The present invention concerns a siphonic roof drain for draining rain water under subatmospheric pressure.

Rain water drainage under subatmospheric pressure is a known system which will be explained hereafter, prior to the account of the present state of the art of siphonic roof drains under subatmospheric pressure.

In rain water drainage systems, the rain water is drained off to one or several points by making the roof slant at least gently.

From the drainage points, the rain water is led towards a drain pipe via an opening in the roof or in a gutter. In conventional rain water drainage systems, the rain water so to say falls through the drain pipe merely under the influence of gravity.

Downstream, the drain pipe is connected in an appropriate manner to a further drain.

In subatmospheric pressure rain water drainage systems, in short subatmospheric pressure systems, the drainage of the rain water through the drain pipe is additionally reinforced by the subatmospheric pressure which is created when air is prevented from being sucked in at the top of the drain pipe. Subatmospheric pressure systems are known and usually comprise a drain pipe leading from a roof or collection point near the roof to a lower zone. The higher end of the drain pipe is connected to a trough- shaped element then which is larger than the section of the drain pipe as seen from above. The higher edge of this trough-shaped element is situated higher than the feed opening of the drain pipe.

A cover plate is often provided at a distance above the feed opening of the drain pipe. The cover plate has a larger surface than the section of the feed opening, but a smaller surface than the trough-shaped element.

The circumferential edge of the cover plate is provided under the top edge of the trough-shaped element, such that rain water will have to flow predominantly radially in the feed opening of the drain pipe there.

The combination of the trough-shaped element, also called the drain bottom, and the cover plate are usually called the siphonic roof drain. In case of heavy rainfall, the water level in the siphonic roof drain rises above said cover plate, such that air is prevented from being sucked in at the top of the drain pipe . Thus, a subatmospheric pressure is created. The pipe is entirely filled with water. Also, this is often called a full-flow system. In other words, subatmospheric pressure systems make use of the difference in height between the siphonic roof drain and the outflow point to create a subatmospheric pressure. Subatmospheric pressure systems offer a strongly accelerated drainage of the rain water, not only because better use is made of the drain pipe to discharge water with a restricted amount of air, but also thanks to the increased rate of flow resulting from the subatmospheric pressure.

All this makes it possible to use drain pipes with a considerably smaller section. As explained, the existing siphonic roof drains comprise a trough-shaped element, called the drain bottom, and a cover plate, usually called the air valve.

At the bottom, the drain bottom is usually provided with a drain connector, fit to be connected to a complementary pipe connector provided to a drain pipe.

Upward, the drain bottom has a widening trough evolving laterally in a flat flange, designed to be provided between two different roofing layers.

Near their circumferential edges, the customary cover plates are provided with downward directed protrusions or ribs serving as spacers in relation to the base of the drain bottom on which the cover plate can rest. These ribs prevent or simultaneously suppress vortex flows of the water round the drain, and they also prevent leaves and the like from being discharged via the drain pipe. In order to prevent leaves and the like from ending up in the drain, it is also customary to provide an additional cap with appropriate openings on top of and/or over the drain bottom and the cover plate. In order to simplify the cleaning of the drain, this cap can be made partly or entirely removable.

A disadvantage of such known siphonic roof drains is that their manufacture, in particular the manufacture of the drain bottom, is very expensive.

The present invention aims to remedy one or several of said and/or other disadvantages. To this end, the invention concerns a siphonic roof drain for draining rain water under subatmospheric pressure, which siphonic roof drain comprises at least a drain bottom, fit to be connected to a separate drain connector for the further coupling of a drain pipe to a complementary pipe connector, whereby the drain bottom is provided with passages for connecting means to connect the drain bottom or a part to the drain connector.

A major advantage which is thus obtained is that the drain bottom must not be provided with flanges with bolt passages at the bottom, with a threaded part or with any other connecting means making the construction and production of the drain bottom complex and expensive. In order to better explain the characteristics of the invention, the following preferred embodiment of a siphonic roof drain for draining rain water under subatmospheric pressure according to the invention is described with reference to the accompanying drawings, in which: figure 1 is an exploded view in perspective with disassembled front segments of a siphonic roof drain according to the invention;

figure 2 represents an alternative exploded view in perspective of the siphonic roof drain from figure 1 ; figure 3 is an assembled view in perspective with disassembled front segments of the siphonic roof drain from figure 1.

Figures 1 to 3 represent a siphonic roof drain 1 according to the invention. The representations are proportional and the aspects which can be derived from the figures are part of the invention.

