TECHNICAL FIELD

[0001] The present subject matter relates, in general, to pumps, and in particular to a cutter pump assembly used for pumping fluids with flexible solid and/or semi-solid particles.

BACKGROUND

[0002] Fluids with flexible solid and/or semi-solid particles, such as sewage, may have to be pumped for transportation from one location to another. The solid or semisolid matters, when being pumped, can get stuck in the suction passage of the pump and clog the pump. To avoid this, the pumps used for pumping sewage materials include a shredding mechanism, such as a cutter, for cutting, grinding, or shredding flexible solids or semisolid matter. Such pumps, which include a shredding mechanism, are also referred to as cutter pumps. The sewage material is desirably shredded into smaller particles by the shredding mechanism of the cutter pump, allowing the resulting fluid with particulate matter to be pumped and transferred through smaller diameter pipes. However, as the solid/ semi-solid particles may be flexible and of varying dimensions, the cutter pumps nevertheless tend to get clogged from time to time.

BRIEF DESCRIPTION OF DRAWINGS [0003] The detailed description is given with reference to the accompanying figures. In the figures, the left-most digit(s) of a reference number identifies the figure in which the reference number first appears. The same numbers are used throughout the drawings to reference like features and components.

[0004] Fig. 1(a) shows a perspective view of a cutter unit of a cutter pump assembly, in accordance with an example implementation of the present subject matter. [0005] Fig. 1(b) shows a top view of a cutter unit of a cutter pump assembly, in accordance with an example implementation of the present subject matter.

[0006] Fig. 1(c) shows an imaginary ellipse for designing a profile of a cutter protrusion, in accordance with an example implementation of the present subject matter.

[0007] Fig. 2 shows a perspective view of a cutter housing of a cutter pump assembly, in accordance with an example implementation of the present subject matter.

[0008] Fig. 3 shows a perspective view of a locking assembly of a spinner nut and locking screw, in accordance with an example implementation of the present subject matter.

[0009] Fig. 4 shows a perspective view of a cutter unit housed in a cutter housing, in accordance with an example implementation of the present subject matter. [0010] Fig. 5 shows a cross-sectional view of a cutter unit housed in a cutter housing, in accordance with an example implementation of the present subject matter.

[0011] Fig. 6 shows a cross-sectional view of a cutter pump assembly, in accordance with an example implementation of the present subject matter. [0012] Fig. 7 shows an enlarged or detailed view of a plurality of radial grooves in a cutter pump assembly, in accordance with an example implementation of the present subject matter.

[0013] Fig. 8 shows a control system of a cutter pump assembly, in accordance with an implementation of the present subject matter. DETAILED DESCRIPTION

[0014] The present subject matter relates to a cutter pump assembly having a cutting unit for cutting of solids present in a fluid being pumped. As used herein, solids will be understood to refer to any solid or semi- solid or particulate material and may be of any flexibility, consistency, or dimension.

[0015] A cutter pump is generally used in transporting sewage that has entrained solids. A cutter is used in the cutter pump for shredding the solids to a smaller particle size for easier transport of the sewage through smaller diameter pipes. The cutters used conventionally have a horizontal blade profile, such as in the form of blades provided on veins of an impeller. Such cutters cannot deal with long flexible solids and are not very efficient. Moreover, if the cutter pump gets clogged, the pump has to be stopped and cleaned manually.

[0016] The present subject matter provides a cutter pump assembly with a cutter unit and a cutter housing for shredding solids present in fluids, such as sewage, being pumped. The cutter unit has multiple shear areas for cutting or shredding the solids in the fluid. Further, aspects of the present subject matter facilitate counter rotation of the cutter unit in case of clogging and allow the cutter unit and the cutter housing to cut the solids during the counter rotation as well. The cutter unit and the cutter housing are accordingly provided with cutting edges and suitable structures which enables the shredding of solids in both clockwise and anti clockwise directions of rotation of the cutter unit. Therefore, the likelihood of clogging of the cutter pump assembly is reduced and, even on clogging, the cutter pump assembly may be cleaned by operating it in a reverse direction for a short time duration. Hence, the cutter pump assembly of the present subject matter is more efficient compared to cutter pump assemblies known in the art and allows for near continuous pumping operations for pumping sewage and similar fluids.

