WO2001092137A1

WO2001092137A1 - Floating cover, reservoir comprising such a cover and method for covering such reservoir

Info

Publication number: WO2001092137A1
Application number: PCT/DK2001/000376
Authority: WO
Inventors: Bjarne Kongsgaard
Original assignee: Echberg Manutech Systems A/S U.Stiftelse
Priority date: 2000-05-30
Filing date: 2001-05-30
Publication date: 2001-12-06
Also published as: AU6377001A; DK200000853A

Abstract

A floating cover for an upwardly open liquid reservoir, comprising an edge area connected with the edge of the reservoir. The cover comprises an upper film extending beyond the edge of the reservoir. A rim area thereof is connected with an area adjacent to the edge. The upper film is supported by an inflatable chamber provided beneath and imparting a vault extending up over the edge of the reservoir to the upper film and which is resting against a part of the reservoir or the liquid therein.

Description

FLOATING COVER, RESERVOIR COMPRISING SUCH A COVER AND METHOD FOR COVERING SUCH RESERVOIR

Background of the Invention The present invention concerns a floating cover for an upwardly open liquid reservoir, comprising an edge area connected with the edge of the reservoir. The invention furthermore concerns a reservoir comprising such a cover. Furthermore, the invention concerns a method for covering an upwardly open reservoir comprising an edge in that a cover is connected with the edge of the reservoir.

Different kinds of covers for a liquid reservoir are known. A cover of the kind mentioned in the introduction is thus known from US patent no. 4,971,217. The cover for the reservoir described in this publication, is a so-called floating cover where a film is resting directly on the liquid surface. This gives rise to problems with water collecting on top of the cover. Furthermore, this cover is not suited for collecting gases from the reservoir or if stirring of the liquid is to take place.

Furthermore, so-called floating lids for liquid manure tanks are known. These lids consist of elements laid out on the liquid surface in a liquid manure tank for reducing the vaporisation from it. With such lids, an increased amount of liquid is occurring in the liquid manure tank during rain. This is unwanted with regard to storing capacity.

For liquid manure tanks, floating lids of the kind disclosed in the US patent have been proposed. Here, the film is also resting directly on the liquid surface. In order to solve the problem with water collection* it has been proposed to mount pumps which are pumping the water away from the surface of the cover. However, it is uncertain whether this amount of rain water may be led directly to recipient or to a storage container.

The known floating lids are not suited for collecting gases exuding from the liquid manure, e.g. by biological gasification, by aeration, by nitrification or by other processes. Covers secured at an edge area at the upper edge of the reservoir are also known. In these situations, we are speaking of a solid cover which may be relatively costly when the case is containers with a large surface area.

It is the purpose of the present invention to provide a system which in a technically simple way enables establishing a cover of a reservoir, such as liquid manure tanks and similar, irrespectively of cross-section or size of such containers, in order to avoid penetration of rain water and enabling collection of gases in the interspace under the cover and stirring of the liquid, and which enables an automatic adaptation to the liquid level in the reservoir.

This is achieved with a cover of the kind mentioned in the introduction which is peculiar in that the cover comprises an upper film extending beyond the edge of the reser- voir, that a rim area thereof is connected with an area adjacent to the edge, that the upper film is supported by an inflatable chamber provided below and formed in that a lower film is fastened to the upper film and forming the chamber together with the film, and which imparts a vault extending up over the edge of the reservoir to the upper film and rests against a part of the reservoir or the liquid therein.

According to a particular embodiment, the cover is connected airtight with the edge of the reservoir, and that in the cover there are provided air locks for extracting gases from the interspace between the cover and the liquid in the reservoir. This enables extracting gases, which e.g. may be formed by gasification of liquid manure, sewage, or similar in a digestion tank, a liquid manure tank or similar liquid reservoir. These gases may be led to external gas tanks or directly to places of consumption.

The reservoir according to the invention is peculiar in having a round, oval or polygonal cross-section, and that along one or more points along the outer side of the upper film, within the walls of the reservoir, there are provided openings for the passage of equipment associated with the reservoir, and that the film is provided in close connection with such equipment. The reservoir may preferably be provided with a centrally located agitator aerating the liquid which preferably is liquid manure or other biological sewage. In this situation, the cover will rest on a net, allowing the agitator to be located floating on the liquid surface. Alternatively, the cover may rest on legs or annular supports arranged on the liquid surface so that the agitator is situated within such legs or supports.

