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CROSS REFERENCE TO RELATED APPLICATION 
     This application is a continuation of International Application PCT/CH98/00565, filed Dec. 30, 1998, the disclosure of which is incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a stench trap for a urinal, having an interchangeable pot for insertion in the urinal and a cover for covering the pot. The cover has an opening for introducing urine into the pot, a baffle projecting into the pot for restraining sewer stench from the outlet connection, and a stench trap floating on the urine intended to accumulate in the pot. 
     From the prior art urinals are known, which must be flushed with water following each use. Due to the reduction of the amount of flushing water as a consequence of higher water prices and/or smaller amounts of water being available, such urinals require a disproportionate cleansing expenditure. Due to the mixture of urine with water, the formation of urine stones is promoted, and not only parts of the urinal, but also in particular the siphon-bearing discharge pipes leading away from this, are reduced in cross section by formation of urine stones within a few months and must consequently be cleansed. In addition to the high costs for the required flushing water, there arc those for the periodic cleansing/repair of the pipes. 
     For these reasons, waterless urinals have already been proposed. From German published patent application DE-A1 28 16 597 (Ernst), a pot-shaped insert is known, which is inserted into a recess located at the deepest point of the urinal and is connected with the outlet pipe. In the insert an annular space is formed, in which a cylindrical jacket-shaped tube is inserted from above, which subdivides the annular space into two regions, an inner and an outer, which are connected with each other and form a stench barrier or a siphon. A barrier liquid of lower density than water, for example oil, is present in the outer annular space. The urine entering into the container passes through the barrier liquid due to its higher specific gravity and thus reaches the outlet and from there the sewer system. This device has the disadvantage that the barrier liquid, which can contain additional active disinfecting agents and optionally fragrant substances, is successively flushed away by the strong stream of water passing through the barrier liquid during the periodic cleansing of the urinal with a strong torrent of water and consequently loses its action. 
     In International Patent Application publication WO 97/15735, an insert for a waterless urinal with a barrier liquid is disclosed which, through the special geometrical construction of the insert container, should prevent the barrier liquid from floating away. Even if the floating away of the barrier liquid is substantially prevented there, it cannot be avoided, however, that its active ingredients, which are necessary to create a flawless protection against stench, are successively degraded, and consequently even with this arrangement, the barrier liquid must frequently be replaced. Also, the substances which are used for the barrier liquid are not completely harmless, and can lead to problems with wastewater processing. Monitoring the momentary condition of the barrier liquid can create additional difficulties, since this is not directly examinable, and in principle, only the nose decides whether enough of it is present, or whether this has already been degraded or indeed flushed away. 
     SUMMARY OF THE INVENTION 
     The objective of the present invention is the creation of a stench trap, which manages without barrier liquid. This objective is accomplished by a stench trap of the type described at the outset, wherein the stench trap is constructed as a float designed to seal off the opening in the cover. Advantageous embodiments of the invention are described in the following and in the dependent claims. 
     The arrangement according to the invention operates completely without barrier liquid and can accordingly, if necessary, be periodically thoroughly cleansed without further ado with a torrent of water. Moreover, a doubled stench trap is present, in which first of all the dammed up liquid, namely the urine, flawlessly blocks the stench from the sewer system and moreover, as a second seal, the linear or strip-shaped contact of the float on the collection surface prevents the exit of odors. A build up of urine stones is completely absent, since the portions of water necessary for their formation are not present. The water optionally used with periodic cleansing is negligible for the formation of urine stones, because this can only react with the urine residue for a short time. The lift of the lifting element is so proportioned, that the amount of urine (liquid column) collecting in the cover suffices to depress or raise the lifting element temporarily to the extent that the urine can flow off downwardly. When using a spherical lifting element, this necessarily always lies on the circular opening. In addition, sealants applied to the opening can be installed to increase tightness. In a special embodiment of the invention, a magnet can be arranged below the first container section, in which the lifting element floats, by which the lifting element can be sporadically pulled down and thus the amount of urine situated above its surface can be completely drained off. In this maimer, at times when the urinal is little used, the dammed up amount of liquid can be sporadically removed. Advantageously, the magnet is activated by a capacitor charged by a light sensitive cell. 
