DE20109422U1 - Impeller for a side channel machine and compressor with one - Google Patents

Description

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Impeller for a side channel machine and compressor with such a

The invention relates to an impeller for a side channel machine according to the preamble of claim 1 and to a compressor with such an impeller.

A side channel machine which has an impeller according to the preamble of claim 1 can be found in DE 196 49 529 A1. This side channel machine is particularly intended for use in the dental field.

The present invention aims to further develop the impeller of such a side channel machine so that the side channel machine operates with even greater efficiency.

This object is achieved according to the invention by an impeller 0 for a side channel machine, which has the features listed in claim 1.

In the impeller according to the invention, the blades which force the gaseous medium onto a toroidal spiral and thus convey it from the inlet to the outlet of the casing of the side channel machine have a radially outer section of one of their boundary walls which is inclined relative to the main plane of extension of the blades. This inclination is selected so that the outer sections of the moving blades are better adapted to a spiral geometry.

In other words, the inclined sections of the boundary walls of the blades facilitate the entry and exit of gaseous medium, which is conveyed along a flow path from the inlet to the outlet of the side channel machine.

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which has the shape of a torus spiral (similar to a long coil spring closed in a circle). This better adaptation of the geometry of the impeller to the flow pattern in the side channel results in better delivery performance of the impeller. There is also less noise.

Advantageous developments of the invention are specified in subclaims.

The development of the invention according to claim 2 ensures that the flow cross-section defined between successive blades expands towards the edge of the impeller. This promotes the "collection" of the gaseous medium.

The development of the invention according to claim 3 is advantageous with regard to simple machining of the blades. With the angle of inclination between the planes of the blade end sections and the main extension planes of the blades, which is small in practice, a flow pattern is obtained that is largely free of local turbulence.

With the further development of the invention according to claim 4, an even better spatial adaptation of the boundary surfaces of the blades to the spatial flow pattern in the side channel is obtained.

The measure according to claim 0 5 also serves the same purpose.

In an impeller as specified in claim 6, an intensive exchange of gaseous medium to be conveyed takes place between the recess of the impeller and the side channel. Such an impeller could be

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as a side channel machine impeller with a certain amount of centrifugal impeller characteristics.

Claims 7 and 8 specify preferred geometries of the 5 impeller.

With the development of the invention according to claim 9, an impeller operating with good efficiency is obtained in a simple manner, which can simultaneously form two compressor stages.

A compressor according to claim 10 also ensures, by increasing the radial dimension of the side channel in a section thereof, that the exchange of gaseous medium to be conveyed between the recess of the impeller and the side channel takes place well and effectively.

The oversize provided in a peripheral section of the side channel is preferably set according to claim 11. 20

The invention is explained in more detail below using embodiments with reference to the drawing.

In this show:
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Figure 1: an axial section through a two-stage side channel suction machine with an inlet opening located on the housing axis and an additional inlet-side pre-compressor and deflection stage, 0 which is integrated into the impeller;

Figure 2: a plan view of the underside of an upper housing part of the suction machine according to Figure 1, with a plan view 5 of the underside of the impeller also shown in one quadrant

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is ;

Figure 3: a plan view of the upper side of a lower housing part of the suction machine shown in Figure 1, with in one quadrant additionally

a top view of the impeller is shown;

Figure 4: a perspective view of a modified impeller whose blades are better adapted to the

geometry of the side channel flow is adapted; and

Figure 5: an axial view of a further modified impeller for a side channel machine with the

Flow in the side channel of adapted geometry together with an associated upper housing part of the side channel machine.

0 The drawing shows a side channel suction machine for dental purposes, designated overall by 10, with a housing which has an upper housing part 12 and a bowl-shaped lower housing part 16 with a peripheral wall 14. The latter has a central inlet connection 18 which is connected to the outlet of a separating unit indicated only by dashed lines at 2 0. The latter separates liquid and solid components from the air coming from the dentist's workplace, so that the suction machine 10 is only exposed to dry air.

The housing parts 12 and 16 together define a pump chamber 22 in which an impeller 24 rotates.

5 The impeller 24 is suspended on the end of a motor

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shaft 26, which belongs to an electric motor 28 attached to the top of the upper housing part 12. Its upper motor housing part is designated 30. An upper end section of the motor shaft 26 carries a fan wheel 32. An outer housing 34 is placed on radial ribs of the motor housing part 30, which guides the air flow generated by the fan wheel 32 over the outer surface of the motor housing part 30.