The method according to the invention is peculiar in that the cover comprises an upper film which is connected with and extends beyond the edge of the reservoir, that a rim area of the film is connected with an area adjacent to the edge, that a film provided beneath is connected with the upper film for forming a chamber, that the chamber is brought to support the upper film by inflating so that it is imparted a vault extending over the edge of the reservoir as the chamber at its underside rest against a part of the reservoir or the liquid therein.

As the cover comprises an upper film and an inflated chamber provided beneath, it is possible to provide a vault ensuring that the rain hitting the upper side of the upper film runs out over the edge of the reservoir. By means of the inflatable chamber, it is possible in a simple way to ensure that the cover maintains an upwardly directed vault. This is regulated by a little pressure provided in the chamber. It is possible to provide the inflatable chamber between two films resting on nets or the like extending over the upper level of the reservoir, e.g. at level with the upper edge of the reservoir. Alternatively, it is possible to form a chamber of an upper and lower film where the lower film is resting directly on the liquid surface.

The cover is suited for used by collecting gases exuding from the liquid manure, e.g. by biological gasification, by aerating, by nitrification or by other processes when the cover is connected airtight with the reservoir. The collecting may occur through air locks mounted in the cover and which may be opened and closed manually or by means of control systems opening and closing in dependence of gas concentration, gas pressure or other parameters. If the chamber is resting directly on the liquid surface, venting means are provided. These venting means may let out a certain amount of air as the liquid level in the reservoir is rising. Venting means may thus comprise means for registering the liquid level in the reservoir, which are regulating the ventilation as a result of this regulation. A particular simple embodiment comprises the venting means in a float resting on the liquid surface and which is connected with a spring biased valve. The float opens the valve via a rod connection and empties a part of the air in the chamber when the liquid level and thereby the float are lifted, and pushes with a force overcoming the spring force in the valve due to the force of buoyancy acting on the float. In this way, it is possible to adjust the pressure in the chamber so that the upper film will constantly maintain a vault extending with the edge of the reservoir and thereby ensuring that rain water is not collected at the top of the upper film but runs out over the edge of the reservoir.

If the chamber is resting on a support construction mounted permanently in the reservoir, it is possible to provide a simple roof construction. By providing the inflatable chamber between two layers of film, it is possible to distend the film and to inflate it when it is resting on the net. By such a construction, no great requirements to the strength in the support construction. On the basis thereof it is possible to use a net or the like which is distended over the reservoir. With such an embodiment, venting means are not necessary as the chamber may maintain a permanently inflated pressure.

The chamber may be formed by a lower film being fastened to the upper film along an edge area thereof. The film may have any shape adapted to the reservoir. The film may thus be round, oval or polygonal depending on the shape of the reservoir. The lower film may have any shape enabling formation of a chamber which keeps the other film distended with its vaulted configuration over the reservoir. The lower film is preferably provided with a dimension approximating the inner area of the reservoir and is fastened to the upper film at its edge area. Alternatively, the lower film may only be provided over a central part and/or as several columnar chambers which are provided by using several lower films forming separate inflatable chambers which are resting on liquid surface and/or a supporting construction secured to the reservoir. It is also possible to use an annular downwardly directed part which has the shape as one or more annular chambers abutting on the inner side of the side wall of the reservoir.

In order to achieve the best shape for a given reservoir and for providing the desired shape on the vault, e.g. with continuous curvature or with an edged shape, the film is preferably formed of one or more pieces of material made into shape. Preferably, the lower film with have less elasticity than the upper film. Hereby, by pumping up the chamber it is ensured that the upper film assumes its vaulted configuration in a simple way.

Alternatively, it is possible to provide the upper film without stretchability. Hereby is ensured by the inflation a uniform shape of the vault when an overpressure is formed in the chamber. This configuration is maintained even if small pressure variations occur in the inflatable chamber.

