Abstract:
An impeller radial pump includes a pump chamber with a central suction and with a pump chamber outlet, wherein an impeller is provided in the pump chamber. Radially outside of the impeller, a circular ring shaped and circumferential pump chamber ring section is provided as a part of the pump chamber, wherein the pump chamber ring section essentially has an extension along the axial direction of the pump from the impeller against the suction direction. The pump chamber ring section has a varying width and is configured to be narrower in a compression region in the circulation direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to German Application No. 10 2012 210 554.9, filed Jun. 22, 2012, the contents of which are hereby incorporated herein in its entirety by reference. 
     TECHNOLOGICAL FIELD 
     The invention relates to a pump as can well be used in particular for home appliances such as dish washers or washing machines, wherein the pump is configured as a radial pump. 
     BACKGROUND 
     Such radial pumps are known for example from U.S. Pat. No. 8,245,718 B. They comprise a pump chamber with a central suction pipe and a pump chamber outlet, wherein an impeller rotates in the pump chamber in order to transport fluid from the suction pipe in the radial direction out of the impeller into the pump chamber and after several circulations in the pump chamber out of the same via the pump chamber outlet. Outside the impeller or in the fluid path, so to say downstream of the impeller, in the pump chamber an essentially circular ring shaped pump chamber ring section is provided, which section extends in the axial direction of the pump, namely away from the impeller opposite to the direction of the suction pipe into the pump, i.e. towards the pump chamber outlet. 
     In particular when starting a pumping procedure after a longer period of time, air can accumulate in the pump chamber, in particular on a pump chamber bottom close to the impeller. During the start of the pumping procedure, said air interferes with the efficiency of the pump. In order to now discharge the air more quickly, it was proposed to arrange guide elements with blades or the like in the pump chamber, in particular close to the impeller. This is also shown, for example, by the aforementioned EP 2150165 B. However, said guide elements involve an additional constructional effort or effort in terms of components, respectively. 
     BRIEF SUMMARY 
     The object underlying the invention is to provide an abovementioned pump by means of which problems of the prior art can be solved, and in particular a pump can be provided that performs efficiently and most important that can discharge air present in the pump chamber during the start of the pumping procedure. 
     Said object is achieved by means of a pump. Advantageous as well as preferred embodiments of the invention are contained in the further claims and will be described in more detail in the following. The wording of the claims is incorporated into the content of the description by explicit reference. 
     The pump comprises a pump chamber with central suction and with a pump chamber outlet, wherein in the pump chamber an impeller rotates for transporting fluid or for discharging the fluid from the suction in radial direction out of the impeller into the pump chamber. The discharged fluid is moved for circulation in the pump chamber towards the pump chamber outlet, wherein said fluid also flows in axial direction of the pump from the impeller against the suction direction towards the outlet. Radially outside the impeller, a circular ring shaped and circumferential pump chamber ring section is provided as a part of the pump chamber, wherein the pump chamber ring section essentially has an extension along the axial direction of the pump. 
     In said pump, it is provided according to the invention that the pump chamber ring section has a varying width in the circulation direction and is configured to be narrower in a compression region. In this case, a narrow width, in particular in the radial direction, can be at least 20% or 30% of the maximum width. However, in particular said minor width is less than 70%. 
     By means of said narrow configuration of the pump chamber ring section, the pressure in the transported fluid can be altered or increased, respectively, and the circulation rate of the fluid can be increased for an improved transporting. In particular, air accumulated in the pump chamber can be better removed or transported away by means of said pressure increase. Furthermore, the maximum air volume in the pump chamber is reduced since there is less space available, what also helps for that purpose. 
     In one embodiment of the invention it is provided that the pump chamber ring section becomes gradually or continuously narrower in the circulation direction of the fluid transported towards the compression region, so that then a small width present along the circulation direction is essentially constant over a certain length of the compression region. That can be at least 20% to 30% of the circumference, preferably up to 40% or 50%. Advantageously, downstream thereof, the width increases again in the circulation direction, wherein that can be slower and over an even greater length than towards the compression region. 
