EP3779201B1 - Scraper element for the leading edges of impellers of waste water pumps - Google Patents

Description

The invention relates to a sewage pump with a volute housing with an inlet opening and an impeller with at least one blade, the leading edge associated with the respective blade running outwards from the impeller hub and curved backwards.

Wastewater can contain different types of solids such as fibrous matter, the amount and structure of which can depend on the wastewater source as well as the time of year. For example, plastics, hygiene items, textiles, etc. are common in cities, while wear and tear particles may be present in industrial areas. Experience has shown that the biggest problems with sewage pumps are caused by fibrous materials such as rags, cloths and the like, which can get stuck on the leading edges of the blades and wrap around the impeller hub. Such incidents result in frequent service intervals and reduced pump efficiency.

There are already various approaches that use cutting tools or scraping tools in order to be able to remove the pollutants that have settled on the inlet edges during pump operation.

The U.S. 2009/123270 A1 discloses a sewage pump for pumping solids-laden sewage with a finger for scraping dirt.

The aim of the present invention is to improve existing solutions.

This object is achieved by a sewage pump according to the features of claim 1. Advantageous designs of the sewage pump are the subject matter of the dependent claims.

The starting point for the invention is a sewage pump for pumping sewage containing solids. The sewage pump consists of an impeller with at least one backward-curved impeller blade. The impeller is non-rotatably connected to a rotating shaft and sits in a volute-shaped pump casing with an inlet port. The inlet port may be axially aligned and/or cylindrical. The leading edge of the at least one impeller blade extends radially outwards from the impeller hub with the aforementioned backward-curved blade shape. A finger is firmly connected to the pump housing on the inner wall of the inlet opening. In the area of the transition from the finger to the inner wall of the inlet opening, there is a groove which is formed in the suction-side side wall of the pump housing and runs outwards in the radial and tangential direction in the pump housing wall.

The finger extends radially inward from the inlet inner wall toward the axis of rotation of the impeller. An upper finger surface facing the leading edge runs at a defined distance from the leading edge and essentially parallel to the leading edge, so that the upper finger surface facing the leading edge or the lateral contact surface of the finger results in the desired wiping effect. The interaction of the backward curved leading edge and fingers favors the removal of solids stuck on the impeller leading edge. With the help of the finger, the deposited solids are fed into the groove and conveyed by the rotational movement of the impeller, so that they reach the area of the casing pressure nozzle directly via the groove. The impeller and the finger are specially matched to each other for this task.

According to the invention it is provided that the impeller leading edge is set at an angle α of 5° to 75° to the vertical projection surface of the axis of rotation of the impeller is. This means that, in addition to the rotational movement and the resulting radial force, an axial component also has an effect on the solids when scraping off the solids. This optimizes the removal of the scraped solids through the groove. The angle α can preferably lie in a value range between 10° and 45°.

The upper finger surface of the finger can also be inclined by the angle α with respect to the vertical projection surface to almost the same extent. However, the upper finger surface and the leading edge do not necessarily have to run exactly parallel, so that deviating angles α to the projection surface are also conceivable here. In particular, it can be provided that the upper finger surface is not planar but curved instead, so that a varying angle a for the finger surface and consequently also a varying distance between the leading edge and the upper finger surface can result. The upper finger surface can preferably provide a curvature both in the radial and in the tangential direction. Ideally, the upper finger surface has a cone-like curvature in the radial and tangential direction.

The sewage pump can be operated both dry and submerged in the pumping medium in any orientation. The volute casing of the pump has a spur and a pressure port. Furthermore, in the area of the inlet opening, the pump housing can have a separate housing insert, such as a suction cover or a wear wall, into which the aforementioned groove can be introduced or the finger can be attached to it.

During pump operation, the leading edge of the at least one blade moves past the upper finger surface at an angle β to the lateral contact surface of the finger. Ideally, this angle β should be around 90° in order to achieve an optimal scraping effect. In order to reduce the risk of solids becoming trapped between the impeller leading edge and the finger, the angle β should increase outwards in the radial direction. This means that as the radius increases (starting from the impeller hub), the angle β should also increase. According to the invention here angular values in the radial direction at r/r _suction =0.2, ie in the area near the impeller hub, between 50° and 120° and at r/r _suction =1 between 85° and 160° are provided. The radius r _suction corresponds to the radius of the cylindrical inlet opening of the housing. The angle between the aforementioned support points can vary essentially uniformly, ideally the angle between the support points should increase steadily.

