DE102013105536A1 - blower - Google Patents

Abstract

The invention relates to a fan wheel (3) attached to the rotor of an electric motor (1), the fan wheel (3) having a fan wheel axis (x) and a fan wheel blades (7) covered by a rotating cover part (8), the fan wheel blades ( 7) have an extension in the axial direction. In order to further improve a fan wheel of the type in question, in particular in terms of flow technology, it is proposed that the cover part (8) cover the fan wheel blades (7) radially on the outside in the direction of the axis (x) by half or more of the axial extent of the fan wheel blades (7) ,

Description

The invention relates to an impeller attached to the rotor of an electric motor, the impeller having an impeller axis and, covered by a co-rotating ceiling part impeller blades, further wherein the impeller blades have an extension direction in the axial direction.

Blower wheels of the type in question are known. These are preferably driven by an electric motor, wherein the impeller is further preferably non-rotatably attached to the rotor axis of the electric motor. As a result of the fan blades arranged, an air flow is achieved via the rotating fan wheel, in particular for cooling the electric motor, more preferably in the arrangement of the electric motor and fan wheel, for example in a vacuum cleaner or the like, for building up a suction air flow. The impeller blades are covered by a co-rotating ceiling part. This essentially serves for the targeted direction of flow in the area of the fan wheel, so on, in particular for achieving a radial fan. In this case, the air is preferably sucked in the axial direction, more preferably centrally of the impeller, more preferably passing through a corresponding opening of the ceiling portion, and passed at least according to the arrangement of the impeller blades radially outward.

An electric motor with such an impeller is, for example, from the DE 10 2008 014 642 A1 known.

In view of the known prior art, a technical problem of the invention is seen in an impeller of the type in question, in particular fluidically to further improve.

A possible solution of the problem is given according to a first inventive concept in an impeller in which it is geared to that the cover part covers the impeller blades radially outward in the direction of the axis to half or more of the axial extent of the impeller blades. As a result of this embodiment, in particular the radially outwardly directed opening areas between the impeller blades are at least partially covered radially on the outside, so that at least a partial deflection of the air flow and optionally entrained by the air flow particles results in this area. Accordingly, the ceiling part extends from an axial overlap of the impeller blades into an at least partially radial overlap, which results in a preferred embodiment, a ceiling part with one, the radially outwardly facing end edges of the impeller blades overlapping, circumferential wall area.

Further features of the invention are explained below, also in the description of the figures, often in their preferred association with the subject matter of claim 1 or with features of further claims. But they can also be in an assignment to only individual features of claim 1 or the respective further claim or each independently of importance.

Thus, it is provided in a further preferred embodiment that the cover part radially covers the impeller blades in the inflow direction of the air or in the direction of extent of the axis to a given in this direction end of the impeller blades. Correspondingly, the cover part extends at least in a region comprising the impeller blades radially outward, more preferably with respect to a cutting plane extending in the axial direction of the impeller at least approximately parallel to the inflow direction of the air, further approximately parallel to the axis of rotation of the impeller. More preferably, such, the impeller blades radially outwardly overlapping portion of the ceiling portion at an acute angle to the impeller axis, accordingly oriented at an acute angle along an axis parallel. The ceiling part further preferably extends with the fan blades radially outwardly surrounding portion at least up to an axial end of the impeller blades, in particular an axial end of the radially outward preferably free existing front edge of the impeller blades, which end is further preferably opposite to the covered by the ceiling part axial end , More preferably, this section of the ceiling part extends beyond the axial end, in particular the free end edge of the edge of the impeller blades, more preferably also via a, the impeller blades carrying bottom part of the impeller.

The impeller blades are formed in a further preferred embodiment in a radial overlap region with the ceiling part at least over a part of the given length in the axial direction with respect to a radially outer end of an impeller with radial clearance to an inner surface of the ceiling part. This results in a further preferred embodiment, a gap portion, in particular a circumferential gap portion with respect to the axis of rotation between the radially outer ends of the impeller blades and the facing inner surface of the ceiling portion. Through this gap, a flow of air and possibly entrained particles is possible, more particularly with a Tendency in the axial direction, more preferably at least approximately the same direction to the inflow direction of the air.

It is further preferred that in a radial covering area to the fan wheel blades, the ceiling part extends widening radially outward in the direction of the axis. It results in this respect preferred - with respect to a vertical section through the impeller - an example. Conical expansion. In preferably parallel to the rotational axis of the impeller extending free end edge edges of the impeller blades results here more preferably an example. Wedge-shaped enlargement of the gap between the edge edge edge and facing inner surface of the ceiling part.

