WO2014139578A1

WO2014139578A1 - Impeller

Info

Publication number: WO2014139578A1
Application number: PCT/EP2013/055295
Authority: WO
Inventors: Anders Anderson
Original assignee: Grundfos Holding A/S
Priority date: 2013-03-14
Filing date: 2013-03-14
Publication date: 2014-09-18

Abstract

The present invention relates to a pump impeller (1) having a front plate (2), a back plate (3), and impeller blades (4) between the front and the back plates (2, 3), wherein the impeller blades (4) consist of a base material, which is more resilient than the base material of the front plate (2) and/or the back plate (3).

Description

The invention relates to a pump impeller according to the preamble of claim 1 .

Pumps which are used for pumping water which contains foreign mat- ter like sand particles or the like are subject to strong wear due to the abrasive effect of such particles. Specifically, when impeller pumps are used for such purposes, the impeller and the guide vanes will be worn down quickly. Also, some problems exist with pumps known from prior art in that some foreign matter contained in water, like e.g., ochre. Or- chre in pumps is a layer which can build up inside the pump housing on its contact surfaces and the impeller. The layer consists of ironoxide and biofilm and its consistency is stiff and brittle. Thus, eventually, there is a risk that the pump will get clogged. In order to deal with these problems, pumps have been proposed in prior art that offer an improved wear resistance against sand by increasing the wall thickness of the materials from which the pump is formed. However, this solution does not prevent the effect of wear but only slows it down.

Also, it is known†o use a ceramic coating in large pumps which, however, is hard to implement and thus, rather expensive. EP 2 143 954 Bl discloses an impeller which is coated with silicon at if s flow leading parts. It is manufactured of a plastic composite material. A problem of this plastic composite material is that the geometry of the impeller depends on the form of the mould core which has to be drawn out radially after the injection moulding. Therefore, it is an object of the present invention to provide an impeller for a pump which is resistant against wear from abrasive foreign matter, as e.g., sand particles, which still may be produced in an economic manner and which can be fluidic optimised.

This problem is solved by a pump impeller having the features according to claim 1 . Preferred embodiments of the invention are defined in the dependent claims.

According to the present invention, a pump impeller is provided having a front plate, a back plate and impeller blades between the front and the back plate, wherein the impeller blades consist of a base material, which is more resilient than the base material of the front plate and/or the back plate. The inventive pump impeller may be used in all pumps, especially where sand wear, ochre build-up and other fouling is a problem. Since the impeller blades are made of a wear resistant soft part, e.g., rubber, , ochre will not stick to the soft surfaces of the impeller so that its surface can be kept free of such build-up. Thus, clogging is avoided. Also, a sufficient wear resistance can be achieved. On the other hand, to obtain the necessary material strength, the front plate and the back plate including a hub are made of a more stiff material, like plastic or metal. Due to the inventive configuration with a pump impeller with blades made from a flexible material, the design freedom is increased when designing the hydraulics of the impeller since undercuts may be realized easily. Due to the resilience of the impeller blades the blades comprise a specific elasticity which allows the back plate and the front plate a certain movability and rotatablity to each another.

According to a preferred embodiment, at least the inner surface of the front plate and/or the back plate are at least partly covered by the base material of the impeller blades which increases the wear resistance of said covered surfaces.

The apertures in the front plate and/or the back plate may preferably be filled with the base material of the impeller blades which further increases the wear resistance and the connection of the resilient material of the impeller blades to the front plate or the back plate respectively is increased. Further, if is preferred that the outer surface of the front plate and/or the back plate is at least partly covered by the base material of the impeller blades which still further increases the wear resistance.

Also, the base material of the impeller blades may extend through the apertures in the front plate and/or the back plate on the outer surface of the front plate and/or the back plate. This may ease the manufacturing process of the impeller because during the production process the base material can be applied from at least one position to form the impeller blades and it can spread through the apertures and form all needed layers.

Preferably, at least parts of the pump impeller are injection moulded so that the production process is rather easy and suitable for mass production as well as economical.

According to another preferred embodiment, at least the impeller blades are moulded using reactive injection moulding.

The front plate and/or the back plate may consist of a plastic material, preferably thermoplastic polyester or polyamide. Specifically, composite materials comprising a polymer matrix reinforced with fibers may be used. A preferred material would be PET comprising 30 % glass fibers. According†o still another preferred embodiment, the front plate and/or the back plate consist of a metal. A preferred material may be stainless steel, especially in cases where the impeller is used in harsh environ- ments.

The impeller blades may consist of an elastomer, preferably, of a silicon- based elastomer. As flexible material for the impeller blades, however, virtually any suitable flexible material may be used, for example, liquid silicon rubber having a hardness of 50 Shore A. Liquid silicone rubber has proven fo be very resistant to sand wear and further, it has a non- sifck effect. Therefore, the use of liquid silicone rubber as a material for a pump impeller fo be used in a submersible pump is beneficial. Also, the moulding of the impeller blades using rubber as a material makes the de-moulding process easier since collapsible cores are not necessary. Usually, if would not be possible to mould a surface layer inside the impeller due to the limited space and the undercuts in the geometry. However, when using rubber, specifically, liquid silicone rubber, for the entire vanes between the back plafe and the front plate, it is possible to use the elasticity of the rubber material fo facilitate the de-moulding procedure. A further advantage of the use of rubber is that it has a higher corrosion resistance compared, e.g., to stainless steel.

