Patent Application
20090304501
The invention relates to a pond pump comprising an impeller which rotates about an axis of rotation within a pump housing, wherein the pump housing comprises a suction inlet that is axial to the impeller, a pressure outlet for the water that is to be conveyed, said pressure outlet being disposed in a radial to tangential direction relative to the impeller, the housing further including a section between the suction inlet and pressure outlet, wherein the impeller comprises a radially disposed disk with vanes that are arranged on one side thereof, and wherein the housing segment associated with the open side of the impeller disc having the vanes is a counterflow plate surface, and wherein flow channels are formed between the vanes, the disc and the counterflow plate.
A pump of this type is known from U.S. Pat. No. 5,713,719 as a rotary or centrifugal pump with an open impeller. The impeller includes pump wheel vanes. A flow channel is formed between the pump wheel vanes, one of the pump wheel vane carrying discs and a housing section. These flow channels expand in their cross section going from the radial inward side towards the outer side.
WO 94/03731 discloses a centrifugal pump with a non-dog impeller, in which the flow channels are defined between full pump vanes, which extend from the rotation axis of the impeller to the radial periphery, and short pump vanes, which are located at the outer ring area of the impeller. These flow channels likewise exhibit a cross-section, which increases from inwards towards outwards.
From US 2004/0126228 A1 an impeller pump with a special geometry of the spiral housing is known, in which a closed pump wheel with first and second cover discs and therein disposed flow channels is provided.
Further, centrifugal pumps are known from the general state of the art, which have a rotating impeller for conveying water. The pumps are usually employed by full emersion in the water to be conveyed (submersion pumps). Of course the suction side can also be placed in communication with the water to be conveyed via a pump conduit for suction. In the case of a dry set-up the pump must be placed next to the pond below the water level. On the pressure side the conveyed water is conveyed via a pipeline, for example, to a pond filter, a fountain, an artificial waterfall, or the like.
Centrifugal pumps operate according to a hydrodynamic conveyance principal, where the water to be conveyed is supplied in the vicinity of the rotation axis of the impeller, is taken along with the rotating impeller with its thereupon located vanes and is forced to a circular or orbital track. By the centrifugal force acting upon the water rotating in the circular track the water is radially forced outward. Accordingly, a vacuum is produced close to the rotation axis at the water intake (suction side) and an over pressure is produced at the periphery of the impeller (pressure side).
Centrifugal pumps are very reliable and, when fully encapsulated, can be electrically driven as pond pumps, for example also for swimming ponds. Further, with appropriate design of impeller and associated pump housing, water with solids can be conveyed, without having to be concerned about clogging. Therein the impeller is designed as a so-called non-dog impeller, so that the permitted solid size can be for example 6 mm (spherical passage-through).
Therewith on the suction side the flow-through amount is limited essentially by the gross or large-scale filter element with corresponding mesh width.
However, the non-dog impellers have a somewhat poorer degree of effectiveness due to circulation short-circuits and therewith internal pressure equalization in comparison to pumps with a closed impeller. Pumps with a closed impeller are, however, more susceptible to clogging, so that a correspondingly finer filter must be provided on the suction side, which provides a corresponding resistance on the free circulation.
Since pond pumps have very long life duration, and in some instance must work day and night, an improvement in the effectiveness, with a simultaneous admittance of a larger particle size, for example up to 6 mm, is desirable for an economical operation. The task of the invention is to correspondingly optimize a centrifugal pump of this general type.
The task is solved with a centrifugal pump according to claim 1. Surprisingly, it has been discovered with experiments, that a centrifugal pump with open impeller has an improved degree of effectiveness or efficiency, when the flow channels formed between the vanes have a cross-section, which diminishes in the direction of flow from the radial inner side towards the outer side. Obviously the cross-sectional narrowing of the flow channels in radial direction from the rotation axis towards the outside brings about an increase in the centrifugal flow and herewith the hydrodynamic conveyance pressure. Preferably, the degree of narrowing at the flow channel is 15% to 40%, or preferably 20% to 35%.
In the design of the above described pond pump with open impeller, the narrowing of the of the flow channel cross section can preferably be realized thereby, that the counterflow plate is in the form of a wide open conical surface segment with a angle (α) between 5° and 20° to the plane oriented radial to the rotation axis in the direction of the impeller.
Alternatively or in addition the flow channel cross section reduction is achieved thereby, that the disc of the impeller is in the form of a wide open conical surface with a angle (β) between 5° and 20° to the plane oriented radial to the rotation axis in the direction of the counterflow plate.
Further, the degree of effectiveness of the pond pump is increased when the height of the vanes of the impeller measured axially to the rotation axis decreases from the radial inner side towards the outer side, so that the open side of the impeller is spaced apart from the counterflow plate with an essentially even gap. When the gap width is smaller than or equal to 1 mm, preferably smaller than 0.5 mm, the pressure loss by flow short-circuits between the impeller and counterflow plate are reliably prevented.
To avoid clogging in the flow channels of the impeller by solid particles, the height of the vanes at the radial outer side is larger than or equal to the width of the flow channels.
