The invention relates to a device for thermally insulating underground pipes for transporting hot or cold media.

Such devices are used, for example, to-insulate pipes in long distance heating distribution systems or central-heating systems, including also the supply of, for example, hot water or steam. A further exemplary application of the insulating device may also be for central air _. conditioning systems in which the pipes conduct a cooling medium.

Insulating devices of the invention should have good heat insulating properties as well as a relatively high structural strength to withstand mechanical forces acting thereupon. They should also be resistant to the seepage water, at the top and sides yet' from the bottom allow the drainage of condensed water vapour.

It is known in the art to provide elongated insulating bodies provided with longitudinally extending grooves therein for receipt of the pipes. Upon placing two such grooved bodies or shell parts upon each other,

with the grooves facing each other, a longitudinally split insulating body having channels for receipt of the pipes is provided. The pipes are held in a restrained fashion within the grooves (by means of clamps), and the grooves have a diameter corresponding to that of the pipes to be inserted therein.

This known insulating device exhibits, however, the drawbacks that moisture may be trapped in the insulating bodies and that the pipes, in order to be clamped between the two insulating bodies, must have a substantial over¬ burden placed on the upper insulating body. Also, signifi¬ cant linear thermal expansion of the pipes may lead to a possible rupture of the insulating material. Moreover, various pipe diameters necessitate individually manufactured insulating bodies because their grooves must conform closely to the prevailing pipe diameters.

The device according to the invention is characterized by a set of pipe receiving boxes and a set of lids placed thereupon, which pipe receiving boxes and lids are made from a thermally insulating hydrophobic plastic foam material and are water impermeable with the exception of draining sites located at the bottom of the respective pipe receiving boxes; each pipe receiving box comprising at least one elongated chamber open against the lids and intended to loosely receive at least one pipe; the joints between lids and pipe receiving boxes having a section which in the installed state of the device marks an angle with the horizontal plane such to prevent an inflow of flowing water; and by a water barrier impervious sealing member located at the areas of the joints between the respective tops, sealingly and lockingly interconnecting adjacent lids. Preferably,

the impervious water barrier sealing member lockingly interconnect the lids with the respective pipe receiving boxes located thereunder.

The subject of the invention will now be explained more fully in conjunction with the accompanying drawings wherein.

Figure 1 is a perspective view of a device for thermally insulating underground pipes, and

Figure 2 is another embodiment of the device illustrated in Figure 1.

Figure 1 shows a plurality of pipe receiving boxes 1 which are positioned in an end to end contacting relationship with each other and which are covered by lids 2. The preferred hydrophobic materials for the pipe receiving boxes 1 and lids 2 are synthetic resinous foams having a low water permeability and a low compressi¬ bility such as extruded polystyrene foam (for example "STYROFOAM" brand plastic foam manufactured by The Dow Chemical Company) preferably aving from 96 - 100 per- cent closed cells; expanded polystyrene foam ("headboard"); closed cell polyurethane foam preferably having from 88 - 96 percent closed cells, or polyvinylchloride foam.

In the embodiment illustrated in Figure 1 the pipe receiving box 1 is provided with three chambers 6 in which the pipes 7 are located. It will be obvious to persons skilled in the art that the box can be provided with a fewer or greater number of chambers, depending on the need. The length of the individual pipe receiving boxes 1 and lids 2, respectively, can be of any convenient size, for example, anywhere from one to

three meters. The thickness of the boxes 1 or lids 2 may also be of any convenient thickness, and may pref¬ erably be in the range of from 50 to 150 mm thick. The lids 2 are preferably arranged in a staggered rela- tionship relative to the boxes 1 such that the respec¬ tive joints between the boxes and ^' the lids are out of alignment with'each other.

The pipes 7 may be flexible or rigid pipes. The pipes may be constructed of a synthetic plastic material or of a metal, for example, copper. Preferred for many applications are oxygen-impermeable pipes. It is important to note that the pipes 7 are loosely posi¬ tioned within the chamber 6 such that they are not restrained at any place, allowing for an unrestrained thermal expansion between the pipes 7 and the pipe receiving boxes 1. The embodiment shown in Fig. 1 may be used in conjunction with a central heating system which also supplies hot water to domestic kit water outlets. The first pipe 7 located on the left hand side in Figure 1 may be conducting hot water from a boiler to a heating site while an adjacent pipe, e.g. the pipe arranged in the center chamber 6, may be employed as the return pipe. The right hand chamber may contain two pipes for conducting hot water, wherein one of the pipes is a hot water supply pipe and the other pipe is the recirculating pipe. As can be seen, the dimensions of the chambers are chosen independently from the dimensions of the pipes. Considering the - pipes of the heating system a given chamber can receive pipes of various diameters and considering the hot water system a given chamber may even contain two pipes.