[0017] In one example, a cutter pump assembly of the present subject matter includes a pump casing, a base stand, an impeller, a shaft, a cutter housing, and a cutter unit. The shaft extends into the pump casing and the pump casing encloses a distal end of the shaft. The impeller is axially mounted on the distal end of the shaft and enclosed between the casing base stand of the cutter pump assembly end. The cutter unit is in-turn mounted on a suction end of the impeller. The cutter unit includes first cutting edges or blades projecting outwards from a cylindrical body.

[0018] The cutter housing, on the other hand, is mounted on the base stand. The cutter housing includes an annular housing body and housing protrusions protruding from an inner surface of the annular housing body. The cutter housing comprises second cutting edges or blades on the inner circumference area. In one example, the second cutting edges are present in a first portion of the cutter housing. The first cutting edges and second cutting edges are configured to be in close tolerance to each other in the first portion of the cutter housing. A second portion of the cutter housing has an even inner surface, i.e., does not include the second cutting edges and therefore has free space with respect to the cutter unit.

[0019] The present subject matter provides a cutter pump assembly that performs multiple shredding actions on the solids in the pumped fluid and hence is more efficient than conventional cutter pump assemblies. Further, the cutter pump assembly can shred in clockwise as well as counter clockwise direction of operation to help in de-clogging. This provides an advantage in case of clogging because in the cutter pump known in the general state of art, once the cutter pump is clogged, the cutter needs to be cleaned manually, whereas in the present subject matter, the clogged cutter pump assembly can be automatically de-clogged.

[0020] Further, as the cutting edges are provided vertically with reference to the inlet of the cutter pump, the cutter pump assembly can perform a more efficient cutting action. As the cutter unit is more efficient, smaller sized cutter units can be used. The smaller sized cutter unit saves on weight, cost of construction, power consumed, and cost of operation of the cutter pump assembly.

[0021] The above and other features, aspects, and advantages of the subject matter will be better explained with regard to the following description and accompanying figures. It should be noted that the description and figures merely illustrate the principles of the present subject matter along with examples described herein and, should not be construed as a limitation to the present subject matter. It is thus understood that various arrangements may be devised that, although not explicitly described or shown herein, embody the principles of the present disclosure. Moreover, all statements herein reciting principles, aspects, and examples thereof, are intended to encompass equivalents thereof. Further, for the sake of simplicity, and without limitation, the same numbers are used throughout the drawings to reference like features and components.

[0022] Fig. 1(a) illustrates a perspective view of a cutter unit 100 of a cutter pump assembly, in accordance with an example implementation of the present subject matter. In one example, the cutter unit 100 includes a cylindrical body 102 with an annular center 104. The cylindrical body 102 may have a plurality of cutter protrusions 106 protruding from the cylindrical body 102. Each cutter protrusion 106 may include a first cutting edge 108. The first cutting edges 108 are hence provided on the outer circumferential area of the cylindrical body 102 of the cutter unit 100. The portion of the cutter unit 100 between two consecutive cutting edges of the first cutting edges 108 can have a curved profile. The geometry of the cutter unit 100 helps in allowing smooth flow of the fluid while the solid particles are shredded by the first cutting edges 108.

[0023] A first side 110 of the cutter unit 100 has a pair of holes 112 and a circular projection 114 protruding outward around the annular center 104. The pair of holes 112 are used to couple the cutter unit 100 with an impeller, which will be discussed later. A second side 116 of the cutter unit 100, opposite to the first side 110, may have a plane surface around the annular center 104. A spinner nut may be coupled to the cutter unit 100 from the second side 116, as will be explained later.

