The present invention relates to a mobile vacuum stowage unit for temporary field applications such as field hospitals, summer camps, scout camps etc., or for emptying stations for collected sewage on small boats in marinas or vehicles where the vacuum unit needs to be moved indoor at winter time avoiding breakage due to low temperatures and frost.

Liquid ring screw pumps are now commonly used in vacuum sewage systems on board ships and on offshore installations. However, such systems are also increasingly being used on land due to reduced water requi remen t/ava liability , sewage disposal and easy handling and treatment of waste water, as well as its flexibility as regards installation of piping and layout given by such systems.

The applicant of the present application introduced in 1987, cf, EP patent No. 0 28? 350, for the first time the novel vacuum sewage system where the vacuum in the system was generated by means of a liquid ring screw pump of this Kind and where the pump is used as well to discharge the sewage from a vacuum tank or the like to which it is connected.

EP patent No. 0 454 794, also filed by the applicant, further shows a revolutionary improvement of a vacuum sewage system where the liquid ring screw pump is provided with a grinder or macerator and is connected directly with the suction pipe of the system, whereby vacuum is generated in the sewage suction pipe and sewage is discharged directly from the system by means of the pump. Liquid ring screw pumps of the above-mentioned type commonly comprise a housing with a suction inlet part at one end and a pressure outlet part at the other end and within the housing rotatable provided Archimedes screw {screw rotor) which is driven preferably by an electric motor via a shaft. In the known prior art pump and motor, as for instance shown in the above EP patent No, 0 464 794, the rotor is commonly provided at or close to the centre axis of the pump housing,

It is commonly known to use the liquid ring pump in two different modes; a continuous mode where the pump is more or less continuously running to keep the vacuum at a set level, approximately 50% vacuum (continuous vacuum systems - CVS), and systems where the pump and started and stopped when flushing Is needed (vacuum on demand - VOD). CVS mode is commonly used in systems with more than two toilets/urwais, while VOD mode is more normally used In cabins/houses and smaller mobile systems with one or two toilets,

Further is well known to use integrated vacuum solutions based on liquid ring screw pumps in moveable or mobile cabins/trailers, small boats and house trailers. Such applications are usually based on VOD solutions.

With the present invention is provided a mobile vacuum sewage unit which can be connected to an arrangement of vacuum toilets, urinals and/or greywater sinks for instance in a field hospital, a summer camp, scout camp or an application for emptying sewage tanks on small boats or vehicles as mentioned above. The unit according to the present invention is simple and cheap, small, lightweight, reliable and simple to use and operate, It Is novel in its kind In the market.

The invention is characterized by the features as defined In the attached independent claim 1.

Advantageous embodiments of the invention are further defined in the attached dependent claims 2 - 8.

The Invention will be further described in the following by way of examples and with reference to the drawings where:

Fig, 1 shows in perspective view a vacuum sewage field unit according to the invention.

Fig. 2 shows in perspective view an assembly of all components as such of the unit shown in Fig. 1.

Fig. 3 shows a longitudinal vertical view of the unit shown in Fig, 1

Fig. 4 shows a left transversal vertical view of the unit as shown in Fig. 1

Fig. 5 shows the same unit as shown in Fig, 1 in perspective, but including an outer cladding.

Fig. 1 shows in perspective view, as stated above, a mobile vacuum sewage field unit according to the invention. The components of the unit, which will be further described below, are provided on a pallet 1 (see Fig. 3) such as Euro pallet and within a frame construction 4 including a top cover 16, The pallet 1 and frame construction 4 may preferably be made of aluminium to reduce! weight The frame with its water tight top cover 16 is a part of the frame structure holding the unit together. Furthermore, the unit's frame is designed such that it does not have to toe placed on a Euro pallet for transportation, even though the example as shown in the figured includes a Euro pallet.