The impeller 24 has two plane-parallel end faces. In the edge area of the upper end face, as seen in a radial sectional view, there are generously pierced pockets 36 with rounded rectangular corners and elongated semicircular cross-sections in the middle, between which side channel compressor blades 38 remain. In line but offset by half a pitch (see Figure 5), pockets 40 are pierced in the edge area of the lower end face of the impeller 24, between which side channel compressor blades 42 remain. As can be seen from Figure 5, the rear end of the end face of the compressor blades 38, as seen in the direction of rotation, is designed to be set back at an angle of 45 to the center plane of the impeller 24.

A first side channel 44 is formed in the underside of the upper housing part 12 in alignment with the path of the compressor blade 38, the angular extent of which (measured at its center line running in the circumferential direction) is approximately 330°. The side channel 44 has a radially outwardly extending outlet section 46 which is connected to an axial connecting channel 48 of the lower housing part 14 and leads to an inlet section 50 of a second side channel 52 which is provided in the upper side of the lower housing part 16 and is aligned with the path of the compressor blades 42.

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The circumferential extent of the side channel 52 is again approximately 330 , as can be seen from Figure 3. An outlet section 54 of the side channel 52 is connected to an outlet nozzle 56 of the lower housing part 16.

Thus, webs 45 and 53, which remain between the ends of the side channels 44, 52, have a circumferential extension of 3 0° (again measured at their radial center). In other embodiments, this angular extension can be between about 2 0° and about 4 0°. With this choice of angular extension of webs 45 and 53, one has, on the one hand, a satisfactory seal between the ends of the two side channels, which are under different pressures, and, on the other hand, a large circumferential extension of the side channels, which is advantageous with regard to the generation of high pressure differences and high efficiency of the side channel machine.

A silencer 58 is inserted into the outlet nozzle 56 and is surrounded by a silencer housing 60 which has an outlet opening 62, only indicated schematically, which is connected to an exhaust air line on the building side.

In a central area of the impeller 24, compressor blades 64 of a pre-compression stage are provided which are curved in the direction of rotation and are covered by a curved, rotationally symmetrical guide wall 66, the inlet-side end section of which is parallel to the axis, while its outlet-side section is at only a small angle to

a transverse plane. The lower end faces of the compressor blades 64 slope inwardly from the edge to a hub portion 68 of the impeller 24.
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The inlet-side end of the guide wall 66 is aligned with the upper edge of a conical inlet opening 70 of the housing, which is provided in the bottom of the lower housing part 16. The inner surface of the inlet opening 70 essentially represents a smooth continuation of a conically widened end section of the inlet nozzle 18, which is tightly fitted onto the lower housing part 12 via a seal 72 and is positioned there with an axial edge section 74 via a circular positioning rib 16 .

An intermediate channel 78 is provided in the underside of the upper housing part 12 axially above the outlet-side ends of the compressor blades 64, the depth of which increases in proportion to its angular extent in the direction of a coplanar connecting channel 80 which leads outwards to an inlet section 82 of the first side channel 44. The connecting channel 80 is connected to an axially parallel secondary air channel 84 to which a secondary air control unit 86 is connected, as indicated schematically in Figure 1. Via the latter, secondary air can be fed directly to the second inlet of the two-stage side channel compressor, which is formed by the compressor blades 38, 42 and the side channels 44, 52, bypassing the compressor inlet stage formed by the compressor blades 64.

As can be seen from the above description and also from Figure 1, the compressor blades 64 provided in the central region of the impeller 24 do not increase either the axial or the radial dimensions of the suction machine. The housing of the suction machine consists of only two housing parts 12 and 16, which can easily be manufactured by casting.

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An upper wall 90 of the upper housing part 12, which runs in the circumferential direction, forms a lower motor housing part together with the top wall of the housing part 12. Positioning ribs 92 project radially inwards from the wall 90, which have an oversize in the cast blank for the housing part 12 and are then turned to the final size so that they accommodate the stator 94 of the electric motor 28 in a form-fitting manner. By turning the positioning ribs 92 to different extents, the wall 90 can form a lower motor housing part for electric motors of different power.

As can be seen from Figure 2, the connecting channel 80 opens into the radially inner boundary wall 96 of the inlet section 82 of the side channel 44. The angle of attack to this section of the boundary wall is approximately 60°, and the radially outer wall of the connecting channel 80 passes through the corner point which would enclose the radially inner boundary wall 96 with a rear boundary wall 98 of the inlet section 82 if the boundary wall 96 were continuous. The radially inner boundary wall of the connecting channel 80 merges via an inclined surface which widens the channel into the radially inner boundary wall 96 of the side channel 44, forming an angle of approximately 30°.

From the point where the inclined surface 100 meets the radially inner boundary wall 96 of the side channel 44, a guide wall 102 extends which is narrow compared to the width 0 of the impeller pockets and which

a radius ray passing through its center forms an angle w of approximately 40. At the same time, the guide wall 102 is essentially perpendicular to the longitudinal axis of the connecting channel 80.
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The guide wall 102 is formed with its lower end onto the bottom of the side channel 44 and extends with its front surface exactly into the front surface of the housing part 12. The downstream edge of the guide wall 102 is provided with a chamfer 104.

