Arrangement in a detention well

Abstract

An arrangement in a detention well, comprising a water inlet pipe (1 c) and an outlet pipe (1d), the arrangement further comprising a detention mechanism (2) which comprises an outlet opening allowing water to flow into the outlet pipe (1 d), a float (8) movable with the water level, and a cleaning mechanism provided with a blade element arranged to be movable over the outlet opening. Preferably, the detention mechanism (2) comprises at least two outlet openings, of which, when one is completely open, the other outlet openings are completely closed.

Description

[0001] ARRANGEMENT IN A DETENTION WELL

[0002] The present Invention relates to an arrangement in a detention well as defined in the preamble of claim 1 .

[0003] Preferably, the invention relates to structures used in property and municipal in- frastructure applications. In particular, the invention concerns a cleaning arrange- ment for an outlet opening in detention wells used for stormwater drainage.

[0004] Detention wells prevent stormwater sewers from flooding by slowing down the flow of water. They are particularly useful during heavy rainfall. Preferably, a de- tention well comprises a water tank, an inlet connection and an outlet connection, as well as a detention structure for delaying the discharge of water entering the tank. The inlet and outlet connections of the tank may, for example, have a diam- eter of 110 mm. A detention well usually also includes an overflow pipe, the open upper end of which is located at a certain height from the bottom of the tank. The detention structure of the detention well comprises at least one discharge flow opening, i.e. an outlet opening, the sizing of which regulates the outflow of the water that has entered the well and the residence time of the water in the tank. The opening is dimensioned so that the water is discharged from the tank suffi- ciently slowly. The detention well can be connected via its inlet connection to a water pipe extending, for example, from a rainwater gully, before the municipal or other receiving network. During heavy rainfall, the detention well fills up and slows down the flow of water further downstream. After the rain, the detention well empties slowly through its outlet opening.

[0005] The purpose of detention wells is to provide a sufficiently long residence time of water in the tank before stormwater is conveyed to the municipal network or to another corresponding stormwater network. This requires a sufficiently small out- flow rate, especially in the case of detention wells with a small capacity. The out- flow rate is limited by the sizing of the outlet opening diameter, so a small outflow rate is achieved with a small opening diameter. Typically, a suitable opening di- ameter would be only about 5-10 mm. However, stormwater contains debris such as plastic films, tree needles and leaves, so a small outlet opening becomes eas- ily clogged. This increases the need for maintenance of the detention well. In order to avoid clogging, the outlet opening should therefore often be larger than would be necessary to achieve a sufficiently small outflow and a sufficiently long residence time. A sufficiently long detention may not necessarily be achieved with solutions according to the known art.

[0006] The clogging problem of the outlet opening of a detention well has been ad- dressed, among other things, with automatic cleaning systems for the opening. One such known detention well, including a detention structure and a cleaning system for the outlet opening, is disclosed in Finnish patent application No. FI20225691 . One problem with the solution according to the patent application is the complexity of the detention structure. The detention well comprises a protec- tive pipe attached to an overflow pipe, and inside the protective pipe there is a float that moves with the water level. An overflow pipe is connected to the protec- tive pipe, and at the lower end of the overflow pipe there is an outlet opening that slows down the flow of water, through which water is allowed to flow out of the detention well when the water level is above the outlet opening but below the open upper end of the overflow pipe. The detention structure further requires a separate protected cord pipe and a spring pipe, which are connected to the frame of the actual cleaning mechanism. A spring acts in the spring pipe and rotates the shaft of the cleaner when the water level in the detention well rises. Corre- spondingly, the float rotates the shaft of the cleaner directly via the cord when the float falls along with the water level in the detention well. One problem in this arrangement is also that the water flow is interrupted when the cleaning blade is located above the small outlet opening. In such a case, the water level in the tank cannot decrease at all, and the float becomes stuck in place. Such a situation may persist for a long time. Another problem is that adjustment of the spring force may cause difficulties in this structure. In addition, a further problem is that when the water level rises, the cleaner shaft rotates continuously in only one direction. Correspondingly, when the water level falls, the cleaner shaft rotates continu- o-sly only in the opposite direction. As a result, long and tough materials such as thin branches and grasses may bend in the direction of rotation and remain clog- ging the outlet opening until the direction of rotation changes.

