The present invention relates to a well, according to the preamble of Claim 1. A well of this type is generally comprised of a well pipe which in operating mode has an open upper end and a lid which covers the end. Often, the well comprises a telescopic ring which is attached to the lid, in which case one end of a telescopic pipe is fitted into the telescopic ring, while the other end of the telescopic pipe is covered by a well cover. The use of wells for instance in areas over the surfaces of which traffic passes include wells housing valves, manholes, inspection wells and access wells.

Typical applications of wells are in pipe systems for sewage, storm or rain water and district heating or district cooling.

Generally, the wells are made of plastic whereas the well cover, i.e. the covering of the well over which traffic passes, is made of cast iron and designed to withstand the weight of traffic. The lower part of a valve well, the well pipe and the lid which covers the pipe is often comprised of polyethylene or similar thermoplastic material. The lid is formed of a flat plate or a round disc. Even though the telescopic pipe is not rigidly attached to the lid, loads are still transferred from the cast iron cover to the pipe. In fact, soil and traffic loads impose a burden on the lid. Movements in the ground, caused for instance by frost, also generate loads directed towards the well pipe and its lid. Therefore, when in use, the plastic lid tends to be deformed by loads from the traffic and the weight of the soil mass. Over time, these loads may lead to a need for repair or even replacement of the well pipe and the lid, which is costly and difficult.

One of the purposes of the present invention is to solve the problems associated with known valve wells and similar wells, such as pump wells and inspection wells, and to provide a well of a new design, one having improved mechanical properties.

The present invention is based on the principle that, instead of using a flat cover made of a round disc or a plate, the well pipe is covered by a domed pipe section the cross section of which is arcuate. Such a lid is easily made from a pipe, even on-site, and it exhibits substantially greater rigidity and strength against forces which are directed vertically against the well pipe.

More specifically, the present invention is characterised by what is stated in the characterising part of Claim 1.

Considerable advantages are achieved with the present invention. Because the top of the well pipe is arcuate, a structure is achieved which suffers much less deformation caused by traffic and weight of soil masses than a flat lid does. Because the top of the well pipe is more rigid, the loads on the bonding between the top and the other parts are greater, as well. Due to the arch, water does not accumulate on the top of the well and consequently, there is no water to freeze or leak into the well. During replacement of soil, soil masses will flow down from the top and for instance an excavator can be employed. It is easy to use the same or a higher degree of ring rigidity at the top of the well as in the other parts.

Instead of for example using an injection moulded conical part, the exploitation of semifinished goods, such as pipes, for the manufacture of the lid, permits these goods to be chosen according to strength requirements and dimensions which typically are available in stores. This offers many options and combinations compared to parts that have been injection-moulded. From a financial standpoint, the use of a pipe half, i.e. a lid which is part of a pipe wall periphery having the same radius as the well pipe or one which is larger, is very advantageous.

The construction according to the present invention is suitable for, among others, valve wells, inspection wells and pump wells and similar wells which have covers and which are designed to be sunk into the ground. A suitable well construction comprises both a well pipe and its lid, and a telescopic ring which is attached to the lid, which, in turn, is placed onto the upper end of the well pipe, a connecting pipe, for instance a telescopic pipe, one end of which is fitted into the telescopic ring, and a well lid which covers the other end of the connecting pipe.

In the following, the present invention will be examined more closely with the aid of the accompanying drawings. As shown in Figures 1 and 2, the well comprises two main parts, specifically the well pipe 1 and its lid 2, plus a telescopic pipe 4, the upper end of which is connected to a well cover (designed for streets) 5 and the lower end of which is inserted into a telescopic ring 3. As the figures show, the well pipe 1 is cylindrical and made of a thermoplastic material, such as polyethylene or polypropylene. However, it is possible to manufacture the well pipe from many other materials, such as insulated acid-proof steel pipes, sandwich structures having an inner/outer pipe made of solid material [polymer, metal (solid or as polyethylene-coated spirally coiled steel, i.e. culvert pipe)] and with foam between them. Typically, the sizes vary between 300 and 3500 mm. In the operating mode, the well pipe is usually installed in such a manner that its central axis is vertical.

The well pipe may be fabricated with or without insulation. A suitable insulation material is comprised of thermoplastic such as polyurethane (PUR).

According to an embodiment, the well pipe has a hollow wall, which comprises a spirally coiled plastic profile in which the adjacent profile loops are welded together to form the pipe wall. Such a construction is described for example in WO- A-03028980.