During operation, the intermediate channel 78 running in the circumferential direction is supplied with pre-compressed air, as described above. The air flow emitted by the connecting channel 80 can fan out into the inlet section 82 and also fan out due to the inclined surface 100. Due to the guide wall 102, the air flow is dammed and diverted upwards in a direction perpendicular to the plane of the drawing in Figure 2 (i.e. downwards in Figure 1). The diverted air thus reaches the pockets 40 provided in the top of the impeller 24.

Since the guide wall 102 is perpendicular to the longitudinal axis of the connecting channel 80, a good damming effect is achieved. Conversely, since the guide wall 102 is tilted with respect to the pitch circle of the impeller marked with 106 and thus also the curved longitudinal axis of the side channel 44, the deflection of the air flow takes place progressively in the direction of rotation of the impeller. This asymmetrical arrangement of the guide wall 102 thus promotes the formation of a helical flow, which would only occur in stationary operation of the side channel compressor after the impeller rotates by an angle 24 0 larger.

As can be seen from the drawing, the circumferential extent of the guide wall 102 corresponds to the circumferential extent of approximately three consecutive pockets 40 (equal to three pockets 36).

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The better entrainment of air from the intermediate channel 80 results in better efficiency and better negative pressure.

As Figure 2 shows, a downstream end wall 107 of the side channel 44 is tilted at an angle e against a radius beam passing through its center, which in the embodiment shown is 35. In this way, the compressed air is increasingly decoupled from the impeller and deflected in a radial direction.

In the embodiment described above, the angle of attack w of the guide wall 102 was 40 . In practice, improvements over the prior art were achieved with angles of attack lying between 20° and 50°, with the range between 35 and 45 , in particular 40°, producing the best results.

0 Figure 3 shows a similar coupling of the air to be conveyed into the inlet section 50 of the second compressor stage. The connecting channel 48 is connected to a radial channel section 108 which intersects the end of the side channel 52 in the radial inward direction.

A guide wall 110 is set at an angle W relative to a radius beam passing through its center. In the embodiment considered here, this is equal to the angle w, i.e. 4 0 . The upper face of the guide wall 110 again has a downstream chamfer 112.

The intersection point of the guide wall 110 and the reference circle designated 114 for the lower impeller pockets 36 or the lower side channel 52 is located slightly behind the downstream limit when viewed in the direction of rotation 5.

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sion wall of the channel section 108. Thus, approximately the upper third of the guide wall 110 covers the channel section and in this area the wall of the side channel is also pulled through to the guide wall 110 without any breakthroughs.

That part of the channel section 108 which, viewed in the direction of rotation, lies in front of the radial center line of the channel section 108 and radially outside the pitch circle is covered by a web 116. From the longitudinal center plane of the channel section 108, the edge of the web 116 then extends in a straight line in the radial direction outwards to the outer end of the guide wall 106, as shown at .

This design of the transition between the channel section 108 and the side channel 52 also promotes an asymmetrical flow to the pockets 36 of the impeller 24 with respect to the pitch circle 114. Added to this is the effect of the guide wall 110, which serves as an asymmetrical weir with respect to the pitch circle 114. The slanted front edge 118 of the web 116 has proven itself in terms of good flow conditions and low noise development.

The guide wall 110 again has a small thickness compared to the pocket width, corresponding to the thickness of the compressor blades 38, 42, and again extends in the circumferential direction over three pockets of the impeller.

As can also be seen from Figure 3, the end wall 12 0 of the side channel 52, which is located at the front in the direction of rotation, is tilted by an angle relative to a radius beam passing through its center, which angle is designated by E in the drawing. This angle is approximately 35° in the embodiment shown in Figure 5. As a result,

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the decoupling of the air from the guide system formed by the impeller 24 and the side channel 52 and its deflection in the radial direction is promoted.

As can be seen from Figure 4, the compressor blades 38 delimiting the pockets 36 each have a rear boundary surface, seen in the direction of rotation, which has two sections inclined towards each other: a radially inner section 122 of the rear boundary surface lies in a radial plane which intersects the wheel axis, and a radially outer section 124 of the rear blade boundary surface is tilted in the forward direction, so that the thickness of the compressor blades 38 measured in the circumferential direction decreases towards their free end.

In addition, the section 124 of the rear blade boundary surface is also tilted in a second direction, namely forward in the direction of rotation, such that the thickness of the compressor blades 3 8 decreases from the root to the free back thereof.