It is particularly advantageous if the upper finger surface of the finger is at a distance of 0.05 to 3 mm from the leading edge of the blade, at least in some areas. This ensures optimal scraping of the solids from the impeller inlet edge. If the distance is too large, there is a risk that small solids and fibers will not be caught by the scraper finger.

It makes sense for the lateral contact surface of the finger or a tangent to the contact surface to have a (tangential) angle δ in relation to the tangential course of the groove with a value between 120° and 180°, preferably between 140° and 180° and particularly preferably a value between 160 ° and 180°. The rule here is that as the angle δ increases, the discharge of the scraped-off solids into the groove is made easier. An angle δ of 180° would be ideal.

In order to influence the flow in the impeller inlet as little as possible, the finger should have a streamlined shape. Good properties are achieved when the finger is designed as a three-sided pyramid with curved side surfaces. To ensure a sufficient scraping function and, if necessary, to achieve an optional cutting effect, it is advantageous if the front surface, ie the contact surface of the finger, is set at an angle γ of 0° to 30° relative to a parallel to the axis of rotation of the impeller. The posterior surface of the finger is less critical and may also be more inclined to the parallel where appropriate. Here an angle ε of the back surface of the finger to the parallel of the axis of rotation of the impeller between 0° and 50° is recommended.

Due to the curved side surfaces of the finger in connection with the aforementioned defined angular ranges, it is very difficult for solids to settle on the surface of the finger. Ideally, the rear surface is double-curved, in particular double-curved in different directions. This also reduces the flow-influencing area of the finger.

The orientation and specific placement of the finger within the inlet is critical to the effectiveness of the wiping action. In this context, the relative position of the finger to the spur of the volute casing and consequently to the discharge nozzle is relevant. It is advantageous if the finger is arranged in the vicinity of the spur, preferably after the spur in the direction of rotation. Such an arrangement has a further advantage, particularly in the case of horizontal pumps. Solid objects, such as stones, may collect in the lower part of the pump casing or impeller. By arranging the finger 30 in the vicinity of the spur, it is positioned outside of this danger point.

The exact position of the finger can be determined, for example, by the angle ϕ. The angle ϕ corresponds to the angle of wrap, which is defined by the angle of intersection between the perpendicular and a tangent of the contact surface of the finger that intersects the axis of rotation of the impeller, with the tangent preferably running through the point on the contact surface that is furthest away from the axis of rotation in the radial direction. Possible angular values of the angle φ are 0° to 45°, preferably between 15° and 35° and ideally between 20° and 30°.

In a further advantageous embodiment of the sewage pump, the selected finger length corresponds to at least 30% of the total radius r _suck of the cylindrical inlet opening, preferably at least 50% and ideally between 70% and 80%.

Optionally, it can also be provided that the finger provides at least one section designed as a cutting edge, in particular on the side of the front contact surface of the finger, but the cutting edge extends perpendicularly to the stripping edge, ie parallel to the axis of rotation. The cutting edge is preferably provided in the transition area of the finger to the fastening element of the finger.

Figur 1:

eine perspektivische Ansicht der erfindungsgemäßen Abwasserpumpe mit geöffnetem Pumpengehäuse,

Figur 2:

ein Vertikalschnitt durch die erfindungsgemäße Abwasserpumpe,

Figur 3a,3b:

eine Detailansicht des Gehäuseeinsatzes mit Abstreiffinger für die erfindungsgemäße Abwasserpumpe

Figur 4:

eine Detailansicht des Laufrades der erfindungsgemäßen Abwasserpumpe,

Figur 5a bis 5d:

Detailansichten des Abtreiffingers der erfindungsgemäßen Abwasserpumpe

Figur 6:

eine saugseitige Ansicht auf den Gehäuseeinsatz der erfindungsgemäßen Abwasserpumpe mit eingesetztem Laufrad

Figur 7a, 7b:

Schnittansichten entlang der Drehachse R durch den Gehäuseeinsatz samt Laufrad gemäß Figur 6

Figur 8:

eine Detailansicht des Abstreiffingers nebst Nut gemäß der Figur 6 und

Figur 9:

eine Diagrammdarstellung des normalisierten Radius (r-r_saug) gegenüber dem Winkel β.

