EP2886796A1

EP2886796A1 - Volumetric pump

Info

Publication number: EP2886796A1
Application number: EP14184321.9A
Authority: EP
Inventors: Roberto Manzini
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-09-17
Filing date: 2014-09-10
Publication date: 2015-06-24
Also published as: ITBO20130502A1

Abstract

Described is a volumetric pump comprising a containment chamber (3) having a first and a second flow pipe (7, 8) for a liquid to be pumped; a rotor (2) housed in the chamber (3) and having a central axis (A1), a central hub (9) and a plurality of deformable vanes (4) distributed at equal angular intervals around the periphery of the hub (9); and drive means for setting the rotor (2) in rotation about a respective axis of rotation (A2).

Description

This invention relates to a volumetric pump.
More specifically, the invention relates to a volumetric pump used for transporting food liquids such as, for example, those typical of the wine sector.
As is known, volumetric pumps used in the wine industry have a rotor housed in a containment chamber in which the inlet pipe and the outlet pipe for the liquid to be pumped converge.
In the wine sector, volumetric pumps are normally used for transferring fluids, such as must or wine in various stages of its production, from one container to another.
Indeed, stringent protocols dictated not only by market standards but also by current rules and regulations (consortiums, geographical production regions, typical designations, etc) require extremely high efficiency in the transfer of the fluids from one cask or container to another, the term "cask" being used generically to denote both vats and casks.
In a volumetric pump of the aforementioned kind there is a rotor which is equipped with a plurality of elastically deformable vanes, usually made of rubber, and which is keyed to the output shaft of a respective motor.
The containment chamber and the rotor are not concentric (in other words, they are either mounted eccentrically or, for example, part of the containment chamber is flattened towards the rotor) so that during the rotation of the rotor the vanes are pressed against and wipe the corresponding stretch of the inside of the chamber.
Thus, intake and subsequent compression of the liquid are obtained by elastic deformation of the rotor vanes.
In other words, as the rotor rotates, the vanes are continuously deformed so as to take in the liquid and then force it out towards the outlet pipe. Volumetric pumps of the kind summarily described above have major disadvantages.
One disadvantage is due to the fact that the direction of transfer is strictly correlated with the direction of rotation of the rotor, which means that to reverse the flow - an extremely frequent operation in wine cellars - it is necessary to reverse the direction of rotation of the rotor, which leads to rapid deterioration of the deformable vanes.
In effect, as is known, alternate flexing of any material (that is, compression alternated with traction) causes rapid deterioration of the mechanical properties of the material and breakage of the part subjected to such flexing. Moreover, during periods in which the pump is not used, the rotor remains idle for lengthy periods (think of the typically seasonal use of pumps of this kind). As a result, the vanes tend to adopt a deformed configuration and to stiffen in a particular shape which, if the direction of transfer flow is reversed, easily causes breakage.
Furthermore, although, on the one hand, elastically compliant vanes are useful for the reasons stated above, such vanes are not, on the other hand, always capable of imparting the necessary force on the liquid because they themselves tend to bend instead of pushing the fluid.
In the past, the Applicant developed a pump which contributed to solving the above mentioned problems by reversing the direction of liquid flow without having to reverse the direction of rotation of the impeller or rotor and by also varying the reciprocal position between the rotor and the respective liner or containment chamber.
This solution, although technically effective, was not fully appreciated by all users because reversal of flow direction required operation of a lever. This, being a manual operation, meant that an operator needed to be physically present on site, and in practice prevented remote management of pump operations, which by now has become an imperative market demand.
A further disadvantage connected with the use of volumetric pumps of known type is due to the high noise level generated during rotation of the impeller.
This invention therefore has for an aim to provide a volumetric pump capable of overcoming the above mentioned disadvantages.
A further aim of this invention is to provide a volumetric pump which is improved in efficiency and practical and functional to use.
More specifically, this invention has for an aim to provide a volumetric pump which is capable of remaining efficient even after the rotor has reversed its direction of rotation frequently and repeatedly.
A further aim of the invention is to provide a high-performance volumetric pump.
The technical features of the invention, with reference to the above aims, are clearly described in the appended claims and its advantages are more apparent from the detailed description which follows, with reference to the accompanying drawings which illustrate preferred, non-limiting example embodiments of it, and in which:

Figure 1 is a schematic front elevation view of a portion of the volumetric pump according to this invention;
Figure 2 is a schematic perspective view of a detail from Figure 1 in a non-assembled configuration;
Figure 3 is a schematic front elevation view of the detail of Figure 2;
Figure 4 is a schematic front elevation view, with some parts cut away, showing the detail of Figure 2 in a configuration of use;
Figure 5 is a schematic front elevation view, with some parts cut away, showing a variant embodiment of the detail of Figures 2 and 3;
Figure 6 shows an ellipse;
Figure 7 schematically represents the steps in the operation of the volumetric pump according to the invention;
Figure 8 is a sectional view of the detail of Figure 3 through the line VIII-VIII.

As illustrated in Figure 1, the numeral 1 denotes in its entirety a portion of a volumetric pump comprising a rotor 2 and a chamber 3 containing the rotor 2.
The rotor 2 comprises a plurality of deformable vanes 4.
Advantageously, the vanes 4 are made at least partly of natural or synthetic rubber.
The containment chamber 3 has an inside surface 5, also referred to as liner.
The inside surface or liner 5 has a profile 6.
The profile 6 of the liner 5 is not circular in shape since, as is known, there is a stretch in which the vanes 4 must be made to bend in such a way as to modify the volume between two successive vanes 4, thus determining the operation of the volumetric pump.
With reference to Figure 1, the containment chamber 3 of the rotor 2 comprises a first flow pipe 7 and a second flow pipe 8 for a liquid to be pumped.
The first and second flow pipes 7, 8 are both in fluid communication with the containment chamber 3 of the rotor 2.
Depending on the direction of rotation of the rotor 2, the liquid flow pipes 7, 8 alternately adopt the function of inlet pipe and outlet pipe for the liquid to flow into and out of the containment chamber 3.
According to the direction of rotation of the rotor 2 illustrated in Figure 1, represented by the arrow F, the first pipe 7 is an outlet pipe through which the liquid is pumped out of the pump towards the use points, whereas the second pipe 8 is an inlet pipe through which the liquid flows into the pump. The first and second pipes 7, 8 give onto the containment chamber 3 by way of respective openings 7a, 8a.
The openings 7a, 8a have an elliptic shape.
As illustrated in Figure 2, the rotor 2 has a central axis A1 and a central hub 9.
The plurality of deformable vanes 4 extend from the central hub 9, projecting radially from the hub 9 itself.
The vanes 4 are distributed at equal angular intervals around the periphery of the hub 9.
As illustrated in Figure 8, the rotor 2 has a metallic core 10 comprising a cylindrical portion 11 and a flange 12 which are integral with each other.
The volumetric pump 1 also comprises a rotary shaft, not illustrated, designed to drive the rotor 2 in rotation about a respective axis of rotation A2. When the rotor 2 is assembled in the pump 1, the two axes A1 and A2 coincide.
The flange 12 advantageously, but not necessarily, has a splined hole 13, shown in Figure 2, designed to engage a respective splined profile, not illustrated, formed on the aforementioned shaft.
With reference to Figures 2 and 8, the flange 12 is located in a median position relative to the axis A1 of the rotor 2, so as to allow suitable sealing means to be placed axially inside the selfsame rotor 2, thus limiting the overall dimensions of the pump 1.
The aforementioned rotary shaft, not illustrated, in combination with motor means of known type, also not illustrated, defines for the volumetric pump 1, respective drive means for the rotor 2, designed to set the rotor 2 in rotation about its axis of rotation A2, thus determining the liquid pumping action.
As illustrated in the accompanying drawings, each vane 4 is joined bilaterally to the hub 9 by way of two respective connecting portions 14 and these connecting portions 14 have an elliptic profile P.
The expression "elliptic profile" referred to the portions 14 by which the vanes 4 are connected to the hub 9 of the rotor 2 means, in this specification, that the profile P of the portions 14 is shaped substantially like an elliptic arc, and more precisely, the perimeter arc extending between two successive intersections of the perimeter with the axes of the ellipse.
In other words, also with reference to Figure 6, where it is drawn with a thicker line, the elliptic profile P substantially represents a quarter of the perimeter of the ellipse, that is to say, the outer perimeter of each of the four segments into which the ellipse appears to be divided by its major axis X1 and its minor axis X2.
Experiments showed that optimum results in the resistance of the vanes 4 are obtained with elliptic profiles P belonging to an ellipse whose ratio of major axis to minor axis is between 2 and 10.
Advantageously, the optimum was obtained by selecting elliptic profiles P belonging to an ellipse whose ratio of major axis to minor axis is between 4 and 8.
Still more advantageously, elliptic profiles P belonging to an ellipse whose ratio of major axis to minor axis is between 6 and 7 were selected.
As illustrated in Figure 2, the rotor 2 has an axial end edge 15 which, on the flank of each vane 4, has a reduced thickness s1 compared to the total thickness s2 of the vane 4 itself.
Advantageously, the reduced thickness s1 allows limiting the extent of the rubber of the rotor 2 in contact with the side covers.
In effect, as a result of the bending they are cyclically subjected to, the vanes 4 are axially deformed with a sort of protuberance which scrapes the metallic cover, not illustrated, usually made of stainless steel and located at the axial ends of the rotor 2.
Advantageously, reducing the size of the edge 15 compared to the thickness s2 of the vane 4 significantly reduces the friction between the rotor 2 and the covers, thereby effectively improving pump performance. Another advantage connected with the aforementioned reduced thickness of the edge 15 is that the rubber of the rotor 2 is less subject to wear and is not abraded, which means less particles of rubber are scraped off and consequently do not contaminate the liquid circulating inside the chamber 3.