In this way, the pockets 36 each have a funnel-shaped, widened section at their radially outer end. Due to this geometry, gas that is conveyed on a torus spiral in the side channel machine can enter and leave the pockets 36 particularly well.

The impeller according to Figure 5 differs from that according to the previously described figures in that the pockets 3 6 are open in the radial outward direction.

The compressor blades 38 each have a radially inner blade section 126, which lies exactly in a plane intersecting the wheel axis. The radial

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inner blade section 126 carries an outer blade section 128 which is tilted forward in the direction of rotation with respect to the main extension plane of the compressor blade 38 (plane of the blade section 126).

The tilt angle a in the example considered here is about 20 degrees. Good results are also achieved with tilt angles of about 15 degrees to about 30 degrees, depending on the diameter of the impeller and its operating speed (normally 3000 rpm).

The radially outer blade sections 128 are wedge-shaped. The compressor blades 38 taper to a point towards their edge. The blade boundary surfaces are rounded at the joints between the blade sections 126 and 128.

In the exemplary embodiment considered, approximately two thirds of the total radial dimension of a compressor blade 38 is allocated to the radially inner blade section 126 and approximately one third to the outer blade section 128.

In the impeller according to Figure 5, the compressor blades 64 belonging to the first compressor stage are not curved but flat. They lie in planes which are each spaced from the impeller axis.

In the embodiment according to Figure 5, the side channel 44 has a first channel section 130 which, viewed in the direction of rotation, lies between an outlet 132 and an inlet 134. The channel section 130 has an outer diameter 130 such that the impeller 24 cooperates with the outer wall of the channel section 130 with the tightest possible sealing clearance.

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In a further channel section 136, which lies between the inlet 134 and the outlet 132, the side channel 44 has a larger diameter than the impeller 24. In the exemplary embodiment considered, the diameter difference is approximately equal to half the radial extension of the compressor blades 38.

Claims (11)

1. Impeller for a side channel machine, with a hub section, with a disk section carried by the latter, which has a flat front surface and is provided with a plurality of pockets ( 40 ) which recede from the front surface and are separated from one another by intermediate blades ( 38 ) which run predominantly in the radial direction, characterized in that the blades ( 38 ) each have at least one boundary surface which is inclined to the radial main extension plane of the respective blade ( 38 ) at least in a radially outer region ( 124 ; 128 ). 2. Impeller according to claim 1, characterized in that the blades ( 38 ) taper to a point in their radially outer section ( 128 ). 3. Impeller according to claim 1 or 2, characterized in that the inclined sections ( 122 ; 128 ) of the boundary surfaces of the blades ( 38 ) are flat. 4. Impeller according to one of claims 1 to 3, characterized in that the inclined sections ( 122 ) of the boundary surface of the blades ( 38 ) are inclined in two directions with respect to the radial main extension planes of the blades ( 38 ). 5. Impeller according to one of claims 1 to 4, characterized in that radially outer end sections ( 128 ) of the blades ( 38 ) are inclined overall to the main extension plane of the blades. 6. Impeller according to one of claims 1 to 5, characterized in that the pockets ( 36 ) are open in the radial outward direction. 7. Impeller according to one of claims 1 to 6, characterized in that the angle of inclination of the inclined sections ( 122 ; 128 ) of the blades ( 38 ) to the main extension plane of the blades ( 38 ) is between about 15 degrees and about 30 degrees, preferably about 20 degrees to about 25 degrees. 8. Impeller according to one of claims 1 to 7, characterized in that the radial dimension of the inclined sections ( 122 ; 128 ) of the blades ( 38 ) is about 20 percent to about 40 percent, preferably about 33 percent of the total radial dimension of the blades ( 38 ). 9. Impeller according to one of claims 1 to 8, wherein the hub portion carries further vanes ( 68 ) which can form a further compressor stage, characterized in that the further vanes ( 68 ) are flat and their planes are spaced from the impeller axis, the inclination of the planes of the further blades ( 68 ) with respect to radial planes being opposite to the inclination of the inclined portions ( 122 ; 128 ) of the blades ( 38 ). 10. Compressor with an impeller according to one of claims 6 to 9, characterized in that a side channel ( 44 ) of a housing part ( 12 ) running in the circumferential direction, with which the impeller ( 24 ) cooperates, has in a channel section ( 130 ) lying between an outlet ( 132 ) and an inlet ( 134 ) substantially the same outer diameter as the impeller ( 24 ) and in a channel section ( 136 ) lying between the inlet ( 134 ) and the outlet ( 132 ) has a larger outer diameter than the impeller ( 24 ). 11. Compressor according to claim 10, characterized in that the outer diameter of the second channel section ( 136 ) is approximately half the radial dimension of the compressor blade ( 38 ) larger than the outer diameter of the impeller ( 24 ).