The subject of the invention relates to a wastewater lifting pump with improved features, which contains a sump with a reception space, an input part-unit serving to feed the wastewater into the sump and an output part-unit serving to discharge the wastewater from the sump, where the output part-unit has a pump unit located in the reception space of the sump and a transmission duct connected to it also, at least partly, located in the reception space of the sump, the pump unit has a housing with a wall delimiting the medium transmission space and an impeller located in the medium transmission space in such a way so that it may rotate, the wall of the housing has an input opening and output opening connected to the medium transmission space, and the transmission duct is connected to the output opening of the housing.

In recent times wastewater lifting sumps with pump units fitted are being increasingly used for the transmission of industrial, but especially communal wastewater. The essence of these is that the wastewater coming from the wastewater emission is transported through a pipe of wide diameter to a small sized temporary storage space. The sump contains a lifting pump, which is switched on or off depending on the amount of wastewater entering the sump. When the level of wastewater reaches a given height, then the pump is switched on, and the wastewater in the sump is discharged from the sump through the transmission duct connected to the pressure side of the pump towards the main sewage system network. Such a solution may be seen in utility model specification HU 1.154, among others.

However, several problems make the transmission of the lumpy wastewater from the reception space of the sump to the transmission duct difficult. A solution appearing in patent specification registration number HU 215.012 was created to reduce the unreliability of transmission, in which a mixing blade ensuring the continuous movement of the wastewater was fixed to the impeller of the pump unit. This construction undoubtedly prevents the compaction of the wastewater in the sump, and

excludes the possibility of the pump impeller being unable to move the medium due to it being stuck in the dense wastewater.

A phenomenon frequently occurring in the lifting sumps of pressurised wastewater systems is that due to the pressure and velocity conditions prevailing in the street ^' collector ducts, the pressure established in the part of the transmission duct outside of the sump sucks the wastewater out of the transmission duct and, through this, from the sump as well. At this time the wastewater disappears for a short time from around the impeller of the pump unit, that is the base of the sump, and it is replaced by air. When, after this, a new amount of wastewater arrives in the sump, while the level is rising the wastewater traps the air in the medium transmission space around the pump impeller, which then forms an air blockage there. When the pump is switched on the impeller only comes into contact with this air block, and so "runs dry" and is unable to pump the wastewater through the output opening of the medium transmission space into the transmission duct. On the one hand, the phenomenon has a damaging effect on the lifespan of the pump unit. On the other hand, the amount of energy consumed is significantly increased without the energy consumption involving the actual transportation of wastewater. A general and significant disadvantage of the known constructions is that they are not suitable for overcoming this damaging phenomenon.

Our aim with the invention was to overcome this deficiency of the wastewater lifting pumps in use and to create a solution that would stop the dry running of the impeller of the pump unit, and so reduce unnecessary use of energy and, furthermore, increase the lifespan of the pump unit.

The recognition that led to the construction according to the invention was that due to the increase in the level of wastewater in the sump - according to the basic principles of physics - gradually increasing pressure is formed in the base of the sump. Therefore, in the section of route serving for the transportation of the wastewater where the air block has been formed the pressure on the air block also increases. If, then, at the location of the formation of the air block, blow-off gaps are created in suitably selected places in

the wall of the housing of the pump unit, or even blow-off openings in a practical section of the shell of the transmission duct, which we either leave open or fit with an air bleed valve, then the increasing pressure around the impeller and in the route serving for the transmission of the wastewater will have an effect on the air block and force the trapped air out through the blow-off gaps and blow-off openings, or through the air bleed valves fitted into these, as a consequence of which the air block will be terminated, and again the wastewater to be transported will again be able to flow into the empty medium transmission space, which, after this, the pump unit will again be able to properly transport into the transmission duct, and so the task can be solved.

In accordance with the set aim the wastewater lifting pump with improved features, - which contains a sump with a reception space, an input part-unit serving to feed the wastewater into the sump and an output part-unit serving to discharge the wastewater from the sump, where the output part-unit has a pump unit located in the reception space of the sump and a transmission duct connected to it also, at least partly, located in the reception space of the sump, the pump unit has a housing with a wall delimiting the medium transmission space and an impeller located in the medium transmission space in such a way so that it may rotate, the wall of the housing has an input opening and output opening connected to the medium transmission space, and the transmission duct is connected to the output opening of the housing, - is set up in such a way that in the operating condition of the pump unit in the part of the wall of the housing above the base plane of the impeller one or more blow-off gaps are formed linking the medium transmission space with the external environment, practically with the reception space of the sump, and/or in the shell of the transmission duct one or more blow-off openings are formed between its internal space and the external environment, practically with the reception space of the sump.

A further feature of the wastewater lifting pump according to the invention may be that at least one of the blow-off gaps in the wall of the pump unit housing is located in the part of the wall above the upper plane of the impeller.