According to a special embodiment, the cover is peculiar in that the reservoir is formed with largely vertical, freely standing walls, and that the fastening edge of the reservoir comprises an annular collar which is clamped on the outer side of the reservoir and comprises fastening means in the shape of rings or similar which are interact- ing with corresponding fastening means in the shape of hooks or similar formed in the edge area of the upper film.

As the cover is very light, it will be necessary to have a suitable fastening to the reservoir or an area bordering on the reservoir. Alternatively, it is also possible to avoid the collar and to perform a fastening with fastening means, e.g. hooks, rings or the like which are fastened directly at the edge of the reservoir and/or the side wall of the reservoir. The fastening of the cover may occur by using elastic straps which are e.g. known from fastening tarpaulins on lorries. Alternatively, the fastening may be established by means of an elastic rope which is passed through eyelets in cover and reser- voir. Alternatively, by inflating an annular chamber formed by a downwardly directed part of the cover there may be formed a fastening of the cover which is only established by friction between the cover and the inner side of the side wall of the reservoir.

In a reservoir there is preferably provided openings for passages and equipment, as e.g. pumps, aerators, drain-pipes and supply pipes and the like which may be necessary for using the container. In such a configuration, the film will be provided in close connection with an equipment. The close connection may preferably be provided by using an upwardly directed elastic collar enclosing the equipment and which is welded, bonded, or in similar way fastened to the upper film.

Using the cover and the reservoir occurs very simply by the upper film with an inflatable chamber provided beneath being connected with and extending beyond the edge of the reservoir. The rim area of the film is connected with an edge area of the upper side of the reservoir. The chamber is then inflated and brought to support on the liquid surface and/or a solid support on the reservoir until the upper film assumes the desired vaulted shape over the edge of the reservoir. If the chamber is resting directly on the liquid surface, by empty reservoir it will be inflated so that it is approximately extends toward the bottom of the reservoir. As liquid is filled into the reservoir, due to venting means there is provided ventilation of the chamber corresponding to the rise in the liquid level so that the upper film retains its vaulted configuration and without an unsuitable high pressure is formed in the chamber.

In the present application, by film is meant any plastic and/or rubber film with or without reinforcements. Also, the case may be impregnated canvas or other means enabling security against penetration of rain water. If the film is used directly for forming the inflatable chamber, the film is simultaneously to be of a kind which is airtight.

With the film according to the invention it is suitable that the support provided by the inflatable chamber not only ensures draining of rain water but additionally is dimensioned with such strength as to withstand snow pressure in area with risk of snow. Alternatively, it will be possible to make the cover with such vaulting that snow automatically slides off. By using plastic films, small friction is attained, enabling great self-cleaning effect for snow layers on top of the cover.

Description of the drawing

The invention will now be explained more closely with reference to the accompanying drawing, where:

Fig. 1 shows a side view of a first embodiment of a reservoir and a cover according to the invention,

Fig. 2 shows a view from above of the cover and reservoir in Fig. 1,

Figs. 3-5 show views corresponding to Fig. 1 for illustrating alternative embodiments for cover and reservoir according to the invention, Fig. 6 shows a perspective view for illustrating a further embodiment for a cover and a reservoir according to the invention, and

Fig. 7 shows a view corresponding to Fig. 1 for illustrating an embodiment with an airtight cover.

In the different Figures of the drawing, identical or corresponding elements are desig- nated with the same reference and are therefore not explained in detail in connection with each Figure.

There is shown a reservoir 1 with a sidewall 2 and containing a liquid 3 with a liquid surface 4. The side walls 2 have an upper edge area 5.

On the upper edge area 5, there is provided a cover 6 comprising an upper film 7 which is provided with an upward directed vaulted shape. A lower film 8 is fastened at its edge region 9 in an airtight manner to the under side of the upper film 7 so that an inflatable chamber is formed. The chamber 10 may be inflated by means of pump and inflating valve (not shown). The upper film 6 rest at a rim area 11 which possibly may be provided with suitable reinforcements on the rim area 5 of the reservoir. Along the outer edge area 12 of the upper film 6 there is provided fastening means 13 in the shape of hooks interacting with eyelets 14 which are fastened on the upper edge area of the side walls 2. Alternatively, the hooks may be fastened on a collar 15 as schematically illustrated in Fig. 3.

