WO1984004257A1

WO1984004257A1 - Scraping device for sedimentation basins

Info

Publication number: WO1984004257A1
Application number: PCT/SE1984/000147
Authority: WO
Inventors: Bernt-Aoke Sandberg
Original assignee: Zander & Ingestroem
Priority date: 1983-05-05
Filing date: 1984-04-18
Publication date: 1984-11-08
Also published as: FI850006L; FI850006A0; NO850050L; GB2146548A; GB8428820D0; SE8302563D0; DE3490207T1; SE436097B

Abstract

Scraping device at sedimentation basins for removing sediment collected on the bottom of the basin, comprising a wagon which reciprocates on the botton of the basin by means of rope drive means and which is provided with scraping members (11, 12) taking in one direction of the wagon a scraping position, and in the other direction of movement a passive return position. The device is easily pulled and easily guided in that it is provided with guiding wheels (22, 23) for guidance along a guiding beam (21) arranged in the basin centrally relative to the wagon, while the weight of the wagon is taken up by special carrying wheels (15, 20) abutting against the bottom of the basin. The traction ropes (27, 28) for traction of the wagon are fastened directly in the wagon framing, and the operation of the scrapes between their working position and return position is separated from the ropedriving in that the scrapes are tilted at both ends of the basin when contacted by stationary shoulder members within the basin.

Description

Scraping device for sedimentation basins

The invention concerns a scraping device at sedimentation basins for removing sediment collected on the bottom of the basin, comprising a wagon which is arranged to perform a reciprocating movement on the bottom of the basin by means of a rope drive device and traction ropes, and which is provided with scraping members which are arranged in one direction of movement of the wagon to take a preferably vertical working position for scraping of sediment from one end of the basin to a sedimentation discharge end, for instance to a sludge pocket, and which in the other direction of movement of the wagon take a preferably horizontal passive return position. Prior art

For scraping away sediment on the bottom of sedimentation basins, for instance at sewage plants, a scraping device is required having construction elements which at least partly have to work below the basin surface. Since the environment in sedimentation basins as a rule are extremely corrosive due to addition of chemical precipitation means, the corrosion risk is constituting the perhaps most dangerous threat to the function reliability of the device and to operation disturbances in the long time perspective. An important aspect is also to provide a maximum of mechanical simplicity and operation reliability considering the extreme uncomfort working environment for repair work in a filled basin, or the operation disturbance connected with emptying of the basin for repair work.

A scraping device often used at sedimentation basins comprises chain scrapes having a number of scraping blades extending across the basin and being transported forwards by means of continuously operating chains. This device has a good function reliability in a short time perspective, but repair work and exchange of chains as well as scrapes due to corrosion will be, in a long time perspective, both expensive and labour consuming due to the solidity of the device.

One has also proposed travelling crab devices, driven above the water surface in the sedimentation basins, with vertically adjustable scrapes mounted on the travelling crab. However, at existing sedimentation, basins, which as a rule are provided with different equipment above the basin, such travelling crab means would require considerable reconstruction work, or be entirely uncombinable with other desiderata for the plant.

Further, one has proposed arrangements comprising a wagon reciprocatable on the bottom of the basin, on which tiltable scraping flaps are suspended to take a scraping position in one direction of movement and a passive return position in the other direction of movement of the wagon. The Swedish patent 423 968 describes an arrangement of this kind, comprising a rope driven rectangular wagon, reciprocated on the bottom of the basin rolling by means of two wheels on each of two rails. The traction ropes required for the reciprocating movement of the wagon are fastened at a forward and a rear hingedly suspended scrape in order to interconnect the tilting of the scrapes, when the wagon reaches its respective end positions, with the rope driving device for the reciprocation movement of the wagon. This arrangement is connected with some disadvantages, however. The interconnection of the scrape tilting and the traction, of the wagon by means of rope driving leads to a relatively complicated system of movable mechanical members of the device situated below the liquid surface, comprising several pulley wheels for the rope function, rope stretching, etc., which may jeopardize the function reliability. Further, the movement of the wagon by means of centrally therein fastened traction ropes, and guiding of the wagon along two rails on each sides of the central traction composant, leads to a risk of inclination of the wagon by the so called "drawer effect", whereby a heavy traction resistance may arise and jeopardize the function reliability. In order to reduce the risk of derailing of a rail-going wagon of this kind, further, a relatively heavy wagon is probably required and, therefore, the possibility of providing a light and less material requiring device of more expensive corrosion resistant material is thereby limited. The device disclosed in the above patent specification also seems to require a significant weight of the rail-going wagon due to the fact that the tilting of the scrapes, interconnected with the line driving, means that the traction composant of the traction ropes would have to be situated relatively high above the wheel axes of the wagon.