Fig. 2 shows in perspective view an arrangement of the components of the vacuum sewage unit as such, as shown in Fig. 1 , The components are shown in this view to ease the understanding of the invention and enable the reader more easily to seeing each respective component of the inventive solution. However, to further ease the understanding of the invention, reference is also made to Figs. 2 - 3 when describing the invention in the following: The "heart" of the vacuum unit is the vacuum pump 7 provided with a grinder as explained above. The present unit as shown in the figures is provided with two such vacuum pumps 7, The pumps are controlled by a VTS or PLC controller 9 and are programmed to be run singularly, in parallel or in series, depending on the required vacuum demand, i.e. the use of the toilets, urinals and/or greywater sinks. Even though the example shown in the figures depicts and describe two pumps, the unit according to the invention may be provided with one or more pumps, whatever capacity is needed, In addition to the pumps, the vacuum unit is equipped with an accumulating tank 6, which Is functioning both as a manifold to distribute the sewage to the pumps and as a vacuum reservoir to obtain sufficient vacuum accumulation in the system and thereby ensuring proper operation of the vacuum unit at ail operating situations. Multiple inlets of such tank/manifold 6 gives baiance to the system ensuring that more than 50% of the accumulated vacuum is available and is "pulling" towards the pumps for each discharge of an interface (including extreme flushing situation where the majority of the toilets and urinals of the system to which the unit is connected are flushed simultaneously). The unit is provided with an inlet piping arrangement 14 connected to the tank and including at least one inlet connection 8 to be connected to the field sewage system (not shown). The inlet of the pump Is connected to the tank 6 via a piping arrangement 10. Further, the outlet of the pump is provided with an outlet piping arrangement 12 with an outlet connection 15 that can be connected to an external sewage storage tank or a local sewage system if such exists in the area where the inventive vacuum sewage field unit is used.

The vacuum sewage field unit works as described in the following, As explained above, the field unit may be used for different applications such as field hospitals or small boat marinas for the emptying of sewage form small boat sewage storage tanks. For instance, when used in connection with a field hospital, a main sewage drainage collector pipe {not shown) will be provided to transport sewage form the different toilets, urinals and/or greywater sinks (in some cases the greywater may be treated separately by filtration etc.) The collector pipe from the hospital is connected to the vacuum drainage unit with the connection 8 on the unit. The pumps 7 being provided beforehand with sufficient water to enable proper working of the pumps, is then started and vacuum builds up in the system, Whenever a toilet or urinal is flushed in the field hospital a slug of sewage will be generated and together with air arrive in the tank/manifold 6. The tank/manifold 6 is designed such that there is no backflow of sewage once it has entered into the tank. From the tank the sewage is passed through the piping 10 and arrives at the pump 7 which at the time is running. Sewage then passes through the pump and is further conveyed to an external tank {not shown) or local sewage drainage system (neither not shown) if such is available. As to the running of the pumps, the controller 9 is preferably programmed to initially only run one pump, if necessary up to full speed, to obtain the required set vacuum level, approximately 50% vacuum, if further capacity is needed by increased flushing of the toilets/urinals, then the second pump is started and is incorporated in the vacuum generation and pumping process. By such smart running of the pumps, energy is saved as the pumping capacity is increased on demand. Even though this smart running is a preferred embodiment of the invention, the pumps may for instance be run in parallel and be operated on an on/off basis where the pumps are started and stopped based on set vacuum levels, for instance between 45 - 50% vacuum respectively.

The unit as shown in the drawings is preferably also provided with a freshwater pump 5 and freshwater distribution pipe connections 13 to ensure proper water pressure given to water taps, toilets or other applications connected to the system. This may be a preferred option in field applications such a* camps and hospitals.

As stated above, the components of the unit may preferably be provided within a frame construction 4. In Fig 5 ia shown an embodiment where the unit is provided with side wall covers or panels 2, 3 to shelter the components from rain and enow. In this preferred embodiment the panels are made of coloured Plexig!as.