Abstract
A centrifugal pump (1) including: a pump housing (3) enclosing a pump chamber (13), the pump chamber (13) including a suction inlet (15) and a pressure outlet (17); an impeller (19) rotatably arranged within the pump chamber (13) for being driven to rotate about a rotor axis (R), the suction inlet (15) being located coaxial with the rotor axis (R); and at least one stationary scraper (39). The impeller (19) includes an impeller base (31) and at least one or more impeller vanes (33) extending from the impeller base (31) towards the suction inlet (15). Each of the impeller vanes (33) includes a radially innermost vane path (45) describing during impeller rotation a central volume (41) that is wider towards the suction inlet (15) than towards the impeller base (31) and configured to receive the at least one scraper (39) projecting from the suction inlet (15) into the central volume (41).
Claims
1. A centrifugal pump comprising: a pump housing enclosing a pump chamber, wherein the pump chamber comprises a suction inlet and a pressure outlet; an impeller rotatably arranged within the pump chamber for being driven to rotate about a rotor axis, wherein the suction inlet is located coaxial with the rotor axis; and at least one stationary scraper wherein the impeller comprises an impeller base and one or more vanes extending from the impeller base towards the suction inlet, wherein each of the impeller vanes comprises a radially innermost vane path describing during impeller rotation a central volume that is wider towards the suction inlet than towards the impeller base and that is configured to receive the at least one stationary scraper projecting from the suction inlet into the central volume, wherein each of the impeller vanes comprises a leading edge extending from a leading edge base point at the impeller base to a leading edge ridge point at a vane ridge surface, wherein the leading edge is backwardly swept from the leading edge base point to the leading edge ridge point, wherein the leading edge has a distance in radial and/or circumferential direction from the radially innermost vane path, each of the one or more vanes has a concave surface directed radially inward toward the rotor axis.
2. The centrifugal pump according to claim 1, wherein the at least one stationary scraper comprises a radially outward scraper surface acting as a first scraping path and positioned to form a scrape gap to the radially innermost vane path acting as a second scraping path during impeller rotation.
3. The centrifugal pump according to claim 2, wherein the scrape gap is in the range of 0.1 to 5 mm.
4. The centrifugal pump according to claim 2, wherein the scrape gap is constant or varies along the radially innermost vane path.
5. The centrifugal pump according to claim 1, wherein the at least one stationary scraper is mounted to or an integral part of the suction inlet at a scraper connection angle in the range of 110° to 170°.
6. The centrifugal pump according to claim 1, wherein the at least one stationary scraper comprises a guiding surface facing backward in a circumferential direction of impeller rotation, and wherein the guiding surface is inclined against the circumferential direction of impeller rotation from the suction inlet towards the impeller base.
7. The centrifugal pump according to claim 1, wherein the at least one stationary scraper extends straight in an axial direction.
8. The centrifugal pump according to claim 1, wherein the vane ridge surface of each impeller vane faces towards a cover surface of the suction inlet, wherein the impeller is positioned relative to the cover surface to form a cover gap between the vane ridge surface and the cover surface.
9. The centrifugal pump according to claim 8, wherein the cover gap is in the range of 0.1 to 1 mm.
10. The centrifugal pump according to claim 8, wherein the cover surface comprises at least one groove extending from a groove inlet port at an inner radius of the cover surface to a groove outlet port at an outer radius of the cover surface.
11. The centrifugal pump according to claim 10, wherein the groove inlet port extends between a first angular end and a second angular end, wherein the first angular end and the second angular end have an angular distance of less than 90° to each other, wherein the second angular end is located behind the first angular end in a circumferential direction of impeller rotation, wherein the at least one stationary scraper is located at the second angular end.
12. The centrifugal pump according to claim 1, wherein the leading edge is swept backwardly by a leading edge sweep angle of at least 20° at the leading edge ridge point.
13. The centrifugal pump according to claim 12, wherein the leading edge sweep angle is larger at the leading edge base point than at the leading edge ridge point, wherein the leading edge sweep angle is least 20° between the leading edge base point and the leading edge ridge point.