Description on the invention

One object of the present invention is to provide a scraping device for sedimentation basins, comprising a rope driven scraping wagon reciprocatable on the bottom of the sedimentation basin, and having a simple and less material requiring light design, which makes it possible to use non-corrosive material and to obtain an intact function during long periods of time.

A further object of the invention is to provide an easily tractable scrape wagon design, at which the above said "drawer effect" in connection with traction by means of a centrally in the wagon fastened wire is eliminated, and the wear of the rope transmission function is minimized.

Further, an object of the invention is to provide a rope driven scraping device having a minimum of elements movable below the basin surface in order to achieve a maximum of operation reliability.

These and other objects have been obtained according to the invention in a scraping device which primarily is characterized in that the wagon is provided with guiding wheels for guidance along a guiding beam arranged within the basin centrally relative to the wagon, that the wagon is provided with lateral carrying wheels for abutment against the bottom of the basin on both sides of and spaced from said guiding beam, that the traction ropes for forward and return movement of the wagon are fastened directly on the framing of the wagon, and that an optional number of scrapes are hingedly suspended from the wagon, which scrapes are formed in cooperation with stationary shoulder members, arranged in the basin near the two end positions of the wagon, to be turned at one of said end positions to a passive return position, and at the other of said end positions to be turned to an active working position.

By locating the guidance of the wagon to one single rail extending aligned with traction ropes fastened centrally in the wagon, an easily tracted wagon is obtained, and the above mentioned "drawer effect" is eliminated. According to a preferred embodiment of the invention guiding of the wagon is obtained by means of guiding wheels arranged at the wagon for rotation in a horizontal plane while abutting the sides of the guiding beam. Preferably the guiding means comprise at least two different groups of guiding wheels, one of which groups is situated at the front part of the wagon, and the other group being situated at the rear part of the wagon. By arranging the guiding wheels for rotation in a horizontal plane, further, the advantage is obtained that the guiding function can be released from carrying the weight of the wagon. Thus, the wagon is preferably provided with three carrying wheels which preferably comprise, apart from one lateral carrying wheel close to both lateral ends of the wagon framing, a third carrying wheel arranged centrally for abutment against the guiding beam.

The above said supporting abutment at three places makes it possible to provide a simple and to a minimum material requiring wagon framing having a triangular form, which secures constant abutment against the bottom of the basin for the lateral carrying wheels, which are preferably arranged on a beam constituting one side of the framing triangle, whereas the central carrying wheel is placed near the opposing triangle apex at a maximum distance from the beam that is resting on the lateral carrying wheels.

The tilting of the scraping members from working position to passive return position, and vice versa, which according to the invention is separated from the rope driving of the reciprocating movement of the wagon, gives for the application here in question several important advantages. The number of movable parts below the basin surface, required for the rope driving, is reduced to an absolute minimum and need only comprise one pulley wheel at each end of the basin for one traction rope fastened directly in the front part of the wagon framing, and one traction rope for the return movement fastened in the rear part, of the wagon framing. Further, the pulley wheels and the fastening points for the traction ropes in the wagon framing may be chosen optionally low, so that the traction composants may be placed close to the bottom of the basin, and lifting moment with respect to the guiding wheels may be minimized. Thereby any requirement of weight of the wagon, concerning the risk of derailing, is eliminated.

