Pump for pumping liquid comprising solid matter
Patent Information
- Application Number
- PCT/EP2026/058378
- Authority / Receiving Office
- WO · WO
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2025-03-27
- Filing Date
- 2026-03-24
- Publication Date
- 2026-10-01
Smart Images
Figure EP2026058378_01102026_PF_FP_ABST
Abstract
Description
[0001] PUMP FOR PUMPING LIQUID COMPRISING SOLID MATTER
[0002] Technical field of the Invention
[0003] The present invention relates generally to the field of pumps configured to pump liquid comprising solid matter. Further, the present invention relates to the field of submergible pumps, such as sewage / wastewater pumps, especially configured to pump liquid such as sewage / waste-water that may comprise polymers, hygiene articles, fabrics, rags, disposable gloves, face masks, etc., i.e. solid matter of different material and shape. The present invention relates specifically to a pump comprising a hydraulic unit that comprises an impeller seat and an open impeller. The impeller seat of a pump is also known under the terms suction cover and inlet insert. The present invention relates specially to a pump configured to reduce or prevent clogging thereof.
[0004] The present invention relates to a pump suitable for pumping liquid comprising solid matter, wherein the pump comprises a hydraulic unit that comprises an impeller seat and an open impeller. The open impeller has a cover plate, a centrally located hub and at least one spirally swept blade connected to the cover plate and to the hub, wherein each blade of the impeller comprises a leading edge adjacent the hub and a trailing edge at the periphery of the impeller and a lower edge, wherein the lower edge extends from the leading edge to the trailing edge and separates a suction side of the blade from a pressure side of the blade. The impeller seat has an axial inlet defined by an inlet wall and an upper surface located downstream the inlet wall and facing in the axial direction, wherein said impeller seat comprises a guide pin connected to and extending radially inwards from said inlet wall. Wherein the leading edge of the blade of the impeller is configured to cooperate with the guide pin of the impeller seat during operation of the pump and wherein the lower edge of the blade is located opposite the upper surface of the impeller seat, and wherein an axially extending centre axis (A) of the impeller seat is located at a relative radius R* equal to 0 and a circular intersection between the inlet wall and the upper surface of the impeller seat is located at a relative radius R* equal to 1.
[0005] Background of the Invention
[0006] In sewage / wastewater treatment plants, septic tanks, wells, pump stations, etc., it occurs that solid matter / contaminations such as socks, sanitary towels, papers, disposable diapers, disposable gloves, face masks, rags, etc. obstruct the pump that is submerged in the basin / tank, i.e. socalled hard clog of the pump. This means that solid matter has entered the pump inlet and prevents the impeller from rotating. Thus, the pump is jammed by some solid matter being wedged between the impeller and the pump housing / volute. There is also a problem that solid matter gets entangled around the guide pin, which may not entirely block the pump but will have great negative impact on the efficiency of the pump. The solid matter may also get entangled around the pump and / or the cut water of the pump without wedging the impeller, socalled soft clogging. This will also have great negative impact on the efficiency of the pump.European patent EP 1357294 discloses a pump that comprises an impeller that is arranged to rotate in the volute of the pump, said impeller being suspended by a drive shaft, and the pump comprises an impeller seat having a guide pin and a feeding groove. The impeller is located at a fixed distance in the axial direction in relation to the impeller seat. The guide pin is connected to the inlet wall of the impeller seat and extends straight towards the centre of the impeller and towards the centre of the impeller seat. The leading edge of the guide pin is configured to scrape off the solid matter from the leading edge of the impeller and is configured to guide / transfer the solid matter radially outwards towards the feeding groove arranged at the upper surface of the impeller seat. Thereafter the solid matter will be trapped between the lower edge of the blade of the impeller and the feeding groove, whereby the solid matter is transferred radially outwards towards the outlet of the pump. The pump is configured to transport the solid matter through the pump in an undivided state together with the liquid.
[0007] When the impeller and the impeller seat are positioned at a fixed distance from each other, the pollutants are sometimes too large to simply pass through the pump. Large pieces of solid matter may in worst case cause the impeller to become wedged, thus seriously damaging the pump, such as bearings and drive unit. Such an unintentional shutdown is costly since it entails expensive, tedious and unplanned maintenance work. In other situations, the solid matter is torn / tugged into smaller but still large pieces of solid matter which eventually will pass the pump. However, it is energy consuming to pull apart solid matter into pieces able to pass through the pump.
[0008] European patent EP 1899609 discloses a pump that has a different solution than having a fixed distance between the impeller seat and the impeller. The pump comprises an impeller that is arranged to rotate in the volute of the pump, said impeller being suspended by a drive shaft, and the pump comprises an impeller seat having a guide pin and a feeding groove. This impeller is displaceable in the axial direction in relation to the impeller seat during operation of the pump in order to allow larger pieces of solid matter to pass through the pump, contaminations that otherwise would risk blocking the pump or wedge the impeller. The guide pin is connected to the inlet wall of the impeller seat and extends straight towards the centre of the impeller and towards the centre of the impeller seat. The impeller is displaced by the solid matter. The solid matter is first guided / transferred radially outwards by means of the leading edge of the blade and the leading edge of the guide pin and thereafter the solid matter enters between the lower edge of the blade and the upper surface of the impeller seat whereby the impeller is displaced in the axial direction by the solid matter during the time it takes for the solid matter to be transferred away from the interface between the impeller and the impeller seat.