[0007] The purpose of the present invention is to solve the problems described above and to provide a simple and reliable arrangement by means of which the outlet opening of a detention well can be cleaned automatically without interrupting the water flow through the outlet opening during cleaning. The arrangement allows a freer sizing of the outlet opening, as the size of the well, the amount of water entering it, and the desired residence time do not limit the size of the opening. The arrangement according to the invention is characterized by what is defined in the characterizing part of claim 1 . Other embodiments of the invention are char- acterized by what is defined in the other claims.

[0008] For implementing its purpose, the arrangement according to the invention in a detention well comprises a water inlet pipe and an outlet pipe, and the arrange- ment includes a detention mechanism which comprises an outlet opening allow- ing water to enter the outlet pipe, a float moving with the water level, and a clean- ing mechanism provided with a blade element arranged to be movable over the outlet opening. Preferably, the detention mechanism comprises at least two outlet openings, of which, when one is completely open, the others are completely closed.

[0009] One advantage of the invention is that a uniform water flow is achieved through- out the entire detention period. In this case, the water flow does not stop, nor does the float become stationary and jam the entire cleaning operation, since a discharge channel having the area of the outlet opening is always open. In a structure with two outlet openings, the mutual spacing between the holes and the cleaning blades is dimensioned so that when the first outlet opening is completely closed, the second outlet opening is completely open, and when the first outlet opening is partially closed, the second outlet opening is open to the same extent, and vice versa. A further advantage is that the reciprocating movement of the cutting blades over the discharge openings cleans the discharge openings better than, for example, a device having only one large rotating blade, which only oc- casionally changes its direction of rotation and gradually collects tough material causing clogging between the blade and the base surface of the outlet opening serving as the counter surface of the blade.

[0010] Since the water level in the detention well rises and falls, the movement of the float following the water level provides the force directly for moving the blade el- ement without any external actuator, such as a spring or a separate operating member.

[0011] The invention is described in more detail by means of one embodiment with ref- erence to the accompanying schematic and simplified drawings, in which

[0012] Fig. 1 presents, in a side view and in cross-section, a lower part of a deten- tion well provided with a detention mechanism according to one em- bodiment of the invention, presents, in a side view, the detention mechanism according to Fig. 1 with the protective meshes of the lower and upper parts removed, presents the detention mechanism according to Fig. 1 as seen from the rear, presents the detention mechanism according to Fig. 1 as seen from the front, presents the detention mechanism according to Fig. 1 as seen from above, presents the detention mechanism according to Fig. 1 as seen from below,

[0013] Fig. 7 presents, in a bottom view, one cleaning mechanism of the detention mechanism according to the invention, with the blade element in its first extreme position, Fig. 8 presents, in a bottom view, one cleaning mechanism of the detention mechanism according to the invention, with the blade element in its second extreme position,

[0014] Fig. 9 presents, in a front view, partially sectioned and on an enlarged scale, the cleaning mechanism according to Figs. 7 and 8, and

[0015] Fig. 10 presents, in a bottom view, in an exploded view and on an enlarged scale, the blade element of the cleaning mechanism according to Figs. 7 and 8.

[0016] In the following, the structure and operation of one advantageous embodiment of the invention are explained with reference to the above-mentioned figures.

[0017] Figs. 1-6 present a detention arrangement according to one embodiment of the invention. In Fig. 1 , the detention mechanism 2 of the arrangement according to the invention is presented in a cross-sectioned lower part 1 of the detention well as seen from the side, and in Figs. 2-6 the same mechanism is presented as seen from the side, from the rear, from the front, from above, and from below, and separately without the mesh protector of the lower end of the frame part 4. The upper part of the detention well, which comprises, for example, a telescopic cover, is not presented in Fig. 1 , since it is not related to the solution according to the invention.

[0018] The body of the detention well is formed by a tank, which in its lower part 1 is, for example, a cylindrical pipe closed at its bottom end by a base 1 b. Through the wall section 1 a of the lower part 1 of the detention well, an inlet pipe 1 c is ar- ranged, which is dimensioned according to the system supplying the water. The inlet pipe 1 c is positioned at a distance from the bottom 1 b. Through the wall section 1 a of the lower part 1 of the detention well, an outlet pipe i d is also ar- ranged, which is connected, for example, to a municipal stormwater network.

