the upper support structure 24 can extend along a curved line, especially along an arc of circumference. Each unit 18, therefore, behaves as a substantially rigid segment, conformed as a curved portion, in particular as an arc of circumference.

Each unit 18 can comprise more than ten rollers 21. In the illustrated example, twenty-five rollers 21 are interposed between the first hinge pin 19 and the second hinge pin 20. In a tank 2 having a diameter of the order of 30-40 metres, the motion transmitting device 17 can comprise about fifty units 18, each unit 18 having a length of about 2-3 metres.

The motion transmitting device 17 is rotated about the axis Z by a driving device 25, shown in Figures 5 and 8, which can comprise a driving wheel 26 or sprocket, provided at a periphery thereof with a plurality of recesses, each of which is suitable for engaging with a roller 21. The driving wheel 26 can be formed by starting from a flat disc in which the tooth spaces are made, for example by milling.

A cog is defined between two consecutive recesses, which cog can have a different profile from the standard involute profile usual in cog wheels. In particular, the cogs of the driving wheel 26 can have a base, i.e. an anchoring port.ion to the driving wheel 26, which is relatively wide. The width of the base of the cog depends on the distance between two consecutive rollers 21, which can be greater than 100 mm. Thus cogs having a very wide base can be used, which enables the resistance to stress of the cog to be increased without using a very thick driving wheel 26.

The driving wheel 26 is rotated by a motor 27, which can be hydraulic, electric or other, and which can be coupled to a reducer, for example an epicyclic reducer. During operation, the support frame 8, the scraper elements 9, the motion transmitting device 17 and the driving wheel 26 are arranged submerged in the liquid. In the illustrated example, as can be seen in Figure 8, the motor 27 is disposed above the liquid and is connected to the driving wheel 26 via a shaft 28 of an appropriate length.

In an embodiment that is not illustrated, the motor 27 could also be submerged, i.e. arranged below the free level of the liquid. In this case, the motor 27 is arranged internally of a sealed closed housing, i.e. designed such as to prevent ingress of liquid which might compromise the functioning of the motor 27.

In an embodiment which is not illustrated, more than one driving device can be used, for example a pair of driving wheels, driven by respective motors and arranged in diametrically-opposite positions along the perimeter of the tank 2.

As shown in Figure 5, the scraper device 7 is connected to the motion transmitting device 17 by means of a pair of connecting elements, arranged respectively upstream and downstream, of the scraper device 7 with respect to the rotation direction of the motion transmitting device 17. The connecting elements can be elongate and comprise, for example, respective rods 29.

Each rod 29 can be connected pivotingly both to the support frame 8 supporting the scraper elements 9 and to the motion transmitting device 17, for example by interposing bushes.

In an alternative embodiment, illustrated in Figure 8, a single rod 29 can be used, which connects the motion transmitting device 17 only to one side of the scraper device 7.

If two rods 29 arranged on opposite sides of the support frame 8 are used, it is however possible further to reduce the stresses acting on the components of the apparatus 1. According to the position of the scraper device 7 and also according to whether the driving wheel 26 is in either thrust or braking phase, one of the two rods 29 can work more than the other. In other words, by using two rods 29 it is possible to distribute the stresses between the two rods 29 in a more uniform way.

The motion transmitting device 17 is supported by a wall of the tank 2, especially by the side wall 3, by means of a plurality of support elements which can comprise respective brackets 30, uniformly distributed along the side wall 3. A bracket 30 is shown in detail in Figures 6 and 7. The bracket 30 comprises an anchoring portion 31, which can be substantially vertical, suitable for being fixed to the side wall 3 of the tank 2 for example by means of threaded connecting elements 32. A support portion 33 is fixed to the anchoring portion 31, which support portion 33 is suitable for supporting the motion transmitting device 17 and can be substantially horizontal. The anchoring portion 31 and the support portion 33 can be connected to one another by an oblique bar 34.