The siphonic roof drain 1 as represented comprises, when mounted and as represented in the figures from bottom to top, a drain connector 2, a bottom clamping piece 3, a top clamping piece 4 and an air valve 5.

The bottom clamping piece 3 and the top clamping piece 4 form the drain bottom which according to an aspect of the invention is built up of separate parts.

The drain connector 2, which is not fixed to the drain bottom, is designed to be coupled to a complementary pipe connector 6, in this case a collar 8, provided on a drain pipe 7.

The pipe connector 6 may be provided on a pipe section which can be connected to the drain pipe 7. Such a pipe section is further also called a drain pipe 7.

The drain connector 2 is predominantly tub-shaped in this case, with a first bottom 9 and a first standing edge 10, and whereby the first bottom 9 is provided with a first central feed-through opening 11 for the feed-through of the drain pipe 7.

Near the first standing edge 10 are provided first threaded rod passages or bolt passages 12, in the present embodiment three .

For clarity's sake, such threaded rod or bolt passages 12 are further simply called bolt passages 12.

The bottom clamping piece 3 is also predominantly tub- shaped, with a second bottom 13 and a second standing edge 14 provided with a first flange 15 at a distance from the second bottom 13 which is directed mainly parallel to the second bottom 13.

The second bottom 13 is provided with a second central feed-through opening 16. Near the second standing edge 14 are provided three bolt passages 17 as well in this case. The shape and dimensions of the second bottom 13, of the second standing edge 14, and in particular of the connection of the second standing edge 14 to the second bottom 13 on the lower side in the figures are such that an appropriate connection to the first standing edge 10 of the drain connector 2 is made possible.

The top clamping piece 4 is predominantly trough-shaped and to that end consists of a second flange 18 which evolves in a trough-shaped centre piece 19 towards the middle with a third central feed-through opening 20.

Near the passage of the flange 18 and the trough-shaped centre piece 19 are provided three bolt passages 21 in this case as well.

The shape and dimensions of the drain connector 2, the bottom clamping piece 3 and the top clamping piece 4 are such that when these parts are properly assembled, the flanges 15 and 18 can link up near or mainly against one another, the bolt passages 12, 17 and 21 can be aligned, the trough-shaped centre piece 19 can be led with its lower free edge mainly in line or through the second central feed-through opening 16, all this in view of a possible connection onto or a feed-through in the central opening of the drain pipe 7 where the pipe connector 6 is situated, in this case the collar 8 which is directly or indirectly provided on a drain pipe 7. In this embodiment, the second flange 18 of the top clamping piece 4 has an outer diameter which is smaller than the outer diameter of the first flange 15 of the bottom clamping piece 3. The air valve 5 comprises a central cover plate 22 whose diameter is in this case larger than the largest diameter of the trough-shaped centre piece 19, i.e. the diameter of the transition line between the second flange 18 and the trough-shaped centre piece 19.

This cover plate 22 has no openings. In the perimeter of the cover plate 22, i.e. on its circumferential edge 23, the air valve 5 is provided with lamellas 24 which are continuously connected to one another in this case, alternately at the bottom and at the top. The lamellas 24 are higher on the outer perimeter of the air valve 5, and the lower connections are situated near the outer perimeter of the air valve 5, such that when the parts are assembled, they will not be placed on or above the second flange 18 of the top clamping piece 4 but in its perimeter.

The higher connections 25 of these lamellas are provided with openings 26. Near the circumferential edge 23 of the cover plate 22, also the air valve 5 is provided with in this case three bolt passages 27, also in line with the bolt passages 12, 17 and 21 mentioned above. The shape and dimensions of the air valve 5, the bottom clamping piece 3, the top clamping piece 4 and the drain connector 2 are such that their assembly is fit to be used as a whole as a siphonic roof drain. The assembly and mounting of the siphonic roof drain 1 according to the invention is simple and as explained below .

Starting from a pipe connector 6, in this case a collar 8, appropriately provided on a pipe section which can be connected to a drain pipe 7, a drain connector 2 is provided over the pipe section.

Optionally, the drain connector 2 is composed of at least two parts, such that it can be provided round a fit drain pipe 7 which is already provided with a pipe connector 6. The outer diameter of the collar 8 is larger than the diameter of the central feed-through opening 11, which is larger, however, than the outer diameter of the drain pipe 7 there. In a subsequent step, the bottom clamping piece 3 can be provided, particularly with the bolt passages 17 in line with the bolt passages 12 of the drain connector 2.

The shape and dimensions of the second bottom 13, the second standing edge 14, and in particular of the connection of the second standing edge 14 to the second bottom 13 on the lower side as seen in the figures are such that an appropriate connection to the first standing edge 10 of the drain connector 2 becomes possible.