[0024] The cutter protrusions 106, and therefore the first cutting edges 108, may be provided vertically, i.e., along the length of the cutter unit 100, and may extend from a first end of the cylindrical body 102 towards the first side 110 to a second end of the cylindrical body 102 towards the second side 116. In one example, each of the first cutting edges 108 can help in cutting solid particles when the cutter unit 100 rotates, in either clockwise or anti-clockwise direction, around an axis passing vertically through the annular center 104 because of the configuration of the cutter protrusions 106 as explained below with reference to Fig. 1(b).

[0025] The vertical provision of the first cutting edges 108 and ability to cut in both directions of rotation leads to a more efficient cutting action and allows for automatic de-clogging of the cutter pump assembly as will be explained later. Hence, fluids with solids can be pumped efficiently with a smaller sized cutter unit 100 than cutter units used conventionally. The reduction in the size of the cutter unit 100 helps in a reduction of the weight and cost of construction. In addition, the cutter unit 100, having a reduced weight, requires less power for operation, and therefore, consumes less energy.

[0026] Fig. 1(b) shows a top view of a cutter unit 100 of a cutter pump assembly, in accordance with an example implementation of the present subject matter. In one example, each cutter protrusion 106 includes a curvilinear edge 118 and a straight edge 120. The curvilinear edge 118 has a curved portion 118a protruding from a periphery of the cylindrical body 102 and ending in a linear portion 118b. A first cutting edge 108 is formed at a junction of the straight edge 120 and the linear portion 118b.

[0027] In one example, each of the first cutting edges 108 can form an angle between 10° to 120° between the straight edge 120 and a tangent to the circumferential surface of the cutter unit adjacent to the straight edge. In one example, as shown in Fig. 1(b), the angle can be 84°. The first cutting edges 108 act as blades and help in shredding of the solids in the fluid being pumped.

[0028] Due to the profile of the cutter protrusion 106, the first cutting edge 108 can help in cutting the particles in both clockwise and anti-clockwise direction of rotation of the cutter unit 100. [0029] In one example, as shown in Fig. 1(c), the curved portion 118a of each cutter protrusion 106 lies on an imaginary ellipse 122 partially overlapping a circular cross-section 124 of the cylindrical body 102. Thus, the curved profile between two cutter protrusions 106 includes overlapping circular and elliptical profiles. Such a curved profile helps in smoothening the flow of the fluid around the cutter unit 100 as the solids are shredded by the first cutting edges 108 of the cutter protrusions 106.

[0030] As will be appreciated, the number of cutter protrusions 106, and therefore first cutting edges 108, provided in the cutter unit 100 can vary according to the size of the cutter unit 100, the cutter housing in which the cutter unit 100 is to be housed, the nature of fluid to be pumped, the type of entrained solids expected to be present in the fluid, and the like. Further, other geometric parameters, such as the diameters of the imaginary ellipse 122 and the circular cross-section 124, the length of the straight edge 120 and the linear portion 118b of the curvilinear edge 118, and the angle of the straight edge 120 may also vary based on the size of the cutter unit 100 and other operational requirements. In one example, the cutter unit 100 can include three or more first cutting edges 108.

[0031] Fig. 2 illustrates a perspective view of a cutter housing 200 of a cutter pump assembly, in accordance with an example implementation of the present subject matter. The cutter housing 200 can enclose the cutter unit 100 when assembled in a cutter pump assembly, as will be explained later.

[0032] In one example, the cutter housing 200 includes an annular housing body 202 and housing protrusions 204 provided on the inner circumferential area 206 of the annular housing body 202. The housing protrusions 204 include second cutting edges 208 for shearing the solid particles in the fluid to be pumped in association with the first cutting edges 108 of the cutter unit 100.

[0033] Each housing protrusion 204 may be formed as a triangular prism over the inner surface of the annular housing body 202, with edges of the triangular prism forming the second cutting edges 208, which act as blades. Thus, each of the housing protrusions 204 may comprise a first blade side 210 and a second blade side 212. The second cutting edges 208 are formed at a junction of the first blade side 210 and second blade side 212.