The penetration of water, into the insulating device such as by seepage after a rainfall or flooding should be prevented, white condensed water vapour which may be formed in the chambers 6 must be allowed to drain. For this purpose, adjacent lids 2 are provided with, for example, intermeshing tongue and groove joints 11. A sealing member or tape is applied over the joints 11 between the lids 2 and extends over side walls of the lids and, preferably, over the outer side walls of the underlying pipe receiving box 1. During installation of the insulating device a protective strip or tape which is preferably provided with a pressure sensitive adhesive is placed over the joints 11 of the lids 2. After the device has been located in its final position the protective strip is peeled off leaving the pressure sensitive adhesive on the respec¬ tive lids 2 and boxes 1. Thereafter a strip of a water impervious material is placed onto the adhesive such that adjoining lids 2 are sealingly and lockingly interconnected. Due to the fact that the water imper¬ vious strip extends downwardly along the outer side walls of the pipe receiving boxes 1, the lids 2 are additionally connected to the underlying pipe receiving boxes 1 in an interlocking relationship with the boxes. Accordingly, water flowing from above through the ground is prevented from entering the joints between the lids 2 and the chambers in the pipe receiving boxes 1. The boxes 1 are also provided with projections or ledges in the side walls of the boxes. The grooves form inclined surfaces 8 relative to a horizontal plane which are slanted upwardly as seen in a direction from the outside to the inside of the boxes. Thus, water flowing downwardly along the outer side walls of the lids 2 and the boxes 1 can not enter the chambers 6

since the water will be prevented from flowing upwardly over the upwardly inclined surfaces 8.

In order to allow condensed water vapour to drain from the box, each chamber 6 is provided with a drainage channel 4, preferably positioned at the longi¬ tudinal ends of the box.

The channels 4 are located at the facial end surfaces of the respective pipe receiving box 1 and extends from the bottom of the respective pipe receiving chambers 6 to the bottom surface 5 of the respective pipe receiving box 1. Two of the adjacent channels 4 of the end to end adjoining pipe receiving boxes 1 form a through-hole through the respective bottom sections 3 allowing for the drainage of any water vapour which may condense at, for example, the walls of the pipes or chambers 6.

As an alternative, drainage channels extending through the respective bottom sections 3 may be provided at a point remote from the facial end surfaces. Alter- natively, each chamber 5 may be provided with a plurality of drainage channels. A combination of drainage channels located at the facial end surfaces, and located at points remote therefrom, such as stated above, may form a further embodiment.

Figure 2 illustrates a variety of further embodiments which may be applied individually or in combination. The device comprises the pipe receiving boxes 1 covered by the lids 2. As a modification of the tongue and groove joint 11 illustrated in Figure 1, adjacent lids 2 of the embodiment shown in Figure 2 may have a ship lap joint 12, as illustrated.

The joints between the respective lids 2 and pipe receiving boxes 1 are illustrated as having a vertical step in order to prevent the penetration of ground water flowing into the boxes. Similarly, a tongue and groove configuration may here be employed. If the surrounding ground or soil has a low water permeability, the insulating device is preferably placed onto a layer of drainage material such as, for example, sand, gravel, or crushed stones to a water permeable bed 15. Additionally, a drainage pipe 16 may be placed under the pipe receiving boxes 1 to enhance the drainage of water seeping into the ground as well as any condensed water which may be drained from the chambers 6.

In the chamber located on the right hand side of the box shown in Figure 2, for example, a vapour barrier 14 may be inserted in order to cover the bottom and side walls of the chamber. Correspondingly, a vapour barrier strip 13 may be mounted to the lower surface at the corresponding location of the lid 2.

These vapour barrier layers 13, 14 may be for instance a film laminate, a metallized polyester film which additionally reflects radiant energy to reduce heat losses.

The left hand side chamber of Figure 2 illus¬ trates a number of further embodiments which may be employed in any suitable manner. In contrast to the bare pipes 7 employed in Figure 1, the pipes 7 may here be provided with an additional thermal insulation material 17 such as, for example, a cross-linked polyethyl¬ ene foam, polyurethane foam or mineral fibers which forms a jacket around the pipe 7.

The space between the pipes 7 and the walls of the chambers 6 may alternatively or additionally be partially filled with sand and/or gravel to give addi¬ tional structural integrity. Thermal insulation mate- rial such as a jacket, sleeve or wrapping extending around the pipes 7, or insulating members or even granular insulating material 18 filling the space " substantially or completely may be inserted between the pipes 7 and walls of chambers 6. Such embodiments may be useful specifically when the pipes 7 transport fluid for a central heating system, which fluid has such a high temperature that the pipe receiving boxes 1 arid lids 2 could be detrimentally influenced.

If the thermal insulating material 17 or 18- between the pipes 7 and the walls of the chambers 6 is a moisture sensitive insulation material, a further moisture barrier, for instance a polyethylene film 19 extending over the insulating jacket 17 or a moisture barrier 20 extending over the insulating material 18 can be used to protect the moisture sensitive material from humidity of water intrusion.

As an alternative embodiment to the draining channels 4, illustated in Figure 1, draining sites may be formed merely by the abutting facial end surfaces 10 of the adjoining pipe receiving boxes 1, illustrated in Figure 2. These facial end surfaces 10 may be rather roughly structured to allow enough drainage spaces . extending from the chambers 6 to the bottom 5 of the boxes 1 into the soil or drainage layer located there- below.

Because the outside surfaces of the pipe receiving boxes 1 as well as of the lids 2 may deterio¬ rate if not protected against UV-Radiation, a further embodiment provides for a UV-resistance treatment in which the exposed surfaces may be, for example, provided with a coat of paint.