The bracket 30 supports the motion transmitting device 17 by means of revolving means which can comprise a plurality of discs mounted on a lower surface of the support portion 33. For example, a pair of rest discs 35 can be fixed to the bracket 30, each rest disc 35 having a side surface 36 which is suitable for restingly receiving the lower support structure 23 of the units 18. Each rest disc 35 is free to rotate about an axis which, in the illustrated example, is horizontal, the side surface 36 extending about this axis. Each rest disc 35 is further provided with a collar 37 which projects from the side surface 36. The rest discs 35 of a same pair are mounted such that the collars 37 are facing externally of the disc pair. In this way, when the lower support structure 23 of a unit 18 rests on the rest discs 35, the collars 37 laterally contain the lower support structure 23, thereby preventing the structure 23 from disengaging from the rest discs 35. In this way, the motion transmitting device 17 is kept in a radially centred position with respect to the tank 2. A pair of guide discs 38 are also fastened to the bracket 30, which discs 38 engage with the upper support structure 24 of the unit 18 in order to keep the structure in a radially centred position with respect to the tank 2. The guide discs 38 are freely rotatable about respective rotation axes, for example vertical, and are each . delimited by a side guide surface 39 arranged to interact with a flank of the upper support structure 24. Each guide disc 38 further comprises an annular lip 40, which projects from the side guide surface 39. The guide discs 38 are mounted such that the annular lip 40 is arranged higher than the side guide surface 39, such as to hinder upwards displacement of the units 18 during functioning.

The apparatus 1 can further comprise a covering device 42, having a circular shape and being suitable for covering the tank 2. For clarity of illustration, only a portion of the covering device 42 has been shown in Figures 1 to 3. In particular, in Figures 1 and 3 a portion of the covering device 42 is shown which covers a quarter of the tank 2, while in Figure 2 a portion of the covering device 42 is shown which covers about half the tank 2.

During functioning, the motor 27 rotates the driving wheel 26 which engages with consecutive rollers 21, thus moving the motion transmitting device 17. As the rollers 21 are free to rotate with respect to the corresponding pins 22, the rollers 21 engage with the cogs of the driving wheel 26 without dragging significantly with respect to the flanks of the cogs. This enables wear on the rollers 21 and the driving wheel 26 to be reduced. Furthermore the substantially-circular cross section of the rollers 21 ensures that the rollers 21 engage effectively with the cogs of the driving wheel 26 even where there are imprecisions in the distance between the axis of the roller 21 and the axis of the driving wheel 26. The units 18 give the motion transmitting device 17 a much greater rigidity with respect to that of the chains used in traditional apparatus. The roller 21 which engages with the driving wheel 26 can exert not only a traction action on the rollers 21 which are still to interact with the driving wheel 26, but can also exert a thrust action on the rollers 21 which have already interacted with the driving wheel 26, via the lower support structure 23 and the upper support structure 24. This enables a better distribution of the forces required for moving the motion transmitting device 17 among the rollers 21, and thus enables the stresses acting on the device to be reduced.

At the same time, the first hinge pins 19 and the second hinge pins 20 which connect adjacent units 18 make the motion transmitting device 17 sufficiently flexible not to be negatively influenced should, as often happens, the motion transmitting device 17 not be perfectly concentric with the tank 2 or in a case in which the motion transmitting device 17 and/or the tank 2 are not perfectly circular.

As the units 18 are arcs of circumference, the force directed towards the centre of the tank 2 which the units 18 apply to the support brackets 30 is very low. This enables a reduction in the risks that the support brackets 30 might detach from the side wall 3.

The motion transmitting device 17, moved by the driving wheel 26, rotates about the axis Z of the tank 2, while the units 18 are supported by the support brackets 30. Owing to the rest discs 35 and the guide discs 38, which are free to rotate about the respective axes, the friction between the units 18 and the support brackets 30 is limited. Further, the rest discs 35 and the guide discs 38 ensure that the motion transmitting device 17 is kept in a radially centred position internally of the tank 2.