[0034] In one example, the housing protrusions 204 may be provided along a length of the annular housing body 202 in one portion of the annular housing body 202. For example, the housing protrusions 204 may be provided along the length in a first portion 214 of the annular housing body 202 while a second portion 216 of the annular housing body may have an even surface. The first portion 214 of the cutter housing may extend from a fluid inlet end of the cutter housing 200 along a partial length of the cutter housing 200. In another example, the housing protrusions 204 may be provided along the full length of the annular housing body 202. The relative lengths of the first portion 214 and the second portion 216 may change depending on the size of the cutter housing 200 and the nature of the fluid and solids to be pumped.

[0035] In one example, the outer surface of the annular housing body 202 has a housing fixture 218 disposed thereon. The housing fixture 218 may be a circular band with a pair of mounting arms 220 provided diametrically opposite to each other. The pair of mounting arms have a second pair of holes 222 to mount the cutter housing 200 on a base stand in a cutter pump assembly. The housing fixture 218 may be provided centrally on the annular housing body 202 and towards the first portion 214, depending on the size of the annular housing body 202 and the length of the first portion 214.

[0036] As will be appreciated, the number of housing protrusions 204, and therefore second cutting edges 208, in the cutter housing 200 can vary according to the size of the cutter housing 200 and the cutter unit 100 to be housed in the cutter housing 200, the nature of fluid to be pumped, the type of entrained solids expected to be present in the fluid, and the like. Further, other geometric parameters, such as the lengths of the first blade side 210 and second blade side 212 may also vary based on the size of the cutter housing 200 and other operational requirements. In one example, the cutter housing 200 may include three or more second cutting edges 208.

[0037] Fig. 3 illustrates a perspective view of a locking assembly 300 of a spinner nut 302 and locking screw 304. A first end 306 of the spinner nut 302 includes a tapered surface 308 having an outwardly reducing diameter, i.e., a diameter which reduces towards the first end 306 of the spinner nut 302, and a hollow center 310. A second end 312 of the spinner nut may be a flat disc with the hollow center 310 extending into the second end 312. The locking screw 304 is a threaded screw with a cylindrical body comprising a head 316 and a tail 318. The tapered surface 308 of the spinner nut 302 guides long or large solids in the pumped fluid into the cutter housing 200, protecting the cutter pump assembly from blockage due to abrupt suction of large or long solids.

[0038] Fig. 4 illustrates a perspective view 400 of the cutter unit 100 housed in the cutter housing 200, in accordance with an example implementation of the present subject matter. As shown in the perspective view 400, the cutter unit 100 is housed in the cutter housing 200, and the spinner nut 302 (not shown) and the locking screw 304 (not shown) are fastened to the cutter unit 100. The locking assembly 300 enables the cutter unit 100 to be detachably fastened to a shaft of the cutter pump assembly. The locking screw 304 passes through the annular center 104 (not shown) of the cutter unit 100 such that the head 316 of the locking assembly 300 is towards the second side 116 of the cutter unit 100 and the tail 318 is towards the first side 110 (not shown) of the cutter unit 100. The locking screw 304 can be coupled to the cutter unit 100 by threading methods known in the art such that the cutter unit 100 is coupled to the spinner nut 302 and the locking screw 304. The coupling of the cutter unit 100 with the shaft of the cutter pump assembly by the locking assembly 300 enables the cutter unit 100 to rotate along with the shaft.

[0039] A close tolerance, i.e., a small gap, is provided between the first and second cutting edges so that they do not come into contact during rotation of the cutter unit 100 and are able to efficiently cut the particles in the fluid being pumped. Thus, the cutter unit 100 makes no contact with the cutter housing 200 and a suction passage 402 of varying width is formed between the cutter unit 100 and the cutter housing 200.

[0040] The assembly of the cutter unit 100 and the cutter housing 200 enables the first cutting edges 108 and the second cutting edges 208 to shred/ cut the solids in the pumped fluid material. The solids in the pumped fluid material are continuously cut-off or chopped during rotation of the cutter unit 100 because of the presence of the first cutting edges 108 on the cutter unit 100 and the second cutting edges 208 on the cutter housing 200. The presence of two opposing cuttings edges improves the cutting action. Furthermore, the free space above the housing protrusions 204 in the second portion 216 ensures smooth flow/ passage of the pumped fluid material.