14. The centrifugal pump according to claim 1, wherein the distance in at least one of the radial direction and the circumferential direction between the leading edge and the radially innermost vane path increases towards the impeller base.
15. The centrifugal pump according to claim 1, wherein each of the impeller vanes is radially outwardly tilted from the impeller base to the vane ridge surface by a tilt angle of up to 60°.
16. The centrifugal pump according to claim 1, wherein the radially innermost vane path comprises a first section having a convex shape and a second section having a concave shape.
17. The centrifugal pump according to claim 1, wherein a height in an axial direction of the at least one stationary scraper is at least 50% of a depth in an axial direction of the central volume.
18. A centrifugal pump comprising: a pump housing enclosing a pump chamber, wherein the pump chamber comprises a suction inlet and a pressure outlet; an impeller rotatably arranged within the pump chamber for being driven to rotate about a rotor axis, wherein the suction inlet is located coaxial with the rotor axis; and at least one stationary scraper wherein the impeller comprises an impeller base and one or more vanes extending from the impeller base towards the suction inlet, wherein each of the impeller vanes comprises a radially innermost vane path describing during impeller rotation a central volume that is wider towards the suction inlet than towards the impeller base and that is configured to receive the at least one stationary scraper projecting from the suction inlet into the central volume, the radially innermost vane path comprises a first section having a convex shape and a second section having a concave shape, each of the one or more vanes has a convex surface being directed radially outward away from the rotor axis.
Description
BRIEF DESCRIPTION OF THE DRAWINGS
(1) In the Drawings:
(2) FIG. 1 is a front view on an embodiment of a pump housing of a centrifugal pump according to the present disclosure;
(3) FIG. 2 is a longitudinal sectional view on the embodiment as shown in FIG. 1;
(4) FIG. 3 is a detail sectional view on plane C-C as outlined in FIG. 2;
(5) FIG. 4 is a more detailed sectional view showing the interaction of an impeller vane with a scraper according to the present disclosure;
(6) FIG. 5 is a perspective view of an impeller of the embodiment of a centrifugal pump according to the present disclosure;
(7) FIG. 6 is a front view of the impeller shown in FIG. 5;
(8) FIG. 7a is a sectional front view of a suction inlet with scraper of the embodiment of a centrifugal pump according to the present disclosure;
(9) FIG. 7b is a sectional rear view, respectively, of a suction inlet with scraper of the embodiment of a centrifugal pump according to the present disclosure;
(10) FIG. 8a is a view showing the interaction of an impeller vane with a scraper according to the present disclosure in an angular position of the impeller during rotation, wherein the figure on the left is a bottom view and the figure on the right is a corresponding sectional view on plane H-H as outlined in the figure on the left;
(11) FIG. 8b is a view showing the interaction of an impeller vane with a scraper according to the present disclosure in a different angular position of the impeller during rotation, wherein the figure on the left is a bottom view and the figure on the right is a corresponding sectional view on plane H-H as outlined in the figure on the left;
(12) FIG. 8c is a view showing the interaction of an impeller vane with a scraper according to the present disclosure in a different angular position of the impeller during rotation, wherein the figure on the left is a bottom view and the figure on the right is a corresponding sectional view on plane H-H as outlined in the figure on the left;
(13) FIG. 9 is a top view of the cover surface of the embodiment of a centrifugal pump according to the present disclosure;
(14) FIG. 10 is a top view of an alternative embodiment of a cover surface of a suction inlet of a centrifugal pump according to the present disclosure;
(15) FIG. 11a is a rear view of the pump housing;
(16) FIG. 11b is a cross-sectional view on plane B-B as outlined in FIG. 11a with the cover surface as shown in FIG. 10;
(17) FIG. 12a is a sectional partial view of another embodiment of a centrifugal pump according to the present disclosure;
(18) FIG. 12b is a sectional partial view of the another embodiment of the centrifugal pump according to the present disclosure;
