EP0265453B1 - Closed cell foam layer and apparatus for its creation - Google Patents

Abstract

Process and system for using a toilet whereby, prior to deposition of excreta in the toilet pan (10), foam is produced in the form of a layer (18) having a height equivalent to at least twice the means foam bubble diameter.

Description

The invention relates to a closed-pore foam carpet for odorless depositing of excrement in toilet bowls, urinals or the like as a result of a mixture of foaming agent and rinsing water during the rinsing process, and a device for forming such a foam carpet.

DE-C 20 23 133 discloses a method for odorless depositing of excrement in a toilet bowl provided with a water flush of the usual type, in which a foam cushion is placed in the toilet bowl with a foam-forming preparation in tablet form or in an aerosol can before depositing the excrement is generated, which is removed together with the excrement when the water flush is actuated. This procedure has never been put into practice. The reason for this is in all likelihood that tablets or an aerosol can can be used to produce a foam pillow, which at most serves as an odor barrier for 5 minutes until rinsing, and this is only relatively complex, i.e. by separate manipulation of the user. In addition, it is not possible to distribute the foam cushion evenly over the entire toilet bowl using tablets or an aerosol can.

From DE-C 10 30 267 a system for preventing the spread of odors when using a toilet is also known. This has at least one nozzle connected to a water pipe and located in the toilet bowl, a distributor cone being arranged behind the mouth of the water pipe, which configures the escaping water into a water film bell shielding the bowl bottom.

The device according to DE-C 10 43 969 only deals with the odor removal in a toilet bowl. The situation is similar with the extremely constructionally complex arrangement according to US Pat. No. 4,571,752. Here 1 cm³ chemical = 288 gr per day is distributed every 5 minutes without later binding to the environment and every 5 minutes the toilet bowl smell is blown up with a fan.

Furthermore, DE-A 30 18 048 describes an arrangement for producing foam in which the foaming is carried out using compressed gas. The foam developed in this way in the chamber can be introduced via a line into a toilet bowl, urinal bowl or the like. On the one hand, the complex construction of this known arrangement is disadvantageous due to the fact that additional units for the compressed air supply have to be provided. On the other hand, a particular disadvantage of this arrangement is the generation of the foam separately from the water supply. When it is brought into contact with the water present in the toilet bowl, urinal bowl or the like, its chemical composition changes suddenly. The foam collapses.

Finally, the foam is produced by means of the device known from US Pat. No. 4,321,714, likewise in a container separate from the water container, again via compressed air, which is supplied from a compressed air generator connected via a line. This device likewise has the disadvantages mentioned above in connection with DE-A 30 18 048. In addition, a foam carpet with a very specific configuration cannot be achieved with this device, since, due to the different residence times of the individual foam bubbles in the container, no uniform size distribution can be achieved.

The present invention is based on the prior art, the task of creating a foam carpet of the type mentioned and a device for its formation, with which a foam cover is produced in the toilet bowl, which serves not only as a permanent odor barrier , but in particular also has an anti-spray effect and at the same time makes cleaning the toilet very easy.

This object is achieved by a closed-pore foam carpet in accordance with the characterizing features of claim 1 and with respect to the device by the characterizing measures of claim 5.

Preferred developments of the basic ideas of the invention defined in the cited claims are described in the associated subclaims.

The inventive design of the foam carpet ensures absolutely safe spray inhibition, even in the case of a deep-flush toilet or cascade toilet. Experiments with an elongated or sausage-shaped mass with a weight of 45 g, a length of 9 cm and an average diameter of 25 mm, which is dropped from a height of 30 cm onto a water-covered surface, have confirmed this. Above all, these experiments have shown that it is necessary to form the foam homogeneously and closed-pore in such a way that foam bubbles of different diameters are present, the height of the foam carpet being at least twice as large as the average foam nose diameter, which is preferably around 4 Should be -6 mm.