[0041] Fig. 5 illustrates a cross-sectional view of the cutter unit 100 housed in the cutter housing 200, in accordance with an example implementation of the present subject matter. The cross-sectional view is along a line A - A’ shown in Fig. 4. The first end 306 of the locking assembly 300 and the first portion 214 of the cutter housing 200 is towards the second side 116 of the cutter unit 100. The gaps between the cutter housing 200 and the cutter unit 100, such as gaps between the first cutting edges 108 and the cutter housing 200, between the second cutting edges 208 of the cutter housing 200 and the cutter unit 100, and between the inner surface of the cutter housing 200 and outer surface of the cutter unit 100, form the suction passage 402 for intake of the fluid.

[0042] Fig. 6 illustrates a cross-sectional view of a cutter pump assembly 600, in accordance with an example implementation of the present subject matter. The cutter pump assembly 600 comprises a pump casing 602, a base stand 604, a shaft 606, an impeller 608, the cutter unit 100, the cutter housing 200, a fluid inlet end 612, and a fluid outlet end 614. The shaft 606 extends into the pump casing 602 and the distal end of the shaft 606 is enclosed in the pump casing 602. The shaft 606 is driven by a motor that can rotate both in the clockwise and anticlockwise direction.

[0043] The impeller 608 is mounted axially on the distal end of the shaft 606 and enclosed between the pump casing 602 and base stand 604. The cutter unit 100 is coupled to a suction end of the impeller 608 using a pair of locking pins 610 so that the cutter unit 100 rotates with the impeller 608 and there is no slippage in between them. As illustrated, the cutter unit 100 is provided towards the fluid inlet end 612 of the cutter pump assembly 600 so as to receive the fluid to be pumped.

[0044] The cutter unit 100 is detachably fastened to the shaft 606 with the locking assembly 300. The tail 318 (not shown) of the locking screw 304 passes through the cutter unit 100 and is coupled to the distal end of the shaft 606, while the head 316 (not shown) of the locking screw 304 is coupled to the spinner nut 302 over the cutter unit 100. This structure provides additional support to the cutter unit 100 during rotation.

[0045] The base stand 604 is a solid structure to support the cutter pump assembly 600. The base stand 604 comprises a plurality of radial grooves near the impeller 608 for secondary cutting action. The cutter housing 200 is mounted on the base stand 604 using general fastening methods known in the art, such as, screws, nuts, bolts, rivets, etc. The cutter housing 200 can be fixed to the base stand 604 to allow it to remain stationary during the operation of the cutter pump assembly 600. The base stand 604 is coupled to the pump casing 602 such that the cutter housing 200 encloses the cutter unit 100 whereby the first cutting edges 108 of the cutter unit 100 have a small clearance/ gap with the second cutting edges 208 of the cutter housing 200. The free spaces between the cutter housing 200 and the cutter unit 100 form the suction passages 402.

[0046] The shaft 606 is driven by a motor (not shown) to rotate the impeller 608 and cutter unit 100 and create a suction force in the suction passages 402. The fluid with the entrained solid is pulled into the suction passage 402 of the cutter pump assembly 600 from a fluid inlet end 612 and the entrained solids are shredded due to the action of the first and second cutting edges of the cutter unit 100 and the cutter housing 200, respectively. Further, the fluid with the shredded solid particles moves towards the impeller 608, where the impeller 608 in combination with the plurality of radial grooves performs a second shredding action on the particulate solids. The fluid with the further shredded solids is pumped out from the fluid outlet end 614. Thus, the cutter unit 100, in combination with the cutter housing 200, shreds, grinds, or cuts the solids before passing the fluid and the shredded solids into other pipes, such as of a sewage transport system, on the fluid outlet end 614. As a result of the arrangement of the cutter unit 100, cutter housing 200, base stand 604, and impeller 608, multiple cutting actions occur on the solids in the pumped fluid material making it easy to transport it downstream from the cutter pump assembly 600.