In a possible version of the wastewater lifting pump the blow-off gap located in the housing wall is a bore hole with a diameter of at least 0.5 mm. And the blow-off gap located in the wall of the housing of the pump unit may have a monotonically increasing cross-section increasing from the medium transmission space of the housing towards the reception space of the sump.

From the point of view of the wastewater lifting pump it may be favourable if at least one of the blow-off gaps in the wall of the pump unit housing is a cleft starting from the input opening of the wall of the housing and extending to above the upper plane of the impeller.

In a still further different embodiment of the invention the transmission duct is supplemented with a flow-direction restriction part-unit, and the one or more blow-off openings belonging to the transmission duct are located in the section of the shell of the transmission duct between the output opening of the pump unit and the flow-direction restriction part-unit. The flow-direction restriction part-unit is a non-return valve.

In a still further different embodiment of the wastewater lifting pump the blow-off opening located in the shell of the transmission duct is a bore hole with a diameter of at least 0.5 mm. And the blow-off opening located in the shell of the transmission duct may have a monotonically increasing cross-section increasing from the internal space of the transmission duct towards the reception space of the sump.

In a further embodiment of the invention an air bleed valve is fitted in at least some of the blow-off gaps and/or blow-off openings.

The most important advantage of the wastewater lifting pump according to the invention is that due to the uniquely arranged blow-off gaps and blow-off openings the dry running of the pump impeller can be stopped, which reduces the energy consumption of the wastewater lifting pump a great deal and also increases the lifespan of the pump.

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Another advantage that can be listed is that in the case of wastewater lifting pumps that have already been installed the blow-off gaps and blow-off openings according to the invention can be created in the pumps and transmission ducts using simple equipment and a small amount of physical work. As a consequence of this not only newly installed wastewater drainage networks can be operated with favourable energy characteristics, but systems built in the past with unfavourable energy usage features can be transformed, which on the overall economic level may result in significant energy savings.

In the case of known wastewater lifting pumps, due to faulty pump operation the smell of the wastewater spreads in the given area, which causes a great deal of damage to the feeling of comfort of the people living in the district. This circumstance has an unfavourable effect on the performance ability of people and on their health. From the point of view of the construction according to the invention it is also advantageous that due to the fault-free operation of the new wastewater lifting pumps such burdens on the environment can be reduced or even terminated, which then has a favourable effect on the living circumstances of people, and through this on their abilities, and on the protection of health.

Also another advantage to be listed is that the blow-off gaps and blow-off openings can be made using simple equipment and traditional manufacturing technology step, and so with a minimal increase in cost a significantly more effective method of wastewater transportation can be realised, which, taking into consideration the sum total of investment, operation and maintenance costs, results in significantly lower specific costs than was usual in the case of the traditions solutions.

In the following the wastewater lifting pump is presented in more detail, on the basis of drawings. On the drawings

figure 1 shows a possible version of the wastewater lifting pump according to the invention in side view, in partial cross-section,

figure 2 shows a favourable realisation of the pump unit of the wastewater lifting pump, figure 3 shows another version of the pump unit of the wastewater lifting pump figure 4 shows a detail of the transmission duct in the vicinity of the blow-off opening in longitudinal cross-section.

Figure 1 shows a version of the wastewater lifting pump according to the invention in which the sump 10, according to the usual construction, consists of a circular base 12, a circular top 13 and a mantle 11 in the form of a truncated cone widening downwards. The mantle 11, the base 12 and the top 13 enclose the reception area 14, in which the input part-unit 20 and the output part-unit 30 are located. The input part-unit 20 includes a feed pipe-end 21 and an inlet pipe 22, of which the inlet pipe 22 creates the connection between the wastewater source and the sump 10. There is an input opening 15 formed in the mantle 11 of the sump 10 to admit the feed pipe-end 21 of the input part-unit 20. Also found in the mantle 11 of the sump 10 there is an outlet opening, through which the extension of the transmission pipe 31 of the output part-unit 30 leaves the reception space 14 of the sump 10.

Apart from the transmission pipe 31 the output part-unit 30 also includes the pump unit 32. And in the case of the present embodiment the flow-direction restriction part- unit 40 is fitted into the transmission pipe 31, which is a normally constructed nonreturn valve. The task of the flow-direction restriction part-unit 40 is to prevent the wastewater that has passed through the sump 10 to the transmission pipe from flowing backwards.

Figure 1 shows well that the pump unit 32 has a housing 33, the wall 34 of which surrounds the medium transmission space 35. The impeller 36 is found in this medium transmission space 35, which is fixed to an axle 37. The axle 37 - in a way known in itself- is fitted to the housing 33 of the pump unit 32 in a way so that it may rotate, and it is linked to a motor located in the housing 33. The wall 34 has an input opening 34a - several in the case of the present version - connecting the reception area 14 of the sump

10 with the medium transmission space 35, and furthermore, has an output opening 34b connecting the medium transmission space 35 with the internal space 31b of the transmission pipe 31 enclosed by its shell 31a.