The motion transmitting device 17, owing to the rods 29, transmits motion to the support frame 8. The scraper elements 9, which are fixed to the support frame 8, are thus moved about the axis Z and scrape the sludge which is deposited in contact with the bottom wall 4. Since each scraper element 9 is inclined with respect to the radial direction, the scraper elements 9 convey the sludge towards a central collection zone, from which the sludge can be removed by devices of known type. The purified liquid is conveyed into the channel 6 by devices of known type.

Claims

. CLAIMS

1. Apparatus comprising a cleaning device (7) for cleaning a tank (2), the tank (2) being suitable for containing a liquid to be treated, a motion transmitting device (17) for moving the cleaning device (7), the motion transmitting device (17) comprising a plurality of units (18), a unit (18) of the motion transmitting device (17) being connected to two adjacent units (18) respectively by a first hinge element (19) and by a second hinge element (20), characterised in that each unit (18) comprises at least one roller (21) interposed between the first hinge element (19) and the second hinge element (20) .

2. Apparatus according to claim 1, wherein each unit (18) comprises a support structure (23, 24) for supporting said at least one roller (21) , the support structure (23, 24) giving the corresponding unit (18) a configuration of a substantially rigid segment .

3. Apparatus according to claim 2, wherein said substantially rigid segment extends along a curved line, in particular along an arc of circumference.

4. Apparatus according to claim 2 or 3, wherein said at least one roller (21) is freely rotatable about corresponding support means (22) fixed to the support structure (23, 24).

5. Apparatus according to claim 4, wherein the support structure (23, 24) comprises a plate-form lower support structure (23) supporting a first end of the support means (22) of said at least one roller (21) and a pl.ate-form upper support structure (24) supporting a second end of the support means (22) of said at least one roller (21) .

6. Apparatus according to any preceding claim, wherein the motion transmitting device (17) is movable in contact with revolving means (35, 38), the revolving means (35, 38) being mounted on support elements (30) fixed to the tank (2).

7. Apparatus according to claim 6, as appended to any one of claims 2 to 5, wherein the revolving means (35, 38) comprise rest revolving means (35) for restingly receiving the support structure (23, 24) and guide revolving means (38) for laterally guiding the support structure (23, 24).

8. Apparatus according to any preceding claim, wherein respective rollers (21) are mounted about the first hinge element (19) and about the second hinge element (20) .

9. Apparatus according to any preceding claim, and further comprising a driving device (25) for moving the motion transmitting device (17), the driving device (25) comprising a wheel (26) having a plurality of recesses suitable for receiving consecutive rollers (21) .

10. Apparatus according to claim 9, wherein the driving device comprises at least one motor for rotating the wheel (26) , the motor being arranged near the wheel (26) such as to be operatively submerged in the liquid to be treated.

11. Apparatus according to claim 9, wherein the driving device (25) comprises at least one motor (27) for rotating the wheel (26), the motor (27) being connected to the wheel (26) by a shaft (28) having a length which enables the motor (27) to be operatively external of the liquid to be treated.

12. Apparatus according to any preceding claim, wherein the cleaning device (7) comprises a support frame

(8), in particular extending along a radial direction, which supports at least one scraper element (9) .

13. Apparatus according to claim 12, wherein the support frame (8) is connected to an annular frame (11) which is rotatable about a central body (12) of the tank (2) .

14. Apparatus according to claim 13, wherein the annular frame (11) supports a plurality of guide wheels (14) and/or a plurality of rest wheels (16), the rest wheels (14) being suitable for rotating in contact with the central body (12) and the rest wheels (16) being suitable for rotating in contact with a bottom wall (4) of the tank (2) .

15. Apparatus according to any one of claims 12 to 14, and further comprising at least one connecting element (29) , in particular a rod, connected pivotingly to the support frame (8) and to the motion transmitting device (17).

16. Apparatus according to claim 15, wherein two connecting elements (29) are provided, the connecting elements (29) being arranged respectively upstream and downstream of the support frame (8).