[0009] However, having an axially displaceable impeller may entail that solid matter, such as rags, may be trapped between the impeller and the impeller seat or entangled around the impeller, without jamming the impeller but blocking / preventing liquid flow. Sometimes large pieces of solid matter, i.e. so large that the solid matter displace the impeller from the impeller seat, is still toolarge to pass the enlarged gap generated between the impeller and the impeller seat. The impeller is sometimes not jammed but the pumping ability is reduced and more solid matter will accumulate at the inlet of the impeller seat and thereby the risk for clogging is rapidly increasing. Thereto, when transporting large pieces of solid matter passed the impeller, there is an increased risk that the solid matter will clog the cut water of the pump and / or clog the downstream piping of the pump station.
[0010] Another difficulty of having an axially displaceable impeller is that it is hard to secure a correct and optimal axial distance between the lower edge of the impeller and the impeller seat, since the axial displaceability unfortunately entails an instability / tiltability of the impeller in relation to the impeller seat, which entails unbalanced forces. An axial distance between the impeller and the impeller seat that is greater than optimal, in order to prevent that the impeller may come into contact with the impeller seat, entails decreased efficiency of the pump. Thereto, each time the impeller is displaced away from the impeller seat during operation, the duty of the pump is decreased.
[0011] Such pumps and applications are also protected by suitable monitoring and control units that monitors the operation of the pump and controls the operation of the pump based thereon. For instance, when the rotational speed of the impeller decreases and / or the power consumption increased the guide pin and / or the volute of the impeller is partly clogged and the monitoring and control unit enters a cleaning sequence that comprises the step of rotating the impeller in the backward direction, i.e. opposite the direction of rotation of the impeller during normal operation of the pump. However, when a cleaning sequence is initiated and during the cleaning sequence the duty of the pump is non-existing at the same time as the pump consumes power.
[0012] Known pumps according to the above, has a large feeding groove inlet located at the circular intersection between the inlet wall and the upper surface of the impeller seat, in order to secure that solid matter, initially caught by the leading edge of the blade of the impeller and then scraped off by the leading edge of the guide pin and guided radially outwards to the inlet wall of the impeller seat, will easily enter the feeding groove and is then quickly forced through the volute of the pump due to the interaction between the lower edge of the blade of the impeller and the feeding groove at the upper surface of the impeller seat. The large feeding groove inlet is located upstream the guide pin, seen in the normal direction of rotation of the impeller, i.e. when the impeller transport liquid from the pump inlet to the pump outlet.
[0013] However, a large inlet of the feeding groove and a large cross section area of the first part of the feeding groove, especially in applications having large pressure difference between the pressure side of the blade and the suction side of the blade, will entail a large back-flow of liquid over the lower edge of the blade each time the blade passes the feeding groove. Which may have negative effect on the ability to guide / transfer solid matter radially outwards by the guide pin and impeller.If the pump is blocked / jammed / clogged, it leads to an unintentional shutdown, i.e. the pump is stopped and requires maintenance / repair, which is costly since it entails expensive, tedious and unplanned maintenance work, and thereto the pump station risk to become flooded.
[0014] Thus, there is a specific need to provide a pump and hydraulic unit that operates in an accurate, reliable and cost-efficient manner, also when the liquid comprises solid matter.
[0015] It should also be mentioned that submersible pumps of the above kind are used to pump liquid from basins that are difficult to maintain and that pumps often operate for 12 or more hours daily. It is therefore utterly desirable to provide a pump with long working life, efficient operation and a pump that is configured to reduce or prevent clogging thereof.
[0016] of the Invention
[0017] The present invention aims at obviating the aforementioned disadvantages and failings of previously known pumps, and at providing an improved pump.
[0018] A primary object of the present invention is to provide an improved pump of the initially defined type that reduce or prevent clogging of the pump, and thereby secure efficient operation of the pump also when pumping liquid comprising solid matter. It is also an object of the present invention to provide an improved pump of the initially defined type, wherein said pump is able to disintegrate the solid matter in order to decrease the risk of clogging the cut water of the pump and / or the risk of clogging the downstream piping of the pump station. It is also an object of the present invention to provide an improved pump that is able to disintegrate solid matter without suffering from harmful power spikes in connection with disintegration of the solid matter. It is also an object of the present invention to provide an improved pump, wherein the design of the guid pin entails that the shearing force needed to disintegrate the solid matter is spread over a longer period of time than prior art solutions.
[0019] of the Invention
[0020] According to the invention at least the primary object is attained by means of the initially defined pump having the features defined in the independent claim. Preferred embodiments of the present invention are further defined in the dependent claims.
[0021] According to the present invention, there is provided a shearing angle (a) between a projected tangent to the leading edge of the guide pin and a projected tangent to the intersection between the leading edge of the blade and the pressure side of the blade, between a first relative radius R* equal to 0,35 and a second relative radius R* equal to 0,95. The shearing angle (a) is alternating between a major-value range and a minor-value range upon rotation of the impeller in relation to the impeller seat, the minor-value range being limited by a lower value that is equal to or more than -30 degrees and an upper value that is equal to or less than 30 degrees and the major-value range being limited by a lower value that is equal to or more than 70 degrees and anupper value that is equal to or less than 100 degrees, wherein transition from the major-value range to the minor-value range occur at least two times.