Also belonging to the pump unit 32 is the level regulation control part-unit 50, the ^' task of which is to switch on or switch off the operation of the pump unit 32 depending on the level of the wastewater in the reception area 14 of the sump 10.

On figure 1 it can be seen that - differing from the usual construction - there is a blow-off gap 34c formed in the part of the wall 34 of the housing 33 of the pump unit 32 of the output part-unit 30 above the upper plane 36b of the impeller, furthermore, there is a blow-off opening 31c formed in the part of the shell 31 a of the transmission pipe 31 between the upper plane 36b of the impeller 36 and the flow-direction restriction part- unit 40.

In this case the blow-off gap 34c is a small, 1 mm in diameter, conical bore hole, the cross-section of which monotonically increases from the direction of the medium transmission space 35 of the pump unit 32 towards the reception space 14 of the sump 10, while the blow-off opening 31c is a cylindrical bore hole 1 mm in diameter. This version of the blow-off gap 34c can be formed by drilling, punching or even casting, while the blow-off opening 31c can be made by drilling or punching. The advantage of drilling and punching is that using this technology the blow-off opening 31c and the blow-off gap 34c can be made subsequently in the given component.

Figure 2 shows a version of the pump unit 32 in the wall of which 34, starting from the input opening 34a and extending over the base plane 36a of the impeller 36 the thin, cleft-like blow-off gap 34c can be found. Such a blow-off gap 34c can be formed by sawing or casting in the wall of the pump unit.

Figure 3 shows a detail of a pump unit where there is an air bleed valve 38 fitted in the blow-off gap 34c of the wall 34. It is practical to fit an air bleed valve 38 into the blow-off gap 34c in such cases when due to the composition of the transported

wastewater it is better to leave a larger air flow opening, but it is important that the releasing of any air blocks formed is carried out when certain pressure conditions are reached.

Figure 4 shows the section of the transmission pipe 31 in the vicinity of the blow-off opening 3 Ic, in which blow-off opening 31c there is also an air bleed valve 38 fitted.

Here we must mention that the number of blow-off openings 31c and blow-off gaps 34c, their size and position is always dependent on the physical characteristics of the transported wastewater, the operation parameters of the pump unit 32 and its geometric dimensions, as well as on the method of connecting the pup unit 32 to the transmission pipe 31, so these may differ in different cases. In every case, however, it is important for there to be at least one blow-off gap 34c or blow-off opening 31c in the output part-unit in order to avoid the formation of air blocks.

During the operation of the wastewater lifting pump according to the invention, wastewater flowing in through the feed pipe-end 21 of the input part-unit 20 in the reception space 14 of a normally constructed sump 10 that has an output part-unit 30 with one or more blow-off gaps 34c and/or blow-off openings 31c, covers the base 12 of the sump 10 and starts to rise in the reception space 14. When the level of the wastewater reaches and exceeds the upper edge of the input openings 34a formed in the wall 34 of the pump unit 32, then the air in the area of the medium transmission space 35 of the wall 34 in the vicinity of the impeller 36 gets stuck. The hydrostatic pressure deriving from the height of the wastewater continuing to rise in the reception space 14 of the sump 10 attacks the lower part of the air block stuck in the medium transmission space 35 with a continuously increasing force. When this force reaches a limit value, then the air in the air block leaves the medium transmission space 35 or the section of the internal space 31b of the transmission pipe 31 that forms the continuation of the medium transmission space 35 through the blow-off gap 34c, or through the air bleed valve 38 fitted in it, or through the blow-off opening 31c, or through the air bleed valve 38 fitted in it, and so the wastewater is able to flow into the part of the medium

transmission space 35 of the wall 34 surrounding the impeller 36. And when the wastewater itself surrounds the impeller 36 of the pump unit 32, then it is able to transport wastewater. So the adjustment of the level regulation control part-unit 50 is to be carried out so that the height of the level of the wastewater reaches the value needed to cause blow-off before the level regulation control part-unit 50 switches on the pump unit 32.

The wastewater lifting pump according to the invention can be used well in all areas where due to the pressure difference between the collection pipe and the sump, it may happen that the wastewater is essentially completely drained from the reception space of the sump and a s a consequence of this the impeller may run dry.

List of references

sump 11 mantle

12 base

13 top

14 reception space

15 input opening

16 output opening

input part-unit 21 feed pipe-end

22 inlet pipe

output part-unit 31 transmission pipe 31a shell

31b internal space 31c blow-off opening

32 pump unit

33 housing

34 wall

34a input opening 34b output opening 34c blow-off gap

35 medium transmission space

36 impeller 36a base plane 36b upper plane

37 axle

38 air bleed valve flow direction restriction part-unit level regulation control part-unit