Particularly in situations where a toilet is flushed with a relatively small quantity of water, as is the case in a modern, water-saving toilet with a cistern of small volume, the speed of the waste flow is often not sufficient to transport the solid parts along the full length of the discharge pipe into the sewage system. The consequence hereof is that these solid parts remain behind in a relatively flat portion of a discharge pipe and there form an obstacle on which the solid parts of subsequent flushing actions become lodged. An accumulation will thus be eventually created which will result in blockage of the discharge pipe.

In order to prevent this it is already known to locally accelerate the waste flow consisting of liquid and solid parts. Use is often made for this purpose of a flow increaser or'booster'through which the waste flow is guided. In this flow increaser the waste flow is temporarily stored in a tank or reservoir, until after a few flushes the level in the tank has risen to such an extent that it overflows. There then results a siphoning action whereby the waste flow is'sucked'as it were out of the tank of the flow increaser. The waste flow hereby attains a considerably greater speed than it had when leaving the cistern, so that the solid parts will be

carried over a greater distance, thus reducing the danger of blockage of the discharge pipes.

A drawback of this method is that de flow increaser must take a relatively voluminous form in order to ensure a sufficient capacity and therefore a sufficiently great acceleration of the waste flow. A flow increaser is thus currently being marketed by applicant under the name of"Gustavsberg's Water Saving System", which is provided with a relatively narrow but high tank which is so large that it can only be considered suitable for use in high-rise projects. Also known is a flow increaser of applicant with a relatively flat structure which is intended for installation in the crawl-space of low-rise dwellings. This flow increaser, which is described in WO 98/03743, while being lower is also wider than the above described model, so that a relatively large amount of space must also be kept clear therefor.

As stated, a method is also already known from US-A-3 661 261 which comprises the measures of the preamble of claim 1. This method is applied in the draining of waste flows in a municipal sewage system and has for its object to prevent accumulation of solid parts in for instance drains or manholes. In this known method a part of the waste flow is drawn off and held in a storage tank. Drawing-off takes place by extracting air at the top of the tank using a water pump. The drawn-off part of the waste flow is thus held fast by the thus created underpressure. When a determined level is reached in the storage tank a valve is lifted by a float, whereby air can flow in and the drawn-off liquid flows back into the main stream and thus accelerates it. Application of this method thus requires a relatively powerful suction installation which takes up a lot of space and is in addition costly and requires intensive maintenance.

The invention now has for its object to provide a method of the above described type, wherein said drawbacks do not occur. According to the invention this is achieved in such a method in that at least the

separation and/or acceleration of the liquid is carried out in hydrodynamic manner.

By having the separation and/or acceleration carried out in hydrodynamic manner it is possible to dispense with the use of a separate suction installation.

Furthermore, the flow increaser can be embodied considerably more compactly by guiding therethrough only that part of the waste flow which actually contributes to the acceleration, i. e. the liquid. This is the particular result of the fact that the flow increaser is normally slightly overdimensioned because the speed in the flow increaser itself is relatively low and the danger of blockage is therefore relatively high. In addition, the response of the flow increaser is in this way improved because it will no longer be influenced by the presence of solid parts in the flow increaser, while the acceleration caused by the flow increaser moreover becomes reproducible.

Preferably applied variants of the method according to the invention are described in the dependent claims 2-4.

The invention further relates to a system for discharging a waste flow consisting of liquid and solid parts which is adapted to perform the above described method. According to the present invention such a discharge system, which can comprise at least one discharge pipe for the waste flow, means connected to the discharge pipe for separating at least a part of the liquid from the waste flow, means placed in series with the separating means for accelerating the separated liquid and means connected to the acceleration means for feeding the accelerated liquid back to the waste flow, is characterized in that at least the separating means and/or the acceleration means are of a hydrodynamic nature. Due to the presence of the separating means it is possible to prevent solid parts flowing through the acceleration means, whereby these latter can thus be given a relatively compact form, while the operation

thereof is moreover improved. Because these means are further of a hydrodynamic nature, the system is simple in structure and has no moving parts, while the operation thereof is controlled by the waste flow itself. No separate drive is therefore required.

As known per se, the acceleration means can herein be adapted to collect the separated liquid and to accelerate it only after a determined volume has been reached. The acceleration means can for instance comprise for this purpose a siphon installation.

The siphon installation is then preferably provided with a feed opening which is connected to a substantially vertical part of the discharge pipe, and the separating means comprise an inflow edge at least partially bounding the feed opening and connecting smoothly onto a wall of the substantially vertical part of the discharge pipe. In this manner the liquid can be separated very simply by making use of the fact that the liquid will flow predominantly along the walls of the vertical part of the discharge pipe, while the solid parts usually drop downward through the middle of the pipe.