According to a preferred embodiment, the impeller is mounted on a shaft, wherein the front plate and/or the back plate are/is locked, in particular, permanently locked, fo the shaft.

According to another preferred embodiment, the impeller is mounted on the shaft, but only the back plate is locked fo the shaft, whereas the front plafe is mounted on an actuator or the other way around (front plate is locked the shaft and the back plate is mounted on an actuator) . According to still a further preferred embodiment, the impeller is self- adjustable within a predetermined range with respect to the impeller height, i.e., the distance between the front plate and the back plate and/or the impeller angle, i.e., the angle between the front plate and the back plate.

The self-adjusting geometry of the impeller with respect to its height and/or its angle may be dependent on the rotational speed of the im- peller. Preferably, this is achieved in that the elastic and flexible blades with increasing rotational speed will bulge more and more outwards such that the distance between the front and back plates will be reduced. Also, due to the changing force ratios and pressure conditions acting on the impeller with increasing rotational speed, a certain amount of tilting of the front and back plates with respect to each other will occur, thus modifying the overall geometry of the impeller.

Moreover, according to a further preferred embodiment, an abutment element, in particular, a stopper, may be provided for delimiting the predetermined range for self-adjustment of the impeller.

The above features and advantages of the present invention will become yet more apparent upon reading the following detailed description along with the accompanying drawings.

Fig. 1 A and I B are respective views of a pump impeller according to an embodiment of the invention;

Fig. 2A and 2B are respective views of the pump impeller shown in

Fig. 1 A and Fig. I B before removal of the injection moulding tool core; Fig. 3A and 3B are respective views of the pump impeller shown in Fig. 1 A and Fig. I B after removal of the injection moulding toll core; and Fig. 4A, 4B, and 4C are respective views of the pump impeller shown in

Fig. 1 A and Fig. 1 B mounted on a shaft.

Fig. 1 A and I B are respective views of a pump impeller 1 according to an embodiment of the invention whereby Fig. 1 A is a back view of the pump impeller 1 and Fig. I B is a sectional view through the pump impeller 1 . The pump impeller 1 may be used in a ground water pump and is suited for pumping fluids comprising particles that can cause wear, like for example, sand particles. The pump impeller 1 has a front plate 2, a back plate 3 (including a hub as part of the back plate), and impeller blades 4 between the front and the back plates 2, 3. The impeller blades 4 comprise a base material, which is more resilient than the base material of the front plate 2 and the back plate 3.

Generally, the term base material is to be understood as the supporting material, namely, with respect to the front plate 2 and the back plate 3, this may be a hard plastics or metal, and with respect to the impeller blades 4, this is a soft polymer.

In the embodiment, the base material of the impeller blades 4 is liquid silicone rubber (LSR) . The front plate 2 and the back plate 3 are both made from a plastic material which in fact is stiffer than the rubber material of the impeller blades 4. In the embodiment, PET comprising 30 % glass fibers is used as material for the front plate 2 and the back plate 3. Further, in the embodiment shown, the inner surface 5 of the front plate 2 and the outer surface 6 of the front plate 2 are both covered by the base material of the impeller blades 4, namely, by the liquid silicone rubber. Also, the inner surface 7 of the back plate 3 and the outer sur- face 8 of the back plate 3 are covered by the base material of the impeller blades 4. Apertures 9 provided in the front plate 2 and the back plate 3 are also filled with the base material of the impeller blades 4. Fig. 2A and 2B are respective views of the pump impeller 1 shown in Fig. 1 A and Fig. I B before removal of the injection moulding tool core 10 whereby Fig. 2A is a front view of the pump impeller 1 and Fig. 2B is a sectional view through the pump impeller 1 . The moulding tool core 10 is used during injection moulding of the pump impeller 1 and in Fig. 2A and Fig. 2B is shown in its moulding position. For moulding, preferably reactive injection moulding is used. Further, since the pump impeller 1 is injection moulded, it is possible to optimize the shape of the blades 4 to realize hydraulically necessary undercuts. Fig. 3A and 3B are respective views of the pump impeller 1 shown in Fig. 1 A and Fig. I B after removal of the injection moulding tool core 10 which - due to the elastic properties of the blades 4 - can be easily removed, since during de-moulding, the soft blades 4 will stretch and give room for the de-moulding process. No collapsible cores need to be used for this and the tool core 10 may further be shaped so as to be thicker in the central region than at the outer rim region.

