Wiping element for impeller leading edges of wastewater pumps

Abstract

The invention relates to a wastewater pump for conveying solids-laden wastewater with a spiral housing with an inlet opening, an impeller with at least one vane, wherein the leading edge which is assigned to the respective vane runs from the impeller hub in a backwardly curved manner towards the outside, and at least one finger for wiping off contaminants from the leading edge, wherein the finger is arranged on the inlet inner wall and extends in the direction of the rotational axis R of the impeller, and wherein at least one groove which is made in a suction-side inner wall of the housing is provided, and the leading edge of the impeller and the upper finger surface which faces toward the leading edge are at an angle α with respect to the perpendicular projection area of the rotational axis R of from 5° to 75°.

Description

[0001] Description

[0002] Wiper element for impeller entry edges of wastewater pumps

[0003] The invention relates to a wastewater pump with a spiral casing having an inlet opening and an impeller with at least one blade, wherein the leading edge associated with the respective blade curves backwards outwards from the impeller hub.

[0004] Wastewater can contain various types of solids, such as fibrous materials, the quantity and structure of which can depend on the wastewater source and the season. For example, plastics, hygiene products, textiles, etc., are common in cities, while industrial areas may contain wear particles. Experience has shown that the biggest problems with wastewater pumps are caused by fibrous materials such as rags, cloths, and the like, which can become lodged on the leading edges of the impeller blades and wrap around the impeller hub. Such incidents lead to frequent maintenance intervals and reduced pump efficiency.

[0005] Several solutions already exist that utilize cutting or scraping tools to remove pollutants adhering to the entry edges during pump operation. The present invention aims to improve existing solutions. This objective is achieved by a wastewater pump according to the features of claim 1. Advantageous embodiments of the wastewater pump are the subject of the dependent claims.

[0006] The invention is based on a wastewater pump for pumping solids-laden wastewater. The wastewater pump consists of an impeller with at least one backward-curved impeller blade. The impeller is non-rotatably connected to a rotating shaft and is located in a spiral pump housing with an inlet opening. The inlet opening can be axially oriented and / or cylindrical.

[0007] The leading edge of at least one impeller blade extends radially outwards from the impeller hub with the aforementioned backward-curved blade shape. A finger is rigidly connected to the pump housing on the inner wall of the inlet opening. A groove adjoins the finger at the transition to the inner wall of the inlet opening. » which is formed in the suction-side side wall of the pump housing and extends outwards in the pump housing wall in radial and tangential directions.

[0008] The finger extends radially inwards from the inner inlet wall towards the impeller's axis of rotation. An upper finger surface facing the leading edge runs at a defined distance from the leading edge and essentially parallel to it, so that the desired scraping action is achieved by the upper finger surface facing the leading edge, or by the finger's lateral contact surface. The interaction of the backward-curved leading edge and the finger facilitates the removal of solids adhering to the impeller's leading edge. The finger guides the deposited solids into the groove, where they are carried along by the impeller's rotation. » so that they pass directly into the area of ​​the housing pressure port via the groove. The impeller and the finger are specially matched to each other for this task.

[0009] According to the invention, the leading edge of the impeller can be set at an angle α of 5° to 75° to the perpendicular projection surface of the impeller's axis of rotation. This results in an axial component acting on the solids, in addition to the rotational movement and resulting radial force, for scraping off the solids. This optimizes the conveyance of the scraped solids through the groove. Preferably, the angle α can be in a range of 10° to 45°.

[0010] The upper surface of the finger can also be inclined at an angle α relative to the vertical projection surface. However, the upper surface and the entry edge do not necessarily have to be exactly parallel, so that angles α relative to the projection surface are also conceivable. In particular, the upper surface of the finger can be curved rather than planar, resulting in a varying angle α for the finger surface and consequently a varying distance between the entry edge and the upper surface. Preferably, the upper surface of the finger can be curved in both the radial and tangential directions. Ideally, the upper surface of the finger has a conical curvature in both the radial and tangential directions.