Based on a cross-section, in a further preferred embodiment, the radial extension over the length of the axis is formed, including different angles with the axis. Thus, it is further preferred that the area of the ceiling part formed in radial overlap with the impeller blades is rectilinear with respect to a cross-section, evenly spaced from the axis, while an adjoining, preferably free-terminating end portion of the ceiling part encloses an altered acute angle with respect to the axis , This end region further preferably extends below the impeller, in particular in the region of a formed diffuser.

The radially free end region of the ceiling part preferably encloses a larger angle with the axis than a middle region of the ceiling part, in particular as a region formed in radial overlap with the fan wheel blades. Thus, this range preferably includes an acute angle of 5 ° to 30 °, more preferably 10 ° to 20 °, while the free end portion of the ceiling portion preferably includes an angle of 30 ° to 75 °, more preferably 45 ° to 60 ° to the rotation axis ,

The ceiling portion extends in a preferred embodiment in the direction of the axis of the impeller blades by an amount beyond, which preferably corresponds to half or more of the axial height of the impeller blades, more preferably half or more of the largest axial height of the impeller blades in the course of their radial extent. More preferably, the ceiling part extends up to a three times the axial height of the impeller blades in the direction of the axis on the impeller blades.

It is further preferred that a radially free end region of the ceiling part passes through a motor housing of the electric motor in a plane transverse to the axis. In this case, enforcement of a partial region of the motor housing is furthermore preferably provided, more preferably such that the co-rotating cover part is at least further covered by a section of the motor housing at least in the region extending radially beyond the fan wheel blades in the axial direction.

A radial free end region of the ceiling part, in particular an end region of the ceiling part which extends beyond the fan wheel blades in the direction of the axes, is surrounded in a preferred embodiment by an annular receiving space such that optionally conveyed liquid is supplied to the receiving space on an inner side of the ceiling part. Any fluid particles entrained with the air flow or solid particles are first, in particular due to the design of the ceiling part, further derived from the resulting centrifugal forces along the inside of the ceiling part in the direction of the free end region and delivered into the receiving space adjoining this end region. The end region can end here with a small distance to the receiving space. In a further embodiment, it is provided that the end region extends into the receiving space. As a result of this refinement, a separation, in particular of liquid particles, from the air stream is achieved, which liquid particles are purposefully collected at least temporarily in the receiving space.

The fluid possibly collected in the receiving space is discharged regularly in one embodiment, for example. In this regard, it is preferred that the receiving space in any case has an outlet opening extending in the direction of the axis. More preferably, the outlet opening, in particular a central axis of the outlet opening, extends oriented parallel to the axis of rotation of the impeller. About this outlet opening delivered in the receiving space liquid or the like can be selectively removed. For example. can connect to the outlet opening a drain line, for example. In the form of a hose. More preferably, the outlet opening is associated with a bottom of the receiving space, which latter is designed in a trough-like manner in a preferred embodiment with respect to a cross section.

The acting centrifugal forces in the operation of the blower, the liquid phase is imparted a swirling energy, which leads in a preferred embodiment in the annular receiving space to a corresponding promotion of the liquid phase in the same. In order to prevent a possibly multiple circulation of the liquid phase in the receiving space, it is provided in a preferred embodiment that the outlet opening is associated with a Abteilausformung at a distance radially inward to an outer wall of the receiving space and the outlet opening projects. Preferably, this Abteilausformung is formed out of a radially outer annular wall of the receiving space. Due to the stagnation-like Abteilausformung the liquid phase is directed to the outlet opening. As a result, a multiple orbiting of the liquid phase is counteracted, which would otherwise lead to a reduction of the spin energy. Due to the selected measure, the system can be used regardless of location.

In addition, it is preferred that the compartment formation ends projecting freely in the projection in a projection corresponding to a center axis of the outlet opening. Thus, in such a projection, the compartment formation preferably extends from an edge of the outlet opening over 20% to 80% of the largest cross-sectional dimension of the outlet opening freely into the outlet opening.

The ceiling part is preferably covered by a fixed motor housing section. More preferably, the ceiling part is completely covered by the fixed motor housing section rotates accordingly during operation of the fan in a hiding position. Here, the motor housing portion in cooperation with areas of the ceiling part form a barrier against in particular liquids between the ceiling part and the motor housing portion. In a preferred embodiment, this is achieved by a labyrinthine interaction of the ceiling part and the motor housing section.

The ceiling part preferably forms, at least in a covering area, seen transversely to the axis, to the electric motor or motor housing, in cooperation with the motor housing, a radially directed channel between an upper side of the motor housing and an underside of the ceiling part. Through this channel, the separated, liquid phase is directed towards the receiving space, which receiving space preferably connects to the channel. The channel is in this case further preferably formed circumferentially with respect to the axis. Essentially projects into this channel, the free end portion of the ceiling part, which includes a larger angle with the axis. With respect to a cross section, the upper side of the motor housing and the underside of the cover part extend at least approximately parallel, so that the channel formed thereby has a constant extent over its entire (tendency) radial length.