[0019] The frame part 4 of the detention mechanism 2 is preferably a cylindrical pipe, which is fastened in a substantially vertical position to the inner surface of the wall section 1 a of the detention well by means of a fastening structure 3. Prefer- ably, a desired vertical distance is left between the lower end of the frame part 4 and the bottom 1 b of the detention well.

[0020] The detention mechanism 2 according to the embodiment has a cross-sectional size smaller than the inner diameter of the detention well, so that the detention mechanism 2 fits well inside the lower part 1 of the detention well.

[0021] The preferably cylindrical and elongated frame part 4 comprises, in addition to the fastening structure 3, an outlet connection 5, which, in connection with the mounting of the detention mechanism 2, can be positioned at the height of the outlet pipe 1 d and connected in a watertight manner to the outlet pipe 1d.

[0022] At the upper end of the frame part 4 there is preferably a plate-like cover structure 6, and at least one overflow opening 4a for an overflow situation. There may be, for example, 2-4 overflow openings 4a cut in the wall of the upper end of the frame part 4 below its upper edge. Preferably, the overflow openings 4a are pro- tected on the outside by a protective mesh 13a, so that debris cannot enter the inside of the frame part 4 and further into the outlet pipe 1d with the water. Thus, the frame part 4 simultaneously functions as an overflow pipe.

[0023] Correspondingly, at the lower end of the frame part 4 there is preferably a plate- like bottom structure 7, which comprises at least two outlet openings 14 through which the water that has entered the well is allowed to flow, in a delayed manner, through the lower part of the frame part 4 to the outlet connection 5 and from there further to the outlet pipe 1 d. Preferably, a protective mesh 13b is also pro- vided at the lower end of the frame part 4 to prevent debris carried by the water from entering inside the frame part 4 and the cleaning mechanism 12 located at the lower end of the frame part below the bottom structure 7.

[0024] The detention mechanism 2 further comprises operating means 8, 8a, 10, 18, and 18a for moving the blade element 16 that keeps the outlet openings 14 clean. In the embodiment according to the example, the above-mentioned operating means comprise a float 8 that moves according to the water level in the well, a rotating element 8a corresponding to a nut, and a rod-like motion screw 10 pref- erably provided with a double thread 10b having a large pitch, as well as an ec- centric element 18 at the lower end of the motion screw 10, the eccentric element being provided with a downwardly directed movement pin 18a that performs a circular motion around the rotational axis of the motion screw 10.

[0025] The float 8 is positioned outside the frame part 4, between the frame part and the inner surface of the lower part 1 of the well. The cross-sectional shape of the float 8 may vary, and the float may be multi-part, for example an element assembled partially or entirely around the frame part 4 from three or more cylindrical parts.

[0026] For stabilizing the float 8, the float is supported by two support arms 9 or by a corresponding supporting structure, by which the float is supported to support arms 1 1 attached to the frame part 4, the support arms 1 1 supporting the float 8 to move up and down according to the water level. Preferably, both support arms 1 1 are fastened at their upper ends to the cover structure 6 and at their lower ends to the botom structure 7, which structures are rigid, plate-like structures.

[0027] The rotating element 8a, attached to the float 8 and rotating the motion screw 10, may in its simplest form be a tubular element having on its inner surface two short pins located 180° apart from each other and extending towards the centreline of the element, the pins being finable into the double thread of the motion screw 10 such that the first pin is in the first thread of the motion screw 10 and the second pin is in the second thread of the motion screw 10. Thus, the rotating element 8a rotates the motion screw 10 as the float 8 moves up or down according to the water level.

[0028] The motion screw 10 is supported at its upper end in a substantially vertical po- sition to the cover structure 6 of the frame part 4 by means of a supporting element 10a, such as a support bearing. Thus, the motion screw 10 can be ro fated around its vertical axis.

[0029] Preferably, the thread of the motion screw 10 is a double thread having a large pitch, with a phase angle of 180° between the threads. In this case, the rotating element 8a can be easily positioned onto the motion screw 10 so that the pins of the rotating element 8a are opposite each other at substantially the same height on opposite sides of the motion screw 10.

[0030] Figs. 7-10 present in more detail the cleaning mechanism 12 of the structure according to the above-described embodiment, including the blade element 16 and the eccentric element 18.