The mechanism for tilting of the scrapes, which is released from the rope drive, may be made very simple and mechanically robust. In the basin at both end positions of the wagon there are arranged fixed shoulder means which, immediately before the wagon reverses its direction, are hit by corresponding shoulder means which are fastened on the scrapes and which are formed so that the scrapes will be tilted from vertical to horizontal position, and vice versa, when the wagon moves a small remaining distance before it reverses. The joints for the suspension of the scrapes on the wagon framing preferably are situated below the centre of gravity of the scrapes, so that the scrapes in their horizontal return position rest firmly against the part of the wagon framing intended therefore. The driving device for providing the reciprocating movement of the wagon in the basin is arranged outside the basin and comprises a motor coupled to a driving shaft, which is driving simultaneously two separate winding drums, one of which cooperates with the first traction rope fastened in the wagon framing for traction in the one direction of movement, the other drum cooperating with a traction rope fastened in the wagon framing for traction in the other direction of movement. This known rope driving system is advantageous in this connection owing to the fact that it does not require rope stretching means down within the basin, which are not easily available. According to a preferred embodiment of the driving device one of the winding drums is adjustably fastened at the other winding drum in order to, by rotation of one drum relative to the other, obtain any required rope stretching. Apart from this there is needed for the rope driving only one pulley wheel for each of the traction ropes, which pulley wheels preferably are arranged one at each end of the basin close to its bottom. Perferred embodiment of the invention

The invention will be further disclosed by description of a preferred embodiment thereof, reference being made to the accompanying drawing, where Fig. 1 shows surveyably a section through a sedimentation plant with a scraping device according co the invention, Fig. 2 shows a scraping wagon seen from one side, Fig. 3 shows the wagon in Fig. 2 seen from above, Fig. 4 shows how the scraping members are tilted at the sludge discharge end of the basin, and Fig. 5 shows how the scraping members are tilted at the other end of the basin.

In Fig. 1 there is shown in section a sedimentation basin 1, at the left end of which there is a sludge pocket 2. Along a guiding beam 3 in the middle of the basin a scraping wagon 4 is arranged for movement to and fro by means of traction ropes 5 and 6 fastened in the wagon framing. The traction ropes are driven by two separate drums in a driving device 7 situated above the basin. The traction rope 6 is fastened in the front part of the wagon framing for traction of the wagon 4 towards the sludge, pocket 2, and is driven by one of the drums via a pulley wheel 8 situated at a level close to the bottom of the basin for the obtainment of a substantially horizontal traction composant. The other traction rope 5 for traction of the wagon in the return direction is driven by the other drum via pulley wheels 9 and 10, the pulley wheel 9 also having a low position for the obtainment of a horizontal traction composant.

The scrape wagon shown in Fig. 2 and 3 supports two different scraping members 11 and 12, which extend across the whole width of the basin. The scrapes are hingedly suspended in spacing levers

13 which are fastened in a beam 14 resting at both ends on lateral carrying wheels 15. The framing of the wagon is formed by the beam 14, a lower central beam 16 and stay beams 17 arranged above the scrapes from the central beam 16 at the front part of the wagon to the beam 14. In order to make room for the tilting of the scrapes into horizontal position the stay beams 17 are indirectly fixed at the beam 14 through a beam 18, which is arranged behind the beam

14 and, through angular supports 19, is fastened to the beam 14. A third carrying wheel 20 is arranged at the tapered front of the wagon framing for abutment against the central guiding beam 21. At the framing point there is also a first pair of guiding wheels 22 journalled in the wagon for rotation in a horizontal plane and abutment against the guiding beam 21 from the side. In the same manner a second pair of guiding wheels 23 is arranged for abutment against the side of the guiding beam 21 at the rear part of the wagon. On the scraping blades 11 and 12 there are fastened shoulder means 24, the appearance and function of which are illustrated in detail in Fig. 4 and 5. The scraping blades 11 and 12 are suspended in joints 25 on the spacing levers 13 at a level lower than the centre of gravity of the scrapes, so that the latter shall take a stable position in their passive horizontal position. During the scraping operation the scrapes are kept in their vertical position by abutment against shoulders (not shown) on the beam 14. A traction rope 27 is fastened in a front part of the wagon framing for traction of the wagon while scraping, and another traction rope 28 is fastened at the beam 16 for return traction of the wagon.