[0022] Thus, the present invention is based on the insight that for some pumps and applications it is not optimal to try to transfer the solid matter in undivided state through the pump. The solution proposed by the inventor is to distinctly disintegrate the solid matter into smaller pieces in order to prevent clogging of the impeller, prevent clogging of the cut water of the pump, and prevent clogging of the downstream piping. The inventor has found that the most optimal shearing angle (a) between a projected tangent to the leading edge of the guide pin and a projected tangent to the intersection between the leading edge of the blade and the pressure side of the blade, is generally about fifteen degrees. However, different materials in the wastewater have different characteristics / properties and thereby different optimal shearing angle (a), thereto different operational speed of the pump will have effect on the optimal shearing angle (a). Thereto, it is practically impossible to provide an impeller and impeller seat having such an optimal shearing angle along the entire length of the leading edge of the guide pin, i.e. the guide pin would take up too much space of the inlet of the pump and thereby block solid matter from reaching the impeller. By providing a novel and inventive shape to the leading edge of the guide pin, wherein the leading edge of the guide pin is wave-shaped, the shearing angle (a) will alternate between an angle that is in the vicinity of the optimal shearing angle for different materials and operational speed, and an angle that promotes that the solid matter is guided radially outwards. Thereby the solid matter of all material is effectively disintegrated at the same time as the guide pin will not block the inlet of the pump, i.e. the length of the leading edge of the guide pin is made as short as possible. At the same time the shearing action is spread out along the entire leading edge of the guide pin and thereby also spread out in time.
[0023] According to various embodiments of the present invention, the leading edge of each blade of the impeller are swept backwards from an inner end located at the hub of the impeller towards an outer end located at the intersection between the inlet wall and the upper surface of the impeller seat. This will further optimise the size and shape of the guide pin.
[0024] According to various embodiments of the present invention, the leading edge of the guide pin has the shape of a differentiable function / line between the first relative radius R* equal to 0,35 and the second relative radius R* equal to 0,95. Thus, the leading edge of the guide pin is constituted by a smooth line without any break or angle, i.e. mathematically each and every location of the leading edge of the guide pin can be approximated by a linear segment. Thereby, no sudden spikes in the torque will be generated when the impeller and the guide pin disintegrate solid matter therebetween during rotation of the impeller in the normal / forward direction of rotation.
[0025] According to various embodiments of the present invention, the intersection between the leading edge of the blade and the pressure side of the blade has the shape of a differentiable function / line between the first relative radius R* equal to 0,35 and the second relative radius R*equal to 0,95. Thus, the intersection between the leading edge of the blade and the pressure side of the blade is constituted by a smooth line without any break or angle, i.e. mathematically each and every location of said intersection can be approximated by a linear segment. Thereby, no sudden spikes in the torque will be generated when the impeller and the guide pin disintegrate solid matter therebetween during rotation of the impeller in the normal / forward direction of rotation.
[0026] According to various embodiments of the present invention, the shearing angle (a), between a first relative radius R* equal to 0,35 and a third relative radius R* equal to 0,75, is alternating between a major-value range and a minor-value range upon rotation of the impeller in relation to the impeller seat, the minor-value range being limited by a lower value that is equal to or more than 0 degrees and an upper value that is equal to or less than 30 degrees and the majorvalue range being limited by a lower value that is equal to or more than 70 degrees and an upper value that is equal to or less than 100 degrees, wherein transition from the major-value range to the minor-value range occur at least two times.
[0027] According to various embodiments of the inventive pump, the radially innermost part of the guide pin is located radially outside the hub of the impeller. Thereby no solid matter will be able to get stuck between the axial surface of the hub of the impeller and the upper surface of the distal end of the guide pin.
[0028] Further advantages with and features of the invention will be apparent from the other dependent claims as well as from the following detailed description of preferred embodiments.
[0029] Further elucidation or prior art
[0030] CN110836188 disclose a guide pin having a serrated leading edge cooperating with the leading edge of the impeller blades, but uses a chopping action between the leading edge of the impeller and the leading edge of the guide pin to disintegrate the solid matter.
[0031] Brief description of the drawings
[0032] A more complete understanding of the abovementioned and other features and advantages of the present invention will be apparent from the following detailed description of preferred embodiments in conjunction with the appended drawings, wherein:
[0033] Fig. 1 is a schematic cross-sectional side view of the hydraulic unit of an inventive submergible pump, i.e. a wastewater pump, comprising an impeller seat and an open impeller,
[0034] Fig. 2 is a schematic cross-sectional view from above of the hydraulic unit according to figure 1, wherein the open impeller is removed,
[0035] Fig. 3 is a schematic perspective view from below of an open impeller,
[0036] Fig. 4 is a schematic cross-sectional side view of the impeller according to figure 3,Fig. 5 is a schematic perspective view from above of an impeller seat,
[0037] Fig. 6 is a schematic view from above of the impeller seat according to figure 5, and Figs. 7-14 are schematic views from above of the impeller seat according to figures 5 and 6, together with a projected representation of the lower edges and leading edges of the open impeller according to figures 3 and 4, wherein the impeller is rotated to different positions in relation to the guide pin of the impeller seat.