[0031] Fig. 7 presents the cleaning mechanism 12 as seen from below, with the blade element 16 in the first extreme position of its movement path, and Fig. 8 presents, as seen from below, the same cleaning mechanism with the blade element 16 in the second extreme position of its movement path.

[0032] Correspondingly, Fig. 9 presents the lower end of the motion screw 10 in the lower part of the frame part 4 and the above-mentioned cleaning mechanism 12 as seen from the front, partially sectioned and on an enlarged scale, and Fig. 10 presents the blade element 16 of the cleaning mechanism 12 as seen from below, in an exploded view and on an enlarged scale.

[0033] The motion screw 10 is supported at its lower end to the bottom structure 7 of the frame part 4 by a supporting element 19, which allows the motion screw 10 to rotate around its central axis. At the lower end of the motion screw 10, there is an eccentric element 18, which is arranged to rotate with the motion screw 10 in a circular opening 7a provided in the bottom structure 7, the diameter of the open- ing being larger than the greatest dimension of the eccentric element 18. The cleaning mechanism 12 comprises two parallel slide guides 15 spaced apart at a horizontal distance from each other, and a blade element 16 arranged to be moved back and forth on sliding surfaces of the slide guides 15. The slide guides 15 are fastened to the lower surface of the bottom structure 7 substantially cen- trally at least in one main direction, and the blade element 16 is moved back and forth immediately below the bottom structure 7.

[0034] The blade element 16 comprises two plate-like cleaning blades, a first cleaning blade 16a and a second cleaning blade 16b, whose cutting edges 16c are oppo- site to each other in the blade element. When viewed from below, the cutting edges 16c are in an oblique position relative to the reciprocating movement path of the blade element 16. The blade element 16 is assembled into a single unit by a guide rail 20 attached to each side edge of the cleaning blades 16a and 16b, the sliding surface 20a of the guide rail being arranged to slide against the sliding surface of the slide guides 15.

[0035] In addition, the first cleaning blade 16a comprises, near the first end of the blade, a movement opening 21 transverse with respect to the movement direction of the blade element 16, the movement pin 18a of the eccentric element 18 being fit- table into the movement opening 21 .

[0036] Figs. 5-8 present two outlet openings 14 provided in the bottom structure 7 of the frame part 4, which are preferably of the same size and spaced apart from each other at a horizontal distance.

[0037] In the arrangement according to the invention, the cutting edges 16c of the clean- ing blades 16a, 16b are preferably spaced apart by the same horizontal distance D from each other as the above-mentioned outlet openings 14.

[0038] The detention mechanism 2 of the arrangement according to the invention oper- ates so that, as the water level rises in the detention well, the float 8 moves up- ward with the water surface, and the rotating element 8a attached to the float 8 rotates the motion screw 10. In this case, the movement pin 18a, which is at- tached to the lower end of the motion screw 10 and positioned eccentrically with respect to the rotational axis of the motion screw 10, rotates in the movement opening 21 of the cleaning blade 16a along with the motion screw 10 around the rotational axis of the motion screw 10 and moves the blade element 16 back and forth in a horizontal direction.

[0039] When the water level in the detention well falls, the float 8 descends along with the water surface, and the rotating element 8a rotates the motion screw 10 in the opposite direction compared to when the water level rises. In this case, the move- ment pin 18a moves the blade element 16 back and forth in the same manner as when the water level rises.

[0040] The location and size of the outlet openings 14, as well as the movement path of the blade element 16 and the distance D and position between the cutting edges of the cleaning blades 16a, 16b, are adapted so that one outlet opening 14 or a part of both outlet openings 14 is always open, whereby the water outflow re- mains substantially constant. This is due to the fact that the distance between the opposite cutting edges 16c of the cleaning blades 16a, 16b is the same as the distance between the outlet openings 14.

[0041] In the structure with two outlet openings 14, the spacing between the openings and the cleaning blades 16a, 16b is dimensioned so that, when the first outlet opening is completely closed, the second outlet opening is completely open, and when the first outlet opening is partially closed, the second outlet opening is open by the same amount, and vice versa.