Furthermore, tests have shown that foam bubbles that are too large do not inhibit spraying. Four foams preferably contain no foam bubbles with a diameter greater than 20 mm. On the free surface of the foam carpet, however, the bubbles can sometimes have a diameter of up to 40 mm. Finally, a foam carpet is particularly advantageous in which the proportion of foam bubbles with a diameter of less than 5 mm is greater than the proportion of foam bubbles with a diameter of greater than 5 mm. The proportion of foam bubbles with a diameter of less than 5 mm is advantageously about 60 to 80% by volume of the total foam, the foam bubble diameter should be at least about 1 mm. With the above-mentioned statistical distribution of the foam bubbles, on the one hand a high degree of spray inhibition and on the other hand an extremely good uniform distribution of the foam over the entire area to be covered is achieved, and indeed within an extremely short time of, for example, less than 1.5 seconds. The foam bubble distribution as well as the degree of spreading over time is also a measure of the viscosity of the foam to be used. The foam viscosity of a particularly effective foam is combined with a rotary viscometer from Haake, Karlsruhe, type VT 181 with FL 10 wing rotating body with U4 speed level 5 liter container with 20 cm diameter measured and should be 25-60 divisions at 20 ° C ambient temperature.

The weight of the foam designed according to the invention, including the non-foamed foaming agent, is preferably about 5 to 20 grams per liter of foam. Furthermore, the foam is advantageously designed in such a way that a foam carpet sorted from bottom to top results in bubble size. In a lower layer, small bubbles with a diameter of approximately 1.0-4.0 mm inhibit the excrement impact force, so that splashing and pelvic contamination can be avoided. Large bubbles with a diameter of about 4-40 mm form a foam net on the top or in the upper layers of the foam carpet, which extends over excrement tips and thus prevents odors and bacteria from escaping. The flow rate of the foam at 20 ° C ambient temperature is preferably at least 1 cm / sec. The foam surface tension at 20 ° C ambient temperature is about 15-70% of the water surface tension. At these values, the foam formed spreads quickly enough to the side of the bowl, under splash and odor-resistant covering of the surface affected by excrement.

The "water half-life" of the formed foam carpet, ie the time within which the water content of the foam carpet is around, is also of minor importance half decreases. This is preferably at least 10, preferably over 20 minutes.

A particularly simple solution of the invention is characterized in that a foam former is added to the rinsing water to form the foam carpet in such a way that it rinses with the rinsing water into the toilet bowl simultaneous foaming occurs. With regard to the associated device, reference is made to claims 5 to 17.

However, the foam can also be newly formed immediately before each use of the toilet and introduced separately from the rinsing water into the toilet bowl, in particular through at least one foaming sieve, as a result of which the foam undergoes additional homogenization.

The foam is preferably introduced into the toilet bowl with the aid of air. With regard to a corresponding arrangement, reference is made to claims 10 and 11.

Overall, the rinse water consumption can be considerably reduced by the foam carpet according to the invention or the arrangement according to the invention for its formation, since cleaning of the toilet bowl is made considerably easier by the antifouling foam carpet designed according to the invention. The foam used preferably consists essentially of fats and alcohols with good sliding and cleaning properties. It can also contain deodorant components.

The arrangement for forming the foam carpet according to the invention are chosen so that standard toilet bowls can be used. The arrangements according to the invention are more or less additional devices that can also be retrofitted.

Regarding the arrangement of foaming screens, it should also be said that these are appropriately disordered in the rear curvature of the glasses, since most of the space is available there. The foaming sieve arrangement is provided with a mouth pointing radially to the glasses, which thus points from behind into the interior of the toilet bowl. Since the rear wall is usually very steep, this ensures that the toilet bowl is filled well with foam. To To control the formation of foam, a valve is provided, which can either be provided directly in the line between the storage container and the foam sieve arrangement, in which case the storage container is pressurized, or a water connection arranged on the side or at the bottom of the glasses can be connected via the valve and a mixer connected to the reservoir can be connected to the foam screen assembly. In the second case, a concentrated foaming agent is used in a pressureless storage container or reservoir, which is then diluted with water in the mixer.

The valve, together with the mixer and the foaming sieve arrangement, is also expediently arranged in the rear curvature of the glasses and is connected to them via very short connecting hoses. This results in a very short lead time after actuation of the valve until foam is generated. The loss of liquid is kept very small and an undesired flow of this liquid into the toilet bowl is prevented.