As illustrated in Figures 1 to 4, the rotor 2 has a plurality of ridges 16 protruding from the hub 9.
Each ridge 16 extends longitudinally along the central axis A1 of the rotor 2 and is interposed between two successive vanes 4.
Advantageously, the profile P1 of each ridge 16 is semi-elliptic.
The presence of the ridges 16 advantageously allows markedly reducing what is known as the clearances of the rotor 2.
The terms "clearances" is used to denote the space occupied by the liquid which recirculates in the volumetric pump 1.
The clearances, when occupied by liquid, do not create any particular problems with the operation of the pump, except insofar as possibly causing the liquid itself to deteriorate, for example by unwanted heating. On the other hand, when the clearance is occupied by a gas, such as air, for example during priming, this condition may create problems because gas is compressible and thus delays the effective liquid pumping action. The ridges 16 thus considerably limit the volume of the clearances, with the advantage of making priming and the liquid pumping action much more rapid.
With reference to Figure 4, where some of the vanes 4 are shown in their configuration of maximum bending, it is evident that the presence of the ridges 16 does not interfere with the vanes 4, thanks to the semi-elliptic profile P1 of the ridges 16 themselves.
Figure 5 shows a rotor 2 made without the ridges 16 described above.
Figure 7 schematically shows a succession of significant positions adopted by two adjacent vanes 4 moving in the direction indicated by the arrow F, the hatched areas representing the space between the vanes 4 themselves.
The hatched area V1 represents the volume between two successive vanes 4 at the end of the constant volume pumping section TP.
The pumping section TP is the one between the end of the liquid inlet opening 8a and the start of the outlet opening 7a, in the direction indicated by the arrow F.
For correct operation of the pump, the volume of liquid between the vanes 4 must remain constant along the pumping section TP.
The hatched area V2 represents the volume of liquid between two successive vanes 4 at the end of the reflow section TR.
The reflow section TR is the section between the end of the liquid outlet opening 7a and the start of the inlet opening 8a, in the direction indicated by the arrow F.
Experimental tests showed that the efficiency of prior art pumps was partly conditioned by the change in the volume between two vanes 4 in the reflow section TR between the liquid outlet opening 7a and the liquid inlet opening 8a. The profile 6 of the liner 5 has therefore been made in such a way as to guarantee that the volume between the vanes 4 in the reflow section TR remains constant.
The angle subtended by the reflow section TR is labelled α_R, whilst the angle made by two adjacent vanes is labelled α_P. For any rotor 2, the value of the angle α_P is given by the relation α_P = 360° NUMBER OF VANES. Experimental tests showed that the optimum results in terms of pump efficiency are obtained when the relation between the two angles is the following: $α_{R} > α_{P}$
As illustrated in Figure 7, therefore, the reflow section TR which subtends the angle α_R is made in such a way that it extends for a length such as to cause the volume V2 between two adjacent vanes 4 in the path between the outlet opening 7a and the inlet opening 8a to be closed.
Again with reference to Figure 7, the hatched area V3 represents the volume between two successive vanes 4 at the start of the pumping section TP.
Since the pumping section TP is, as mentioned above, constant in volume, it follows that the volume V3 at the start of the section TP coincides with the volume V1 at the end of the selfsame section.
As illustrated in the accompanying drawings, in particular in Figure 7, the section of the profile 6 comprising the reflow section TR and the openings 7a and 8a is defined as operating section TO.
So, again with reference to the accompanying drawings, the operating section TO of the profile 6 is defined by the succession of five curved portions with alternating curvature.
In other words, moving along the operating section TO of the profile 6 in the direction indicated by the arrow F, a first curved portion P01 whose concavity is directed towards the centre of the rotor 2 is followed by a second curved portion P02 whose concavity is directed outwards; the second portion P02 is followed by a third portion P03 whose concavity is again directed towards the centre and which is followed by a fourth portion P04 whose curvature is directed outwards. Lastly, there is a fifth portion P05 whose concavity is directed towards the centre.
The succession of curved portions P01, P02, P03, P04, P05, as just described, in the operating section TO brings considerable advantages.
In particular, the above succession of curved sections optimizes the length of the reflow section TR between the liquid outlet and inlet openings 7a, 8a.
Advantageously, the succession of curved portions described above makes it possible to obtain a reflow section TR with a constant radius. The above succession of curved portions P01, P02, P03, P04, P05 also advantageously allows reducing the noise produced by the volumetric pump 1.
In effect, experiments showed that the noise depends largely on the elastic return of the vanes 4 which, at the end of the reflow section TR, spring back very rapidly. The provision of curved portions as described above, which are connected to each other by the respective alternating concavities, advantageously allows minimizing the negative effects, in terms of noise, of the elastic return.
Advantageously, as a whole, the above described features of the liner 5 allow minimizing the noise and maximizing the performance of the volumetric pump 1.