[0042] In a structure having more than two outlet openings 14, the number of cleaning blades may be greater than two and preferably corresponds to the number of outlet openings. Also in this case, the objective is preferably that the total open area of the outlet openings remains substantially constant regardless of the po- sition of the cleaning blades in relation to the outlet openings. The total area of the outlet openings 14 depends, among other things, on the desired detention time. For example, instead of a single outlet opening having a larger diameter, several outlet openings with smaller diameters, arranged for in- stance side by side, may be used. In that case, for example, instead of one outlet opening with a diameter of 15 mm, two outlet openings each having a diameter of 7-8 mm may be used in connection with each cleaning blade.

[0043] When the structure comprises more than two outlet openings 14 in total, one ad- vantageous structural type is such that the outlet openings are aligned with each other in a straight line parallel to the cutting edge of each cleaning blade. In this case, the entire row of outlet openings opens and closes simultaneously. For ex- ample, in a two-blade structure, there may be 2, 3, 4 or more outlet openings 14 in connection with each blade, preferably the same number in connection with each cleaning blade, the outlet openings opening and closing alternately as the blades move over and away from them. There may also be a different number of outlet openings 14 in connection with each cleaning blade, and the areas of the different openings may vary in size.

[0044] An advantage of having several small outlet openings instead of two larger ones is that not all outlet openings become clogged at the same time, and, for example, thicker materials such as branches, which could jam the movement of the clean- ing blades, cannot pass through the outlet openings. These features improve the operational reliability of the device.

[0045] It is to be noted that, although this description has been confined to one type of advantageous embodiment of the invention, this is by no means intended to limit the use of the invention solely to this type of example, but many modifications are possible within the scope of the inventive idea defined by the claims. For a person skilled in the art, it is obvious, for example, that instead of the double thread of the motion screw described above, the motion screw may also have a conventional single thread. It is also obvious to a person skilled in the art that the power transmission from the float to the blade element may differ from that described above. In that case, instead of a threaded rod functioning as the motion screw, the power transmission may employ, for example, a gear rack, a rope, a chain, a belt, or another corre- sponding power transmission element.

Claims

CLAIMS1 . An arrangement In a detention well, comprising a water inlet pipe (1 c) and an outlet pipe (1 d), the arrangement further comprising a detention mechanism (2) which comprises an outlet opening (14) allowing water to flow into the outlet pipe (1d), a float (8) movable with the water level, and a cleaning mechanism (12) provided with a blade element (16) arranged to be movable over the outlet open- ing (14), characterized in that the detention mechanism (2) comprises at least two outlet openings (14), of which, when one is completely open, the other outlet openings (14) are completely closed.

2. The arrangement according to claim 1 , characterized in that the detention mechanism (2) comprises two outlet openings (14), and the blade element (16) comprises two cleaning blades (16a, 16b), and that the spacing between the out- let openings (14) and the cleaning blades (16a, 16b) is such that, when the first outlet opening is completely closed, the second outlet opening is completely open, and when the first outlet opening is partially closed, the second outlet open- ing is open by the same amount, and vice versa.

3. The arrangement according to claim 2, characterized in that the blade element (16) comprises at least two cleaning blades (16a, 16b) provided with cutting edges (16c), a distance (D) between the cutting edges (16c) being the same as the distance between the outlet openings (14).

4. The arrangement according to claim 3, characterized in that the cleaning mechanism (12) comprises two parallel slide guides (15) at a horizontal distance from each other, the blade element (16), whose cleaning blades (16a, 16b) have their cutting edges (16c) facing each other, being arranged to be movable back and forth horizontally on sliding surfaces of the slide guides (15).

5. The arrangement according to any one of the preceding claims, characterized in that the detention mechanism (2) comprises a cylindrical frame part (4), in thebottom structure (7) of which, immediately above the blade element (16), there are two outlet openings (14) of the same size.

6. The arrangement according to any one of the preceding claims, characterized in that the detention mechanism (2) further comprises operating means for mov- ing the blade element (16) that keeps the outlet openings (14) clean, the operat- ing means comprising at least the float (8) movable with the water level in the well, a motion screw (10) provided with a thread (1 Ob), a rotating element (8a) of the motion screw, the rotating element being attached to the float (8) and fitted to the thread (10b), and an eccentric element (18) at the lower end of the motion screw (10), the eccentric element (18) having a downwardly extending movement pin (18a) that moves with the motion screw (10) in a circular motion around the rotation axis of the motion screw (10).

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