(19) FIG. 12c is a sectional partial view of the another embodiment of the centrifugal pump according to the present disclosure;
(20) FIG. 13a is a view of an impeller of a centrifugal pump according to the embodiment shown in FIGS. 12a-c;
(21) FIG. 13b is another view of an impeller of a centrifugal pump according to the embodiment shown in FIGS. 12a-c;
(22) FIG. 14a is a perspective view of the impeller shown in FIG. 13a,b in a rotational position relative to the scraper;
(23) FIG. 14b is a perspective view of the impeller shown in FIG. 13a,b in another rotational position relative to the scraper;
(24) FIG. 14c is a perspective view of the impeller shown in FIG. 13a,b in yet another rotational position relative to the scraper;
(25) FIG. 14d is a perspective view of the impeller shown in FIG. 13a,b in yet another rotational position relative to the scraper;
(26) FIG. 15a is a view of a suction inlet including a cover surface of a centrifugal pump according to the embodiment shown in FIGS. 12a-c;
(27) FIG. 15b is a different view of a suction inlet including a cover surface of a centrifugal pump according to the embodiment shown in FIGS. 12a-c;
(28) FIG. 15c is a different view of a suction inlet including a cover surface of a centrifugal pump according to the embodiment shown in FIGS. 12a-c;
(29) FIG. 16a is a view showing the interaction of an impeller vane with a scraper according to the embodiment shown in FIGS. 12a-c in different angular positions of the impeller during rotation, wherein the figure on the left is a bottom view and the figure on the right is a corresponding sectional view on plane E-E as outline in the figure on the left;
(30) FIG. 16b is a view showing the interaction of an impeller vane with a scraper according to the embodiment shown in FIGS. 12a-c in different angular positions of the impeller during rotation, wherein the figure on the left is a bottom view and the figure on the right is a corresponding sectional view on plane E-E as outline in the figure on the left; and
(31) FIG. 16c is a view showing the interaction of an impeller vane with a scraper according to the embodiment shown in FIGS. 12a-c in different angular positions of the impeller during rotation, wherein the figure on the left is a bottom view and the figure on the right is a corresponding sectional view on plane E-E as outline in the figure on the left.
DESCRIPTION OF PREFERRED EMBODIMENTS
(32) Referring to the drawings, FIG. 1 shows an elongate centrifugal pump 1 as a submersible wastewater pump that can be submersed into a wastewater pit or a duct to pump wastewater with fibrous substances. The pump 1 comprises a pump housing 3, a motor housing 5 and an electronics housing 7 arranged essentially along a vertical rotor axis R, wherein the motor housing 5 is arranged between the pump housing 3 and the electronics housing 7. The pump housing defines a fluid inlet 9 and a fluid outlet 11. The fluid inlet 9 is here a bottom opening in the pump housing 3, wherein the bottom opening is coaxial with the rotor axis R.
(33) It should be noted that the vertical pump setup shown herein is only a preferred setup. The rotor axis R may extend vertically or horizontally or in any other direction. For the sake of convenience, a right-handed Cartesian coordinate system is given in each figure, wherein the z-axis extends along the rotor axis R, i.e. here vertically upwards, the y-axis extends sideways out of the fluid outlet 11, and the x-axis extends forward. The terms “top”, “bottom”, “front” and “rear” thus refer to respective directions along the z-axis or x-axis. The direction of impeller rotation is here counter-clockwise about the rotor axis R when seen from the bottom upwards in z-direction.
(34) FIG. 2 shows that the pump housing 3 encloses a pump chamber 13 comprising a suction inlet 15 and a pressure outlet 17, wherein the suction inlet 15 comprises here an inlet sleeve 18 being coaxially arranged with the rotor axis R and extending from the fluid inlet 9 to the pump chamber 13. The pressure outlet 17 of the pump chamber 13 is arranged radially outward in lateral y-direction. An impeller 19 is rotatably arranged within the pump chamber 13 for being driven to rotate about the rotor axis R. A rotor axle 21 is fixed to a central hub 23 of the impeller 19 and extends upwards in z-direction along the rotor axis R out of the pump housing 3 into the motor housing 5, which is attached to the top of the pump housing 3.