Fig. 4 shows a carrying member 29 which is arranged at the basin end, where the sludge pocket 2 is situated, and on which a roller 30 is journalled in position to contact one leg of a shoulder member 24 fastened to the scraping member 12, and consisting of an angle iron. Thereby, the scraping member 12 is tilted into horizontal position as shown in Fig. 5. At the opposite end of the basin there is arranged also a carrying member 31 with a roller 32, arranged to contact the other leg of the shoulder member 24 in order to tilt the scraping member 12 back into working position.

The function of the device is evident from the above description of the drawing. The wagon 4 is pulled with scrapes in a working position from right to left according to Fig. 1 towards the sludge pocket 2. At the forward end position immediately after the scrape has been tilted up to a horizontal passive position by contact with the shoulder members fixed at the discharge end, the wagon will contact a switch that reverses the current direction for the driving motor, so that the two drums arranged on the same axis will change direction of rotation. The wagon then starts its returning movement until it in its rear end position in the same manner will again contact a switch, the current to the driving motor again being reversed. This type of rope driving device with two separate drums for the two traction ropes has the advantage that no rope stretching device is needed down in the basin. The two drums normally are fastened to each other by means of bolts for common rotation during operation. When stretching of the ropes is required , said bolts are only released and the drums are turned relative to each other until the desired stretching of the ropes is obtained.

Claims

1. Scraping device at sedimentation basins for removing of sediment collected on the bottom of the basin, comprising a wagon which is arranged for reciprocating movement on the bottom of the basin by means of a rope driving device and traction ropes and which is provided with scraping members which in one direction of movement of the wagon are arranged to take a preferably vertical working position for scraping of sediment from one end of the basin to a sediment discharge end, for instance a sludge pocket, and in the other direction of movement of the wagon to take a preferably horizontal passive returning position, c h a r a c t er i z e d i n that the wagon is provided with guiding wheels (22, 23) for guidance along a guiding beam (21) arranged in the basin centrally relative to the wagon, that the wagon is provided with lateral carrying wheels (24) for abutment against the bottom of the basin on both sides of and spaced from said guiding beam (21), that said traction ropes (27, 28) are fastened directly in the wagon framing (16, 17, 18, 19) and that an optional number of scrapes (11, 12) are hingedly suspended in the wagon, said scrapes being formed in cooperation with shoulder members (29, 30, 31, 32), which are arranged stationary in the basin near both end positions of the wagon, to be turned at one of said end positions to said passive return position, and at the other of said end positions to be turned to said working position.

2. Scraping device according to claim 1, c h a r a c t e r i z e d i n that the guiding wheels (22, 23) are arranged at the wagon to rotate in a horizontal plane and to abut against the sides of said guiding beam (21).

3. Scraping device according to any of the preceding claims, c ha r ac t e r i z e d i n that it comprises at least two different groups of guiding wheels (22, 23) for providing guidance against the guiding beam (21) at a front part of the wagon as well as at a rear part of the wagon.

4. Scraping device according to any of the preceding claims, c h a r a c t e r i z e d i n that a further carrying wheel (20) is arranged at the wagon in order to abut against said guiding beam (21), said further carrying wheel (20) being arranged spaced from the connection line between said lateral carrying wheels (24), so that the carrying wheels together form a supporting triangle enclosing the centre of gravity of the wagon.

5. Scraping device according to any of the preceding claims, c h a r a c t e r i z e d i n that said rope driving device

(7) comprises two separate drums, one of which coacts with a first traction rope (5) fastened in the framing of the wagon (4) for traction in one direction of movement, and the other drum cooperating with a traction rope (6) fastened in the wagon framing for traction in the other direction of movement, the two drums being arranged to be rotated by a common driving shaft, and that one drum is adjustably fastened to the other drum in order to provide for an easy rope stretching procedure by turning of one drum relative to the other.

6. Scraping device according to any of the preceding claims, c h a r a c t e r i z e d i n that it comprises a pulley wheel (8, 9) at each end of the basin close to the bottom thereof for each of two traction ropes (6, 5) intended for the two directions of movement of the wagon and fastened to the wagon framing near the horizontal plane of rotation of said guiding wheels (22, 23) in order to provide substantially horizontal traction composants near said plane of rotation.

7. Scraping device according to any of the preceding claims, c h a r a c t e r i z e d i n that said wagon framing (16, 17, 18, 19) as well as said scraping members (11, 12) are made by stainless steel.