[0038] Detailed description of preferred embodiments of the invention
[0039] The present invention relates specifically to the field of submergible pumps especially configured for pumping liquid comprising solid matter, such as sewage / wastewater pumps. Such pumps are configured to pump liquid such as sewage / wastewater that may comprise polymers, hygiene articles, fabrics, rags, disposable gloves, face masks, etc., i.e. solid matter made of different materials and having different shapes. The present invention relates specifically to a pump comprising a hydraulic unit that comprises an impeller seat and an open impeller.
[0040] Reference is initially made to figures 1 and 2, disclosing a schematic illustration of a hydraulic unit of a submergible pump, generally designated 1. A general submergible pump will be described with reference to figures 1 and 2, and the submergible pump 1 is hereinafter referred to as pump.
[0041] The hydraulic unit of the pump 1 comprises an inlet 2, an outlet 3 and a volute 4 located intermediate said inlet 2 and said outlet 3, i.e. the volute 4 is located downstream the inlet 2 and upstream the outlet 3. The volute 4 is partly delimited by an impeller seat, generally designated 5, that encloses the inlet 2. The volute 4 is also delimited by an internal wall 6 separating the volute 4 from the drive unit (removed from figure 1) of the pump 1. Said volute 4 is also known as pump chamber and said impeller seat 5 is also known as suction cover or wear plate or inlet insert. In some applications, the outlet of the hydraulic unit also constitutes the outlet 3 of the pump 1, and in other applications the outlet of the hydraulic unit is connected to a separate outlet 3 of the pump 1. The outlet 3 of the pump 1 is configured to be connected to an outlet conduit (not disclosed). Thereto the pump 1 comprises an open impeller, generally designated 7, wherein the impeller 7 is located in the volute 4, i.e. the hydraulic unit of the pump 1 comprises an impeller seat 5 and an open impeller 7.
[0042] The drive unit of the pump 1 comprises an electric motor arranged in a liquid tight pump housing, and a drive shaft 8 extending from the electric motor through the internal wall 6 and into the volute 4. The impeller 7 is connected to and driven in rotation by the drive shaft 8 during operation of the pump 1, wherein liquid is sucked into said inlet 2 and pumped out of said outlet 3 by means of the rotating impeller 7 when the pump 1 is active. The pump housing, the impeller seat 5, the impeller 7, and other essential components, are preferably made of metal, such as aluminum and steel. The electric motor is powered via an electric power cable extending from a power supply, and the pump 1 comprises a liquid tight lead-through receiving the electric powercable. A seal arrangement 9 is provided at the interface between the drive shaft 8 and the internal wall 6 in order to prevent the pumped liquid from entering into the drive unit of the pump 1. The seal arrangement comprises one or more axial face seals.
[0043] According to preferred embodiments, the pump 1, more precisely the electric motor, is operatively connected to a control unit, such as an Intelligent Drive comprising a Variable Frequency Drive (VFD). Thus, said pump 1 is configured to be operated at a variable operational speed [rpm], by means of said control unit. According to preferred embodiments, the control unit is located inside the liquid tight pump housing, i.e. it is preferred that the control unit is integrated into the pump 1. The control unit is configured to control the operational speed of the pump 1. According to alternative embodiments the control unit is an external control unit, or the control unit is separated into an external sub-unit and an internal sub-unit. The operational speed of the pump 1 is more precisely the rpm of the electric motor and of the impeller 7 and corresponds / relates to an output frequency of the control unit. The control unit is configured and capable of operating the pump 1 and impeller 7 in a normal direction of rotation, i.e. forward, in order to pump liquid, and in an opposite direction of rotation, i.e. backwards, in order to clean or unblock the pump 1 and / or impeller 7.
[0044] The components of the pump 1 are usually cold down by means of the liquid / water surrounding the pump 1. The pump 1 is designed and configured to be able to operate in a submerged configuration / position, i.e. during operation be located entirely under the liquid surface. However, it shall be realized that the submersible pump 1 during operation must not be entirely located under the liquid surface but may continuously or occasionally be fully or partly located above the liquid surface. In dry installed applications the submergible pump 1 comprises dedicated cooling systems.
[0045] The present invention is primarily based on a new and improved impeller seat 5, that is configured to be used in pumps 1 suitable for pumping liquid comprising solid matter, for instance wastewater / sewage comprising solid matter that may risk clogging and blocking the pump 1. When solid matter clog / block the pump 1 the torque and consumed power increases and in order not to strain the pump 1 the control unit may enter a cleaning sequence whereupon the impeller 7 is rotating backwards for a short period of time. If such backward operation, one or several attempts, is not sufficient, maintenance staff need to visit the pump station and manually clean / service the pump 1. It shall be pointed out that there are several ways to detect incorrect / non-optimal operation of the pump 1, which may initiate such cleaning sequence.
[0046] According to the present invention, the impeller 7 is preferably located at a fixed distance from the impeller seat 5 during normal operation of the pump 1, i.e. the impeller 7 is not displaceable in the axial direction in relation to the impeller seat 5 during normal / forward operation of the pump 1. According to alternative embodiments, the impeller 7 is displaceable in the axial direction in relation to the impeller seat 5 during normal operation of the pump 1, wherein the impeller 7 is biased towards the impeller seat 5. In practice the impeller 7 isconfigured to be displaced away from the impeller seat 5 only if / when hard objects enter the pump, i.e. hard objects that cannot be feasibly disintegrated and risk damaging the pump 1.