(35) FIG. 3 shows the pump chamber 13 in more detail when seen essentially in negative y-direction from the fluid outlet 11. The impeller 19 comprises an upper impeller base 31 from which two impeller vanes 33 extend downward towards the suction inlet 15. The suction inlet 15 widens towards the impeller 19 by means of a slightly convexly shaped cover surface 35 arranged at the upper end of the inlet sleeve 18. Each of the impeller vanes 33 comprises a vane ridge surface 37 facing the cover surface 35 with a cover gap h of 0.1 to 1 mm, e.g. approximately 1 mm, between them (see FIG. 4). The vane ridge surfaces 37 slide along the cover surface 35 upon rotation of the impeller 19. A scraper 39 in form of a finger projects essentially upward into a central dome-shaped volume 41 (see FIG. 5) described by impeller rotation and which is not crossed by the impeller vanes 33 during impeller rotation. The central dome-shaped volume 41 has the largest radius of essentially the inner radius of the inlet sleeve 18 at the suction inlet 15 and the smallest radius of essentially the radius of the central hub 23 at the impeller base 31. The scraper 39 is fixed to the inlet sleeve 18 and projects upwards towards the central hub 23 into the dome-shaped volume 41.
(36) FIG. 4 shows the interaction of the scraper 39 and the impeller 19 in more detail. The scraper 39 comprises a machined radially outward scraper surface 43 acting as a first scraping path 43 and being positioned to form a scrape gap g (best visible in FIG. 8c on the right) of 0.1 to 5 mm, e.g. in the range of 0.3 to 2 mm or of approximately 1 mm, to a machined radially innermost vane surface 45 acting as a second scraping path 45. Upon impeller rotation, the second scraping path 45 of the impeller vanes 33 slides along the first scraping path 43 of the stationary scraper 39, whereby fibrous substances are scraped off the second scraping path 45. It is the second scraping path 45 of the impeller vanes 33 that describes the dome-shaped central volume 41 during impeller rotation.
(37) When the impeller rotates, fibrous substances are not cut by the scraper, but rather scraped pushed away by the scraper 39 and by the interaction between the guiding surface 47 of the scraper 39 facing essentially backwardly in circumferential direction of impeller rotation, i.e. here in positive y-direction and the rotating impeller vanes. The guiding surface 47 of the scraper 39, and in this embodiment the scraper 39 as a whole, is inclined backwardly by up to 30° in circumferential direction of impeller rotation, i.e. here in positive y-direction, from the inlet sleeve 18 to a scraper end 49 close to the central hub 23 of the impeller base 31. Except for the first scraping path 43 of the scraper 19, the surfaces of the scraper 39 in general are smoothly curved to reduce the fluidic resistance.
(38) The scraper 19 guides fibrous substances towards the cover surface 35, which comprises grooves 51 along which fibrous substances can be transported radially outward. Each groove 51 extends from a groove inlet port 53 at an inner radius r.sub.1 of the cover surface 35 to a groove outlet port 55 at an outer radius r.sub.2 of the cover surface 35 (best visible in FIGS. 9 and 10). The scraper 39 is located relative to the grooves 51 such that the guiding surface 47 is not far behind a groove inlet port 53 of a groove 51, i.e. at an angular distance of less than 90° forward in circumferential direction of impeller rotation, so that the fibrous substances agglomerated at the guiding surface 47 can easily enter the groove 51. This is illustrated in FIGS. 3, 9, and 10.
(39) FIGS. 5 and 6 show the specific design of the impeller 19 in more detail. The upper impeller base 31 is essentially a base plate comprising the central hub 23 for fixing the rotor axle 21. The two impeller vanes 33 extend essentially axially downward from the impeller base 31, wherein the impeller base 31 and the impeller vanes 33 are formed as an integrally molded impeller 19. Alternatively, the impeller 19 may comprise one or more than two vanes. In case of two or more vanes, the two impeller vanes 33 are arranged with respect to each other in a rotational symmetry. They are curved in form of a spiral section in the xy-plane perpendicular to the rotor axis R.