The inflatable chamber is connected with venting means 16. These comprise a valve

17 which is biased by a spring 18 towards its closed position. Through a rod connection 19, the valve 17 is connected with a float 20 resting on the liquid surface. At the upward movement of the float by rising liquid level, the force of buoyancy will surmount the force in the spring 18 and be opened so that a part of the air may escape from the chamber 10. When a part of the air in the chamber has escaped, a balancing of the spring force and the force of buoyancy occurs so that the valve 17 is closed again. Hereby is ensured the establishment of a pressure in the chamber 10 within predetermined limits which are determined by dimensioning of springs 18 and size of floats 20.

In Fig. 2, the upper film 7 is illustrated as seen from above. With stippled lines are indicated separating lines 21 between separate pieces of material 22 shaped for providing the desired vaulted form. Alternatively, the upper film 7 may be provided in one piece. It is also possible to provide the pieces of material 22 as webs of material ex- tending in parallel. In the edge region 11 there are provided a number of openings 23 which are intended for the passage of equipment for use in the reservoir 1. If t e reservoir 1 is a liquid manure tank, such equipment may comprise supply pipe, drain-pipe, aerator, agitator, and the like. At the lead-ins there may be provided sealings in the form of collars fastened around the equipment and to the upper film 7. If the openings 23 are formed in a rim area outside the chamber 10, such a sealing will be unnecessary.

It is possible to provide a ditch 24 around the outer side of the reservoir 1 for collecting rain water running off the vaulted cover 6. Hereby, the rain water may be collected in containers for use in irrigation, high pressure flushing of machines and equipment and cleaning of stables and the like. Alternatively, the rain water may be led directly to recipient. In Fig. 3 is illustrated an embodiment where the cover is resting on a net 25 distended at the upper edge 5 of the reservoir. The net may be formed of plastic, metal or rope. It does not need to have great strength as the support construction 6 is very light. In this embodiment there will be no need for venting means. When the chamber 10 is inflated, the cover 6 will form a firm, vaulted upper side without need for regulation depending on the liquid level 4 in the reservoir 1.

Fig. 4 differs from Fig. 1 in that the chamber 10 is provided with a relatively limited dimension and is forming approximately a central column for the upper film 7.

Fig. 5 differs from Figs. 1 and 4 by several chambers 10 being provided, e.g. in a number of four, which are providing a column effect supporting the upper film 7 so that it maintains its vaulted shape. In Fig. 5, the venting means are omitted for the sake of clarity.

Fig. 6 shows a further embodiment where the upper film has been omitted. In this embodiment, the chamber is formed by an annular hose 26 that may rest directly on the liquid surface or on a net in the reservoir 1. The annular hose 26 is connected with a number of upwardly extending hoses 27 forming a vaulted support structure. In the shown embodiment, four upwardly extending hose sections 27 are provided. However, it is possible to provide another suitable number. The hose 26 and the hose sections 27 may be mutually connected or may be formed with separate chambers. Besides the hose sections 27, there is provided an upper film 7 (not shown) which is fastened in a way corresponding to that shown in the other Figures.

The chamber formed in the hoses 26,27 may optionally be connected with venting means or be provided without venting means depending on whether it is intended for being placed on the liquid surface or on a support structure in the shape of a net or similar being secured to the reservoir 1. Fig . 7 shows a reservoir 1 where the cover 6 is resting on the liquid surface 4 via an annular chamber 10. The downwardly directed part 10' of the chamber is arranged so that it presses against the inner side of the side wall 2 of the reservoir. The downwardly directed part 10' thus contributes to sealing the interspace 28 formed inside under the cover 6. The downwardly directed part is, as indicated with stippled lines

37, divided into chambers 38. Tins ensures that venting occurs stepwise, whereby is ensured that the downwardly directed part 10' will collapse or bend in the desired positions.

Within the circumference of the annular chamber 10 in the central free area 28, there is provided an aerator 29 in the surface layer of the liquid. This aerator 29 aerates the liquid manure for nitrifying and homogenising the liquid in the reservoir. In the cover 6 there is provided an air lock 30 which via a pipe 31 leads gases to an external container (not shown). The cover 6 is connected to the upper edge area 5 of the reservoir 1 at its edge area 32 by a sealing means 33, e.g. a soft plastic or rubber hose which establishes an airtight connection as the edge area 32 of the cover 6 is clamped to the edge area 5 of the reservoir with a clamping means 34 clamping the film firmly against the outer side of the sealing means 33.

