EP3199816B1

EP3199816B1 - Side-channel blower/aspirator with an improved impeller

Info

Publication number: EP3199816B1
Application number: EP16153453.2A
Authority: EP
Inventors: Pietro Bianchi
Original assignee: Cattani SpA
Current assignee: Cattani SpA
Priority date: 2016-01-29
Filing date: 2016-01-29
Publication date: 2021-05-26
Anticipated expiration: 2036-01-29
Also published as: DK3199816T3; EP3199816A1; US20170218971A1; ES2881049T3; PL3199816T3

Description

The present invention relates to a side-channel blower / aspirator with an improved impeller.
Side-channel (or even air ring) blowers / aspirators provided with an impeller that has a central body from which a plurality of peripheral blades extend are known.
The impeller is enclosed into a casing in which an annular conduit is defined, in which the impeller blades rotate.
The annular conduit has a suction mouth, through which a fluid (normally air) is aspirated and a delivery mouth through which the fluid is expelled. These machines can operate both as vacuum pumps and as compressors.
The operation of this type of machines is based on the principle of the fluid flow caused by the thrust developed by the impeller blades within the annular conduit, during rotation.
In detail, during rotation, the blades push the fluid forwards and, due to the mentioned centrifugal thrust, also outwards.
The walls of the annular conduit then deviate the fluid again between one blade and another.
The joint action of the blades and the walls of the annular conduit define a helical motion in the fluid itself.
Currently, the impellers used in side-channel machines are provided with rectilinear radial blades.
The Applicant, following research and experimentation activities, has observed that the shape of known impeller blades does not allow the operating principle described above to be exploited with full efficiency. The technical task underpinning the present invention is therefore to propose a side-channel blower / aspirator with an improved impeller that makes it able to offer better performance levels with respect to the known art.
Such technical task is reached by the side-channel blower / aspirator obtained according to claim 1.
Further characteristics and advantages of the present invention will become more apparent from the following indicative, and hence nonlimiting, description of a preferred, but not exclusive, embodiment of the machine according to the invention, as illustrated in the accompanying drawings, in which:

figure 1 is an axonometric view of the machine according to the invention;
figure 2 is an exploded view of the machine of figure 1;
figure 3 is a front view of the machine, wherein the containment casing of the improved impeller has been uncovered;
figure 4 is an enlarged detail of the previous figure, wherein an upper zone of the casing, the impeller and the annular conduit afforded in the casing itself are shown;
figure 5 is an axonometric view of the impeller;
figure 6 is a front view of the impeller; and
figure 7 is a diametral sectional view of the impeller.

