The main object of the invention is to suggest a lid construction, which is easy to open, for example for the purpose of inspection and servicing of the piping system, but which efficiently prevents liquid or liquid-borne impurities from unintentionally penetrating into the well hole and pollute water present therein and usually in communication with the subsoil water in the ground.

This object is achieved by means of a safety seal in accordance with the invention, which seal is essentially characterised in that it comprises, in combination, a lid one face of which is turned towards the well hole, and a string, which is inserted in the gap between said well wall and said lid face and which consists of a material that swells upon its contact with a liquid. Owing to this arrangement, the well lid is easy to dismantle as long as no liquid tries to penetrate into the well hole but, should this happen, for instance in consequence of flooding, the lid is arranged to form an efficient seal.

When such undesirable liquid tends to penetrate into the well hole, past the seal string of a material that swells upon its contact with liquid, said seal string will swell as a result of the supply of liquid and efficiently fill the gap between the lid and the well wall, thereby effi- ciently constraining the liquid tending to flow down the well hole, also at high pressures.

Additional characteristics and advantages offered by the inventive object will appear from the following de- scription and appended claims.

In the following, the invention will be described in more detail with reference to the accompanying drawings, wherein:

Fig 1 is a vertical sectional view through an energy well having an inspection space in the upper region closest to ground level, Fig 2 is a cross-sectional view through the upper part of a well casing and its associated closure lid, projecting into the inspection space interior, Fig 3 is a view from below of the lid shown in Fig 2, and Fig 4 is a part cross-sectional view through the lid and the part of a well casing projecting into the lid showing a different seal from that shown in Fig 2.

Fig 1 shows a well hole formed by a well casing 2 implanted in the ground 1. The well casing projects somewhat above the bottom 3 of an inspection space 4 comprising lateral walls 5 and a lid 6 closing the top of the inspection space. The components 3,5 and 6 of the inspection space shown in Fig 1 may be made from con- crete, but also other materials, such as plastics, are possible. Numeral reference 7 designates a lid 7, which in the shown embodiment is designed as a disk-like part 8 bridging the end of the well casing 2. A number of annular grooves are formed in the disk-like part from below, said grooves being mutually concentric in accord- ance with the shown embodiment. The well casing 2 projects into one of these grooves. Owing to the provi- sion of the other grooves it becomes possible to use the same type of lid to close well casings 2 of different diameter size, in which case the well casing 2 projects into another one of the different grooves 9. An annular flange 10 projects downwards at the periphery of the disk-like part 8. Pipe joining pieces 13,14 extend through apertures 11 and 12 formed in the lid, the lower ends of said pieces being connected to pipes 15,16 leading down into the well and the upper ends of which are connected to pipes 17, which extend for instance into a building, and possibly also to a venting pipe 18. It should be appreciated that the various pipes could be

joined together directly and extend through the lid 7, obviating the need for the pipe joining pieces 13,14.

Alternatively, when there is no need for a large-volume space, space 4 could be replaced by a pipe 19, indicated in Fig 2 by dotted lines, which pipe is mounted in an oblique position on top of the lid 7 and is orientated by locating shoulders 27 or the like disposed on the lid top. In addition, the pipe 19 may be fixed to the lid by means of locking screws or the like extending into the shoulders 27. In a similar manner to that shown in Fig 1, the pipe 19 may be fitted at its top with a lid. The pipe 19 may be made from a plastics material as well as from some other suitable material. Numeral reference 20 designates a string of a material of a kind that swells upon its contact with liquid, said string being received in the relevant one of grooves 9. As an example of a material of this kind may be mentioned that marketed by the Japanese enterprise C. I. Kasei Co., Ltd under the trade name Hydrotite@. Preferably, the string 20 of material is inserted in the shape of an annulus for reception of the upper end of the well casing 2 before the lid is applied on top of the well casing. The material may be positioned in the manner shown in Fig 2, and may be placed on the bottom of the groove or even be fitted over the top of the well casing in the manner of a hood 21 so as to enclose the upper part of the well casing. The hood 21 could be inserted in the groove already before the lid is placed on top of the well casing or be positioned on top of the well casing end before the latter is introduced into the groove formed in the lid. Similarly, such strings of a sealing material may be placed between collars 22 23; 24 25 projecting radially from the pipes 13,14. The collars may be at- tached to the pipes in any suitable manner. It should be appreciated that it is possible to place such seals in grooves 26 formed at the periphery of the apertures 11,

12 and indicated in Fig 3 by means of dashed lines. In this case, the collars 22-25 may be omitted.

In the shown embodiment the lid is passed over the end portion of a well casing in such a manner that the well casing end portion projects into annular grooves formed in the lid. However, the invention is not limited to this configuration but could be applied together with other designs to seal a lid against the well hole wall.

Consequently, the well hole need not be formed by a well casing projecting into the lid but could be any kind of hole extending down into the ground and having a com- paratively smooth wall face, to be fitted with a covering lid. In this case a sealing member in accordance with the invention may be inserted in the gap between the lid and the smooth face adjoining the well hole. The seal could be applied on the outer as well as on the inner face of a well casing. The structure and number of pipes passing through the lid could vary largely, depending on the purpose of these pipes. The pipes could be part of a heat-pump system using a special heat carrier medium, as well as form the water pipes used for supplying water from the associated well. The well could be used both for extraction of heat to a heat-pump system and for trans- portation of drinking water. Also a combination of these kinds of pipes is possible in one and the same well without departure from the inventive idea.

As long as the sealing member remains out of contact with liquid and consequently does not expand, the sealing pressure against the surfaces surrounding the sealing member is low. It is therefore easy to remove the various components forming part of the sealing system, possibly after loosening the screws or other fasteners acting between the lid and the well hole wall. Such fasteners could be screwed through suitable, preferably enlarged portions of the lid in the transverse direction of the well casing. This makes it a comparatively easy operation to open up the well for inspection, servicing, or other

measures. Should, however, the upper part of the well be exposed to a liquid, which may happen e. g. in the case of flooding, this liquid will tend to seep through the seal and in doing so initiate the expansion thereof. In con- sequence of its considerable expansion the string seal will be pressed against and efficiently seal against the adjacent surfaces, thus efficiently preventing undesir- able liquid and polluting substances contained therein from passing past the well lid and into the well hole, which would have caused pollution of the groundwater or at least of water present in the well hole. By suitable dimensioning of the sealing member it also becomes possible to obtain air passage past the sealing member because the latter does not seal completely against the surrounding surfaces. This means that during normal operation of the well it becomes possible to achieve efficient pressure equalisation between the well hole and its surrounding. Once the sealing member has expanded, the sealed condition is maintained until the lid is removed and a fresh seal is applied. Preferably this is done when there is no immediate risk for water effects.