When the separating means further comprise a deflecting edge located opposite the inflow edge and at least partially bounding the feed opening, a narrow opening can be created such that the entry of solid parts is prevented in effective manner.

As seen in the direction of fall, the inflow edge herein preferably takes a radially outward inclining form and the deflecting edge a radially inward inclining form. The liquid flow to the siphon installation is thus on the one hand enhanced, while a barrier directed practically transversely of the flow is on the other hand erected against solid parts.

In order to further minimize the space occupied, the siphon installation can be arranged to the side of the standing part of the discharge pipe. Herein the siphon installation preferably runs substantially

parallel to the standing part of the discharge pipe, whereby this pipe need in fact only have a local thickening. The siphon installation is thus suitable for simple accommodation in an existing pipe shaft and does not have to be placed in for instance a crawl-space. This is advantageous when such a discharge system has to be installed in an existing building during a renovation project, while it is also of significance in new house- building, wherein the making of crawl-spaces is increasingly being dispensed with.

So as to still enable the forming of a siphon installation of sufficient capacity in such an arrangement, said installation is then preferably arranged concentrically round the standing part of the discharge pipe. Such a concentric siphon installation can in addition be manufactured and installed relatively simply and at low cost.

Finally, the invention also relates to a siphon installation for use in a discharge system as described above.

The invention is now elucidated on the basis of an embodiment, wherein reference is made to the annexed drawing, in which : Fig. 1 is a partly cut-away, perspective view of a part of a discharge system according to a first embodiment of the invention, Fig. 2 shows a cross-sectional perspective view of a siphon installation as applied in the system of fig.

1 before use, Fig. 3 and 4 show views corresponding with fig.

2 of the siphon installation during different stages of use, Fig. 5 is a schematic cross-sectional view of a siphon installation according to a second embodiment of the discharge system before use, and Fig. 6 and 7 are views corresponding with fig.

5 of the siphon installation during different stages of use.

A system 1 for discharging a waste flow 2 which consists of liquid 3 and solid parts 4 comprises a discharge pipe 5 with a substantially vertical or standing part 6 and a substantially horizontal or lying part 7 (fig. 1). In order to prevent the solid parts 4 remaining behind in conduit part 7 and accumulating there as a result of an insufficient flow speed, discharge system 1 is provided with hydrodynamic means 8 for accelerating waste flow 2. These means are arranged in the standing conduit part 6 and in the shown embodiment comprise a siphon installation 9 arranged concentrically round this conduit part 6. Such a siphon installation has no moving parts and is operated by the waste flow itself.

On the inflow side of siphon installation 9 are arranged means 10 for separating at least part of the liquid 3 from waste flow 2. These separating means 10 comprise a radially outward inclining inflow edge 12 connecting smoothly onto a wall 11 of standing conduit part 6, and a deflecting edge 13 located opposite inflow edge 12 which, as seen in the direction of fall, inclines radially inward (fig. 2). These two edges 12,13 bound an annular feed opening 14 of siphon installation 9.

The siphon installation 9 itself comprises a likewise annular tank 15 which is connected to feed opening 14 and is provided with a discharge opening 16 arranged on the underside of tank 15. Discharge opening 16 is connected to a riser pipe 17 which likewise takes an annular form. Riser pipe 17 is in turn connected over a bend part 18 to an annular fall pipe 19. On the underside of fall pipe 19 is arranged a bent or curved pipe part 20 which functions as a liquid seal but which is dimensioned such that it is open in the rest position.

This bent or curved pipe part 20 functioning as liquid seal then debouches in the standing part 6 of discharge pipe 5.

Tank 15, riser pipe 17, fall pipe 19 and liquid seal 20 are defined by a number of concentric cylinder walls 21,22, 23 and 24 which are mutually connected by

means of radially running partitions 25. Siphon installation 9 is therefore of exceptionally simple construction and can be manufactured at very low cost. In addition, because the feed side and the discharge side of the siphon installation are mutually communicating via conduit part 6, no vent line is necessary therebetween as in conventional flow increasers.