     In an advantageous embodiment of the invention it is provided that along the axial direction of the pump the radial width of the pump chamber ring section remains essentially the same over at least half of the axial length of the pump chamber ring section or of the pump chamber per se, preferably slightly more than two thirds thereof. Preferably, said region is located close to the pump chamber outlet or extends up to said outlet. In the direction towards the impeller, the pump chamber ring section can also be configured slightly more widened, in particular as a transition to the rest of the pump chamber in the region of the impeller per se. 
     In a further embodiment of the invention, it can be provided that the pump chamber tapers monotonously in terms of its width in radial direction, that is quasi relative to its cross sectional area, outside the impeller in axial direction away from the pump chamber bottom. Said tapering is advantageously strictly monotonously. Not before the outlet there is a widening, however here in the circumferential direction. By means of said tapering of the cross section of the pump chamber or of the pump chamber ring section, the pressure conditions can be configured in an advantageous manner for a good transporting and thus a good heating of transported fluid or water, respectively. Furthermore, here the transport rate of the fluid can be increased for an adaption in terms of the heat absorption of the heating device, since the fluid becomes increasingly hotter while circulating in the pump chamber. 
     In yet another embodiment of the invention, a heating device can be integrated into the pump in order to heat the fluid transported by means of the pump. Advantageously it can be provided that an external pump chamber wall is heated as an exterior wall of the pump chamber ring section, partly also of the rest of the pump chamber, or that said wall is a part of a heating device or formed by means of the same. In a particularly advantageous configuration, said pump chamber wall then covers at least 75%, advantageously at least 90% or even essentially the entire axial length of the pump chamber ring section or of the pump chamber, respectively. Such a heating device can then be configured essentially round-cylindrical or as a tube section, that is to say continuous and advantageously seamless also in the circumferential direction. 
     In particular in the case of a heated pump or a pump with integrated heating device, by means of the partially minor pump chamber ring section and the resulting increase of the velocity of the transported fluid, a greater heating power can be introduced in the fluid or the absorption of heat from the heating device can be improved, respectively. 
     In the invention, it is provided that the pump chamber or the entire pump is configured without a guide ring or has no guide elements in the type of a guide ring or the like. Such guide elements are those elements or components that protrude from other walls in the pump chamber and extend into the fluid path for special directing or deflecting of the transported fluid. As a result, the construction of the pump can be simplified. By means of the above described effect of the minor pump chamber ring section, it could be proved in tests that the efficiency of the pump can be improved even without guide elements. 
     In a further embodiment of the invention, it is advantageously provided to configure a lower cover plate of the impeller in such a curved manner that it is curved radially inwards towards an aforementioned suction port that forms the suction, that is to say curved in axial direction away from the pump chamber bottom. Advantageously, the lower cover plate of the impeller is curved in the same axial direction radially outwards. Said curvature can be less pronounced than that radially inwards, but nevertheless can be clearly present. The impeller rotates above said pump chamber bottom in the pump chamber, wherein advantageously the pump chamber bottom is also curved radially outside the impeller with a continuation of the curvature of the lower cover plate of the impeller in the radial outer region. In particular, the curvature is continuous and uniform as viewed in a side sectional view of the impeller and continues essentially continuously and in a uniform manner in the pump chamber bottom. For that purpose, the impeller or its lower cover plate can be slightly inserted into the pump chamber bottom. Then, the pump chamber bottom extends with a certain curvature close to the pump chamber ring section or even up to said section and thus directs the fluid discharged out of the impeller in an oblique angle against the heated pump chamber ring section for heating. 
     Said region of the minimum width or cross sectional area of the pump chamber ring section is advantageously in a region of the pump chamber or of the pump shortly behind the location where the outlet leads out of the pump chamber housing. The outlet out of the pump chamber namely leads outwards advantageously in the region of the greatest width or the greatest cross-sectional area, that means that the integrally shaped outlet in said region moves out of and is shaped out of the shape present for the rest of the pump chamber. 
     In the invention it is provided that the axial length of the pump chamber ring section is the multiple of the width of the pump chamber ring section, namely four times to ten times of said width, preferably of the maximum width of the pump chamber ring section. Preferably said length is about five to seven times the width of the pump chamber ring section, namely the maximum width of the pump chamber ring section. 
