The invention relates to a sanitary unit for a vessel or vehicle, provided with a tank for receiving foul water coming from for instance a toilet. Sanitary units of this type are known. These are generally sanitary units provided with a relatively large tank in which all waste water is collected. Installing such a sanitary unit is expensive, and sometimes practically impossible. As a result of new regulations, but also due to increasing awareness, owners of small existing vessels are in fact obliged to install a sanitary unit on board.

The sanitary unit according to the invention has for its object in the first place to solve the problem outlined above. In addition, the inventive sanitary unit has also been found highly suitable for building into new vessels. The inventive sanitary unit has also been found to be very satisfactory in for instance caravans. According to an aspect of the invention it has the feature that the tank comprises a cylindrical chamber provided with a piston which divides the cylindrical chamber into a foul part and a clean part. An immediate advantage here is that the tank has no connection with the outside air, whereby odour nuisance is precluded and the use of an odour filter is unnecessary. A significant additional advantage is that the cylindrical chamber can be produced to size in simple manner on the basis of standard tubing with several standard diameters. A further important additional advantage is that the cylindrical chambers can be mounted parallel in simple manner, whereby small unused spaces can also be used to accommodate a tank assembled in this manner.

A highly favourable embodiment of the sanitary unit has the feature that the piston is received for free movement in the cylindrical chamber so that a piston rod with the required seal can be omitted.

A further favourable embodiment which is highly suitable for building into an existing vessel has the feature that the sanitary unit comprises pressing means connected to the foul part for pressing foul water into the foul part . The pressing means consist here for instance of an already present macerator pump.

A favourable alternative embodiment, which can take a very light form and is thereby very suitable for building into a vehicle, has the feature that the sanitary unit comprises pump means connected to the clean part of the cylindrical chamber for pressing air into or suctioning it out of the clean part.

A further favourable alternative embodiment which is highly suitable for building into a vessel has the feature that the sanitary unit comprises pump means connected to the clean part of the cylindrical chamber for pressing water into or suctioning it out of the clean part. The advantage here is that the weight of the cylindrical chamber remains the same, so that the navigational characteristics do not change. It is then possible for instance to utilize the cylindrical chamber or cylindrical chambers as ballast.

A further favourable embodiment, wherein a sanitary unit can be realized with minimum components, has the feature that the cylindrical chamber comprises connecting means connected to the clean part for connection to a mains water supply or to locally available pump means. The pressure of the mains water supply or the locally available pump means can then be utilized to empty the foul part of the cylindrical chamber, wherein the clean part is simultaneously filled with clean water.

A further very favourable embodiment has the feature that the piston is provided with a pressure-relief valve. When the foul part has been wholly emptied, the pressure in the clean part will rise, whereby the pressure-relief valve is opened and the foul part and a discharge pipe connected thereto are cleaned. A further favourable embodiment which can easily be built into existing vessels has the feature that the foul part of the cylindrical chamber is provided with two connections or with a T-piece for the connection of for instance a toilet and for the connection of an outlet pipe for foul water. The clean part of the cylindrical chamber is preferably also provided here with two connections or with a T-piece for the supply of clean water and for the discharge of clean water. The clean water is preferably discharged at the moment that the macerator pump presses liquid into the foul part of the cylindrical chamber so that the clean water can advantageously be utilized to fill the toilet with clean water.

A further favourable embodiment has the feature that a wall of the cylindrical chamber is manufactured at least partially from a transparent material so that the sanitary unit can be inspected in simple manner.

A further favourable embodiment has the feature that the sanitary unit is provided with a sensor which can indicate that the cylindrical chamber is at least substantially wholly filled with foul water. The sensor preferably comprises a magnet attached to the piston and a contact attached close to the clean part .

The invention also relates to a cylindrical chamber as part of a sanitary unit according to any of the foregoing claims.

The invention will now be further elucidated with reference to the following figures, in which:

Fig. 1 shows schematically a sanitary unit according to the prior art;

Fig. 2 shows a possible embodiment of a sanitary unit according to the invention;

Fig. 3 shows an alternative embodiment of a sanitary unit according to the invention;

Fig. 4 shows a possible embodiment of a cylindrical chamber in more detail; Fig. 5 shows a possible embodiment of a piston in more detail .