At its edge region, the cover is provided with fastening stays 35 which may be provided in a number between 4 and 60, preferably between 8 and 16 for normal liquid manure tanks. The distance between stays will preferably be 1 - 10 m. Only it is to be ensured that the stays are securing a permanent clamping to edge area of reservoir. I.e. in large reservoirs as e.g. liquid manure lagoons that may be between 300 and 500 m long, there may be a greater number of stays. Also, the net 25 may be fastened to the stays 35.

The stays 35 are fastened in anchor points 36 outside the reservoir, e.g. earth rods or earth anchors. Hereby it is possible to avoid load on the edge of the reservoir as forces/loads are absorbed in the anchoring points. The invention is not limited to the embodiments disclosed above. Thus the reservoir 1 may alternatively have a polygonal cross-section and not a circular cross-section as illustrated. Also, the reservoir 1 may have an oval shape. Alternatively, it is also possible to provide a reservoir formed by digging and having an upper edge area which is even with a ground surface. Only it is to be ensured that the cover is provided with an inflatable chamber imparting the upper film 7 with the necessary vault for rain water to be led away from the container so that it is avoided that rain water is collected on the surface and necessitate use of pump means or similar for removing rain water from the upper side of the film. Also, the connection between cover and reservoir is pref- erably to be airtight.

Claims

1. A floating cover for an upwardly open liquid reservoir, comprising an edge area connected with the edge of the reservoir, characterised in that the cover com- prises an upper film extending beyond the edge of the reservoir, that a rim area thereof is connected with an area adjacent to the edge, that the upper film is supported by an inflatable chamber provided below and formed in that a lower film is fastened to the upper film and forming the chamber together with the film, and which imparts a vault extending up over the edge of the reservoir to the upper film and rests against a part of the reservoir or the liquid therein.

2. A cover according to claim 1, characterised in that the chamber is resting on the liquid surface, and that it is connected with venting means comprising means for registering the liquid level in the reservoir and regulating the ventilation as a result of this registering.

3. A cover according to claim 1, characterised in that the chamber is resting on a net or similar which is distended over an upper level of liquid in the reservoir.

4. A cover according to any of claims 1 -3, characterised in that the upper film has greater elasticity than the lower film.

5. A cover according to any preceding claim, characterised in that the upper film is formed by one or more pieces of material shaped as to impart the desired vaulted shape which may be a continuously curved shape or an edged shape.

6. A cover according to any preceding claim, characterised in that the reservoir is formed with largely vertical, freely standing walls, and that the fastening edge of the reservoir comprises an annular collar which is clamped on the outer side of the reservoir and comprises fastening means in the shape of rings or similar which are interacting with corresponding fastening means in the shape of hooks or similar formed in the edge area of the upper film.

7. A cover according to any preceding claim, characterised in that the venting means comprise a float resting on the liquid surface and connected with a spring biased valve for opening it and emptying a part of the air in the chamber when the liquid level and thereby the float is lifted and opens the valve as the spring force is overcome by the force of buoyancy.

8. A cover according to any preceding claim, characterised in that the cover is connected airtight with the edge of the reservoir, and that in the cover there are pro- vided air locks for extracting gases from the interspace between the cover and the liquid in the reservoir.

9. A reservoir comprising a cover according to any preceding claim, characterised in that it has a round, oval or polygonal cross-section, and that along one or more points along the outer side of the upper film, within the walls of the reservoir, there are provided openings of the passage of equipment associated with the reservoir, and that the film is provided in close connection with such equipment.

10. A method for covering an upwardly open reservoir comprising an edge in that a cover is connected with the edge of the reservoir, characterised in that the cover comprises an upper film which is connected with and extends beyond the edge of the reservoir, that a rim area of the film is connected with an area adjacent to the edge, that a film provided beneath is connected with the upper film for forming a chamber, that the chamber is brought to support the upper film by inflating so that it is imparted a vault extending over the edge of the reservoir as the chamber at its underside rest against a part of the reservoir or the liquid therein.