The operation of discharge system 1 is now as follows. When a toilet is flushed the waste flow 2 coming therefrom will flow through the standing conduit part 6 to the lying conduit part 7. In standing part 6 the liquid 3 herein flows mainly along conduit wall 11, while solid parts 4 drop through the middle of conduit 6. At the position of siphon installation 9 the liquid 3 then follows inflow edge 12, which connects smoothly onto conduit wall 11, and thus flows into tank 15 where in the first instance it is collected (fig. 3). The solid parts 4 fall further through the middle of conduit part 6 together with a small part of the liquid. Since only little liquid is thus available to transport solid parts 4 further, these latter will collect at the beginning of the lying conduit part 7. At each flush the liquid level in tank 15 and in riser pipe 17 rises further until it eventually reaches the upper edge 26 of cylinder wall 23.

When in this situation extra liquid flows into tank 15, riser pipe 17 will overflow into fall pipe 19.

As long as the quantity of liquid flowing into tank 15 is small, the liquid flowing out of riser pipe 17 into fall pipe 19 will eventually flow to the drain via the bent or curved pipe part 20 without this pipe part 20 herein being completely filled with liquid and thus functioning as liquid seal. However, as soon as a larger quantity of liquid flows into the tank 15 already filled up to its edge, as will be the case when a toilet is flushed, so much liquid flows out of riser pipe 17 into fall pipe 19 that the bent or curved pipe part 20 is completely filled with liquid, and thus functions as liquid seal. When

liquid 3 flows out of this pipe part 20 to the discharge pipe, an underpressure is hereby created in fall pipe 19, whereby liquid is then drawn out of riser pipe 17. This liquid again fills pipe part 20, whereby this latter once again functions as liquid seal and an underpressure is again generated in fall pipe 19 as pipe part 20 empties.

This repeated opening and closing of the liquid seal takes place more and more quickly, whereby a continuous flow of liquid will eventually be drawn from riser pipe 17 into fall pipe 19 and through the liquid seal (fig.

4). This continues until tank 15 is empty, whereby air will be drawn into riser pipe 17 and the underpressure in fall pipe 19 is removed. Since in this manner the whole content of tank 15 flushes through discharge pipe 5 at one time, a relatively high flow speed will be created therein, whereby the solid parts 4 which have settled in the lying conduit part 7 are flushed away.

In an alternative embodiment of the discharge system (fig. 5,6 and 7) tank 15 of siphon installation 9 is not annular, nor is it arranged concentrically round the standing conduit part 6. Tank 15 is instead formed by a vessel of random cross-section, in which is arranged a separate discharge pipe which consists successively of a riser pipe 17, a fall pipe 19 and a U-shaped pipe part 20 which functions as liquid seal and which also debouches into standing pipe part 6.

Because the surface area of tank 15 can be relatively large in this embodiment and the rise in the liquid level may thus be relatively small after a flush, installation 9 can herein be provided with siphon enhancing means, for instance of the type as shown and described in applicant's above mentioned patent publication WO 98/03743. When the liquid has risen as far as the edge 26 in riser pipe 17, it is urged in the case of a further rise directly to the opposite wall of fall pipe 19 by these siphon enhancing means, whereby a liquid curtain closing off fall pipe 19 is immediately formed.

In this manner an underpressure is immediately created in

fall pipe 19, whereby the siphoning action is set into operation (fig. 7).

Although in this embodiment the tank takes up more space than the concentric tank of the first embodiment, it is also the case here that the solid parts 4 are not guided through the siphon installation, whereby this can still take a more compact form than conventional siphon installations.

Due to the separated acceleration of the liquid from the waste flow and the thereby possible construction of the flow increaser the following advantages are thus achieved compared with the conventional manner of accelerating the whole waste flow and the classic flow increaser applied therein : - because the flow increaser does not have to be dimensioned for the possible presence of solid parts, it can take a compact form, - because the operation of the flow increaser is not affected by solid parts, the response and the reproducibility are better, - because the solid parts do not lie in the liquid flow to be accelerated but are flushed along thereby, they are always situated at the head of the liquid wave, whereby they will be transported over a greater distance, - because the flow increaser is not accommodated in the discharge pipe but is connected parallel thereto, the capacity of the discharge pipe is not influenced by the presence of the flow increaser, - as a result of the narrower embodiment of the flow increaser, which is possible since only liquid flows therethrough, less turbulence will occur whereby the resistance is reduced and the maximum flow rate is increased, - the concentric placing of the flow increaser round the discharge pipe enables easy adaptation of the shape and dimensions thereof to requirements.

Although the invention is elucidated above on the basis of an embodiment, it will be apparent to the skilled person that it is not limited thereto. Many variations can be envisaged in the configuration of the siphon installation and the separating means. The scope of the invention is therefore defined solely by the appended claims.