[0011] The wastewater pump can be operated dry or submerged in the pumped medium in any orientation. The pump's volute casing features a spur and a discharge port. Furthermore, the pump casing may have a separate insert in the inlet area, such as a suction cover or a wear plate, into which the aforementioned groove can be integrated or to which the finger can be attached. During pump operation, the leading edge of at least one impeller blade moves past the upper surface of the finger at an angle β to the lateral contact surface. Ideally, this angle β should be approximately 90° to achieve optimal scraping action. To reduce the risk of solids becoming trapped between the impeller leading edge and the finger, the angle β should increase radially outwards.This means that as the radius (starting from the wheel hub) increases, the angle β should also increase. Possible angle values ​​in the radial direction at r / r are conceivable here. Saug =012, i.e. in the area near the wheel hub, between 50° and 120° and at r / r Saug =1 between 85° and 160°. The radius r Saug This 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.

[0012] It is particularly advantageous if the upper surface of the finger has a distance of 0.05 to 3 mm from the leading edge of the impeller, at least in some areas. This ensures optimal removal of solids from the impeller's leading edge. A distance that is too large risks small solids and fibers not being picked up by the scraper finger.

[0013] Ideally, the lateral contact surface of the finger, or a tangent to the contact surface, should have a (tangential) angle d between 120° and 180°, preferably between 140° and 180°, and particularly preferably between 160° and 180°, relative to the tangential course of the groove. It is true that with increasing angle d, the removal of the scraped solids into the groove is facilitated. An angle d of 180° would be ideal. To minimize the influence on the flow in the impeller inlet, the finger should have a streamlined shape. Good properties are achieved when the finger is designed as a three-sided pyramid with curved side faces. To ensure sufficient scraping function and, if necessary, to achieve an optional cutting effect, it is advantageous if the front surface, i.e.,The finger's contact surface is angled at 0° to 30° relative to a parallel of the impeller's axis of rotation. The rear surface of the finger is less critical and can be inclined more steeply to the parallel. An angle e of the rear surface of the finger to the parallel of the impeller's axis of rotation of 0° to 50° is recommended. Due to the curved side surfaces of the finger, in conjunction with the aforementioned defined angle ranges, solids have great difficulty adhering to the finger's surface. Ideally, the rear surface is doubly curved, particularly curved in opposite directions. This further reduces the flow-influencing area of ​​the finger.

[0014] The orientation and specific arrangement of the finger within the inlet are crucial for the efficiency of the scraping action. In this context, the relative position of the finger to the spur of the spiral casing, and consequently to the pressure port, is relevant. It is advantageous if the finger is positioned near the spur, preferably downstream of the spur in the direction of rotation. Such an arrangement offers a further advantage, particularly for horizontally oriented pumps. Solid particles, such as stones, can potentially accumulate in the lower part of the pump casing or impeller. By positioning the finger 30 in the vicinity of the spur, it is placed outside this hazardous area.

[0015] The exact position of the finger can be determined, for example, by the angle f. The angle f corresponds to the wrap angle, which is defined by the angle of intersection between the perpendicular and a tangent of the finger's contact surface that intersects the impeller's axis of rotation. The tangent preferably passes through the point on the contact surface furthest radially from the axis of rotation. Possible values ​​of the angle f range from 0° to 45°, preferably between 15° and 35°, and ideally between 20° and 30°. In a further advantageous embodiment of the wastewater pump, the selected finger length corresponds to at least 30% of the total radius r. sa ug of the cylindrical inlet opening, preferably at least 50% and ideally between 70% and 80%.