Fig. 1 shows a schematic view of a sanitary unit according to the prior art, consisting of a foul water tank 1 to which 2 is connected a toilet provided with a macerator pump 3 with which the content of toilet 2 can be pumped via a connection 4 into foul water tank 1. Toilet 2 is provided here with a two-way valve 5 so that using macerator pump 3 clean surface water can also be pumped into toilet 2. Foul water tank 1 is provided with a venting 6 with an odour filter 7, a level switch 8 which gives a warning when foul water tank 1 is almost full, and a connection

9 via which foul water tank 1 can be suctioned empty, for instance in a harbour.

Fig. 2 shows a possible embodiment of a sanitary unit according to the invention, consisting of a cylindrical chamber

10 which is divided by a piston 11 into a foul part 12 and a clean part 13. Connected to foul part 12 is a toilet 2 provided with a macerator pump 3 with which the content of toilet 2 can be pumped via a connection 14 into foul part 12. Piston 11 will here move to the right in the figure, wherein clean water or air present in clean part 13 will flow away via a connection 15. Foul part 12 is provided with a connection 16 via which the foul part 12 can for instance be pumped empty at a harbour. It is also possible to connect connection 15 to a pump such that piston 11 will move to the left in the figure. Foul part 12 can then be emptied independently via connection 16, for instance into a drain or offshore. Connection 15 can also be connected to the mains water supply so that foul part 12 is pressed empty using the mains water pressure .

Fig. 3 shows an alternative embodiment of a sanitary unit according to the invention, consisting of a cylindrical chamber 10 which is divided by a piston 11 into a foul part 12 and a clean part 13. Connected to foul part 12 is a toilet 2 provided with a macerator pump 3 with which the content of toilet 2 can be pumped via a connection 14 into foul part 12. Piston 11 will here move to the right in the figure, wherein clean water present in clean part 13 flows via a connection 15a to a flushing part of toilet 2 or to the surface water. Foul part 12 is provided with a connection 16 via which foul part 12 can be suctioned empty at a harbour. Clean water from the harbour flows here via connection 15b into clean part 13. It is also possible to connect connection 15b to a pump which pumps water from the harbour into clean part 13, whereby piston 11 moves to the left in the figure and foul part 12 can be emptied independently via connection 16.

Connection 15 can also be connected to the mains water supply so that foul part 12 is pressed empty using the mains water pressure.

Fig. 4 shows in more detail a possible embodiment of a cylindrical chamber 10 consisting of a plastic pipe 16 in which piston 11 is received and which is provided with two glued-on caps 17a, 17b. Piston 11 is manufactured from solid plastic and is provided with two sealing rings 18a, 18b and a pressure-relief valve 19. When foul part 12 is pressed empty via connection 15b, piston 11 will move to the left in figure until foul part 12 is completely empty. The pressure in clean part 13 then rises, wherein the pressure-relief valve opens and foul part 12 is flushed. Connections 14, 16 are combined via a T-piece 20, and connections 15a, 15b are likewise combined via a T-piece 21, whereby the forces acting on piston 11 will always be radially symmetrical, thereby preventing misalignment of piston 11 in pipe 16. In addition, it is recommended to give piston 11 a sufficiently thick form, wherein the thickness amounts for instance to half the diameter of pipe 16. Further mounted on piston 11 is a magnet 22 which slides into T-piece 21 when foul part 12 is almost full, wherein a contact 23 known in the field is closed, which activates an indicator light in a manner which is further self-evident.

Cylindrical chambers 10 can have a random length, pipes 16 can have a limited number of standard diameters for which caps 17a, 17b and pistons 11 are available, and they can be easily mounted in parallel, wherein connections 14, connections 16, connections 15a and connections 15b can be mutually connected in simple manner.

Fig.5 shows in more detail a possible embodiment of a piston 11 with sealing rings 18a, 18b, a pressure-relief valve 19 loaded with a draw spring 24 and a plastic rod 25 into which is glued a bar magnet 22 which can close contact 23. The moment at which this takes place can be selected in simple manner by choosing the length of rod 25.