Claims

A volumetric pump comprising:
- a containment chamber (3) having a first and a second flow pipe (7, 8) for a liquid to be pumped, both of the pipes (7, 8) being in fluid communication with the containment chamber (3);

- a rotor (2) housed in the chamber (3), the rotor (2) having a central axis (A1), a central hub (9) and a plurality of deformable vanes (4) distributed at equal angular intervals around the periphery of the hub (9), the vanes (4) projecting radially from the hub (9);

- drive means for setting the rotor (2) in rotation about a respective axis of rotation (A2), characterized in that each of the vanes (4) has, bilaterally thereof, respective portions (14) for connecting it to the hub, the connecting portions (14) having an elliptic profile (P).
The volumetric pump according to claim 1, characterized in that the elliptic profile (P) belongs to an ellipse whose ratio of major axis (X1) to minor axis (X2) is between 2 and 10.
The volumetric pump according to claim 1 or 2, characterized in that the elliptic profile (P) belongs to an ellipse whose ratio of major axis (X1) to minor axis (X2) is between 4 and 8.
The volumetric pump according to any of the preceding claims, characterized in that the elliptic profile (P) belongs to an ellipse whose ratio of major axis (X1) to minor axis (X2) is between 6 and 7.
The volumetric pump according to any one of claims 1 to 4, characterized in that it comprises a plurality of ridges (16) protruding from the hub (9), each of the ridges (16) extending longitudinally along the central axis (A1) and being interposed between two successive vanes (4).
The volumetric pump according to claim 5, characterized in that each of the ridges (16) has a semi-elliptic profile (P1).
The volumetric pump according to any one of claims 1 to 6, where the rotor (2) is made mainly of rubber and comprises a metallic core (10), characterized in that the metallic core (10) comprises a cylindrical portion (11) and a flange (12) which is integral with the cylindrical portion (11) and which is designed to rotationally engage a respective shaft.
The volumetric pump according to claim 7, characterized in that the flange (12) is located in a median position relative to the central axis (A1) of the rotor (2).
The volumetric pump according to any one of claims 1 to 8, characterized in that the rotor (2) has an axial end edge (15) which extends on the flank of the vanes (4) where its thickness (s1) is less than the thickness (s2) of the vanes (4) themselves.