     In a further embodiment of the invention, the lifting element has a U-shaped cross section and covers the upper end of the outlet connection on the container. With this construction the insertion of an additional baffle holding back the stench is dispensed with. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of the invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there arc shown in the drawings embodiments which are presently preferred. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown. In the drawings: 
     FIG. 1 is a side view of a urinal with a recess for insertion of an exchangeable pot; 
     FIG. 2 is a cross section through the urine collection region of the urinal and a pot inserted therein; along line II—II in FIG. 4; 
     FIG. 3 is a longitudinal section through the container of a further embodiment of a pot;  2   
     FIG. 4 is a cross section through the pot along line IV—IV in FIG. 2; 
     FIG. 5 is a longitudinal section through a further embodiment of a pot along line V—V in FIG. 6 with the float lying on the cover; 
     FIG. 6 is a cross section through the pot in FIG. 5 along line VI—VI; 
     FIG. 7 is a longitudinal section through a further embodiment of a pot along line VII—VII in FIG. 8 with the float depressed; 
     FIG. 8 is a cross section through the pot in FIG. 7 along line VIII—VIII; 
     FIG. 9 is a front view of a urinal with solar cells; 
     FIG. 10 is a cross section through the pot in a further embodiment of the invention with a slidable magnetic lifting device; 
     FIG. 11 is a cross section through the pot with a spherical float lying over the cover; 
     FIG. 12 is a cross section through the cover with a spherical lifting element; 
     FIG. 13 is a cross section through the cover with an asymmetrical float; and 
     FIG. 14 is a side view of a further embodiment of a stench trap. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In FIG. 1 a urinal is designated schematically with reference numeral  1 , which is fastened on a wall  3  and is connected below via an outlet connection  5  to a wastewater conduit  7 . The urinal I can be made of ceramics, metal or plastic and has a recess  11  at the deepest point of its collection basin  9 , at whose base the outlet connection  5  opens. In the transition between the collection basin  9  and the recess  11 , a surrounding ledge  13  is preferably formed, on which lies the flange  15  of a pot-shaped insertion container (pot  17  for short) inserted into the recess  11 . 
     In the first embodiment of the pot  17  forming a stench trap, which includes a jacket  19  and whose bottom is penetrated by the upper part  23  of a discharge tube, a container-shaped space, hereinafter called float space  25 , is arranged. At least one part of its jacket can be shared with the jacket  19  of the pot  17 . A chord-form running wall  18  separates the float space  25  from an overflow space  27  and the upper part  23  of the outlet connection  5 , which is connected with the head space  28  of the overflow space  27 . The upper part  23  can be formed by two wall parts  24  or by a pipe (not shown). The upper end  22  of the part  23  lies at a vertical spacing from the ledge  13 . 
     The upper opening of the pot  17  is covered by a frustum-shaped cover  29 , at whose deepest point a circular opening  31  is situated. The opening  31  lies over the float space  25 . The float space  25  and the at least one overflow space  27  are joined with each other below by a connection opening  37 . 
     Within the float space  25  lies a freely movable float  33 , in the first example according to FIG. 2 a sphere, whose specific density is less than the density of urine  35 . The diameter D of the sphere is larger than the diameter d of the opening  31  in the cover  29 . Below the flange  15  on the cover  29  an  0 -ring or an otherwise constructed seal can be arranged. 
     Urine  35 , flowing from above into the collection basin  9 , accumulates on the cover  29 . As soon as the liquid column above the opening  31  in the cover  29  exceeds by weight the buoyancy of the float  33  in the float space  25 , and consequently is greater than the contact pressure of the float  33  on the cover  29 , the float  33  is pressed downwardly and the accumulated urine  35  can flow out downwardly through the opening gap. It then reaches the float space  25 , flows from there through the passage opening  37  to the overflow space  27 , and thereafter flows into the outlet connection  5 . The upper rim of the upper part  23  of the outlet connection  5  lies at a height which assures that the float  33  is pressed against the opening  31 , whereby the contact pressure, that is the lift, suffices to guarantee a faultless scale and at the same time also to enable the discharge already of a small amount (i.e., already a liquid column of, e.g., 10 mm) of urine  35  on the cover  29 . 
     In the second embodiment of the invention according to FIG. 3, the outlet nozzle  23  lies in the center of the float space  25 , which in this example is identical with the pot  17 . The rotation symmetrically-shaped float  33  has a U-shaped cross section and can be manufactured as a hollow body or from a material which has a lesser density than urine. The upper end  23  of the outlet connection  5  comes from below to lie in the cylindrical recess of the float  33 . The cylindrical wall  34  of the float  33  surrounding the outlet connection serves as a baffle. The surface of the float  33  lying on top can be shaped as a hemisphere, an ellipse or a cone (indicated in broken lines), so that a flawless linear contact at the opening  31  and optimal sealing can be guaranteed. 
     In the third embodiment of the invention according to FIGS. 5 to  8 , a cylindrical float  33  with a spherical segment or a cone-shaped upper closure  41  replaces a spherical or cap-shaped float  33 . Advantageously, the float  33  comprises two cylinders of unequal size, in order to generate as much lift as possible in the lower region. The upper cylindrical region serves at the same time as a vertical guide, laterally guided by the guide segments  43  mounted on the underside of the cover  29 . As an alternative to the guide segments  43 , ribs  45  can be applied on the jacket of the float  33 , which serve as vertical guides. If the latter run helically, represented in FIG. 5, then the float  33  rotates when liquid flows past in larger amounts. The contact and sealing surfaces between the float  33  and the rim of the opening  31  are thereby always kept clean. In cross section according to FIG. 6, it is apparent that the float space  25  is configured as a space arranged eccentrically to the pot  17 , likewise constructed cylindrically. 