[0016] Optionally, the finger may also have at least one section designed as a cutting edge, particularly on the side of the finger's front contact surface, wherein the cutting edge extends perpendicular to the wiping edge, i.e., parallel to the axis of rotation. Preferably, the cutting edge is provided in the transition area between the finger and the finger's fastening element. . The advantages and features of the invention will become apparent from the exemplary embodiment shown in the figures. These show:

[0017] Figure 1; a perspective view of the wastewater pump according to the invention with the pump housing open,

[0018] Figure 2: a vertical section through the wastewater pump according to the invention,

[0019] Figures 3a, 3b: a detailed view of the housing insert with scraper finger for the wastewater pump according to the invention.

[0020] Figure 4: a detailed view of the impeller of the wastewater pump according to the invention,

[0021] Figures 5a to 5d: Detailed views of the scraper finger of the wastewater pump according to the invention.

[0022] Figure 6: a suction-side view of the housing insert of the wastewater pump according to the invention with the impeller inserted. Figures 7a, 7b: sectional views along the axis of rotation R through the housing insert including the impeller according to Figure 6.

[0023] Figure 8: a detailed view of the scraper finger including the groove according to Figure 6 and

[0024] Figure 9: a diagram representation of the normalized radius (rr) Saug) opposite the angle β. Figure 1 shows an exploded view of the wastewater pump 1 according to the invention. This pump consists of a spiral casing 10, a suction-side casing insert in the form of a wear plate 12, and the impeller 20 rotating about the axis of rotation R. The direction of rotation is indicated by reference numeral 2. The impeller 20, shown in detail in Figure 4, comprises two backward-curved blades 21a, 21b, through which the pumped medium is drawn in via the cylindrical inlet opening 15 of the wear plate 12 and conveyed via the pumping chamber 16 of the spiral casing 10 to the discharge port 13 and discharged therefrom. The wastewater to be pumped can contain a variety of different solids, for example, fibrous materials, which can become lodged on certain parts of the pump during operation.For this reason, the scraper 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, for the implementation of the invention the wear wall 12 could just as easily be omitted and the finger 30 attached directly to the housing wall in the area of ​​the suction mouth. The design and function of the finger 30 will be discussed in more detail later; first, the construction of the impeller 20 will be described.

[0025] Characteristic of the impeller 20 is the course of the leading edges 23 of the blades 21a, 21b shown in Fig. 4. These begin directly at the impeller hub 22, in particular at the level of the upper, free hub end, and extend radially outwards in a backward curve. The leading edges 23 are the end faces of the blades 21a, 21b facing the suction cover, which extend through the inlet 15.

[0026] These leading edges 23 are further aligned at a defined angle α to the perpendicular projection surface of the axis of rotation R. To illustrate the chosen angle, reference is made to Figures 7a and 7b, which show a sectional view through the impeller 20 and the corresponding wear wall 12. The angle α of the leading edge 23 of the impeller 20 relative to the horizontal, which in the chosen representation corresponds to a perpendicular projection surface to the axis of rotation R, is shown here. The chosen inclination makes it possible to apply an axial force component to the conveyed medium in addition to the radial force, thus optimizing the discharge of solids contained therein that have been captured and scraped off by the finger 30. These solids are discharged via a specially designed spiral groove 11 within the suction-side wear wall 12. Ideally, the angle α should be in the range between 5° and 75° or 10° and 45°.In the embodiment shown here, an inclination angle a of approximately 25° is assumed (see Figures 7a, 7b).

[0027] 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 housing design. The wiping finger 30 is mounted on the inner wall of the inlet 15 of the wear wall and extends in the direction of the axis of rotation R. The length of the wiping finger 30 should be at least 30%, preferably at least 50%, or ideally approximately 70% to 80% of the radius of the cylindrical inlet 15, which is hereinafter referred to as the suction port.

[0028] To minimize the influence of the wiper finger 30 on the flow in the inlet 15 to the impeller 20, the finger 30 is pyramid-shaped with a total of three side surfaces 33, 35a, 35b and the base surface adjacent to the inner wall of the inlet 15. The upper finger surface 33 faces the leading edges 23 of the impeller 20.

