Technical field of the invention

The present invention relates, in general, to a pump for pumping liquid, such as sewage comprising a mixture of liquid and solid matter. By way of example, the pump is a centrifugal pump with either open or closed impeller, or a propeller pump having a propeller. In particular, the present invention relates to a pump comprising a hydraulic unit, which comprises a pump housing, an insert ring and an impeller arranged to rotate in said pump housing, the hydraulic unit comprising an upstream inlet opening and a downstream outlet opening and delimiting in succession an inlet, a pump chamber and an outlet, the insert ring being connected to the pump housing in the area of the transition between said inlet and said pump chamber and being displace- able in the axial direction in relation to said pump

housing, the insert ring being in threaded engagement with the pump housing and being turnable in relation to said pump housing, and at least one locking member being arranged at the interface between the insert ring and the pump housing.

Background of the invention and state of the art

Reference is now made to figure 5 (prior art) that disclose a previously known hydraulic unit of a centrifugal pump comprising an open impeller. Vital for these, and other, pumps is the presence of a correct gap, i.e. a correct distance in the axial direction between the impeller and the insert ring. A too large gap entails reduced pump performance and a too small gap entails risk for collision between the impeller and the insert ring and entails

generation of brake forces.

When such a hydraulic unit is assembled, an arbitrary number of spacing elements is positioned between the insert ring and the inlet funnel of the pump housing and the insert ring is subsequently screwed to the inlet funnel using a plurality of screws. The inlet funnel, with the thereto attached insert ring, is thereafter mounted on the volute of the pump housing. Only thereafter may the above-discussed gap be controlled, for instance by using a thickness gauge that is introduced into the gap.

One disadvantage of this type of design is that if the gap between the impeller and the insert ring turns out to be incorrect, which is almost always the case for a first attempt to assemble the unit or due to wear resulting from the unit being operated for a certain period of time, then everything needs to be dismounted. The inlet funnel must first be detached from the volute of the pump housing and the insert ring must thereafter be detached from the inlet funnel. Once the number of spacing elements has been

adjusted, the insert ring and the inlet funnel need to be remounted before the gap can be controlled. Hence, the control and the adjustment of the gap are complicated as well as time-consuming.

Furthermore, this type of mounting entails that the screw heads of the screws, used to screw the insert ring onto the inlet funnel, face the impeller and the pump chamber. This results in screw heads being worn down by the solid matter present in the pumped liquid. It is an apparent drawback that unscrewing the screws that connect the insert ring and the inlet funnel becomes laborious or downright impossible when the unit has been operated for a certain period of time.

In an alternative, previously known design, the inlet funnel is fixedly connected to the volute of the pump housing whereupon the entire driving unit of the pump needs to be dismounted from the hydraulic unit before the insert ring can be detached from the inlet funnel. Typically, a lift/crane is required to lift the driving unit from the hydraulic unit as the former weighs several hundreds of kilograms . A centrifugal pump with a closed impeller is disclosed in DE3513116, wherein said pump comprises a single

adjustment screw freely movable through the pump housing and being in threaded engagement with the insert ring. By turning the adjustment screw, the insert ring is displaced in the axial direction in relation to the pump housing. The disadvantage of this solution is that the insert ring will become tilted in relation to the impeller and the pump housing, due to the presence of a peripherally extending gap between the insert ring and the pump housing. If a plurality of adjustment screws instead were to be used, it would be virtually impossible not to tilt the insert ring since the adjustment screws are manipulated one by one.

Short Description of the Objective of the Invention

The present invention aims at obviating the above- mentioned disadvantages and failings of the pumps belonging to the prior art and to provide an improved pump. A primary object of the invention is to provide an improved pump of the initially defined type, where the gap between the impeller and the insert ring can be simply controlled and adjusted without time-consuming dismounting/remounting. A further object of the present invention is to provide a pump, where the risk of the insert ring becoming tilted in relation to the impeller is completely eliminated.

Short Description of the Inventive Feature

In accordance with the invention, at least the primary object is obtained by means of the pump as defined in the introduction, having the features defined in the independent claims. The preferred embodiments of the present invention are further defined in the dependent claims.

In accordance with the invention, a pump of the type defined in the introduction is provided, said pump being characterized in that seen from the upstream inlet opening the insert ring is right-threaded and the direction of rotation of the impeller is counter-clockwise.