(40) The essentially downwardly facing vane ridge surfaces 37 of the impeller vanes 33 are machined in this example and do not extend to the central hub 23 of the impeller base 31. Each vane ridge surface 37 has a circumferentially forward end at a leading edge 57 of the impeller vane 33 and a circumferentially backward end at a trailing edge 59 of the impeller vane 33. The leading edge 57 of each impeller vane 33 may be defined as the path of circumferentially most forward vane surface points, i.e. where the impeller vane 33 hits the pumped fluid first. The trailing edge 57 of each impeller vane 33 may be defined as the path of circumferentially most backward vane surface points, i.e. where the fluid separates from the impeller vane 33 towards the radially outward pressure outlet 17.
(41) The leading edge 57 extends from a leading edge base point 61 at the impeller base 31 to a leading edge ridge point 63 at the vane ridge surface 37, wherein the leading edge 57 is backwardly swept from the leading edge base point 61 to the leading edge ridge point 63. The backward sweep is best seen in FIG. 6. The backward sweep at a point of the leading edge means that a tangent plane at that point is inclined “backward” in circumferential direction of rotation with respect to a plane extending along the rotor axis R and through that point. The backward sweep transports fibrous substances towards the leading edge ridge point 63, where it can be effectively pushed and scraped off by the scraper 39. The leading edge 57 is swept backwardly by a leading edge sweep angle α.sub.1 of at least 20° at the leading edge ridge point 63. The leading edge 57 comprises a lower first section 65 and an upper second section 67. The first section 65 extends from the leading edge ridge point 63 upward to the upper second section 67, which ends at the leading edge base point 61. The leading edge sweep angle is larger in the second section 67 than in the first section 65. In particular, the leading edge sweep angle α.sub.2 at the leading edge base point 61 is larger than the leading edge sweep angle α.sub.1 of at least 20° at the leading edge ridge point 63, e.g. α.sub.2≈90°, i.e. there may be effectively no sweep at the leading edge base point 61.
(42) The preferably machined radially innermost vane surface acting as a second scraping path 45 is hatched in FIG. 5. It extends from the central hub 23 to the leading edge ridge point 63. In circumferential forward direction, the second scraping path 45 extends to the first section 65 of the leading edge 57. The second section 67 of the leading edge 57 departs radially outward from the second scraping path 45. Upon impeller rotation, the second scraping path 45 of the impeller vanes 33 describes the dome-shaped central volume 41 into which the scraper 39 can protrude. The dome-shaped central volume 41 is visualized by dashed paths in FIGS. 5 and 6. The dome-shaped central volume 41 is wider towards the suction inlet 15, i.e. downwards, than towards the impeller base 31, i.e. upwards. The bottom radius of the dome-shaped central volume 41 is approximately equal to the inner radius of the inlet sleeve 18, whereas the top radius of the dome-shaped central volume 41 is approximately equal to the inner radius of central hub 23. The depth of the central volume 41 in axial direction in denoted as Hcv in FIG. 6.
(43) The vane ridge surface 37 of each impeller vane 33 is backwardly swept by a sweep angle β of more than 90° at the leading edge ridge point 63, so that the height of the impeller vanes 33 reduces from the leading edge ridge point 63 towards the trailing edge 59. In other words, a normal vector of the vane ridge surface 37 has a vector component directed backwardly against circumferential direction of impeller rotation.
(44) The impeller vanes 33 are radially outwardly tilted from the impeller base 31 to the vane ridge surface 37 by a tilt angle γ of up to 60°, preferably up to 20°.
(45) FIG. 7a,b show the scraper 39 in more detail. The scraper 39 is smoothly curved backward from the inlet sleeve 18 towards the upper scraper end 49. The radially outward scraper surface 43 acting as a first scraping path 43 is hatched in FIG. 7b. The scraper is long enough to scrape off fibers from the central volume 41. The height of the scraper 39 in axial direction in denoted as Hs in FIG. 7a,b. The height Hs is more than 50% of the depth Hcv of the central volume 41 in axial direction as shown in in FIG. 6.