The valve can either be actuated manually using a hand lever, which protrudes laterally, or it can be operated automatically, in which case the valve can be actuated via a pushbutton by opening the cover. A particularly adjustable timer then serves for the automatic specification of the foaming time.

Foam formation can be supported significantly by a blower arranged behind the spray nozzle for foam generation, as is used, for example, for commercially available hair dryers (of course without a heating coil).

An advantageous embodiment of the foaming sieve arrangement is achieved in that at least two foaming sieves with different mesh sizes are arranged one behind the other at a considerably greater distance than the mesh size, with a nozzle emitting the foaming agent being directed at the foaming sieve with the smaller mesh size. With such a foam sieve arrangement, a very favorable ratio between the small size and the large number of foams (ratio of the foam volume to the volume of the liquid foaming agent) is achieved. Foaming numbers of over 100 can be achieved with a size of the foaming screen that is suitable for insertion into the rear curvature of the glasses. Due to the small mesh size and a correspondingly high resistance of the first foaming sieve, a very large number of small bubbles are generated, which in the second foaming sieve with a larger mesh size partially combine to form larger-volume bubbles. In this way, a favorable distribution of foam bubbles is achieved.

A further optimization of the foam generation can be achieved by further foam screens arranged at a corresponding distance from one another, which either have increasing mesh sizes or oscillating mesh sizes, or in which at least two foam screens have essentially the same mesh sizes.

Experiments have shown that the arrangement of foaming sieves in pairs can be advantageous. In a specific exemplary embodiment, the first pair of foaming screens - seen from the foam spray or spray nozzle - consists of a first screen with a 12 mm mesh size and a second screen with an 8 mm mesh size. A second pair of foaming sieves is arranged at a distance of approximately 8 mm, with a first foaming sieve with a 4 mm mesh size and a second foaming sieve with a 4 mm mesh width.

If an additional blower is used to support foam formation, the first effective foaming sieve has a mesh size of only about 1 to 2 mm, in particular 1.5 mm. This "pre-screen" has a kind of braking effect for the emerging foam.

The formation and arrangement of the foam screens naturally depends not least on the foaming agent used and its concentration.

An expedient constructive embodiment is achieved in that the foam screens, which are preferably each contained in a ring, are arranged in a tube or outlet channel, with spacers, preferably in the form of spacer sleeves, being provided for adjusting the distances. The distances can vary. In this way, optimization and adaptation to a different foaming agent or to a different concentration can be brought about simply and quickly.

A spacing of the foam screens or the rings holding them along their circumference from the wall of the outlet channel has proven advantageous, especially in the case of a construction with compressed air-assisted foam formation. Excess foam etc. can flow back along the wall of the outlet channel in order to then be "blown" again into the area of the foam screens.

If the foam carpet is designed independently of the flushing, a manual or automatic activation of a pump or a valve is conceivable. Instead of an arbitrary operation by hand or foot, a use sensor can be provided for dispensing the foam or the foaming agent, which emits a signal before or when the toilet is being used, which activates the dispensing device for the foam or foaming agent for a predetermined period of time.

This usage sensor can be, for example, a light barrier to be arranged directly in front of the toilet, by means of which it is determined that a user has approached the toilet. As soon as this is established, the dispensing device outputs a predetermined amount of the respective agent. A usage sensor can also be provided, which generates a signal as a result of another activity by the toilet user. For example, the door lock or the switching on of the light or the activation of ventilation can be used to emit a signal to release the foam to the corresponding device. A separate switch-on device is also possible according to the invention, in which, by opening the toilet lid, a pushbutton is moved out of its firing position and the valve for dispensing the foam is actuated, possibly with the interposition of a timer.