     In FIGS. 5 through 8 and  10 , a laterally open space  47  is represented below the float space  25 , in which a depression device for depressing the float  33  can be inserted, in case such is desired. The depression device can include an electromagnet or a permanent magnet  49 , wherein the former is activatable by a condenser and/or a battery  55 . The battery  55  can be charged by a solar cell  59 , which is installed at the top of the urinal  1  (FIGS. 9 and 10) and is illuminated by daylight or artificial light. Alternatively, other energy sources or a manual actuation can also be used for depressing and elevating. The opening of the passage for discharging the urine can take place one or more times while using the urinal. 
     When using a permanent magnet  49  (FIG.  10 ), the latter is periodically driven back and forth by a linear drive  57  in the area below the float  33 . Alternatively, the magnet  49  can also be arranged to be vertically slidable. In order to achieve a certain depression of the float  33 , soft iron or a magnetic element  61 , e.g., a soft iron plate or a permanent magnet, is inserted on its bottom. Preferably, the element  61  lies outside the float  33  and as near as possible to the magnet  49 . When using an electromagnet, this can also be rigidly attached. The float  33  can also be depressable with a manually operable device. In FIG. 10, in addition, an alternative liquid discharge inside the pot  17  is represented. The outlet nozzle  23  extends only over a small height and leaves the pot  17  laterally. 
     In the embodiment of the invention according to FIG. 14, the stench trap is made from elements with exclusively cylindrical jacket-shaped walls. In the likewise cylindrical jacket-shaped recess  11 , which can be part of the urinal I or the outlet connection  5 , the pot  17  accommodating the stench trap is inserted. This is closed on the bottom and has on its upper edge at least one overflow opening  28 , through which the urine  35  from the container space  25  can reach the recess  11  and from there the outlet connection  5 . A cylindrical wall part  30  is fastened on the underside of the cover  29 , which serves as a baffle and extends into the vicinity of the bottom  21  of the pot  17  and divides the container space  25 . The wall palt  30  can be an independent element or form a part of the cover  29 . The cover  29  and the pot  17  are preferably firmly connected with one another and are insertable as a unit into the recess  11 . The pear-shaped float  33  in this embodiment is loosely secured in the pot. In the space  47  accessible from outside, the depression device, e.g., a permanent or electromagnet  49  (cf. also FIG.  10 ), can be moved in and out from the side or preferably in a vertical direction from below. 
     In the further embodiment of the invention according to FIG. 11, the float  33  is spherical and lies on the opening  31  of the cover  29 . Along the opening  31  in the cover  29 , a seal  32  can be molded on or secured. 
     An alternative float  33  is represented in FIG.  12 . This has the configuration of a cone, whose tip is guided through opening  31  into the pot  17  and can at least partially dip into the urine  35 . In both embodiments (FIGS. 11 and 12) the float  33  is elevated from the urine accumulating above the cover  29 , so that the latter can reach the container  25  through the gap thereby arising along the float. 
     In a further advantageous embodiment of the invention according to FIG. 13, the float  33  is configured frustum-shaped and has on its upper end an asymmetrically arranged plate  34  which, when the urine level rises, causes the float  33  to be elevated on one side, whereby a gap arises not running parallel along opening  31  and thus makes possible a ventilation of the space lying below during the outflow of the urine. On the jacket of the float  33  grooves  65  can be provided in addition, which after the elevation of the float  33  above the opening cross section in the cover  29  project out and facilitate the outflow (illustrated only in FIG.  12 ). 
     Preferably, in all embodiments a protective screen or lattice  63  can lie over the cover  29 , which bridges over the float  33  and protects the latter from unauthorized access. 
     The pot  17  can obviously also be inserted in urinals  1 , which are not attached to the wall as individual urinals, but rather stand on the floor or are configured as troughs whose deepest point lies in, above or under the level of the floor (not illustrated). 
     It will be appreciated by those skilled in the art that changes could be made to the embodiments described above without departing from the broad inventive concept thereof. It is understood, therefore, that this invention is not limited to the particular embodiments disclosed, but it is intended to cover modifications within the spirit and scope of the present invention as defined by the appended claims.

Summary:
A waterless urinal ( 1 ) is provided with a pot ( 17 ) in which urine ( 35 ) accumulates. A float ( 33 ) floats on the urine ( 35 ) and is pressed upwardly by the buoyancy thereof against an opening ( 31 ) in the cover ( 29 ) of the pot ( 17 ). As soon as a pre-determinable column of urine rises above the float ( 33 ), the float ( 33 ) is pressed downwardly, and the urine ( 35 ) can flow out. In a preferred embodiment, the float ( 33 ) can be pulled downwardly by an electromagnet, in order to sporadically empty the urine ( 35 ), which has accumulated above the float ( 33 ) and the cover ( 29 ).