Further advantages and properties of the invention result from the embodiment shown in the figures. Show it:

Figure 1:

a perspective view of the sewage pump according to the invention with the pump housing open,

Figure 2:

a vertical section through the sewage pump according to the invention,

Figure 3a, 3b:

a detailed view of the housing insert with scraper fingers for the sewage pump according to the invention

Figure 4:

a detailed view of the impeller of the sewage pump according to the invention,

Figure 5a to 5d:

Detailed views of the Abtreiffingers sewage pump according to the invention

Figure 6:

a suction-side view of the housing insert of the sewage pump according to the invention with the impeller used

Figure 7a, 7b:

Sectional views along the axis of rotation R through the housing insert including impeller according to figure 6

Figure 8:

a detailed view of the stripper finger along with the groove according to FIG figure 6 and

Figure 9:

a plot of normalized radius (rr _saug ) versus angle β.

figure 1 shows an exploded view of the sewage pump 1 according to the invention. The impeller 20, in detail figure 4 can be seen, comprises two backward-curved blades 21a, 21b, through which the pumped medium is sucked in through the cylindrical inlet opening 15 of the wear wall 12 and conveyed through the pumping chamber 16 of the volute casing 10 to the discharge port 13 and discharged through this.

The waste water to be pumped can contain a large number of different solids, for example fibrous materials, which can become lodged on certain parts of the pump during pump operation. For this reason, the stripper finger 30 according to the invention is provided, which is attached to the cylindrical inner wall of the inlet 15 and extends in the direction of the axis of rotation R. Although the embodiment shown in the figures has a separate wear wall 12, the wear wall 12 could just as easily be dispensed with for the implementation of the invention and the finger 30 could be attached directly to the housing wall in the area of the suction mouth. The design and mode of operation of the finger 30 will be discussed in more detail later, first the construction of the impeller 20 will be described.

Characteristic of the impeller 20 is the course of the in 4 shown leading edges 23 of the blades 21a, 21b. These begin directly at the impeller hub 22, in particular at the height of the upper, free end of the hub, and extend radially outwards, curved backwards. The front faces of the blades 21a, 21b which are directed towards the suction cover and which extend through the inlet 15 are referred to as the leading edges 23.

These leading edges 23 are also aligned at a defined angle α to the vertical projection surface of the axis of rotation R. To clarify the selected angle is on the Figures 7a, 7b referenced, which show a sectional view through the impeller 20 and the corresponding wear plate 12. The angle α is drawn in here the leading edge 23 of the impeller 20 with respect to the horizontal, which corresponds to a perpendicular projection to the axis of rotation R in the selected form of representation. The selected inclination makes it possible to apply an additional axial force component to the conveyed medium in addition to the radial force, which optimizes the release of solids contained therein, which were grasped and scraped off by the finger 30 . They are discharged via a spiral groove 11 specially provided for this purpose within the wear wall 12 on the suction side. Ideally, the angle α should be in the range between 5° and 75° or 10° to 45°. In the embodiment shown here, an angle of inclination α of about 25° is assumed (see Fig. Figure 7a, 7b ).

In order to optimize the wiping action of the finger 30, its shape and position within the inlet 15 must be adapted to the specific impeller and casing design. The scraper finger 30 is mounted on the inner wall of the inlet 15 of the wear plate and extends in the direction of the axis of rotation R. The length of the scraper finger 30 should be at least 30%, preferably at least 50% or at best about 70% to 80% of the radius of the cylindrical Be inlet 15, which is hereinafter referred to as r _suction .

In order to influence the flow in the inlet 15 to the impeller 20 as little as possible by the scraper finger 30, the finger 30 is shaped like a pyramid with a total of three side surfaces 33, 35a, 35b and the base surface lying against the inner wall of the inlet 15. The upper finger surface 33 facing the leading edges 23 of the impeller 20 is not planar but has a continuous curvature, both in the longitudinal direction of the finger (radial direction KR see Figure 5b ) as well as in the transverse direction (tangential direction KT see figure 8 ). In total, a kind of conical surface 33 results here.