• Fig. 1 den schematischen Querschnitt eines Spülklosetts,
• Fig. 2 eine schematisch dargestellte Möglichkeit für die Abgabe des Schaumbildners aus der zugehörigen Vorratskammer bzw. dem zugehörigen Vorratsbehälter (Reservoir),
• Fig. 3 eine in einer Brille eines Sitzklosetts untergebrachte Schaumerzeugungs-Vorrichtung,
• Fig. 4 ein Ausführungsbeispiel eines Schäumsiebanordnung im Längsschnitt,
• Fig. 5 eine Draufsicht eines großmaschigen zweiten Schäumsiebs,
• Fig. 6 eine Draufsicht eines feinmaschigen, ersten Schäumsiebs (Vorsieb),
• Fig. 7 eine Schaltungsanordnung einer automatischen Ventilsteuerung,
• Fig. 8 ein weiteres Ausführungsbeispiel einer Schäumsiebanordnung mit zugeordnetem Gebläse im schematischen Längsschnitt, und
• Fig. 9 eine Draufsicht eines Schäumsiebs, das längs des Umfanges von der Wandung des Austrittskanals beabstandet ist unter Ausbildung entsprechender Drainagespalte.

Exemplary embodiments of the invention are explained in more detail below with the aid of the attached description. Show it:

• 1 shows the schematic cross section of a flushing toilet,
• 2 shows a schematically represented possibility for the delivery of the foaming agent from the associated storage chamber or the associated storage container (reservoir),
• 3 shows a foam generating device accommodated in a pair of glasses of a seat toilet,
• 4 shows an embodiment of a foaming sieve arrangement in longitudinal section,
• 5 is a plan view of a large-mesh second foam sieve,
• 6 is a plan view of a fine-mesh, first foaming screen (pre-screen),
• 7 shows a circuit arrangement of an automatic valve control,
• 8 shows a further exemplary embodiment of a foaming sieve arrangement with an associated blower in a schematic longitudinal section, and
• Fig. 9 is a plan view of a foaming screen, which is spaced along the circumference from the wall of the outlet channel with the formation of corresponding drainage gaps.

Foam is particularly advantageous as a spray-inhibiting substance floating on the surface, since it can be renewed easily and inexpensively for every use. The use of foam or the foaming agent which gives it together with water also does not lead to environmental pollution, since there are nowadays foaming agents which are biodegradable.

1 is designed as a so-called washdown device, in which there is a large volume of water 11, which extends over the wash bowl 12 from far back to far forward with its surface 13. The water of the water volume 11 is fed from behind via a rinsing water nozzle 14 and washed away to the rear via a waste water nozzle 15.

Below the surface 13, in the front area of the flushing toilet 10, there is mounted an outlet opening 16 which is connected to the water volume 11 and is nozzle-like in the exemplary embodiment and which is supplied with foam generator via a foam line 17. If foam or foaming agent is dispensed through this outlet opening 16, it rises to the surface 13 and forms a foam layer 18 thereon. However, it is equally conceivable to foam through one or more foam conduit (s) opening into the bowl 12 above the water surface 13. initiate.

In the case of FIG. 2 there is a storage chamber 56 or a storage container for the foaming agent. A riser pipe 57 projects into the chamber 56 from above and ends at a distance from the chamber bottom in its area. The riser pipe 57 opens into a water pipe 58 which branches off from a main water pipe and is therefore connected to the pressurized water network of the respective building. In the water line 58, a water valve 59 is connected in front of the chamber 56, which normally blocks the water flow. The opposite The end of the water pipe 58 forms the outlet opening 60 corresponding to the outlet opening 16 of FIG. 1, which points into the interior of the toilet. If the water valve 59 is opened, which can be done by hand or by another actuating device, the pressurized water flows past the riser pipe 57, so that spray-inhibiting substance enters the water line as a result of the water pressure. The water flowing past soaks up the foaming agent in the riser 57, that is to say the arrangement works in the manner of a water jet pump, so to speak. For this it is still necessary that the reservoir 56 has a pressure equalization opening 61 on the upper side. A relatively highly concentrated foaming agent can be located in the container 56. Mixing with the water in the water line 58 results in a dilution to the desired extent. The foaming agent can be, for example, a 30% solution in the container 56, while a 3% solution emerges at the outlet opening 60. An acceleration nozzle 63 can also be arranged in the water line 58.

Finally, it should also be pointed out that in any case a foaming device can be arranged in front of the outlet opening for the foaming agent. In Fig. 2 such is indicated in the form of a foaming sieve 62, which can also be integrated in the outlet opening 60. This is particularly useful when the outlet for the foaming agent is above the surface of the water volume in the toilet.

