[0002] The invention also relates to an arrangement for renovating a well, the arrangement comprising inner casing elements arranged to form the inner casing of the well and a casting between the well and the inner casing.

[0003] The invention further relates to an inner casing element of a well, which is intended to be arranged inside the well in such a manner that several inner casing elements form the inner casing of the well.

[0004] In the course of time old wells, such as drain wells, are dam- aged for instance so that the walls and/or bottom thereof start to leak. The causes of damage include, for instance, corrosion and the movement of the surrounding ground owing to frost heave.

[0005] Attempts have been made to seal wells for instance by coat- ing them from the inner surface with an appropriate material, such as concrete or polyurethane injection. Such a coating forms a fairly thin layer on the inner surface of the well. Although such a thin layer forms a corrosion protection, it does not significantly improve the mechanical strength of the wells. The well is therefore easily liable to be damaged again.

[0006] A solution is also known in which a fairly thin plate provided with bulges is arranged into the well, the bulges keeping the plate off the wall of the well to be renovated. Thus, a moulding cavity, into which concrete is cast, is formed between the plate and the well. Considering the mounting and handling, the plate has to be very thin. This, in turn, means that the moulding has to be carried out in several stages, since a thin plate does not endure a very heavy cast pressure of concrete. Furthermore, it is extremely laborious and difficult to handle and to mount the plate and also for instance to make the joints to be made into the pipes leading to the drain.

[0007] WO publication 91/15634 discloses a method for renovating wells. In this method, semi-circular ring elements are placed inside the well through an opening. Two elements are attached to one another and the ele- ments are stacked in pairs on top of one another. After this, the space between the well and the ring elements is filled with concrete. However, it is very difficult to seal the seams between the ring elements. What has proven to be particu- larly difficult is to provide a tight intersection of the vertical and horizontal seams. Furthermore, the lowest layer of ring elements has to be arranged with the accuracy of a few millimetres to the bottom groove of the well, the slanting bottom, an outlet joint and one or more inlet joints. Also, the lowest layer is to be mounted horizontally in order not to impede the installation of the following layers. In all the installation has proven to be very hard and difficult. The task becomes extremely difficult if the diameter of the inlet or outlet joint exceeds the height of the ring element, in which case the ring element is cut into smaller pieces.

BRIEF DESCRIPTION OF THE INVENTION [0008] It is an object of the invention to provide a new and improved method and arrangement for renovating a well and an inner casing element of the well.

[0009] A method according to the invention is characterized by forming an inner casing element of the well in such a manner that a continuous ring is formed and that the wall thereof is provided with bending points, flatten- ing the inner casing element for mounting it into the well utilizing the bending points and rounding the inner casing element after being mounted into the well.

[0010] An arrangement according to the invention is characterized in that the inner casing element forms a continuous ring provided with bending points on the wall thereof so that the ring-shaped element is bendable from a round shape to a flatter shape in order to mount the element into the well.

[0011] An inner casing element of a well according to the invention is characterized in that the inner casing element forms a continuous ring pro- vided with bending points on the wall thereof so that the ring-shaped element is bendable from a round shape to a flatter shape.

[0012] An essential idea of the invention is to form the inner casing element of the well so as to form a continuous ring. Furthermore, the element is provided with bending points on the wall thereof so that the ring-shaped element can be bent from a round shape to a flatter shape, whereby the ele- ment can be mounted inside the well from an opening in the cover of the well.

Inside the well the element is rounded. A required number of ring-shaped ele- ments are mounted on top of one another. The structure of the elements is self-supporting. When the elements have formed a cylindrical structure of de- sired height, the space between the well to be renovated and the ring elements is cast for instance with fluid concrete. The idea of one embodiment is that the bending points on the wall of the ring-shaped element are formed by making the thickness of the wall at the particular point thinner than the rest of the crosscut of the element. The idea of another embodiment is that the bending point is formed such that the direction of the wall at the bending point differs from the direction of the rest of the wall.

[0013] The invention provides such an advantage that the ring ele- ments are tight as such and that the stack formed of several ring elements can also be made very tight, since the structure comprises only horizontal seams.

Also the structure formed by the ring elements is very stiff and solid, and thus endures extremely well the pressure caused by the material to be cast outside it. Above all the installation of the ring elements is simple and easy. In addition, joining the inlet and outlet joints to the ring elements is fairly easy and fast to implement. Several ring elements can be stacked on top of each other, whereby making joints of, for instance, a large diameter is easy even though the diameter of the joint alone would exceed the height of the ring element, since arranging several ring elements on top of one another allows the inner elements to maintain their circular shape even though one layer of elements were to be broken. The ring elements can be manufactured economically in a very simple fashion. The ring elements may for instance almost entirely be made of one material. When the bending point is formed such that the direction of the wall at the bending point deviates from the direction of the rest of the wall, a structure can easily be formed, in which the inner casing elements placed on top of each other can easily be mounted partly within one another.