[0047] According to various embodiments, the impeller 7 is preferably located at a fixed distance from the impeller seat 5 also during reverse / backward operation of the pump 1. According to alternative embodiments, the impeller 7 is displaceable in the axial direction in relation to the impeller seat 5 during reverse / backward operation of the pump 1, i.e. during cleaning, in order to remove large pieces of solid matter from the pump 1.
[0048] Reference is now made to figures 3 and 4 disclosing a schematic embodiment of the open impeller 7. The impeller 7 comprises a cover plate 10, a centrally located hub 11 and at least one spirally swept blade 12 connected to the cover plate 10 and to the hub 11. According to various embodiments, the impeller 7 comprises at least two spirally swept blades 12 connected to the cover plate 10 and to the hub 11. Said at least two blades 12 are equidistant located around the hub 11. The blade 12 are also known as vanes, and the cover plate 10 is also known as upper shroud.
[0049] The blades 12 are swept, seen from the hub 11 towards the periphery of the impeller 7, in a direction opposite the direction of rotation of the impeller 7 during normal (liquid pumping) operation of the pump 1. Thus, seen from below, i.e. figure 3, the direction of rotation of the impeller 7 during normal operation is counterclockwise.
[0050] Each blade 12 comprises a leading edge 13 adjacent the hub 11 and a trailing edge 14 at the periphery of the impeller 7. The leading edge 13 of the impeller 7 is located upstream the trailing edge 14, wherein two adjacent blades 12 together defines a channel extending from the leading edges 13 to the trailing edges 14. The leading edge 13 is located at the inlet of the impeller seat 5, and the leading edge 13 is spirally swept from the hub outwards, in the same direction as the general sweep of the blade 12. During operation, the leading edges 13 grabs hold of the liquid, the channels accelerate and / or add pressure to the liquid, and the liquid leaves the impeller 7 at the trailing edges 14. Thereafter the liquid is guided by the volute 4 of the hydraulic unit towards the outlet 3. Thus, the liquid is sucked into the impeller 7 and pressed out of the impeller 7. Said channels are also delimited by the cover plate 10 of the impeller 7 and by the impeller seat 5 of the volute 4. The diameter of the impeller 7 and the shape and configuration of the channels / blades determines the pressure build up in the liquid and the pumped flow.
[0051] Each blade 12 also comprises a lower edge 15, wherein the lower edge 15 extends from the leading edge 13 to the trailing edge 14 and separates a suction side / surface 16 of the blade 12 from a pressure side / surface 17 of the blade 12. The lower edge 15 is configured to be facing and located opposite the impeller seat 5 of the pump 1. Thus, the suction side 16 of one blade 12 is located opposite the pressure side 17 of an adjacent blade 12. The leading edge 13 and the trailing edge 14 also separates the suction side 16 from the pressure side 17. The leading edge 13 is preferably rounded.Reference is now made to figures 5 and 6 disclosing an inventive impeller seat 5. The impeller seat 5 comprises an axial inlet 18 defined by an inlet wall 19, wherein the impeller seat 5 has an inlet radius (R) measured from an axially extending centre axis (A) to the circular intersection 20 between the inlet wall 19 and an upper surface 21 of the impeller seat 5.
[0052] The inlet wall 19 is more or less cylindrical or slightly conical having a decreasing flow area in the downstream direction, i.e. upwards in figure 5. The upper surface 21 of the impeller seat 5 is the surface that is seen from above, and the circular intersection 20 is the plane of the impeller seat 5 having the smallest flow area, i.e. the transition between the inlet wall 19 and the upper surface 21. The upper surface 21 may comprise a flat section 21a and an arc-shaped section 21b, wherein the flat section 21a may be located in a horizontal plane or be tilted inwards / downwards and the arc-shaped section 21b interconnects the flat section 21a and the inlet wall 19. According to various embodiments the upper surface 21 only comprises an arc-shaped section 21b extending all the way from the inlet wall 19 to the periphery of the impeller seat 5. According to other various embodiments the upper surface 21 only comprises a flat section 21a extending all the way from the inlet wall 19 to the periphery of the impeller seat 5.
[0053] Said impeller seat 5 comprises a guide pin 22 connected to and extending radially inwards from said inlet wall 19, the guide pin 22 having a tip radius (r) measured from the axially extending centre axis (A) to the radially innermost part of the guide pin 13. The main function of the guide pin 13 is to disintegrate solid matter and to remove solid matter from the leading edge 13 of the impeller 7, during normal operation of the pump 1. The lower edge 15 of the blade 12 is connected to the leading edge 13 at a location corresponding to the circular intersection 20 of the impeller seat 5. Thus, the leading edge 13 of the blade 12 of the impeller 7 is configured to cooperate with the guide pin 22 of the impeller seat 5 during normal operation of the pump 1, wherein the lower edge 15 of the blade 12 is located opposite the upper surface 21 of the impeller seat 7.
[0054] According to various embodiments (not disclosed), said impeller seat 5 may also comprise a feeding groove arranged in the upper surface 21 of the impeller seat 5 and extending from the circular intersection 20 to the periphery of the impeller seat 5. The feeding groove is preferably swept in the direction of rotation of the impeller 7, seen from the inlet wall 19 towards the periphery. The function of the feeding groove is to transfer the solid matter radially outwards, during normal operation of the pump 1, in cooperation with the lower edge 15 of the blade 12 of the impeller 7.