Hence, the present invention is based on the

understanding that by turning the insert ring, the same is displaced in a controlled way in the axial direction. This renders possible fine-tuning of the gap between the impeller and the insert ring without dismounting/remounting of the pump. When the desired position is obtained, the position of the insert ring is easily locked with one or several locking screws/locking elements. Moreover, the feature, the insert ring being right-threaded and the direction of rotation of the impeller being counter-clockwise seen from the upstream located inlet opening, entail that possible forces generated when the pump is operating are generated by the impeller and act via the pumped liquid in order to rotate the insert ring. These forces contribute to the displacement of the insert ring away from the impeller. This entails that even if the locking screw isn't correctly mounted there is no risk of the impeller and the insert ring colliding with each other.

According to a preferred embodiment of the present invention, the insert ring comprises an outer thread and the pump housing comprises an inner thread.

According to a preferred embodiment, the locking screw extends in the axial direction, which entails that the applied force from the locking screw optimally contributes to maximize the frictional force in the threaded coupling between the insert ring and the pump housing.

Further advantages and inventive features of the invention will be clear from the other dependent claims and from the following, detailed description of preferred embodiments . Short Description of the Drawings

A more complete understanding of the above-mentioned and other features as well as advantages of the present invention will be clear from the following, detailed description of preferred embodiments with reference to the accompanying drawings, wherein:

Fig. 1 is a schematic cutaway side view of the hydraulic unit of the pump according to the present invention, Fig. 2 is a close-up of a portion of the view shown in

figure 1, showing the interface between the insert ring and the pump housing according to a first embodiment ,

Fig. 3 is a close-up of a portion of the view corresponding to figure 2 schematically showing the interface between the insert ring and the pump housing according to a second embodiment,

Fig. 4 is a close-up of a portion of the view corresponding to figure 2 schematically showing the interface between the insert ring and the pump housing according to a third embodiment, and

Fig. 5 is a schematic cutaway side view of the hydraulic unit of the pump belonging to the state of the art. Detailed Description of the Preferred Embodiments

The present invention relates, in general, to a pump for pumping liquid, such as sewage comprising a mixture of liquid and solid matter. Reference is initially made to figure 1, where the inventive pump is a centrifugal pump. The present invention will be described in conjunction with the shown centrifugal pump, without in any way being limited thereto .

Only a part of the pump is shown in figure 1, more specifically, the hydraulic unit, generally denoted 1, of the pump is shown. The hydraulic unit 1 comprises a pump housing, generally designated 2, an insert ring 3 and an impeller 4 that is rotatably arranged in said pump housing 2. The impeller 4 is in a conventional way connected to a drive shaft (not shown) that extends from the driving unit (not shown) of the pump to the hydraulic unit 1. The

impeller 4 is rotatably driven about an axially extending centre axis 5 by means of the driving unit via the drive shaft. The impeller 4 is in the shown embodiment a so called open impeller comprising an upper cover plate 6 and one or several blades 7 projecting in axial direction from the upper cover plate. Furthermore, the shown impeller 4

comprises a hub 8, wherein said blades 7 are spiral-shaped and connected to the hub 8. Notwithstanding the above, it should be observed that the impeller 4 also can be a so called closed impeller that, in addition to the upper cover plate and the blades, even comprises a lower cover plate. In an alternative, not-shown embodiment the inventive pump is an axial pump, also known as a propeller pump, comprising an impeller in shape of a propeller with a hub and one or several blades projecting in radial direction from said hub. The inventive pump can also be a so called semi-axial pump.

The hydraulic unit 1 comprises an upstream located inlet opening 9 and a downstream located outlet opening 10, in the shown embodiment the inlet opening 9 faces the axial direction and outlet opening 10 faces the radial direction. The hydraulic unit 1 delimits various spaces, which in succession are an inlet 11, a pump chamber 12 and an outlet 13. The term "in succession" should be construed as the inlet 11 transit into the pump chamber 12 that, in turn, transit into the outlet 13 seen in the downstream direction. The presence of sharp boundaries between the various spaces is however not necessary. In the shown embodiment, the inlet 11 is delimited by an inlet funnel 14 of the pump housing 2, the pump chamber by a volute of the pump housing 2, and the outlet 13 of an outlet funnel 16 of the pump housing 2. The volute 15 and the outlet funnel 16 are in the shown embodiment made as an integral element, and the inlet funnel 14 is detachably connected to the volute 15, preferably by means of a number of axially extending screws 17. In an alternative, not shown, embodiment, the outlet funnel 16 as well as the inlet funnel 14 are fixedly connected to the volute 15, whereafter the insert ring 3 is inserted into the pump housing 2 in downward direction in figure 1.