Furthermore, when such an inner casing element is flattened, the shape thereof becomes partly curved, which makes it easier to slide it inside the well.

BRIEF DESCRIPTION OF THE DRAWINGS [0014] The invention will be explained in greater detail in the ac- companying drawings, in which Figure 1 schematically shows a top view of an inner casing element of a well, Figure 2 schematically shows the inner casing element when being mounted inside the well, Figure 3 schematically shows the inner casing elements when mounted in position inside the well, when the well is shown in crosscut, and Figure 4 schematically shows in cross-section a wall of the inner casing elements.

DETAILED DESCRIPTION OF THE INVENTION [0015] Figure 1 shows an inner casing element 1. The inner casing element 1 is shaped as a continuous ring. The inner casing element 1 is pro- vided with bending points 2, from which a wall of the inner casing element 1 can reasonably easily be bent. The inner casing element 1 is preferably en- tirely made of plastic, such as polyvinyl chloride PVC, polyethylene PE or cross-linked polyethylene PEX. In view of the handling and bending of the in- ner casing elements 1, it is particularly advantageous to form the inner casing element 1 of polypropylene PP.

[0016] The bending points 2 are preferably formed so that the thick- ness of the wall of the inner casing element 1 is made thinner at the bending points than elsewhere in the element. The inner casing element 1 can easily be made for instance in such a manner that a ring-shaped element equally thick throughout each wall is formed and end cleats and grooves in order to form the bending points 2 are machined into the wall. Then again, the inner casing element 1 can also be shaped in a mould for instance by means of rota- tional moulding, in which case the mould is formed such that the walls of the inner casing element 1 are thinner at the bending points. It is possible to form the inner casing element 1 by means of injection moulding as well. In the sim- plest form, the inner casing element 1 is thus made of a single material.

[0017] Figure 2 shows how the inner casing element 1 is being mounted inside a well 3 to be renovated. The inner casing element 1 is pro- vided with bending points 2, whereby the inner casing element 1 is to be flat- tened from its ring-shaped form to a flatter form in order to fit the inner casing element 1 into the well 3 from an opening 4 in the cover inside the well 3. Pref- erably the element 1 comprises four bending points 2. Thus, the element 1 can easily be flattened and when rounded the structure of the element 1 is stiff.

The number of bending points may, if desired, also be a different one.

[0018] If the inner diameter of the well 3 is for instance 1000 milli- metres, the outer diameter of the inner casing element 1 may for instance be 900 millimetres. The element 1 does not therefore have to be supported on the wall of the well 3, but the structure thereof is sufficiently solid to be arranged also for instance inside a rectangular well 3. The height of the inner casing element 1 may in such a case be for instance 300 millimetres. As the inner casing element 1 is flattened, it can be mounted for example through such an opening 4, whose diameter ranges for instance between 400 and 500 millime- tres. Preferably the height of the element 1 is smaller than the diameter of the opening 4 in the cover of the well 3 to be renovated. The element 1 can also be measured such that the height is smaller than half of the diameter thereof.

[0019] When renovating the well, the bottom of the well 3 is at first provided with a plastic layer that takes into account the bottom groove at the bottom of the well, the slanting of the bottom of the well and the pipe joints at the bottom. After mounting the bottom layer a first inner casing element 1 is placed inside the well. Since the inner casing element 1 is a continuous ring, it can easily be cut on the ground into a shape that corresponds to the shape of the bottom and the joints, thus reducing the fitting work that is carried out in difficult conditions. After being placed in position, the inner casing element 1 is rounded again to resemble a circle. Rounding can be carried out manually or an appropriate tool can be used for rounding. The tool may for instance com- prise plates which support the inner casing element on the sides and which are pressed apart using a lever or levers. What can also be used is for instance a tool provided with cylinders or another appropriate solution.