The other side surfaces, ie the side contact surface 35a and the rear side surface 35b, also have corresponding curvatures, with the rear side surface 35b even providing a double curvature in different directions. Compare this in particular Figure 5c . To fulfill the function of scraping off solids and cutting fibers, the front contact surface 35a of the Fingers 30 inclined at an angle γ of 0 ° to 30 ° to the axis of rotation R. In the 8 the angle γ to a parallel P1 of the axis of rotation R is drawn. The rear surface 35b of the finger 30 is less critical and can be inclined at an angle ε relative to the axis of rotation R or the parallel P2 to the axis of rotation R of 0° from 50°. Furthermore, the surface 35c can be rounded tangentially to the adjacent surfaces 35a, 35b. It is very difficult for solids to settle on the finger 30 when this angle definition is taken into account.

During the rotation of the impeller 20 about the axis of rotation R in direction 2, the leading edges 23 of the impeller 20 run towards the lateral contact surface 35a and then move past the opposite finger surface 33. The transition edge between the lateral contact surface 35a and the upper surface 33 forms the so-called scraping edge, through which solids deposited on the inlet edges are scraped off and, due to the radial and axial speed of the pumped medium, are discharged into the spiral groove 11, via which they ultimately pass the impeller 20 be ejected through the pumping chamber 16 to the pressure port 13.

The distance between the leading edge 23 and the surface 33 or the scraping edge of the scraper finger 30 should be in a range between 0.05 and 3 mm, whereby this distance can vary in the radial direction, but should remain within the aforementioned value interval if possible. If the distance is too large, there is a risk that small solids cannot be caught by the scraper finger 30, whereas if the distance is too small, the risk of the scraper finger 30 and the leading edge 23 rubbing against each other increases.

Since, as explained above, the leading edge 23 of the impeller 20 is inclined at an angle α to the vertical projection surface of the axis of rotation R, the finger 30 or the upper surface 33 or at least the scraper edge should also have a corresponding inclination by the angle α. This can also be seen in Figure 7b . However, the angles of inclination of the leading edge 23 and surface 33 do not necessarily have to be exactly identical but can also show minor differences. Despite these angle differences, however, the previously defined distance value should be within the desired value range.

The relative position of the scraper finger 30 to the spur 17 of the volute 10 also influences the delivery of the scraped solids to the pressure port 13. In particular with a horizontally installed pump, it is advantageous if the scraper finger 30, as in the sectional view of the 2 shown in the direction of rotation 2, ie in the representation of 2 clockwise, immediately behind the spur 17. Solid objects, such as stones, may collect in the lower part of the pump casing or impeller. By arranging the scraper finger 30 in the vicinity of the spur, the spur is positioned outside of this danger point.

The relative position of the stripper finger 30 to the spur 17 can be determined by the in 2 define the drawn angle ϕ. The angle φ corresponds to the angle of wrap, which is defined by the angle of intersection between the perpendicular and the straight line G1. The straight line G1 is perpendicular to the axis of rotation R and runs through the point on the lateral contact surface 35a of the stripper finger 30 that is furthest from the axis of rotation R in the radial direction. Recommended values for the angle ϕ are in the range between 0° and 45°, with an angle of 20° to 30° has turned out to be particularly advantageous.

The leading edge 23 of the vanes 21a, 21b moves past the top surface 33 during pump operation. The tangent at the deepest point of the upper surface 33 (point of the smallest distance to the leading edge 23) forms the angle β with the tangent of the leading edge. For the finger 30 to function optimally, the angle β should be approximately 90°. However, in order to reduce the jamming of the fibers between the impeller leading edge 23 and the finger 30, the angle β can also increase with an increasing radius r starting from the impeller hub 22. This means that as the radius r increases, the angle β also increases. For ease of illustration, the normalized radius (r - r _suction ), where r _suction represents the radius of the inlet 15, which is shown in FIG figure 9 shown course can be accepted.

In this figure it can be seen that the angle β can be between 50° and 120° near the center of the impeller 20 and between 85° and 160° at the outer edge. The course of the angle can be freely selected within this range, but optimally a continuously increasing angle β should be selected.

In order to further optimize the wiping effect, the lateral contact surface 35a of the finger 30 should also assume an angle δ of between 180° and 120° in relation to the tangential course of the groove 11 . This angle δ is in figure 3 and has a value of about 165° there.