With reference to the mentioned figures, 1 indicates the side-channel blower / aspirator according to the invention.
The proposed machine 1 comprises an impeller 2 improved with respect to machines of the prior art.
The impeller 2 is provided with a plurality of peripheral blades 21 and is equipped with a central hub 22, fitted onto a shaft 11 (see in particular figure 2), which is placed in rotation by motor means of the known type, for example the electric motor 12 represented in figures 1 and 2.
As will be explained in detail below and as can be seen from the appended figures, the blades 21 of the impeller 2 are not rectilinear like those of the prior art but, on the contrary, have a particular curvature.
The advantages offered by such a special conformation of the blades 21 will be better understood following the description of some general aspects of the machine 1 in which such an impeller 2 is used.
The impeller 2 according to the invention is enclosed in a casing 13, 14 which internally defines an annular conduit C within which the blades 21 rotate, in the direction indicated by the arrow in figure 3.
In more detail, the two parts of the channel C which are ideally separated by the plane orthogonal to the axis of rotation of the impeller 2 coinciding with the plane of symmetry of the machine 1, are called "side channels". As shown in figure 2, the casing is preferably made of two half- shells 13, 14, sealingly fixed, one of which is connected to the electric motor 12, while the other one constitutes a front cover.
According to an aspect of the prior art, the aforementioned annular conduit C has a suction mouth 3 for aspirating fluid (in particular air) taken externally to the machine 1 and a delivery mouth 4 for allowing the fluid to exit from the machine 1 itself (see figure 3).
In practice, through the action of the blades 21 of the impeller 2, the fluid is aspirated by the suction mouth 3 and, after crossing the annular conduit C, is expelled through the delivery mouth 4.
The annular conduit C has a first section which, with respect to the advancement direction of the blades 21 in the conduit, goes from the suction mouth 3 to the delivery mouth 4.
In this first section, there is a free space between the blades 21 in rotation and the internal wall of the annular conduit C, to allow, during use, the formation, within the fluid, of the main motion internal to the machine 1 mentioned during the discussion of the prior art.
The annular conduit C further has a second section, which goes from the delivery mouth 4 to the suction mouth 3, within which, preferably, the blades 21 skim the internal walls of the section itself so as to limit the passage of fluid from the delivery mouth 4 to the suction mouth 3.
As shown in the appended figures, the impeller 2 according to the invention is equipped with blades 21 comprising at least one longitudinally curved portion, defining a substantially curved profile.
In detail, such blades 21 each define a concavity 23 facing the advancement direction of the blades 21 within the conduit C.
In practice, the blades 21 of the impeller 2 according to the invention, rather than being rectilinear, are bent or curved, hence having a concave front surface 23, at least at the respective aforementioned curved portion. In other words, the section (or intersection) of the blades 21 of the impeller 2 taken along an ideal plane perpendicular to the axis of rotation of the impeller 2 defines, at the front surface 23, a curved and not rectilinear line. More precisely, the impeller 2 may comprise a central body 24, preferably axial symmetric, for example discoidal, at the centre of which the aforementioned hub 22 is afforded and from which the blades 21 extend. The blades 21 originate from a circumferential portion 25 of the central body 24 and extend outwards, substantially lying in the plane of the central body 24 itself.
In more detail, each blade 21 includes a proximal portion 210 (i.e. more internal) joined to the central body 24 at its circumferential portion 25.
In the preferential embodiment of the invention, shown in the appended figures, the blades 21 have a curvature along their whole longitudinal extension; in this case, the whole side profile of the individual blade 21 has a continuous curvature, without rectilinear sections (see in particular figures 3 and 4).
Alternatively, the blades may each be provided with one rectilinear portion and at least one curved portion, the latter being for example a longitudinal distal portion comprising the free end of the relative blade 21.
According to a further, non-preferential, variation, the blades may be formed by a plurality of curved sections, defining cuspidal joining zones. The curved or partially curved conformation of the blades 21 allows the machine 1 to operate more efficiently with respect to the prior art, for the reasons illustrated below.
As explained above, during the use of this type of machines, the air found inside the annular channel receives, from the impeller 2, both a thrust forwards (see arrow A of figure 4) and a centrifugal thrust (see arrow B), i.e. away from the centre of rotation of the impeller 2 itself.
Thanks to the curvature of the blades 21 according to the invention, the part of air thrust in the centrifugal direction, which would tend to move radially away from the blades 21, is instead intercepted by the blades 21 themselves and projected forwards.
More precisely, the radial component of the fluid's motion field is in part deviated in the circumferential direction already by the actual blade before the fluid is subject to the action of the closing walls of the annular conduit C.
In this way, a prevailing part of the volume of air included in the annular channel is thrust forwards by the blades 21, allowing the machine 1 according to the invention to obtain improved performance levels with respect to known machines.
Note that known impeller blades, being rectilinear, are not able to "capture" air flows moving in the centrifugal direction within the annular conduit.
Even known impellers equipped with blades formed by angular segments cannot obtain the efficiency provided by the proposed impeller 2, since at the most they will be able to partially deviate centrifugal flows whereas the blades 21 according to the invention retain them much more and thrust them in the rotation direction.
In the preferred embodiment of the invention, the blades 21 of the impeller 2 are placed tangentially to the aforementioned circumferential portion 25 of the central body 24 (see in particular figure 4).
In detail, the mentioned proximal portion 210 of the blade 21 extends from the circumferential portion 25 outwards and along a tangential direction to the circumferential portion 25 itself.
In other words, the proximal (or "base") portion 210 of the blade 21 has a curvature such that it is tangential to the circumferential portion 25.
This aspect is particularly advantageous, in terms of efficiency of use of the proposed machine 1, for the reasons illustrated below.
As mentioned above, during the use of the machine 1, within the annular conduit C swirls of fluid are developed due to the action of the blades 21 of the impeller 2.
In detail, part of the fluid contained in the annular conduit C, furthest from the centre of rotation, tends to move forwards in the rotation direction along an ascending curve; instead, part of the fluid closer to the centre of rotation follows a descending curve until it moves in the retrograde direction upon reaching the internal area affected by the base of the blades 21 (see arrow D in figure 4).
The blades 21 of the impeller 2 according to the invention, being equipped at the base 210 of the aforementioned tangential bend at the joining circumference between blades 21 and central body 24, are able to intercept the aforementioned retrograde fluid and push it forwards, increasing the efficiency of the machine 1.
According to the invention (not depicted in the appended figures), each blade has, in addition to the longitudinal curvature described above, a second curvature along its transversal extension.
Preferably, in this "double curvature" version, each proposed impeller blade has the transversal curvature along its extension, particularly along its whole longitudinal extension and its whole transversal extension.
In other words, consider a diametral plane of the impeller 2 which passes through a prefixed point of the front surface 23 of a blade 21 of the impeller 2.
The section (or intersection) of the blades 21 of the impeller 2 taken along a plane perpendicular to the diametral plane and parallel to the axis of rotation of the impeller 2 defines, at the front surface 23 itself, a curved and not rectilinear line.
Thanks to the second curvature, the blade is able to intercept and project forwards the air flows which would tend to laterally escape from the blade itself.
Therefore, yet again, the invention allows improved efficiency of the machine 1 with respect to the prior art.
Optionally, the blades 21 have a curvature such as to be tangential to a respective diametral plane which passes through the axis of the central body; in detail, the tangency point is located in the rear convex part of the blade 21.
According to the invention, each blade 21 is contained in one of the two semi-spaces defined by an ideal diametral plane that joins the axis of the central body 24 to the joining zone between the blade 21 and the central body 24.
As shown in the figures, in particular in figures 4 and 5, the impeller 2 proposed may include a portion with an annular progression 26, i.e. a geometric surface of revolution about the axis of rotation.
Such an annular portion 26 is incorporated into the blades 21 and extends starting from the circumferential portion 25 mentioned various times of the impeller, in a radial direction, and ends at a shorter distance than the longitudinal extension of the blades 21, for example, substantially half way along their length.
Finally, by way of non-exhaustive example, the impeller 2 proposed may be made of die-cast aluminium or a polymeric material by injection moulding.