Fig. 4A, 4B, and 4C are respective views of the pump impeller 1 shown in Fig. 1 A and Fig. I B mounted on a shaft 1 1 whereby Fig. 4A is a front view of the pump impeller 1 , Fig. 4B is a sectional view of the pump impeller 1 , and Fig. 4C is a further front view of the pump impeller 1 . By locking both the front plate 2 and the back plate 3 to the shaft 1 1 , it will be possible to bend or stretch the flexible blades 4 so that the impeller height and/or the impeller angle may be adjusted as desired. For ex- ample, as can be seen in Fig. 4B and indicated by the arrow, the blades 4 may be stretched in order to increase the distance between the front plate 2 and the back plate 3. Also, as indicated by the arrow in Fig. 4C, it is also possible to rotate the front plate 2 in relation to the back plate 3 in order to adjust the angle. This makes it possible to modify the hydraulic behavior of the impeller 1 in accordance to specific requirements and needs. Two ways to achieve this may be implement- ed. A first possibility is to lock the front plate 2 and the back plate 3 permanently to the shaft 1 1 in order to implement a specific geometry according to user needs or pump requirements. A second possibility is to lock the back plate 3 to the shaft 1 1 and to mount the front plate 2 on an actuator (not shown) . This will allow a continuous regulation of the pump during its operation. Thus, the output and efficiency of the pump impeller 1 may be optimized in accordance with a change in flow and pressure of the pumped fluid. A third possibility may be to implement a self-adjustable impeller geometry wherein the impeller is self- adjustable within a predetermined range with respect to the impeller height, i.e., the distance between the front plate and the back plate and/or the impeller angle, i.e., the angle between the front plate and the back plate. The self-adjusting geometry of the impeller with respect to its height and/or its angle is dependent on the rotational speed of the impeller, whereby the elastic and flexible blades with increasing rotational speed will be bulging outwards more and more such that the distance between the front and back plates will thereby be reduced. Also, due to the changing force ratios and pressure conditions acting on the impeller with increasing rotational speed, a certain amount of tilting of the front and back plates with respect to each other will occur, thus modifying the overall geometry of the impeller. For delimiting the predefined range within which the self-adjustment will occur, one or more abutment elements can be provided, as for example, one or more stoppers, which are not shown in the drawings. Reference Numerals

pump impeller

front plate

back plate

impeller blades

inner surface of front plate outer surface of front plate inner surface of back plate outer surface of back plate apertures

tool core

shaft

Claims

A pump impeller (1 ) having a front plate (2), a back plate (3), and impeller blades (4) between the front and the back plates (2, 3), characterized in that the impeller blades (4) consist of a base material, which is more resilient than the base material of the front plate (2) and/or the back plate (3).

A pump impeller ( 1 ) according to claim 1 , characterized in that at least the inner surface (5, 7) of the front plate (2) and/or the back plate (3) are at least partly covered by the base material of the impeller blades (4).

A pump impeller (1) according to any preceding claim, characterized in that apertures (9) in the front plate (2) and/or the back plate (3) are filled with the base material of the impeller blades (4).

A pump impeller (1) according to any preceding claim, characterized in that the outer surface (6, 8) of the front plate (2) and/or the back plate (3) is at least partly covered by the base material of the impeller blades (4).

A pump impeller (1) according to claim 4, characterized in that the base material of the impeller blades (4) extends through the apertures (9) in the front plate (2) and/or the back plate (3) on the outer surface (6, 8) of the front plate (2) and/or the back plate (3).

A pump impeller (1) according to any preceding claim, characterized in that af least parts of the pump impeller (1) are injection moulded.

7. A pump impeller (1) according to any preceding claim, characterized in that at least the impeller blades (4) are moulded using reactive injection moulding.

A pump impeller (1) according to any preceding claim, characterized in that the front plate (2) and/or the back plate (3) consist of a plastic material, preferably thermoplastic polyester or polyam- ide.

A pump impeller (1) according to any preceding claim, characterized in that the front plate (2) and/or the back plate (3) consist of a metal.

A pump impeller (1) according to any preceding claim, ch terized in that the impeller blades (4) consist of an elastomer.

A pump impeller (1) according to claim 10, characterized the impeller blades (4) consist of a silicon based elastomer.

A pump impeller (1) according to any preceding claim, characterized in that the impeller (1) is mounted on a shaft (11), wherein the front plate (2) and/or the back plate (3) are/is locked, in particular, permanently locked, to the shaft (11).

A pump impeller (1) according to any one of claims 1 to 11, characterized in that the impeller (1) is mounted on a shaft (11), wherein the back plate (3) is locked to the shaft (11) and the front plate (2) is mounted on an actuator or the other way around.

A pump impeller ( 1 ) according to any one of claims 1 to 11 , characterized in that the impeller (1) is self-adjustable within a prede- termined range with respect to the impeller height, in particular, the distance between the front plate (2) and the back plate (3) and/or the impeller angle, in particular, the angle between the front plate (2) and the back plate (3) .

A pump impeller ( 1 ) according to claim 14, characterized in that the self-adjusting geometry of the impeller ( 1 ) with respect to the impeller height and/or the impeller angle is dependent on the rotational speed of the impeller ( 1 ) .

A pump impeller ( 1 ) according to claim 14 or 15, characterized in that an abutment element, in particular, a stopper, is provided for delimiting the predetermined range for self-adjustment of the impeller ( 1 ).