If a flushing toilet is spoken of in the present application, it can be all conceivable types of toilet. Of course, this also means complete toilets with glasses, lids and cisterns.

If materials are used to form foam that form a foam together with water, the water consumption is significantly lower than with conventional flushing toilets due to a high foaming number, even if a flushing process with water follows, since this in turn requires a significantly reduced amount of water. Even greater water savings are achieved when foaming with compressed air and / or with subsequent rinsing with compressed air. This is particularly important in dry areas with water shortages or cold zones, where there is a risk of freezing water pipes and basins.

3 schematically shows an embodiment of an arrangement according to the invention for producing a foam carpet of the type mentioned at the beginning, the foam generating device being arranged in glasses.

The glasses 310 shown in FIG. 3 with hinged lid 311 are provided for mounting on a commercially available toilet bowl, which is not shown for simplicity. A foam generation device arranged below these glasses 310 in a rear spectacle arch 319 is actually not recognizable in the top view and is therefore shown in dashed lines.

A water connection 312 coming from behind in the rear area of the glasses 310 is connected via a valve 313 to a mixer 314 which has an additional line to a storage container 315 for a foaming agent. The valve 313 has a manual actuation lever 316 which also protrudes from behind the glasses 310. The valve 313 is connected via the mixer 314 working in the manner of a water jet pump by means of very short connecting hoses 317, 318 to a spray or spray nozzle 321 directed against a foam sieve arrangement 320. The foaming sieve arrangement 320, the storage container 321, the valve 313 and the mixer 314 are accommodated in a rear curvature 319 of the glasses 310. The mouth of the foam sieve arrangement 320 is brought out on the output side via an angle tube 322 to the inner rim of the glasses in such a way that it points radially into the interior of the glasses 310 and thus into the interior of a toilet bowl connected thereto.

A non-return valve 323 is arranged on the side of the storage container 315, the foaming agent being filled in via a filling hose extending laterally to the edge of the glasses and the non-return valve 323. This also serves to ventilate the storage container 315 and prevents liquid from escaping, for example when the glasses 310 are folded up.

The water connection 312, which in principle can also point downwards or backwards, is connected to a water hose during operation. Controlled by the operating lever 316, water can flow through the mixer 314, whereby concentrated foaming agent is sucked out of the storage container 315 and mixed. The mixed liquid then flows to the foam sieve assembly 320, where foam is formed which can flow through the angle pipe 322 to the toilet bowl. In an embodiment without a water connection, the mixer 314 is omitted and the valve 313 is arranged directly between the storage container 315 and the foam sieve arrangement 320. A ready mixture of a foaming agent with a dilution liquid is then present in the storage container 315, the storage container 315 being able to be designed in the manner of a spray can or having a pump for generating the required spray pressure.

For automatic control of foam formation, the manually operable valve 313 is replaced by a valve 330, which is provided with a sensing element 331, as shown in FIG. 7. This sensing element 331 extends through an opening in the glasses 310 and is held by the lid 311 in the closed position when the lid is closed. A hydraulic timer 332 is connected downstream of the valve 313.

When the cover 311 is opened, the valve 330 also opens, so that foam formation begins immediately. The duration of this foam formation is determined by the timer 332, the holding time of which can also be made adjustable. At the end of this holding time, the further flow of water is blocked by means of the timer 332, so that the foam formation is stopped. The hydraulic time control can of course also be replaced in principle by an electrical control.

4 to 6, the structure of the foam sieve arrangement 320 is explained in more detail. In a tube 333, three foam screens 334-336 are held at a certain distance from one another by means of two tubular spacers 337, 338, which is larger than the largest mesh size. Each foaming sieve 334-336 consists of two individual foaming sieves 334 ', 334˝, 335', 335˝, 336 ', 336˝, which are each held in rings 339-341.

The first foam screen 334 on the input side has a fine mesh structure, as shown in FIG. 6, while the third foam screen according to FIG. 5 has a substantially coarser mesh structure or width. The mesh size of the second foaming screen 335 lying therebetween lies between them or corresponds to the mesh size of one of the other two foaming screens.