Optionally, the finger 30 can be designed with a cutting edge 32 that extends perpendicularly to the surface 33 of the finger in the area of the transition to the fastening element 31 . As a result, the cutting edge runs almost parallel to the axis of rotation R. The stripper finger 30 can be detachably connected to the wear wall 12 or the housing 10 by means of the fastening element 31, whereby care must be taken here that the fastening element 31 does not protrude into the inlet 15 in order to to avoid any influence on the flow properties within the pump.

The 9 shows the angle β between the running leading edge 23 of the running wheel 20 and the finger 30.

Claims (10)

1. Wastewater pump (1) for conveying solid-laden wastewater, having a helical housing (10) having an inlet opening (15), an impeller (20) having at least one vane (21a, 21b), wherein the leading edge (23) which is associated with the respective vane (21a, 21b) extends outward in a manner curved backward from the impeller hub (22), and at least one finger (30) for wiping dirt from the leading edge (23), wherein the finger (30) is arranged on the inlet inner wall and extends in the direction of the axis of rotation R of the impeller (20), and wherein at least one groove (11) which is formed in an intake-side inner wall of the housing (10, 12) is provided, and the leading edge (23) of the impeller (20) and the upper finger surface (33) facing the leading edge (23) exhibit an angle α of 5° to 75° with respect to the perpendicular projection face of the axis of rotation R, characterized in that the leading edge (23) of the impeller (20) forms, with respect to a lateral attack face (35a) of the finger (30), an angle β of which the value in the radial direction at r/r_saug=0.2 is between 50° and 120° and at r/r_saug=1 is between 85° and 160° and preferably varies between these radial points in a substantially uniform manner, wherein the radius r_saug corresponds to the radius of the cylindrical inlet opening of the housing.
2. Wastewater pump (1) according to Claim 1, characterized in that the upper finger surface (33) of the finger (30) has, at least in regions, a spacing of 0.05 to 3 mm from the leading edge (23) of the vane (20).
3. Wastewater pump (1) according to either of the preceding claims, characterized in that the tangential angle δ between the face of the groove (11) which is subjected to flow in the direction of rotation and the lateral attack face (35a) of the finger is in the range between 120° and 180°, preferably between 140° and 180°, and particularly preferably between 160° and 180°.
4. Wastewater pump (1) according to any of the preceding claims, characterized in that the finger (30) has the shape of a three-sided pyramid having curved side faces (33, 35a, 35b), wherein the front face (35a) exhibits an angle γ of 0° to 30° with respect to the axis of rotation R or a parallel P1 of the axis of rotation R and the rear face (35b) exhibits an angle ε of 0° to 50° with respect to the axis of rotation R or a parallel P2 of the axis of rotation R.
5. Wastewater pump (1) according to any of the preceding claims, characterized in that the rear face (35b) of the finger (30) is curved twice in a radial direction in at least two different directions.
6. Wastewater pump (1) according to any of the preceding claims, characterized in that the finger (30) is arranged in the vicinity of a spur (17) of the helical housing (10), preferably lying directly or shortly after the spur (17) in the direction of rotation (2).
7. Wastewater pump (1) according to Claim 6, characterized in that the finger (30) is positioned with a wrap angle ϕ in the range of values from 0° to 45°, particularly preferably 15° to 35° and ideally 20° to 30°, wherein the wrap angle ϕ is defined by the angle of intersection of the vertical with a tangent (G1), intersecting the axis of rotation R, of the attack face (35a) of the finger (30), wherein the tangent (G1) extends preferably through the point of the attack face (35a) that is furthest away from the axis of rotation R in a radial direction.
8. Wastewater pump (1) according to any of the preceding claims, characterized in that the finger length is at least 30% of the radius r of the inlet opening, preferably at least 50% and ideally 70% to 80%.
9. Wastewater pump (1) according to any of the preceding claims, characterized in that the finger (30) is releasably connected to the housing (10) or an intake-side housing insert (12), in particular by means of a fastening element (31) which is formed on the end side of the finger and is able to be screwed to the housing (10) or to the housing insert (12), wherein the fastening element (31) and the arrangement thereof on the housing (10) or on the housing insert (12) is configured such that it does not project into the inlet opening (15) of the housing (10).
10. Wastewater pump (1) according to any of the preceding claims, characterized in that the finger (30) provides at least one small portion embodied as a cutting edge (32), in particular in the transition region of the finger (30) to the fastening element (31) of the finger (30), wherein the cutting edge (32) extends particularly preferably parallel to the axis of rotation R.

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