[0047] Fig. 7 illustrates an enlarged or detailed view of a plurality of radial grooves 702 in the cutter pump assembly 600, in accordance with an example implementation of the present subject matter. The plurality of radial grooves 702 provides a secondary shredding action in combination with the impeller 608. The impeller 608 is a vortex type impeller, in one example. Vortex impellers create a revolving mass of the pumped fluid material which forms a whirlpool. A whirlpool is a funnel shaped opening which is created downward from the fluid surface. When the fluid pumped from the cutter unit 100 forms a whirlpool and comes in contact with the plurality of radial grooves 702 the solids are further shredded to a finer particle size.

[0048] Fig. 8 illustrates a control system of the cutter pump assembly 600, in accordance with an implementation of the present subject matter. The control system includes a controller 802 communicatively coupled to a motor 804. The motor is coupled to the cutter pump assembly 600 for driving the shaft 606. In one example, the controller 802 may be integrated with the motor 804.

[0049] The controller 802 includes a power sensor 808 and a processor 810. The processor 810 may be any kind of processor known in the art. It will be understood that the controller 802 may further include or be coupled to various communication interfaces, input modules, and display modules that are not described or shown for brevity.

[0050] In operation, when the motor 804 is switched ON, for example, through the controller 802, the motor 804 rotates the shaft 606 (refer Fig. 6) of the cutter pump assembly 600 and results in the pumping with cutting action of the cutter pump assembly 600, as discussed above. In case solid particles clog the suction passage 402, the motor 804 gets stalled and the power consumption of the motor 804 becomes higher than a threshold power consumption value. In such a case, the controller 802 may cause the motor 804 to stop and rotate in an opposite direction.

[0051] In one implementation, the power sensor 808 senses the power consumed by the motor 804 and provides a signal to the processor 810. The signal is indicative of the power consumed by the motor 804. The processor 810 monitors the signal and determines whether the power consumed is greater than the threshold power consumption value for a pre-determined period of time. As may be understood, the threshold power consumption value and the pre-determined period of time may be set based on the motor 804 and cutter pump assembly 600 being used. In one example, the pre-determined period of time is in a range of 1-5 minutes.

[0052] In response to sensing that the power consumption is greater than the threshold power consumption value for the pre-determined period of time, the processor 810 causes the motor 804 to rotate in an opposite direction, such as counter-clockwise direction, for a preset time period. In one example, the preset time period can be in a range of 3-5 minutes. In one example, the controller 802 may include a processor-controlled circuit (not shown in the figure) for switching the polarity of the current supplied to the motor 804 to change its direction of rotation.

[0053] The counter rotation of the motor 804 rotates the shaft 606 of the cutter pump assembly 600 in an opposite direction, leading to the counter rotation of the cutter unit 100. The fluid is therefore pumped in a reverse direction for the preset time period and the first and second cutting edges 108 and 208 shred the solid particles during the reverse rotation/pumping as well. This shredding of the solid particles in a reverse direction allows unclogging of the suction passages 402. The profile of the first cutting edges 108 and the second cutting edges 208 as discussed above allow shredding of the solids even in the counter rotation.

[0054] After the preset time period, the processor 810 causes the motor 804 to operate normally, for example, in a clockwise direction of rotation. If the suction passages 402 have not been completely unclogged, the motor 804 may again get stalled and the controller 802 again detects a higher power consumption and again causes the motor 804 to rotate in the reverse direction for the preset time period. This process continues till the cutter pump assembly 600 is unclogged and can resume operation without stalling the motor 804.

[0055] The present subject matter thus discloses a cutter pump assembly that comprises multiple shear areas and performs multiple shredding actions on the solids and can also clear any obstruction in its suction passage by counter rotation in case of clogging of the suction passage. Therefore, it can be ensured that the fluid that is pumped for transport through smaller diameter pipes, such as sewage pipes, does not comprise heavy, large, or long solid materials.

[0056] Although implementations for cutter pump assembly have been described in language specific to structural features, it is to be understood that the present subject matter is not necessarily limited to the specific features described. Rather, the specific features are disclosed as example implementations.