(46) FIGS. 8a-c show on the left bottom views through the inlet sleeve 18 on the impeller 19 at different angular positions during impeller rotation. In FIG. 8a, the second scraping path 45 of one of the impeller vanes 33 starts interacting with the stationary scraper 39. In FIG. 8b, the impeller 19 is rotated further by about 45° so that the second scraping path 45 is in the process of passing by the scraper 39. In FIG. 8c, the impeller 19 is rotated further by about another 45° so that the second scraping path 45 has just fully passed the first scraping path 43 of the scraper 39. The sectional view on plane H-H on the right of FIG. 8c shows that the second scraping path 45 and the first scraping path 43 of the scraper 39 are essentially parallel for a moment with the scrape gap g between them. The scrape gap g is essentially constant along the scraper 39 or increases slightly towards the impeller base 31.
(47) In FIG. 8a on the right, a scraper connection angle φ in the range of 110° to 170° is displayed. The scraper 39 comprises a scraper ridge 52 which the upward flowing fluid hits first, i.e. it acts as a static scraper leading edge. The scraper ridge 52 is a path on a rounded scraper surface from the inlet sleeve 18 to the scraper end 49, whereby the fluidic resistance of the scraper is reduced. In order to prevent fibrous substances from getting entangled at the scraper ridge 52, the scraper ridge 52 is swept in the direction of fluid flow by the scraper sweep angle, which is mostly larger than the scraper connection angle γ and mostly increases towards the scraper end 49. The scraper connection angle γ may be defined by the obtuse angle between a tangent at the radially outermost point of the scraper ridge and an axis parallel to the rotor axis through that point. The scraper sweep angle may be analogously defined for any point along the scraper ridge.
(48) FIG. 9 shows a top view on the cover surface 35 with three grooves 51 that may be identical and arranged in a three-fold rotational symmetry, i.e. at an angular distance of 120° to each other. Each groove 51 extends from a groove inlet port 53 at an inner radius r.sub.1 of the cover surface 35 at a first angular position φ.sub.1 to a groove outlet port 55 at an outer radius r.sub.2 of the cover surface 35 at a second angular position φ.sub.2. The second angular position φ.sub.2 is further forward in the direction of impeller rotation. A radially inner first section 69 of the grooves 51, is curved in form of a spiral section with a relatively slow radial growth of
(49)
A radially outer second section 71 of the grooves 51, is curved in form of a spiral section with a relatively fast radial growth of
(50)
There is a “knee” 73 in the grooves 51 between the first section 69 and the second section 71. This is advantageous to reduce the time needed for fibrous substances to travel along the grooves 51.
(51) The position of the scraper 39 relative to the grooves 51 is indicated by dashed lines in FIGS. 9 and 10. The guiding surface 47 of the scraper 39 is not far behind one of the a groove inlet ports 53, i.e. at an angular distance θ.sub.1 of less than 90° forward in circumferential direction of impeller rotation, so that the fibrous substances agglomerated at the guiding surface 47 can easily enter the groove 51. The angular size θ.sub.2 of the groove inlet ports 53 extending from a first angular end 72 to a second angular end 74 is less than 90°. The guiding surface 47 of the scraper 39 may have a distance θ.sub.1-θ.sub.2 to the second end 74, which is located behind the first angular end 72 in circumferential direction of impeller rotation. Preferably, the distance θ.sub.1-θ.sub.2 is small (see FIG. 10) or zero (see FIG. 15b).
(52) FIG. 10 shows a top view on an alternative embodiment of the cover surface 35 with two essentially identical grooves 51 arranged in a two-fold rotational symmetry, i.e. at an angular distance of 180° to each other. The grooves 51 follow one long spiral path from the groove inlet port 53 to the groove outlet port 55 with an average radial growth of
(53)
The width and/or depth of the grooves 51 increases from the groove inlet port 53 towards the groove outlet port 55.