     Said features and further features arise besides from the claims also from the description and the drawings, wherein in each case the individual features can be realized on their own or in the form of sub-combinations thereof in an embodiment of the invention and in other fields and represent advantageous as well as protectable embodiments per se, for which protection is claimed hereby. The division of the application into individual sections as well as cross-headings does not limit the general validity of the statements made therein. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       Exemplary embodiments of the invention are schematically shown in the drawings and will be explained in more detail in the following. The drawings show in: 
         FIG. 1  sectional longitudinal view of a pump according to the invention, 
         FIG. 2  sectional longitudinal view of the pump of  FIG. 1  turned by about 70°, 
         FIG. 3  plane view of the pump from above, and 
         FIG. 4  sectional transverse view of the pump showing the course of the width of a pump chamber ring section in circulation direction. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1  a pump  11  with a pump housing  12  is shown as generally known from the aforementioned prior art. The pump housing  12  comprises a pump chamber  14  and a central axial suction pipe  15  leads into said chamber and an outlet  16  leads out of said chamber in the tangential direction. The suction pipe  15  leads exactly towards a centrally arranged impeller  18  with a lower cover plate  18   a  and an upper cover plate  18   b . The impeller  18  is driven by a pump motor  19  and extends above a pump chamber bottom  21  having a step-like, central depression adapted to the lower cover plate  18   a.    
     The radially exterior wall of the pump chamber  14  is formed by a tubular heating device  23  as for example known from U.S. Pat. No. 8,245,718 B, namely as a metallic tube having a constant diameter with the ends cut off in a straight manner. On the exterior side of the tube, heating elements not shown are provided for the heating device  23 , advantageously thick-film heating elements. 
     The heating device  23  is supported in the lower region in a V-sealing  26   a  for sealing purposes, wherein the V-sealing  26   a  extends circumferentially radially outside the pump chamber bottom  21  and close to the latter. At the upper end of the pump chamber  14 , i.e. axially away from the impeller  18 , a sealing ring  26   b  having a round cross-section is provided externally on the heating device  23 . As a result, the heating device  23  is in each case sealed outwards against the pump housing  12  and inwards forms the external wall of the pump chamber  14 . As can be seen from  FIG. 4 , the heating device  23  is circular or has a circular cross-section. 
     The pump chamber  14  comprises radially outside of the impeller  18  a transition region at approximately the same axial height, which region merges into a pump chamber ring section  28 . The pump chamber ring section  28  is defined to be essentially the region where the pump chamber  14  has approximately the same width  29  in radial direction, which width does not change in axial direction or which can also decrease. Thus, while the exterior wall also of the pump chamber ring section  28  is formed by the heating device  23 , the internal wall is formed by an inner wall  30  of the pump housing  12 . It can be seen that on both sides in axial direction slightly above the fluid outlet from the impeller  18 , said inner wall  30  and the heating device  23  extend at an approximately constant distance to one another, i.e. the pump chamber ring section  28  having an approximately constant width or even a decreasing width in the axial direction. 
     Then, in the axial direction, the pump chamber ring section  28  has in each case an approximately constant width or the same cross-section or even a decreasing width, wherein the width  29  actually varies in the circulation direction, as can be seen from the sectional view in  FIG. 4 . In  FIG. 1 , a section through a pump  11  is shown, where at the top a width  29   a  of the pump chamber ring section  28  is approximately the greatest, while on the right below a width  29   c  is approximately minimal. The sectional view according to C-C of  FIG. 4  shows that, wherein in this case, the sectional longitudinal view of  FIG. 1  is illustrated as a section A-A. 
     With respect to  FIG. 2 , it is noted that in the sectional plane view of  FIG. 4  according to the section B-B,  FIG. 2  shows a region, where indeed on the right side again a minimum width  29   c  is present at the pump chamber ring section  28 . In contrast, on the left side a moderate width  29   b  is present, which is also illustrated in  FIG. 4 . 
     It can also be seen that the axial length of the pump chamber ring section  28  is about seven or eight times the maximum width  29   a  of this section. Also the outlet  16  is much higher above the impeller. 