[0029] It is not planar, but has a continuous curvature, both in the longitudinal direction of the finger (radial direction KR, see Fig. 5b) and in the transverse direction (tangential direction KT, see Fig. 8). In total, this results in a kind of conical surface 33.

[0030] The remaining side surfaces, i.e., the lateral contact surface 35a and the rear side surface 35b, also exhibit corresponding curvatures, with the rear side surface 35b even having a double curvature in different directions. See in particular Fig. 5c. To fulfill the function of stripping solids and cutting fibers, the front contact surface 35a of the finger 30 is inclined at an angle g of 0° to 30° to the axis of rotation R. In Fig. 8, the angle g to a parallel P1 of the axis of rotation R is shown. The rear surface 35b of the finger 30 is less critical and can be inclined at an angle e to the axis of rotation R or the parallel P2 to the axis of rotation R of 0° to 50°. Furthermore, the surface 35c can be tangential to the adjacent surfaces 35a. » 35b should be rounded. Taking this angle definition into account, it is very difficult for solids to adhere to finger 30.

[0031] As the impeller 20 rotates around the axis of rotation R in direction 2, the entry edges 23 of the impeller 20 approach 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 scraper edge, by which solids deposited on the entry edges are scraped off and, due to the radial and axial velocity of the conveyed medium, are released into the spiral groove 11, through which they are ultimately ejected past the impeller 20 through the conveying chamber 16 to the discharge nozzle 13.

[0032] The distance between the leading edge 23 and the surface 33 or the scraper edge of the scraper finger 30 should be between 0.05 and 3 mm, whereby this distance can vary in the radial direction, but should remain within the aforementioned value range as far as possible. A distance that is too large risks that small solids cannot be captured by the scraper finger 30, whereas a distance that is too small increases the risk of tarnishing of the scraper finger 30 and the leading edge 23.

[0033] As explained at the beginning, the leading edge 23 of the wheel 20 lies 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 wiping edge, should also exhibit a corresponding inclination by the angle α. This is also evident 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 slight differences. Despite these angular differences, the previously defined distance value should nevertheless remain within the desired range.

[0034] The relative position of the scraper finger 30 to the spur 17 of the spiral casing 10 also influences the discharge of the scraped solids to the pressure outlet 13. Particularly with a horizontally mounted pump, it is advantageous if the scraper finger 30, as shown in the sectional view of Fig. 2, is located directly behind the spur 17 in the direction of rotation 2, i.e., clockwise in the representation of Fig. 2. Solids, such as stones, can potentially accumulate in the lower part of the pump casing or impeller. By arranging the scraper finger 30 in the vicinity of the spur, the latter is positioned outside this danger zone.

[0035] The relative position of the wiper finger 30 to the spur 17 can be defined by the angle f shown in Fig. 2. The angle cp corresponds to the wrap angle, which is defined by the angle of intersection between the perpendicular and the line G1. The line G1 is perpendicular to the axis of rotation R and passes through the point on the lateral contact surface 35a of the wiper finger 30 furthest radially from the axis of rotation R. Recommended values ​​for the angle f are in the range between 0° and 45°, with an angle of 20° to 30° proving particularly advantageous.

[0036] During pump operation, the leading edge 23 of the blades 21a, 21b moves past the upper surface 33. The tangent at the lowest point of the upper surface 33 (point of least distance to the leading edge 23) forms an angle β with the tangent of the leading edge. For optimal operation of the finger 30, the angle β should be approximately 90°. However, to reduce the risk of fibers becoming trapped between the impeller leading edge 23 and the finger 30, the angle β can also increase with increasing radius r from the impeller hub 22. This means that as the radius r increases, the angle β also increases. For a simpler representation, the normalized radius (r-rsaug), where rsaug represents the radius of the inlet 15, can be used to assume the curve shown in Figure 9.This figure shows that the angle β near the center of the impeller 20 can range between 50° and 120°, and between 85° and 160° at the outer edge. Within this range, the angle profile is freely selectable; however, a continuously increasing angle β should be chosen optimally.