(54) As shown in FIG. 11a,b, the grooves 51 are arranged in a certain position relative to the pressure outlet 17, so that the groove outlet ports 55 have an angular position φ.sub.2 in the range 20°≤φ.sub.2≤310°, wherein an angular position of φ.sub.2=0° corresponds to the angular position of the pressure outlet 17. The fibrous substances then follow a path as indicated in FIG. 11b by a dashed arrow from the groove outlet port 55 to the pressure outlet 17.
(55) FIGS. 12a-c show another embodiment of the centrifugal pump 1, which have the most aspects and features in common with the previously described embodiment, but differs in some aspects and features. Firstly, in contrast to the previously described embodiment, the suction inlet 15 is here formed as an integral part by the suction sleeve 18, the suction cover including the suction cover surface 35 and the groove 51 and the scraper 39. Such an integral design may reduce the diversity of parts as well as the construction and assembly complexity. In this embodiment, the scrape gap g and the cover gap h may not be individually adjustable, but only together or not at all. Secondly, the embodiment differs from the previously described embodiment in that the suction cover only comprises one single groove 51, which is wider and deeper than the previously described grooves 51. As can be seen in more detail in FIGS. 15a-c, the relatively large groove inlet port 53 is located directly at the scraper 39. Also, the angular position of the scraper 39 within the pump housing 3 is rotated by 180°. Finally, the shape of the impeller vanes 33 differs in some aspects. For instance, the radially innermost vane path 45 is not part of a machined surface, but a path on a smoothly curved non-machined radially inner vane surface (see FIGS. 13a-c). This has the advantage that the risk of cavitation effects is reduced by a fluid-dynamically optimized vane shape with less machined sharp edges. Also the first scraping path 43 on the scraper 39 may be a path on a non-machined surface rather than a machined first scraping surface.
(56) As can be seen in FIG. 13a,b, the leading edge 57 has here no surface points in common with the radially innermost vane path 45. This means that the leading edge has a distance in radial and circumferential direction from the radially innermost vane path 45. This is fluid-dynamically beneficial and still effective to scrape off fibers, because tests have shown that the scraper 39 is physically most effective to transport fibers from the impeller base 31 towards the vane ridge 37. Once the fibers have reached a certain distance from the impeller base 31, the fibers automatically find their way towards the groove inlet port 53. It is further advantageous that the distance in radial and/or circumferential direction between the leading edge 57 and the radially innermost vane path 45 increases towards the impeller base 31. In other words, the distance decreases away from the impeller base 31, which facilitates guiding the fibers into the groove inlet port 53.
(57) As can be seen in FIG. 13a,b, the radially innermost vane path 45 comprises a first section 75 having a convex shape and a second section 77 having a concave shape. The second section 77 is closer to the impeller base 31 than the first section 75. This results in a bell-shaped central volume 41 as the virtual surface of revolution defined by rotation of the radially innermost vane path 45. Consequently, a longitudinal cut of the central volume 41 is concave where the radially innermost vane path 45 is convex and vice versa. Such as bell-shape of the central volume 41 has shown to perform very well for transporting off fibers into the groove inlet port 53.
(58) Similar to the embodiment shown in FIGS. 6 and 7, the height Hs of the at least one scraper 39 in axial direction is at least 50% of the depth Hcv of the central volume 41 in axial direction (see FIG. 13b and 15c). This is beneficial to guide fibers that are located close to the impeller base 31 towards the groove inlet port 53.
(59) FIGS. 14a-d illustrate in different angular positions of the impeller 19 relative to the scraper 39 the distance in radial and/or circumferential direction between the leading edge 57 and the radially innermost vane path 45. So, the leading edge 57 and the radially innermost vane path 45 are completely separate surface paths.
(60) FIGS. 15a-c show the integral suction inlet 15, preferably as an integrally molded part, in more detail. The relatively large groove inlet port 53 has an angular size of 45°<θ.sub.2<90°. As the guiding surface 47 of the scraper 39 is directly located at the second angular end 74 of the groove inlet port 53, the angular distance θ.sub.1-θ.sub.2 is zero.