The insert ring 3 is connected to the pump housing 2 in the area of transition between the inlet 11 and the pump chamber 12 and is displaceable in axial direction in

relation to the pump housing 2 so as to allow adjustment of an axial distance 18, also known as gap, between the insert ring 3 and the impeller 4.

According to the present invention, the insert ring 3 is in threaded engagement with the pump housing 2, whereby the insert ring 3 becomes turnable in relation to the pump housing 2 about the axially extending centre axis 5. At least one locking element 19 is arranged at the interface between the insert ring 3 and the pump housing 2, the pump preferably comprises three such locking elements 19 which are equidistantly separated. The term "arranged at the interface" should be construed so that said at least one locking element 19 is arranged to act between the insert ring 3 and the pump housing 2. The at least one locking element 19 is preferably a locking screw.

In the embodiment shown in figure 1, the insert ring 3 is connected to the inlet funnel 14 of the pump housing 2. When the hydraulic unit 1 is mounted, the insert ring 3 is connected to the inlet funnel 14 whereafter the inlet funnel 14 is connected to the volute 15 of the pump housing 2 in such a way that the insert ring 3 is located in the pump housing 2.

Reference is now also made to figure 2 which disclose a close-up of the interface between the insert ring 3 and the pump housing 2. In the preferred embodiment of the threaded coupling between the insert ring 3 and the pump housing 2, the insert ring 3 comprises an outer thread 20 and the pump housing 2 comprises an inner thread 21. It is furthermore preferred that said outer thread 20 and said inner thread 21 are trapezoidal threads. In an alternative, not shown embody- ment, the insert ring 3 comprises an inner thread and the pump housing 2 an outer thread. In the shown embodiment, the thread 20 of the insert ring 3 and the thread 21 of the pump housing 2 are continuous along its length. It is however conceivable that the thread 20 of the insert ring 3 and/or the thread 21 of the pump housing 2 are divided in segments along its length. According to a not shown embodiment, the outer thread 20 of the insert ring 3 and the inner thread 21 of the pump housing 2 are both double-threaded in order to minimize the risk of incorrect engagement between the outer thread 20 and the inner thread 21.

The interface between the insert ring 3 and the pump housing 2 preferably comprises a peripherally extending cavity 22, in which said threaded coupling between the insert ring 3 and the pump housing 2 is arranged. A first, peripherally extending sealing 23 is arranged at the

boundary between the cavity 22 and the pump chamber 12 and a second, peripherally extending sealing 24 is arranged at the boundary between the cavity 22 and the inlet 11, so as to prevent that the pumped liquid comes in contact with the threaded coupling between the insert ring 3 and the pump housing 2. The cavity 22 is preferably completely or

partially filled with lubricant/grease in order to prevent corrosion in the threaded coupling.

In the embodiment shown in figures 1 and 2, the insert ring 3 comprises at least one recess 25 facing the inlet 11, preferably at least a pair of recesses 25 that are mutually diametrically opposed. The recesses 25 entail that it becomes easier for a service technician to manually or using a tool turn the insert ring 3 in relation to the pump housing 2 in order to adjust the above-mentioned gap 18. When the insert ring 3 is turned in a first direction, the threaded coupling entails that the gap 18 decreases and when the insert ring 3 is turned in a second direction, opposite to the first direction, the gap increases. According to a preferred embodiment, when seen from the upstream located inlet opening 9, the insert ring 3 is right-threaded and the rotation direction of the impeller 4 is counter-clockwise. When the insert ring 3 is turned in clockwise direction the gap 18 is reduced and when the insert ring 3 is turned in counter-clockwise direction the gap 18 is increased. In a not shown embodiment, the insert ring 3 comprises a guide pin, or stripper/wiper, projecting inwards in a radial direction in the area upstream of the leading edges of the blades 7 of the impeller 4. Said guide pin can be used in order to turn the insert ring 3 around the centre axis.