Claims

Side-channel blower or aspirator (1), comprising at least one impeller (2) equipped with a plurality of blades (21) and a casing (13, 14), in which said impeller (2) is enclosed and within which an annular conduit (C) is defined in which said blades (21) rotate, wherein the blades (21) each comprises at least one portion which is curved along a longitudinal extensions of the blade (21), defining a concavity (23) facing the advancement direction of the blades (21) within said conduit; wherein the impeller (2) comprises a central body (24) axial symmetric to which said blades (21) are joined at respective joining zones, the side-channel blower or aspirator characterized in that each blade (21) being completely contained within one of the two semi-spaces defined by an ideal diametral plane which joins the axis of the central body (24) to the joining zone between the blade (21) and the central body (24) and each blade having a second curvature along its transversal extension.
The side-channel blower or aspirator (1) according to the preceding claim, wherein said blades (21) have a longitudinal curvature along their entire longitudinal extension.
The side-channel blower or aspirator (1) according to at least one of the preceding claims, wherein the impeller (2) comprises a central body (24) from which said blades (21) extend, which are arranged tangentially to a circumferential portion (25) of the central body (24).
The side-channel blower or aspirator according to the preceding claim, wherein the impeller (2) comprises a central body (24) from which said blades (21) extend, each blade (21) being provided with a proximal portion (210) joined to a circumferential portion (25) of the central body (24), said proximal portion (210) of the blade (21) being curved so as to be tangential to said circumferential portion (25) of the central body (24).
The side-channel blower or aspirator (1) according to claim 1, wherein each of said blades is equipped with said second curvature along its whole longitudinal extension.