As a result, the distance between the second bottom 13 of this bottom clamping piece 3 on the one hand, and the first bottom 9 of the drain connector 2 on the other hand is determined by the geometry of both parts.

This distance is possibly larger than the height of the collar 8, but preferably it mainly corresponds to and better still is slightly smaller than the height of the collar 8, such that the collar 8 can be clamped between both bottoms 9 and 13 and, when being tightened, can be transformed until the bottom clamping piece 3 links up to the drain connector 2.

To this point, the assembly can take place before the actual installation on site, i.e. in the production workshop of the siphonic roof drain 1.

Optionally, prior to the installation on site, one or several roofing layers 28 may be provided, for example having a surface of one square metre, and the top clamping piece 4 can be provided, mainly according to the method discussed below which alternatively assumes that these steps are carried out on site.

The parts assembled above can be held together in an appropriate manner by making use of adhesives.

In a next step, the parts assembled above are provided in an appropriate manner in the roof construction.

The pipe connector 6 is thereby provided at an appropriate height under the level of the roofing layers to be provided, at the drainage point. Next, one or several roofing layers 28 are provided up to the first flange 15.

Optionally, said one or several roofing layers 28 are connected or attached to the first flange 15, for example by means of gluing.

Next, the top clamping piece 4 is provided, in particular with the bolt passages 21 in line with the bolt passages 12 and 17, such that the second flange 18 is provided on the last-mentioned roofing layer.

Optionally, a chemical bond, for example by means of glue, is provided between said one or several roofing layers 28 and the second flange 18.

As already said, the shape and dimensions of the drain connector 2, the bottom clamping piece 3 and the top clamping piece 4 are such that the trough-shaped centre piece 19 can be placed with its bottom free edge in line with the second central feed-through opening 16 of the bottom clamping piece 3, and/or can be led through this second central feed-through opening 16 of the bottom clamping piece 3.

Optionally, a subsequent roofing layer is provided up to the second flange 18, with an appropriate opening in line with, but preferably larger than the transition of the flange 18 and the trough-shaped centre piece 19, and on condition that the bolt passages 21 are avoided.

In a following step, the air valve 5 is placed on top of the provided top clamping piece 4, in particular with the bolt passages 27 in line with the above-mentioned bolt passages 12, 17 and 21.

The connections located at the bottom of the lamellas 24 are positioned in such a way and sufficiently peripherally that, when the air valve 5 is being assembled with the drain bottom, they will not occupy a place on or above the second flange 18 of the top clamping piece 4 but in its perimeter, optionally on or above the part of the first flange 15 which is not covered by the second flange 18 thanks to its smaller outer diameter.

By subsequently providing threaded rods through the bolt passages 12, 17, 21 and 27, and appropriately providing nuts on the bottom side of the drain connector 2 and on the top side of the air valve 5, and by subsequently tightening the nuts, a functional siphonic roof drain is obtained.

It should be noted that, as shown in figure 2, nuts can also be provided between the bottom clamping piece 3 and the top clamping piece 4 on the one hand, and between the top clamping piece 4 and the air valve 5 on the other hand.

Indeed, tightening the nuts does not only provide a solid connection between the components of the siphonic roof drain 1 according to the invention, but also clamps said one or several roofing layers 28 which is/are provided between the flanges 15 and 18, and also compresses and correspondingly clamps the collar 8 which is being compressed between the first bottom 9 of the drain connector 2 and the second bottom 13 of the bottom clamping piece 3. This compression comes to an end, however, when the bottom clamping piece 3 is linked up to the drain connector 2, such that any possible further clamping of the roofing layer or layers has no influence whatsoever on the compression of the collar 8.

As explained above, the drain connector 2, the bottom clamping piece 3 and the pipe connector 6 can be assembled in the production workshop, and in this case the collar 8, made of HDPE (High Density Polyethylene) and additionally provided with an EPDM sealing, has already been mechanically compressed, and the whole is being held together by means of an appropriate chemical or mechanical coupling of these parts.

The working of the siphonic roof drain 1 according to the invention is simple and as explained hereafter.

Rain water to be discharged flows between the lamellas 24 into the trough-shaped centre piece 19, from where it flows down in an accelerated manner through the specific funnel curve .

In case of heavy rain, the water level in the siphonic roof drain 1 will rise above the cover plate 22, such that air is prevented from being sucked in.

Thus, a subatmospheric pressure is created, resulting in an accelerated drainage of the rain water as explained above.

According to the present invention, the drain connector 2 is coupled or connected to the drain bottom by means of connecting means, in this case threaded rods working in conjunction with nuts, which are driven through at least a part of the drain bottom.