[0055] The axially extending centre axis (A) of the impeller seat 5 is located at a relative radius R* equal to 0 and the circular intersection 20 between the inlet wall 19 and the upper surface 21 of the impeller seat 5 is located at a relative radius R* equal to 1, see figure 2. The guide pin 22 comprises a leading edge 23, a trailing edge 24 and an upper surface 25.
[0056] Reference is now especially made to figures 7-14, wherein the impeller 7 has different orientation in relation to the impeller seat 5 in the different figures. In figures 7-14 the free lowerrim of a blade 12 of the impeller 7 and of the hub 11 of the impeller 7 are projected onto the impeller seat 5. More precisely, the joint action or interface between the leading edge 13 of the blade 12 and the guide pin 22 is illustrated.
[0057] The present invention is based on a new design, configuration and function of the guide pin 22. The design of the guide pin 22 is defined using imaginary circles or relative radius R* originating from the axial centre axis A of the impeller seat 5. The guide pin 22 does not extend all the way to the axial centre axis A, but the tip of the guide pin 22 is located at a distance from said axial centre axis A. A first relative radius R1 is defined equal to 0,35 and a second relative radius R2 is defined equal to 0,95. The tip of the guide pin 22 is located closer to the axial centre axis than said first relative radius Rl. Said first relative radius R1 and said second relative radius R2 are used when defining the shape of the guide pin 22, since the impeller seat 5 comprises a rounded transition between the guide pin 22 and the inner wall 19 and the tip of the guide pin 22 is preferably rounded, due to design and manufacturing reasons. Thereby, the shape of the radially innermost and outermost parts of the guide pin 22 are disregarded when defining the overall shape of the guide pin 22.
[0058] The guide pin 22 has a general arc-shape when observed in an axial direction from above, i.e. a centre line extending from the middle of the base of the guide pin 22 to the tip of the guide pin 22 is arc-shaped.
[0059] According to various embodiments, at least a main portion of an upper surface 25 of the guide pin 22 is a plane surface, said main portion being defined by the first relative radius Rl, the second relative radius R2, the leading edge 23 and the trailing edge 24. In this preferred context the term plane surface means that any straight line joining any two points on the surface lies entirely on said surface. According to various embodiments, said main portion of the upper surface 25 of the guide pin 22 is tilted in relation to a horizontal plane, wherein the distal end (tip) of the guide pin 22 is located upstream the proximal end (base) of the guide pin 22, seen in the axial direction. From the proximal end of the guide pin 22 towards the distal end of the guide pin 22, the guide pin 22 has a decreasing heigh, and the under surface of the guide pin 22 is rounded, in order to prevent solid matter from getting stuck on the underside of the guide pin 22. It is also plausible to alternatively have the upper surface 25 the guide pin 22 bent / curved upstream or downstream in order to follow a corresponding shape of the leading edge 13 of the blade 12 of the impeller 7.
[0060] According to various embodiments, the distance, i.e. the gap height, between the leading edge 13 of the blade 12 and the upper surface 25 of the guide pin 22 is equal to or more than 0,05 mm and equal to or less than 2 mm, preferably equal to or more than 0,1 mm and equal to or less than 1 mm, taken in the axial direction. The same applies to the distance between the upper surface 21 of the impeller seat 5 and the lower edge 15 of the blade 12. According to various embodiments, the radially innermost part (tip) of the guide pin 22 is located radially outside the hub 11 of the impeller 7. Thereby, solid matter may not be trapped between the hub 11 of theimpeller 7 and the upper surface 25 of the guide pin 22, and solid matter raked off during reverse operation of the pump 1 will more easily leave the guide pin 22.
[0061] According to the invention, a shearing angle (a) between a projected tangent 26 to the leading edge 23 of the guide pin 22 and a projected tangent 27 to the intersection between the leading edge 13 of the blade 12 and the pressure side 17 of the blade 12, between the first relative radius R1 and the second relative radius R2, is alternating between a major-value range and a minor-value range upon rotation of the impeller 7 in relation to the impeller seat 5. As can be seen from the figures 8-13, said projected tangents 26 and 27 are drawn from the intersection point between the leading edge 23 of the guide pin 22 and the intersection between the leading edge 13 of the blade 12 and the pressure side 17 of the blade 12. The minor-value range is limited by a lower value that is equal to or more than -30 degrees and an upper value that is equal to or less than 30 degrees and the major-value range is limited by a lower value that is equal to or more than 70 degrees and an upper value that is equal to or less than 100 degrees, wherein transition from the major-value range to the minor-value range occur at least two times. Thus, the leading edge 13 of the blade 12 intersects the leading edge 23 of the guide pin 22 at different relative radius while the impeller 7 is rotating, and the value of the shearing angle (a) for the intersections between the projected tangent 26 to the leading edge 23 of the guide pin 22 and the projected tangent 27 to the intersection between the leading edge 13 of the blade 12 and the pressure side 17 of the blade 12 in the range between 0,35-0,95 relative radius alternate between the majorvalue and the minor-value. The major-value is within the major-value range and the minor-value is within the minor-value range. Thus, the solid matter will in a controlled way be guided radially outwards a little bit when the shearing angle is in the major-value range, then partially disintegrated when the shearing angle is in the minor-value range, then guided radially outwards a little bit, then partially disintegrated, and so on. Thereby, the solid matter contained in the pumped liquid is effectively disintegrated into smaller pieces, wherein the smaller pieces of solid matter have less risk of clogging the cut water of the volute 4 and less risk of clogging the outlet pipe / piping. The inventive design of the impeller seat 5 entails that the solid matter caught between the leading edge 13 of the blade and the leading edge 23 of the guide pin 22 is successively disintegrated / separated and thereby the force needed is decreased and any force spikes are reduced in relation to shearing the solid matter in one single step.