If the flow channels formed between the vanes have the same width from the radial inner side towards the outer side of the impeller, then the degree of effectiveness of the pump is further improved. Presumably, this improvement in effectiveness is attributable to a further reduction of turbulence and therewith flow losses. In addition, clogs are avoided by this design. In particular, the width of the flow channels should be larger than or equal to the maximum permissible particle size, for example larger than or equal to 6 mm.
If the vanes have a sickle shaped cross section in the plane radial to the rotation axis, then a hydro-dynamically particularly effective flow channel geometry is formed between the sickle shaped vanes. By the sickle shaped cross section the vanes exhibit a high inherent stability, so that the impeller has a long durability and lifetime.
With respect to manufacturability it is advantageous when the counterflow plate is an integral component of the pump housing. It is preferred when the pump housing and/or the impeller is produced from acrylonitrile-butadine-styrene (ABS), modified polyphenyleneoxide (PPO; so-called “Noryl”) and/or polyoxymethylene/polyacetal (POM). Therein it is particularly preferred when the pump housing is produced with a one-piece integrated counterflow plate from the shape stable and economical ABS-plastic. The impeller can likewise be produced from ABS-plastic with sufficient shape stability and rigidity as an economical component or, for particularly demanding requirements, can be manufactured from PPO or POM plastic.
For good electrical efficiency with low energy consumption for the pond pump for driving the impeller an asynchronous motor with stainless steel rotor can be provided in a housing, in which a rotor is provided encapsulated in stainless steel, which together with the impeller forms a running unit removable from the housing. For a high tolerance and a long life of the pump the impeller is rotatably mounted in the housing with a ceramic bearing.
In the following an illustrative embodiment of the invention is described in greater detail on the basis of the drawings.
There shown in:
In
The pump housing 1 includes a suction inlet 11, which is located coaxial to the rotation axis X lying opposite to the drive side Y. On the suction inlet 11 a support is formed, upon which the suction line for supplying water to be conveyed can be seated. In the employment of the pump as pond pump the water can also be introduced directly into the suction inlet 11. The water flow on the suction side is indicated with the arrow Ws.
The pump housing 1 forms together with the not shown drive unit Y a surrounding housing of the rotational driven impeller 2, in order to bring about upon rotation of the impeller 2 a hydrodynamic conveyance of the water. Therein the surrounding housing of the pump housing 1 includes a ring shaped collection space or volute 13 about the periphery of the impeller 2, from which an essential tangential to the impeller 2 arranged pressure outlet 14 in the direction of the by the rotation impeller 2 on a circular path accelerated water is guided out of the pump housing in the direction of the water discharge Wo.
Between the suction inlet inlet 11 arranged axial to the rotation axis X and the collection chamber or volute 13 formed in a torus shape peripheral to the impeller 2 it is provided a counterflow plate 12. The counterflow plate 12 forms an annular or circular ring shaped surface, which in the embodiment shown in
The impeller 2 includes a circular disc 22 oriented in a radial plane perpendicular to the rotation axis X, upon which vanes 21 are formed projecting axially in the direction of the suction side.
In
As can be seen from the sectional representation in
In operation of the pond pump the rotor 2 rotates about the rotation axis X. The rotor 2 is then driven by a not shown drive unit Y. On the basis of the rotational movement of the impeller 2 with the vanes 21 formed thereupon on the suction side Ws water is sucked in due to the vacuum created in the center of the impeller and via the flow channels 23 is brought to the circular path. The circular acceleration of the water in the flow channels 23 results, due to the centrifugal force, in an elevation in pressure and therewith to hydrodynamic conveyance of the water to the pressure outlet 14 on the pressure side WD of the pump.
The small gap s of approximately 0.5 mm reliably prevents therein a short circuit of flow, so that the pump works particularly effectively. Likewise, the design of the flow channels 23 with an essentially constant breadth b of 6 mm allows a conveyance of water loaded with solids with a particle size of up to 6 mm through the pump without clogging. Since the height of the vanes 21 at the peripheral outlet of the flow channel 23 have at least the width b, that is, b is smaller than or equal to h, a clogging of the flow channels is avoided also with respect to the height dimensioning.
By the wide opened conical surface shape of the counterflow plate and the thereto conforming or adapted design of the height dimension of the vanes 21, the cross section of the flow channel in the flow direction from the center of the impeller 2 radially towards outwards to the peripheral exit of the flow channel in the illustrated embodiment is reduced by 24%. This cross section reduction leads surprisingly to a higher capacity of the pump.
Compared with the prior commercial generation of pond pumps of the applicant with non-dog impellers, there result the improvements shown in the following Table 1 with the products in accordance with the present invention.
Under the column “Pump type” with the reference “Messner M or as the case may be MPF . . . ” the previously commercially available pump types of the applicant, and “New . . . ” the respective projected next generation model is listed. As can be seen from the table, with the inventive design of impeller and associated pump housing with counterflow plate substantial improvements in the degree of effectiveness or efficiency can be achieved. On the basis of a substantially lower electrical consumption with comparable pump outputs, mainly pumping height and conveyance output or capacity, there is a striking economic advantage over the life expectancy of the pump.
| Number | Date | Country | Kind |
|---|---|---|---|
| 06013788.2 | Jul 2006 | EP | regional |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/EP07/05550 | 6/23/2007 | WO | 00 | 1/5/2009 |