In the preceding embodiment, the threaded rods extend through the bottom clamping piece 3, in particular through the passages 17.

A major advantage which is thus obtained is that the drain bottom must not be provided below with flanges having bolt passages, with screw thread or any other connecting means making the production of the drain bottom complex and expensive .

Indeed, the provision of a flange makes it impossible to use simple, two-piece moulds and/or requires the application of complex connecting techniques.

A screw thread is usually applied by providing a separate threaded part below the drain bottom and by connecting it to the latter, often by means of complex and expensive welding techniques if the parts are made of different metals or metal alloys.

A siphonic roof drain 1 according to the invention or parts thereof can be made among others by die-casting a metal alloy, in particular an aluminium alloy, for example aluminium-silicon, or a plastic.

Alternatively, parts can be made of distorted steel plate.

A siphonic roof drain 1 according to the invention is advantageous in that it can be made in a very economical way, for example by using only two-piece moulds and/or by means of simple sheet distortion techniques.

Such two-piece moulds are significantly easy to produce and also the production of the parts concerned is quicker thanks to the shorter release times, compared with moulds formed of more than two parts.

Moreover, the main characteristic of the siphonic roof drain according to the invention, being that the connection of the drain connector 2 to the drain bottom is obtained by means of connecting means which are led through at least a part of the drain bottom, offers the advantage that mounting the siphonic roof drain 1 and also connecting it to the drain pipe 7 is made easier.

In the given embodiment, the threaded rods also extend through the top clamping piece 4 and the air valve 5, in particular through passages 21 and 27, which is not a requisite of the invention but which considerably simplifies the mounting and general construction of the siphonic roof drain 1.

According to one aspect of the present invention, the drain bottom, disregarding any possible threaded rods, sealings and/or roofing layers, is built of at least two separate parts .

Indeed, the drain bottom is formed of the bottom clamping piece 3 and the top clamping piece 4 here. Such an assembly of separate parts additionally simplifies the production, the mounting and any possible maintenance of a siphonic roof drain. The division of the drain bottom in separate parts additionally results in a lighter, non-massive embodiment which nonetheless offers sufficient resistance to any deformations by possible loads. The bottom clamping piece 3 has a stepped cross-section, offering more rigidity.

The second bottom 13 of the bottom clamping piece 3 serves as a sealing at the collar 8, whereas the first flange 15 of the bottom clamping piece 3 serves as a sealing with said one or several roofing layers 28 provided between said first flange 15 and the second flange 18 of the top clamping piece 4. The second bottom 13 and the first flange 15 do not overlap in plan view, which makes it possible to use a simple mould .

The stepped-section design of the bottom clamping piece 3 offers more rigidity.

This stepped shape in turn results from the fact that the second bottom 13 and the first flange 15 of the bottom clamping piece 3, performing said two sealing functions, are not situated in one and the same plane, i.e. are provided at different heights. Also the top clamping piece 4 as such forms a rigid part, partly thanks to its height, which is the result of the trough-shaped centre piece 19 being provided with the specific funnel curve, as is proportionally represented in the figures.

Also the air valve 5 has a high rigidity and breaking strength, partly thanks to the specific construction of the lamellas 24 which are continuously connected to one another in this case, alternately at the bottom and at the top.

Consequently, the lamellas 24 can be made thinner, which further optimises the hydraulic performance. It is clear that the air valve 5 must not necessarily be fixed by one and the same bolt connection to the other parts of the siphonic roof drain 1 according to the invention. A separate connection is among the possibilities and possibly simplifies any maintenance and/or cleaning.

It is clear that the inventive idea consists in that the coupling or connection of the drain connector 2 to the drain bottom is obtained by means of connecting means which prevent any complex and expensive connecting means having to be provided on the downward-facing side of the installed drain bottom.

As explained, this can be realised by driving connecting means through at least a part of the drain bottom, which is expressed in general terms as providing passages in the drain bottom for connecting means in order to connect the drain bottom or a part thereof to the drain connector 2. It is clear, however, that the invention also covers the variants whereby the connecting means reach in another way up to the side of the drain bottom which is accessible from the top.

Whereas the present document mentions threaded rods and nuts, it is clear that they can be appropriately replaced by bolts and passages which are threaded and/or by otherwise realised connections.

The present invention is by no means restricted to the embodiments described by way of example and represented in the figures; on the contrary, a siphonic roof drain for draining rain water under subatmospheric pressure according to the invention can be made in all sorts of shapes and dimensions while still remaining within the scope of the invention .