(61) Analogous to FIGS. 8a-c, FIGS. 16a-c show the functioning of the embodiment according to FIGS. 12a-c in different angular positions of the impeller 19. FIGS. 16a-c show on the left bottom views through the inlet sleeve 18 on the impeller 19 at different angular positions during impeller rotation (counter-clockwise in FIGS. 16a-c on the left). In FIG. 16a, the second scraping path 45 of one of the impeller vanes 33 is positioned about 90° before the stationary scraper 39. In FIG. 16b, the impeller 19 is rotated further by about 45° so that the second scraping path 45 is closer to passing by the scraper 39. In FIG. 16c, the impeller 19 is rotated further by about another 45° so that the second scraping path 45 is in the process of passing the first scraping path 43 of the scraper 39. The sectional view on plane E-E on the right of FIG. 16c shows that the first scraping path 43 of the scraper 39 scrapes off fibers from the second section 77 of the second scraping path 45 before it scrapes off fibers from the first section 75 of the second scraping path 45. This achieved by the inclination of the scraper 39 against the rotation direction (see FIG. 15c) and facilitates the fiber transport towards the groove inlet port 53. The scrape gap g, however, is essentially constantly about 1 mm along the scraper 39.
(62) In FIG. 16a on the right, the scraper connection angle γ in the range of 110° to 170° is displayed. The scraper 39 comprises a scraper ridge 52 which the upward flowing fluid hits first, i.e. it acts as a static scraper leading edge. The scraper ridge 52 is a path on a rounded scraper surface from the inlet sleeve 18 to the scraper end 49, whereby the fluidic resistance of the scraper is reduced. In order to prevent fibrous substances from getting entangled at the scraper ridge 52, the scraper ridge 52 is swept in the direction of fluid flow by the scraper sweep angle, which is mostly larger than the scraper connection angle γ and mostly increases towards the scraper end 49. The scraper connection angle γ may be defined by the obtuse angle between a tangent at the radially outermost point of the scraper ridge and an axis parallel to the rotor axis through that point. The scraper sweep angle may be analogously defined for any point along the scraper ridge.
(63) Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.
(64) The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.
(65) In addition, “comprising” does not exclude other elements or steps, and “a” or “one” does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.
(66) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.
LIST OF REFERENCE NUMERALS
(67) 1 pump 3 pump housing 5 motor housing 7 electronics housing 9 fluid inlet 11 fluid outlet 13 pump chamber 15 suction inlet 17 pressure outlet 18 inlet sleeve 19 impeller 21 rotor axle 23 central hub 31 impeller base 33 impeller vanes 35 cover surface 37 vane ridge surface 39 scraper 41 central volume 43 first scraping path of scraper 45 second scraping path of impeller vanes 47 guiding surface 49 scraper end 51 groove(s) 52 scraper ridge 53 groove inlet port 55 groove outlet port 57 leading edge 59 trailing edge 61 leading edge base point 63 leading edge ridge point 65 first section of leading edge 67 second section of leading edge 69 first section of the groove(s) 71 second section of the groove(s) 72 first angular end of groove inlet port 73 knee of the groove(s) 74 second angular end of groove inlet port 75 first section of second scraping path 77 second section of second scraper path g scrape gap h cover gap α leading edge sweep angle α.sub.1 leading edge sweep angle at leading edge ridge point α.sub.z leading edge sweep angle at leading edge base point β sweep angle of vane ridge surface γ tilt angle of impeller vanes φ scraper connection angle r.sub.1 inner radius of cover surface r.sub.2 outer radius of cover surface φ.sub.1 first angular position of groove inlet port(s) φ.sub.2 second angular position of groove outlet port(s) θ.sub.1 angular distance between guiding surface and groove inlet port θ.sub.2 angular size of groove inlet port Hs height of the scraper in axial direction Hcv depth of the central volume in axial direction