       FIG. 3  shows a plane view of the pump  11  with the pump housing  12  including suction pipe  15  and outlet  16 , which merges into an outlet port  17 . However, of more interest is  FIG. 4  according to the section C-C of  FIG. 1  illustrated directly below  FIG. 3 , wherein here outlet  16  and outlet port  17  are illustrated in dashed lines. It can be seen that coaxially to the suction pipe  15  the heating device  23  extends as exterior wall of the pump chamber  14 . However, the width  29  of the pump chamber ring section  28  is determined by means of the differently extending inner wall  30 . Approximately shown are the width  29   a , which is approximately maximum, the moderate width  29   b  and the smallest or narrow width  29   c . Said narrow width  29   c  extends over an arcuate angle of approximately 120° almost up to an electric connection plug  24 , which is arranged externally on the heating device  23 . From there, the width  29  of the pump chamber ring section  28  increases again in a continuous manner over the moderate width  29   b  up to the maximum width  29   a . Said maximum width  29   a  is present approximately at the location where the outlet  16  with the tubularly configured outlet port  17  is separated from the pump chamber  14  or the pump chamber ring section  28  per se, i.e. approximately at the illustrated section A-A. As from said region, the width  29  tapers again with a tapering  32  up to the tapering end  32 ′, where then in turn the smallest or narrow width  29   c  starts. The tapering  32  extends over a region of approximately 70°. 
     It can clearly be seen that externally, the width  29  of the pump chamber ring section  28  is determined by the circular ring shaped heating device  23  and internally, by the inner wall  30 . 
     From the plane view in  FIG. 4 , it can also be seen that actually the region of the pump chamber ring section  28  having the smallest width  29   c  is the only region having a constant width. In the region adjacent thereto in the circulation direction corresponding to the clockwise direction, the width increased essentially in a uniform manner in order to then significantly decrease again in the region of the tapering  32 . It can also be seen that approximately the factor  3  applies to the difference between the maximum width  29   a  and the minimum width  29   c.    
     However, at the same time it is also conceivable that the inner wall  30  of the pump chamber  14  or of the pump chamber ring section  28  is circular or concentric relative to the rotation axis of the impeller  18  or to the central longitudinal axis of the suction  15 . Then, the externally surrounding exterior wall, in particular also in the form of a heating device, is non-concentric such that so to say it is offset relative to the same or configured in a non-round manner, respectively. As a further alternative, also both walls could be non-concentric to one another or to the central longitudinal axis of the pump. 
     By means of the narrowed flow cross-section of the fluid circulating in the clockwise direction in  FIG. 4  in the region of the smallest width  29   c  of the pump chamber ring section  28 , the fluid velocity is significantly increased. Inter alia, that supports a de-aeration of the pump  11  in case there are air bubbles present in the region of the pump chamber bottom  21 , regardless of the reason. By means of the enlargement of the width  29  from the minor region  29   c  via the moderate width  29   b  to the greatest width  29   a , the velocity of the fluid is reduced. By means of both the change in the velocity of the circulating fluid which, for example, circulates approximately three to eight times from the discharge out of the impeller  18  into the pump chamber  14  up to the discharge out of the outlet  16  or the outlet port  17 , and the significantly higher velocity in the minor region, trapped air or an air/fluid mixture can be transported out of the pump  11  in an improved manner. For that purpose, otherwise guide rings or similar guide structures were provided and required, as for example known from EP 2150162 B. However, the production thereof as well as the installation are relatively elaborate and can result in problems as well as breakdowns and thus errors in the pump. Furthermore, the heat transfer in the invention from the heating device to the fluid or water is increased due to the increased flow rate of the fluid. 
     It proved to be advantageous, however not mandatory, for the aforementioned effects of improving the de-aeration as well as improving the heating, when, as shown in  FIGS. 1 and 2 , the pump chamber ring section  28  has the same width or even a decreasing width over a certain axial length of said section. However, at the same time it is to be considered that the increased width of the pump chamber ring section  28  is also present in the region radially outside the impeller  18  and at the axial height thereof. Particularly by means of that, the improved de-aeration is supposed to be achieved.