In front of the first foaming sieve 334, the spray or spray nozzle 321 is arranged in the center by means of a holder 342, the spray jet being designed as a full cone and covering the entire surface of the first foaming sieve 334.

At the exit of the first foaming sieve 334, a large number of foam bubbles are generated due to the fine mesh structure or the high resistance of this foaming sieve, which increases in number and / or bubble size in the further foaming sieves 335, 336. In this way, foaming numbers of over 100 can be achieved. Depending on the foaming agent used and its concentration, the number of individual foaming sieves placed on top of one another, the spacing of the foaming sieves from one another, the mesh sizes and their sequence, etc. can be varied. In principle, however, a foaming sieve with a smaller mesh size must be followed by a foaming sieve with a larger mesh size at a greater distance.

Achieving large numbers of foaming is desirable for many other uses, so that the use of the foaming sieve arrangement described is not limited to toilets. Above all, are suitable. Foam sieve arrangements of this type for producing foam for marking lanes in agricultural vehicles, since the low consumption of foaming agents due to the high number of foams has a cost-effective and noticeable effect there.

FIG. 8 shows a particularly advantageous embodiment for the foam formation, in which the foam formation takes place with the aid of air.

According to the embodiment according to FIG. 4, a tubular foam outlet channel is provided with two foaming screens 434 and 435, which are held at a predetermined distance from one another by means of a tubular spacer (not shown). Each foaming sieve 434 and 435 consists of two individual foaming sieves 434 ', 434˝ and 435', 435˝ placed against each other, which are each held in rings not shown in FIG. 8. The first foam screen 434 on the inlet side has a fine mesh structure and serves more or less as a brake screen with regard to the air-assisted foam discharge. The foam screen 435 assigned to the outlet opening 418 is provided with a substantially coarser mesh structure or width. Similar to the embodiment according to FIG. 4, a further foaming screen can be provided between the foaming screens 434 and 435. The foaming screen 434 can also be preceded by a very fine-meshed pre-screen with a mesh size of approximately 1.5 mm, which then serves as the actual brake screen.

In front of the foaming sieve 434, the spray or spray nozzle 421 is arranged in the center, which is an angular nozzle. The spray jet 419 is designed as a full cone and covers the entire area of the first foaming screen 434. The supply to the spray or spray nozzle 421 takes place via a line 420 through which water mixed with foaming agent is conveyed.

The effect of the foam screens 434, 435 is described with reference to FIGS. 4 to 14. To avoid repetition, reference is made to the corresponding statements.

In the embodiment according to FIG. 8, the formation of foam is promoted very considerably by an air blower 411 which is behind the spray or spray nozzle 421 is arranged and generates an air flow 412 which is directed towards the outlet opening 418 or in the spraying or spraying direction. The air blower 411 corresponds to a conventional hair dryer in terms of its performance. The blower 411 shown in FIG. 8 can also be assigned to the foaming sieve arrangement 320 according to FIG. 3 or 16.

The air inlet opening is identified in FIG. 8 by the reference number 422. With regard to this air inlet opening, the spray or spray nozzle 421 is in the center.

In the embodiment with blower 411, the foam screens 434, 435 are arranged within the foam formation and outlet channel 433 in such a way that they are spaced apart along their circumference from the channel wall, so that a drainage between the foam screen 434 or 435 and the wall of the outlet channel 433 Annular gap 416 arises (see FIG. 9). To form this drainage annular gap 416, the foam screens 434, 435 are held within the outlet channel 433 by three spacer elements 413, 414 and 415, which are distributed uniformly over the circumference (see FIG. 9).

The arrangements described above are used to form a foam carpet according to claims 1 to 11 or the statements made at the outset.

The height of the foam carpet is at least 0.5 cm; only then can effective spray inhibition be achieved. Depending on the toilet construction, a height of the foam carpet up to 20 cm can also be required. The Production of such a foam carpet is easily possible with the arrangements or devices described.

In a specific embodiment, the diameter of the foam formation and outlet channel 333 or 433 is approximately 60 mm. The distance between the foaming screens is then approximately 8 mm with a total length of the foam formation and outlet channel 333 or 433 of approximately 4 cm.