The well pipe 1 has a lid 2 which is arcuately domed. Like the pipe, the lid is made of thermoplastic material, such as polyethylene. In the case shown in Figures 1 and 2, the lid is comprised of part of a pipe. The pipe from which the lid is cut may have the same diameter as the well pipe, or it may differ from this. In general, it is preferable to have the diameter of the initial pipe equal to or greater than the diameter of the well pipe.

Generally, the lid is arcuate, and has the same radius or a different, usually greater radius, than that of the well pipe.

In this application, the lid is also called "pipe half or "pipe segment" even though it does not necessarily constitute exactly half a pipe (i.e. a pipe section which is cut in half along the length of the pipe). Thus, the walls of the pipe sections in the cases of the figures comprise approximately 130-150 degrees of the wall periphery of the initial pipe.

Generally, it is possible to select the pipe section, depending on the radius of curvature, so as to constitute between approximately 45 and 225 degrees, preferably about 120-200 degrees, of the wall periphery of a pipe.

The figures also show that the upper edge of the well pipe 1 is modified to fit the lid. Specifically, the wall of the well pipe is cut in such a way that the opposite sides of it have a domed, arcuate shape which corresponds to the inside of the domed lid. On the sides, i.e. 90 degrees from the arcuate section, the wall of the well pipe is cut transversely, preferably slightly chamfered so that it lies evenly against the lid.

Just like the well pipe, the lid, too, can be manufactured from a pipe having a hollow wall which comprises a spirally coiled plastic profile in which the adjacent profile loops are welded together to form the pipe wall. Such spirally coiled pipes are available in large dimensions, for example up to 3500 mm, unlike pipes with solid walls, which are manufactured with dimensions of at maximum 2000 mm. In one embodiment, the lid has a length and a width which mainly correspond to the diameter of the well pipe. According to a more preferable embodiment, the length of the lid (measured along the central axis of the initial pipe or the bent section) exceeds the diameter of the well pipe by at least 5 %, most suitably at least 10 %, preferably not more than 30 % and typically approximately 15 ± 3 %, at least on one side of the well (see reference number 6). In this embodiment, special advantages are achieved, among others regarding welding of the lid onto the upper edge of the well.

The overhang 6 that is formed of an extension of the lid can extend over the entire wall periphery of the well, or only one or two edges (for instance two opposite edges). The cut surface of the lid may vary; it can for example be straight or chamfered.

Because the use of domed lids, which are derived from pipe sections comprised of coiled hollow profiles, results in certain deformations of the edge sections, due to the internal stresses in the structure of the pipe wall profile, it is advantageous to use this overhanging part in these wells. By applying the above-mentioned dimensioning principles, it is possible to carry out the welding of the domed lid in the space between the jacket pipe and the lid periphery where the internal stresses do not affect the geometry and a tight seam can be obtained between the well pipe and the top by means of a welded joint and without the need to stabilise or modify the lid edges. According to the embodiment wherein the domed lid is larger than the well pipe (i.e. the lid length exceeds the well pipe diameter, as described above), an overhang is created, most suitably on opposite sides of the well or preferably extending over the entire well periphery, which can be utilised to provide an advantageous reduction in the load placed on the domed lid. More specifically, it is possible to anchor the overhang in the soil, thus achieving a more robust structure. In this case, the lid can be made thinner than a lid which is not anchored to the area around it. The anchorage can for example consist of wires, strands, bands, chains, poles, guys or similar mechanical devices, one end of which can be attached to the ground and the other to the lid.

For the anchoring, the edge of the lid can be provided with a separate means of fastening to which the anchorage can be secured. Alternatively, the anchorage can be attached by casting onto one end of the lid. A telescopic ring 3 is mounted into the lid 2. The telescopic ring 3 has an inner diameter which is fitted to a telescopic pipe 4. The telescopic ring 3 allows the telescopic pipe 4 to move and is also equipped with a seal (not shown) to prevent water leakage between the telescopic pipe and the ring. The telescopic ring 3 is made of polyethylene. The seal may comprise a polymeric material, such as an elastomer, for instance TPE, or silicone plastic.

The telescopic pipe 4 which is inserted into the ring is usually made of polyethylene and it can be adjusted vertically. The size range of the telescopic pipe is between 300 mm and 1000 mm. The telescopic pipe is provided with a well cover 5 having a frame into which it fits, for surfaces over which traffic passes. The dimensions of the well cover are similar to those of the telescopic pipe, specifically 300-1000 mm.

By joining two similar pipes in the way shown in the figures, a simple structure is achieved, one possessing excellent ring rigidity in relation to the weight of the product. In addition to the examples in the figures with arcuately domed lids, also other shapes are possible, including lids which essentially have the shape of a saddle.