The present invention relates to a device on a biological toilet, comprising a box having an upper opening which is surrounded by a seating ring, under which opening is provided a grid for catching excrement, the box comprising an air inlet, a fan, and an air outlet, and heating devices provided at the bottom of the box to promote the evaporation of collected fluid.

Intense development of biological toilets of this type has been going on for years. At the As Agricultural College a large number of experiments with and studies of such toilets have also been done. Several consumer investigations of such toilets have been made, the conclusion being relatively depressing in the case of most of the models. The degradation is poor, especially in the longer term, and the toilets often give off unpleasant odours.

A major problem about these biological toilets is apparently that getting rid of the surplus fluid is difficult. Every adult person produces on average 1.5 ltr of urine every 24 hours. If four people in a household use the biological toilet regularly, approx. 6 ltr of urine will be supplied each 24 hours. Some of this fluid is used to add the correct moisture to the excrement and paper which stay on the grid over the bottom of the box, however, most of the urine has to evaporate, otherwise the whole box will be filled with fluid quite quickly What then happens is that anaerobic degradation takes place. This is a significantly poorer degradation than aerobic degradation, and anaerobic degradation of material always involves unpleasant odour.

From Norwegian Patent no. 136.737, for instance, a biological toilet is known where an electric heating element is provided at the bottom of the box or container. The heating element principally consists of heating foil covering the whole of the

bottom area of the container. A supply of small amounts of energy only is accepted for heating and evaporation of the fluid in the container, the result being unsatisfactory evaporation of fluid. The reason is that too large amounts of fluid are heated with heating elements that are too small. In addition, fats etc. which stay floating on the surface of the fluid will significantly prevent evaporation. The air current which is conducted across the surface of the fluid also is too slow.

The present invention aims at giving directions for a biological toilet where the above disadvantages are avoided, so that sufficient evaporation of the surplus fluid at the bottom of the toilet may be achieved with small amounts of heat. According to the invention, this is achieved by there being provided on or near the bottom of the box a separate evaporation container or chute with an inlet for supplying fluid from the bottom section of the box, and by the heating device being provided in the ^" separate container.

In a preferred embodiment of the invention, a lid or cover is provided on the separate container. The container and lid are preferably thermally insulated.

In a further development of the invention, the lid is curved or arched, so that a channel is formed above the fluid for ventilation air. The channel is connected to the ventilation fan and air outlet of the toilet.

In yet another further development of the invention, transverse grooves or cams have been provided in the lid so as to produce turbulence in the ventilation air.

By means of the invention, a higher temperature is achieved in the fluid that is to evaporate, without the use of larger amounts of energy in the heating device. Turbulence and the high speed of the ventilation air above the fluid breaks up

the fluid surface, thus increasing the evaporation and preventing fats and other substances in the fluid from formin a film on the surface and thus inhibiting the evaporation. Experiments have shown that a far greater capacity for evaporation is achieved by means of the invention than with previous devices at the same level of power consumption.

The turbulence in the ventilation air is increased by means o the transverse rifles in the lid. Because of the curved or arched ceiling, the cross section of the air channel above th fluid level will decrease as the fluid level rises. Thus, the speed of the air will increase, and thereby the effect also, because of greater air speed and stronger turbulence. This breaks the surface of the fluid and prevents the fats in the fluid from inhibiting the evaporation.

The exhaust fan is directly connected to the separate evaporation container, .and the air inlet is placed inside the toilet container, so that all air leaving the toilet has to g through the evaporator.

In the following, the invention will be explained more closely with references to the drawing, which shows a preferred embodiment for the invention.

Figure 1 is a schematic representation of a cross section through a biological toilet provided with a device according to the invention,

figure 2 is a cross section through the biological toilet along the line II-II in figure 1, and

figure 3 is a cross section along the line III-III in figure 2.

The biological toilet consists of a container 1 which on the top has been provided with an opening 2 with a seating ring 3

and a lid 4. Inside the container, a grid 5 has been provided, on which excrement and paper will stay to be broken down. Urine which is supplied into the toilet container will to som extent be absorbed by the dry substance on the grid, but most of it will run down towards the bottom 7 of the container, where an accumulation of fluid 8 will occur. At the rear lowe corner a separate container 9 is provided, which apart from one or more smaller openings 10 is completely separated from the rest of the container 1. The separate container 9 extends mainly along the whole of the rear edge of the toilet container 1, and near one of its ends it is connected to an air inlet 11 which lets in air near the upper part of the toilet container. The other end of the separate container 9 i connected to the outlet 12 which is provided with a fan 13. The outlet 12 is normally conducted above the roof 14.

Fluid will run through the openings 10 into the separate container and a fluid level 15 will be formed, possibly 15a. At the bottom of the container 9 a heating element 16 has bee provided. The container 9 is insulated, and the same applies to the outlet 12 and optionally also to the inlet 11. The intention behind this is, of course, to economise on heat and prevent condensation from forming in the outlet and run back as fluid to the container 9.

Over the container 9 an insulated lid 17 has been provided, having on the inside transverse rifles 18. This lid is easily detachable for cleaning.

The openings 10 should preferably be placed near the end where the air inlet 11 is connected. If the inlet or inlets 1 are placed near the outlet 12, the fluid level in the container 9 may easily become lower than the level in the container 1 because of the powerful air current. If there are inlets at both ends, circulation may arise in the evaporator, leading to loss of effect.

The heating element 16 will efficiently evaporate what little volume of fluid is in the container 9, and the exhaust fan will provide a powerful air current over the fluid in the container. Even at very low speed, turbulence will occur in the air because of the transverse rifles in the lid 17, and this together with the great speed of the air will tear up th surface 15 and increase the evaporation, while preventing fat etc. from forming a film and thereby inhibiting the evaporation. By incresing the amount of fluid to the surface 15a, a larger surface for evaporation will be obtained.

As is especially apparent from figure 2, all air that is exhausted from the toilet will be conducted through the container 9 over the fluid surface 15 or 15a.

As the heating devices are thermally insulated against the inside of the box, it may be necessary to provide a separate source of heating inside the box so as to obtain optimal conditions for the degradation of the dry substance on the grid.