When the gap 18 is being adjusted, it is preferred, since the inlet funnel 14 is correctly connected with the volute 15 of the pump housing 2, that the insert ring 3 is turned in the first direction so that said insert ring 3 gets in contact with the impeller 4, whereafter the insert ring 3 is turned in the second direction a predetermined number of degrees, preferably about 10-40 degrees. The number of degrees is affected by the pitch of thread of the threaded coupling between the insert ring 3 and the pump housing 2, and the desired size of the gap 18. The pitch is preferably more than 4 mm and less than 10 mm. The gap 18 is preferably less than 1 mm and most preferred less than 0,5 mm, whereas the gap 18, at the same time, is bigger than 0,1 mm and most preferred bigger than 0,2 mm. As an alternative, the gap 18 is adjusted by holding a thickness gauge between the insert ring 3 and the pump housing 2 whereafter the insert ring 3 is turned in the first direction until the thickness gauge obstructs further turning of the insert ring 3. When desired gap 18 has been obtained, the given mutual position between the insert ring 3 and the pump housing 2 is locked by means of the at least one locking element 19.

In the shown, preferred embodiment the locking screw 19 is disposed in a through hole 26 in the pump housing 2, said through hole 26 being completely or partially internally threaded. The first end 27 of the locking screw 19 is disposed so as to abut against the insert ring 3, preferably the first end 27 of the locking screw 19 is disposed so as to abut against a radially extending surface 28 of the insert ring 3. Said surface 28 is preferably located in the cavity 22. The at least one locking screw 19 preferably extends in the axial direction. It is further preferred that the second end 29 of the of the locking screw 19 is arranged so as to be accessible from the outside of the pump housing 2 in order to prevent wear of the same due to the pumped liquid. When the locking screw 19 is screwed, the possibly present axial play in the threaded coupling between the insert, ring 3 and the pump housing 2 disappears.

When the gap 18 is adjusted, the locking element 19 is detached whereafter the insert ring 3 may effortlessly be turned to desired position in accordance with above.

Reference is now made to figure 3 which disclose the interface between the insert ring 3 and the pump housing 2 according to a second embodiment. The parts/functions that are the same in the two embodiments according to the figures 1 and 2 are not mentioned.

In this embodiment, the insert ring 3 has an outer gear rim 30, or similar, said rim being accessible from the outside of the inlet funnel 14 via a through hole 31. By means of a screwdriver, or other tool, the service

technician may turn the insert ring 3 by turning the gear rim 30 in relation to the through hole 31. This design is suitable for instance when an inlet pipe (not shown) is connected to the inlet funnel 14. Reference is now made to figure 4 which disclose the interface between the insert ring 3 and the pump housing 2 according to a third embodiment. The parts/functions that are the same as in the two embodiments according to the figures 1 and 2 are not mentioned.

In this embodiment, the insert ring 3 comprises the inlet funnel 14, and the insert ring 3 and the inlet funnel 14 are in the shown embodiment an integral unit. It should be noted that the insert ring 3 and the inlet funnel 14 may be two elements that are detachably interconnected, but where the axial adjustment of the mutual position isn't present. In this embodiment, the insert ring 3 is in

threaded engagement with the volute of the pump housing 2.

Conceivable Modifications of the Invention

The invention is not limited only to the above- described embodiments nor to the embodiments disclosed in the drawings. In this context, the drawings only have an illustrative and exemplifying purpose. This patent

application is intended to cover all adaptations and

variants of the preferred embodiments described above. The present invention is consequently defined by the wording of the attached patent claims and may hence be modified in any conceivable way within the frame established by said claims.

It should also be noted that all information regarding terms such as above, below, upper, lower etc. should be construed with the equipment being oriented according to the figures, with drawings oriented in such a way that the reference numerals can be read in a correct manner. Thus, similar terms indicate only mutual relations in the shown embodiments, wherein these embodiments may be changed if the equipment of the present invention is provided with a different construction/design.

It should also be noted that although not explicitly stated that the feature (s) belonging to a specific embodiment may be combined with the feature (s) belonging to another embodiment, such a combination, if feasible, is deemed evident.