[0062] Said tangents are projected in the axial direction. It shall be pointed out that the transition from the major-value range to the minor-value range occur at least two times, is determined during the rotation of the impeller 7 in the normal / forward direction of rotation in relation to the impeller seat 5 and when a single leading edge 13 of the impeller 7 is passing the leading edge 23 of the guide pin 22.
[0063] According to various embodiments, the leading edge 23 of the guide pin 22 has the shape of a differentiable function / line between the first relative radius R1 and the second relative radius R2. Thus, the leading edge 23 of the guide pin 22 is constituted by a smooth line without anybreak or angle, i.e. each location of the leading edge of the guide pin can be mathematically approximated by a linear segment. According to various embodiments, the intersection between the leading edge 13 of the blade 12 and the pressure side 17 of the blade 12 has the shape of a differentiable function / line between the first relative radius R1 and the second relative radius R2. Thus, the intersection between the leading edge 13 of the blade 12 and the pressure side 17 of the blade 12 is constituted by a smooth line without any break or angle, i.e. each location of the leading edge of the guide pin can be mathematically approximated by a linear segment.
[0064] Figure 7 illustrates that the guide pin 22 does not overlap with the hub 11 of the impeller 7. From figure 7 the impeller 7 rotates and the leading edge 13 of the blade 12 starts to engage / interact with the leading edge 23 of the guide pin 22, and in Figure 8 the impeller 7 has rotated until the shearing angle a) between the projected tangent 26 and the projected tangent 27 has reached a first major-value. The first major-value is preferably in the range 90-100 degrees.
[0065] Figure 9 disclose further rotation of the impeller 7, and the shearing angle a) between the projected tangent 26 and the projected tangent 27 has reached a first minor-value. The first minor-value is preferably in the range 15-25 degrees. Figure 10 disclose further rotation of the impeller 7, and the shearing angle a) between the projected tangent 26 and the projected tangent 27 has reached a second major-value. The second major-value is preferably in the range 80-90 degrees. Figure 11 disclose further rotation of the impeller 7, and the shearing angle a) between the projected tangent 26 and the projected tangent 27 has reached a second minorvalue. The second minor-value is preferably in the range 0-15 degrees.
[0066] According to various embodiments, the transition from the major-value range to the minorvalue range occur at least three times. Figure 12 disclose further rotation of the impeller 7, and the shearing angle (a) between the projected tangent 26 and the projected tangent 27 has reached a third major-value. The third major-value is preferably in the range 70-80 degrees.
[0067] Figure 13 disclose further rotation of the impeller 7, and the shearing angle a) between the projected tangent 26 and the projected tangent 27 has reached a third minor-value. The third minor-value is preferably in the range -25 - 0 degrees. In figure 13 the shearing angle (a) is negative, i.e. a piece of the solid matter will become trapped and cannot escape radially outwards, but will be inevitably disintegrated. The third minor-value is negative in order to reduce the amount of solid matter that has to be finally disintegrated in the location disclosed in figure 14. Figure 14 disclose further rotation of the impeller 7, and illustrates the final shearing between the leading edge 13 of the blade 12 and the leading edge 23 of the guide pin 22.
[0068] According to various embodiments, the minor-value range is limited by a lower value that is equal to or more than -25 degrees and an upper value that is equal to or less than 25 degrees. According to various embodiments, the major-value range is limited by a lower value that is equal to or more than 75 degrees and an upper value that is equal to or less than 95 degrees.
[0069] According to various embodiments, the shearing angle (a), between the first relative radius R1 and a third relative radius R3 equal to 0,75, is alternating between a major-value range and aminor-value range upon rotation of the impeller 7 in relation to the impeller seat 5. The minorvalue range is limited by a lower value that is equal to or more than 0 degrees and an upper value that is equal to or less than 30 degrees and the major-value range being limited by a lower value that is equal to or more than 70 degrees and an upper value that is equal to or less than 100 degrees, wherein transition from the major-value range to the minor-value range occur at least two times.
[0070] Feasible modifications of the Invention
[0071] The invention is not limited only to the embodiments described above and shown in the drawings, which primarily have an illustrative and exemplifying purpose. This patent application is intended to cover all adjustments and variants of the preferred embodiments described herein, thus the present invention is defined by the wording of the appended claims and the equivalents thereof. Thus, the equipment may be modified in all kinds of ways within the scope of the appended claims. Any subject matter falling outside the scope of the claims is provided for information purposes and for placing the invention into a relevant context.
[0072] It shall also be pointed out that all information about / concerning terms such as above, under, upper, lower, etc., shall be interpreted / read having the equipment oriented according to the figures, having the drawings oriented such that the references can be properly read. Thus, such terms only indicate mutual relations in the shown embodiments, which relations may be changed if the inventive equipment is provided with another structure / design.
[0073] It shall also be pointed out that even thus it is not explicitly stated that features from a specific embodiment may be combined with features from another embodiment, the combination shall be considered obvious, if the combination is possible.