[0037] To further optimize the wiping effect, the lateral contact surface 35a of the finger 30 should assume an angle d between 180° and 120° relative to the tangential course of the groove 11. This angle d is illustrated in Figure 3 and has a value of approximately 165° there.

[0038] Optionally, the finger 30 can be designed with a cutting edge 32 that extends perpendicular to the surface 33 of the finger in the area of ​​the transition to the fastening element 31. Accordingly, the cutting edge runs almost parallel to the axis of rotation R. The wiper finger 30 can be detachably connected to the wear wall 12 or the housing 10 by means of the fastening element 31, taking care to ensure that the fastening element 31 does not protrude into the inlet 15 in order to avoid any influence on the flow characteristics within the pump.

[0039] Fig. 9 shows the angle β between the leading edge 23 of the wheel 20 and the finger 30.

Claims

A 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 a leading edge (23) which is associated with the respective vane (21a, 21b) extends outward in a manner curved backward froman 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 rotation axis 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 an 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 ߟ whose value in the radial direction at r / rsaug=0.2 is between 50° and 120° and at r / rsaug=1 is between 85° and 160° and varies between these radial points, wherein the radius rsaug corresponds to the radius of the cylindrical inlet opening of the housingThe wastewater pump (1) as claimed claim 1, characterized in that the upper finger surface (33) of the finger (30) has at least in regions a spacing of from 0.05 to 3 mm from the leading edge (23) of the vane (20).The wastewater pump (1) as claimed in claim 1, characterized in that the tangential angle δ between the face of the groove (11) which is subjected to flow in a rotation direction and the lateral attack face (35a) of the finger is in the range between120° and 180°The wastewater pump (1) as claimed in claim 1, characterized in that the finger (30) has the shape of a three-surface pyramid having curved side faces (33, 35a, 35b), wherein the front face (35a) has an angle γ of from 0° to 30° with respect to the rotation axis R or a parallel P1 of the rotation axis R and the rear face (35b) has an angle ε of from 0° to 50° with respect to the rotation axis R or a parallel P2 of the rotation axis RThe wastewater pump (1) as claimed claim1, characterized in that the rear face (35b) of the finger (30) is curved twice in a radial direction in at least two different directionsThe wastewater pump (1) as claimed in claim 1, characterized in that the finger (30) is arranged in the vicinity of a spur (17),the helical housing (10) located in the rotation direction (2) directly or shortly after the spur (17).The wastewater pump (1) as claimed in claim 6, characterized in that the finger (30) is positioned with a wrap angle φ in the value range from 0° to 45°, from 15° to 35° and ideally from 20° to 30°, wherein the wrap angle φ is defined by the angle of intersection of the vertical with a tangent (G1) of the attack face (35a) of the finger (30), wherein the tangent (G1) extends through the point of the attack face (35a) furthest away from the rotation axis R in a radial direction.The wastewater pump (1) as claimed in claim 1, characterized in that the finger length is at least 30% of the radius r of the inlet openingThe wastewater pump (1) as claimed in claim 1, characterized in that the finger (30) is releasably connected to the housing (10) or an intake-side housing insert (12), by means of a securing element (31) which is formed at the end side on the finger and which can be screwed to the housing (10) or the housing insert (12), wherein the securing element (31) and the arrangement thereof on the housing (10) or the housing insert (12) is configured in such a manner that it does not protrude into the inlet opening (15) of the housing (10).The wastewater pump (1) as claimed in claim 1, characterized in that the finger (30) provides at least one small portion which is in the form of a cutting edge (32), in the transition region of the finger (30) to the securing element (31) of the finger (30), wherein the cutting edge (32) extends in parallel with the rotation axis R

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