100201 After mounting the inner casing element 1 an opening is formed therein for a pipe 5. If the diameter of the pipe to be joined is very large, as shown in connection with the lowest pipe 5 in Figure 3, then two or more inner casing elements 1 are at first joined on top of each other. It is there- fore preferable in Figure 3 to arrange the three lowest inner casing elements 1 on top of one another and only thereafter form a hole for the lowest pipe 5. A couple of inner casing elements 1 can be handled together fairly easily. Fur- thermore, when the inner casing elements 1 have been arranged on top of one another, they all remain stiff and the structure remains round even though the second lowest inner casing element 1 must in its entirety be cut when the opening of the pipe 5 is being made in order to mount the pipe 5. After the cut- tings have been performed the lowest inner casing element 1 is welded to the plate placed at the bottom and the inner casing elements 1 are welded to the connecting pipes 5. The inner casing elements 1 are piled as a cylinder of re- quired height. The cylindrical portion of the well 3 may be for instance 2 to 3 metres high. A stiffer structure is provided when the bending points 2 of the inner casing elements 1 are staggered, i. e. placed in different places. The structure according to the invention is so solid and stiff that the cylindrical bot- tom part of this size can be cast in one go. A casting that seals and reinforces the structure is thus cast between the well 3 to be renovated and the inner cas- ing elements 1 for instance with fluid concrete 6. Other materials can also be used instead of concrete 6, for example polyurethane foam.

[0021] Figure 4 shows in crosscut a part of the wall of two inner cas- ing elements 1 placed on top of each other. The walls of the inner casing ele- ments 1 are formed to be corrugated. Thus, the thickness of the wall does not have be very large but the structure of the inner casing element 1 still remains very stiff. Such a corrugated inner casing element 1 can be formed for instance using rotational moulding. The inner casing element 1 may also be such that the outer surface thereof is corrugated but the inner surface is smooth. A smooth inner surface can be formed by means of a thin casing plate, for ex- ample. Such a thin casing plate can also be formed of a material that is lighter in colour than the rest of the inner casing element 1, in which case the colour of the inner surface of the inner casing element 1 remains light without having to employ expensive colouring agents in the entire structure. If the structure of the inner casing element 1 is to be further strengthened, the space between the casing plate of the inner surface and the corrugated outer surface can be foamed. The corrugated outer surface, the smooth inner surface and the foamed intermediate layer can also be formed in a single stage, for instance using rotational moulding.

[0022] The lower inner casing element 1 in Figure 4 is crosscut at a bending point 2. The bending point 2 is obviously not provided with corruga- tions but the wall is straight at that point. Furthermore, the bending point 2 is formed such that the direction of the wall of the element 1 deviates at that point from the direction of the rest of the wall. It is therefore easy to provide a struc- ture, in which the upper inner casing element 1 can be mounted within the lower inner casing element. In addition, a space for a seal 7 can easily be pro- vided between the elements. Only the horizontal portion between the inner casing elements 1 has to be sealed in this structure, whereby the seal 7 en- ables to easily make the cylinder formed of the inner casing elements 1 ex- tremely tight. The inner casing elements 1 are provided with locking claws that allow locking the inner casing elements placed on top of each other together extremely well. In addition, the locking claw of the lower inner casing element is pressed tightly against the seal 7, and the joint thus becomes very tight. In addition to or instead of locking claws the inner casing elements 1 placed on top of each other can be joined together for instance using an electric welding joint in a manner known per se. Furthermore, when inner casing elements placed on top of each other are joined, the memory of the material can also be utilized. The portion of the cleat and/or the claw can for instance be bent out- wards when mounting the element, whereby the placing of the elements on top of each other becomes easy. Thereafter the elements can be heated, in which case the memory of the material allows placing the cleat and/or the claw in position again and locking the elements placed on top of each other together.

[0023] As the direction of the wall at the bending point 2 deviates from the direction of the rest of the wall, the bending point concerned does not bend straight when the inner casing element is being flattened, instead the ring shapes like an arc. Considering the handling of the inner casing element 1, such bending does not, however, provide any significant damage. Such a flat- tened partly arched inner casing element 1 can be slid into the well even more easily than a completely straight ring in a flattened shape. To shape the direc- tion of the wall of the bending point to be such that it deviates from the direc- tion of the rest of the wall can be formed for instance in a rotational moulding mould.

[0024] When the wall has been corrugated, flattening the corruga- tion at the desired points can form the bending point 2. Flattening can be car- ried out so that the bending points are provided with a memory for the material from the state, in which the corrugation is not flattened. Thus, after placing the element in position the bending points can be returned into a shape, in which the corrugation is not flattened, for instance by means of heat. This increases the ring stiffness of the inner casing element placed in position.

[0025] The drawings and the description associated therewith are merely intended to illustrate the idea of the invention. The details of the inven- tion may vary within the scope of the claims. The well 3 to be renovated is for instance a drain well, such as a sanitary sewer well or rainwater sewer well.

The well 3 may be made of round concrete rings, for example. The cross sec- tion of the well 3 may also be angular and the well 3 may also be made of bricks, for instance.