[0074] Throughout this specification and the claims which follows, unless the context requires otherwise, the word "comprise", and variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or steps or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.
Claims
Claims1. Pump (1) for pumping liquid comprising solid matter, the pump (1) comprising a hydraulic unit that comprises an impeller seat (5) and an open impeller (7),- the open impeller (7) having a cover plate (10), a centrally located hub (11) and at least one spirally swept blade (12) connected to the cover plate (10) and to the hub (11), wherein each blade (12) of the impeller (7) comprises a leading edge (13) adjacent the hub (11) and a trailing edge (14) at the periphery of the impeller (7) and a lower edge (15), wherein the lower edge (15) extends from the leading edge (13) to the trailing edge (14) and separates a suction side (16) of the blade (12) from a pressure side (17) of the blade (12), and- the impeller seat (5) having an axial inlet (18) defined by an inlet wall (19) and an upper surface (21) located downstream the inlet wall (19) and facing in the axial direction, wherein said impeller seat (5) comprises a guide pin (22) connected to and extending radially inwards from said inlet wall (19),wherein the leading edge (13) of the blade (12) of the impeller (7) is configured to cooperate with the guide pin (22) of the impeller seat (5) during operation of the pump (1) and wherein the lower edge (15) of the blade (12) is located opposite the upper surface (21) of the impeller seat (5), and wherein an axially extending centre axis (A) of the impeller seat (5) is located at a relative radius R* equal to 0 and a circular intersection (20) between the inlet wall (19) and the upper surface (21) of the impeller seat (5) is located at a relative radius R* equal to 1,characterized in that a shearing angle (a) between a projected tangent (26) to the leading edge (23) of the guide pin (22) and a projected tangent (27) to the intersection between the leading edge (13) of the blade (12) and the pressure side (17) of the blade (12), between a first relative radius R1 equal to 0,35 and a second relative radius R2 equal to 0,95, is alternating between a major-value range and a minor-value range upon rotation of the impeller (7) in relation to the impeller seat (5), the minor-value range being limited by a lower value that is equal to or more than -30 degrees and an upper value that is equal to or less than 30 degrees and the major-value range being limited by a lower value that is equal to or more than 70 degrees and an upper value that is equal to or less than 100 degrees, wherein transition from the major-value range to the minor-value range occur at least two times.
2. The pump (1) according to claim 1, wherein the leading edge (13) of each blade (12) of the impeller (7) being swept backwards from an inner end located at the hub (11) of the impeller (7) towards an outer end located at the circular intersection (20) between the inlet wall (19) and the upper surface (21) of the impeller seat (5).
3. The pump (1) according to claim 1 or 2, wherein the leading edge (23) of the guide pin (22) has the shape of a differentiable function / line between the first relative radius R1 equal to 0,35 and the second relative radius R2 equal to 0,95.
4. The pump (1) according to any of claims 1-3, wherein the intersection between the leading edge (13) of the blade (12) and the pressure side (17) of the blade (12) has the shape of a differentiable function / line between the first relative radius R1 equal to 0,35 and the second relative radius R2 equal to 0,95.
5. The pump (1) according to any preceding claim, wherein the minor-value range being limited by a lower value that is equal to or more than -25 degrees and an upper value that is equal to or less than 25 degrees.
6. The pump (1) according to any preceding claim, wherein the major-value range being limited by a lower value that is equal to or more than 75 degrees and an upper value that is equal to or less than 95 degrees.
7. The pump (1) according to any preceding claim, wherein the transition from the major-value range to the minor-value range occur at least three times.
8. The pump (1) according to any preceding claim, wherein the shearing angle (a), between the first relative radius R1 equal to 0,35 and a third relative radius R3 equal to 0,75, is alternating between a major-value range and a minor-value range upon rotation of the impeller (7) in relation to the impeller seat (5), the minor-value range being limited by a lower value that is equal to or more than 0 degrees and an upper value that is equal to or less than 30 degrees and the majorvalue range being limited by a lower value that is equal to or more than 70 degrees and an upper value that is equal to or less than 100 degrees, wherein transition from the major-value range to the minor-value range occur at least two times.
9. The pump (1) according to any preceding claim, wherein the radially innermost part of the guide pin (22) is located radially outside the hub (11) of the impeller (7).
10. The pump (1) according to any preceding claim, wherein the radially innermost part of the guide pin (22) is located upstream the radially outermost part of the guide pin (22) seen in the axial direction of the pump (1).
11. The pump (1) according to any preceding claim, wherein a gap between the leading edge (13) of the blade (12) of the impeller (7) and the leading edge (23) of the guide pin (22) is equal to or more than 0,05 mm and equal to or less than 2 mm, taken in the axial direction.
12. The pump (1) according to any preceding claim, wherein the open impeller (7) comprises at least two spirally swept blades (12) connected to the cover plate (10) and to the hub (11).
13. The pump (1) according to any preceding claim, wherein a first minor-value range is 15-25 degrees, and a second minor-value range is 0-15 degrees14. The pump (1) according to claim 13, wherein a third minor-value range -25-0 degrees.
15. The pump (1) according to any preceding claim, wherein a first major-value range is 90-100 degrees, and a second major-value range is 80-90 degrees16. The pump (1) according to any preceding claim, wherein a third major-value range 70-80 degrees.