The viscosity of the foam is of essential importance for the rapid distribution of the foam formed in the toilet bowl or introduced into the toilet bowl. The preferred viscosity range is mentioned at the beginning. The viscosity of the foam is also important for spray inhibition, i.e. Dampening of the falling or discharged excrement.

Claims (17)

1. Closed-cell foam layer for the odourless deposition of excreta in toilet pans, urinals or the like as a result of a mixing of foaming agents and flushing water during the flushing operation, characterised by a height which is at least twice as great as the mean foam bubble diameter, the foam bubbles having a diameter of about 1 mm to 30 mm, the content of foam bubbles with a diameter of < 5 mm is greater than the content of foam bubbles with a diameter of > 5 mm and the flow rate being at least 1 cm/s at a temperature of 20°C and the "water half-life" (= time within which the water content of the foam layer decreases by half) being at least 2, preferrably 10, especially over 20 min.

2. Foam layer according to Claim 1, characterised in that the bubble size increases from the bottom (about 1.0 to 4.0 mm bubble diameter) towards the top (over 4 mm bubble diameter).

3. Foam layer according to Claim 1 or 2, characterised in that its weight, including unfoamed foaming agent, is about 5-20 g per litre of foam.

4. Foam layer according to one of Claims 1 to 3, characterised in that the surface tension at a temperature of 20°C is about 15 to 70% of the surface tension of water.

5. Device for forming a closed-pore foam layer in a toilet pan or urinal bowl or the like according to one of Claims 1 to 4, characterised by a mixer (314) or a pipe (58) in which a foaming agent can be fed in water under pressure, a foam generating spraying nozzle (60, 321, 421) which is arranged downstream of the mixer (314) or the pipe (58) and is directed at at least one, in particular two or more, foaming screens (62, 334, 335, 336, 434, 435) arranged in series, and by a foam outlet opening (322, 418) which adjoints the latter, is separate and opons into the toilet pan in the region of the upper rim of the pan.

6. Device according to Claim 5, characterised in that the mixer (314) or the pipe (58) are connected to a storage container (56, 315) for the foaming agent.

7. Device according to one of Claims 5 or 6, characterised in that a valve (59, 313) is arranged upstream of the mixer (314) or the pipe (58).

8. Device according to one of Claims 5-7, characterised in that the spraying nozzle (321, 421) is arranged centrally in front of the foaming screen (334, 434).

9. Device according to one of Claims 5-8, characterised in that the spraying nozzle (321, 421) is designed as an angled nozzle.

10. Device according to one of Claims 5-9, characterised in that the spraying nozzle (421) is arranged in front of an air inlet opening (422) through which air can be blown in in the spraying direction (419) or in the direction of the foam outlet opening (418), preferably under a pressure of up to about 6 bar.

11. Device according to Claim 10, characterised in that a fan (411) is arranged behind the air inlet opening (422).

12. Device according to one of Claims 5-11, characterised in that the foaming screens (434, 435) are arranged within a foam formation and outlet channel (433), drainage openings (416) being provided at least in the lower peripheral region of the latter.

13. Device according to Claim 12, characterised in that, along their periphery, the foaming screens (434, 435) are in each case arranged or positioned within the foam formation and outlet channel (433) with a clearance with respect to the wall of the latter.

14. Device according to one of Claims 5-13, characterised in that the foaming screens (334, 335, 336, 434 435) in each case comprise two individual foaming screens (334′, 334˝, 335′, 335˝, 336′, 336˝, 434′, 434˝, 435′, 435˝) placed one against the other.

15. Device according to one of Claims 5-14, characterised in that the foaming screens (334, 335, 336, 434, 435) have different mesh structures or widths, the mesh width of the inlet-side foaming screen (334, 434) nearest to the spraying nozzle (321, 421) being the smallest and increasing with each downstream outlet-side foaming screen (335, 435; 336).

16. Device according to Claim 15, characterised in that the foaming screens (334, 335, 336) are arranged at a mutual interval which is larger than the largest mesh width.

17. Device according to one of Claims 5-16, characterised in that the valve (313), the mixer (314), the storage container (315), the foaming screens (334, 335, 336) and the outlet opening (322), in particular in the form of an ell, are accommodated in a rear bulge (319) of the seat (310).

Images