This given perpendicular to the flow direction of the channel width of the channel corresponds in a preferred embodiment a third or less of the given radially outside at the free end free height of the impeller blades. More preferably, the width corresponds to 0.2 to 1 times the radially outside given free height of the impeller blades. In a further embodiment, the gap dimension selected (width of the channel) corresponds to about 1% to 5%, more preferably about 2% of the maximum diameter of the channel considered in a plane oriented transversely to the axis.

The given in the flow direction length of the channel preferably corresponds to 0.1 to 0.3 times the diameter of the impeller at the free end of an impeller blade, here possibly based on the largest diameter of the impeller if it changes over the axial height of the impeller blades , In a further embodiment, the gap length of the channel given thereby corresponds to approximately 5% to 15%, more preferably approximately 9% of the largest channel diameter with respect to the axis.

More preferably, the length of the channel at least approximately corresponds to the given in cross-section length of the region of the ceiling part, which includes a larger acute angle with the axis.

From the outlet opening, the liquid phase is optionally conveyed away in a preferred embodiment with a partial air flow against gravity. This partial air flow results from the total air flow, which is constructed by the activated impeller. The partial air flow in this case preferably corresponds to up to 10% of the intake air volume and is preferably guided through the channel and the receiving space to the outlet opening, with the preferred support of the removal of the liquid phase from the receiving space.

With regard to the disclosure, the ranges and / or ranges of values or multiple ranges given above also include all intermediate values, in particular in 1/10 increments of the respective dimension, if necessary also dimensionless, in particular 1.01 times etc., on the one hand for delimitation the aforementioned range limits from below and / or above, alternatively or additionally, but also with regard to the disclosure of one or more singular values from the respectively specified range.

The invention is explained below with reference to the accompanying drawings, which, however, illustrate only one embodiment. The drawing shows:

1 : An electric motor with a partially hidden in a motor housing arranged impeller in perspective view;

2 : the section according to the line II-II in 1 ;

3 : the section according to the line III-III in 2 ;

4 a perspective sectional view substantially of the area IV in 2 ,

Illustrated and described first with reference to the 1 and 2 an electric motor 1 with one on a rotor shaft 2 arranged impeller 3 and a diffuser in the form of a diffuser 4 , The fan wheel 3 is non-rotatable on the rotor shaft 2 arranged and is rotated about this, wherein the rotor shaft 2 rotatably with a rotor, not shown, of the electric motor 1 connected is. The rotor interacts with a stator, not shown, of the electric motor. The diffuser 4 is not rotatable in one, the electric motor 1 essentially receiving motor housing 5 attached.

The fan wheel 3 more preferably initially has a substantially aligned transversely to the axis of rotation x fan base 6 on. This is thickened hub-like, in particular in the central area, for non-rotatable connection to the rotor shaft 2 ,

On the fan wheel floor 6 , in particular the electric motor 1 averted are fan blades 7 educated. These are further preferred in particular in the design of the fan wheel 3 from a plastic injection molded part in one piece and of the same material with the fan wheel bottom 6 formed. The fan blades 7 extend substantially from radially inward to radially outward, in particular to the edge of the fan wheel bottom 6 , more preferably in relation to a floor plan or a projection on the impeller base 6 curved in a circular segment.

The fan blades 7 preferably have a constant height h over their radial longitudinal extent. This preferably corresponds to about 0.1 to 0.3 times the impeller diameter.

The fan blades 7 are more preferably on the impeller bottom 6 opposite side of a ceiling part 8th at least for the most part covered. This ceiling part 8th initially has a preferably parallel or substantially parallel to the fan wheel bottom 6 extending ceiling section 9 on, in which centrally an inflow opening 10 is left.

The ceiling part 8th is rotatable with the impeller 3 connected, turns accordingly when operating the electric motor 1 With.

Starting from the ceiling section 9 the ceiling part extends 8th at least in radial overlap to the radially outer ends of the impeller blades 7 , more preferably starting from the ceiling section 9 to above the level of the fan wheel floor 6 out.

This radial extension 11 extends with respect to a cross section according to 2 at an acute angle α of 5 ° to 15 °, more preferably about 10 ° to an axis parallel. More preferably, the radial extension extends 11 starting from the ceiling section 9 up to a measure above the fan wheel bottom 6 which is about 0.5 to 1 times the impeller height h. Here, the radial extension runs 11 in cross-section, starting from the ceiling section 9 towards the free end area expanding radially.

The radial extension 11 goes over into a free end area 12 , This is as well as the radial extension 11 , in cross-section according to 2 formed elongated rectilinearly, in this case more preferably an angle β of 40 ° to 60 °, more preferably about 45 ° to 50 ° to an axis parallel enclosing. The free end area 12 extends from the radial extension 11 expanding radially towards the free end.

The length l of the free end region 12 in cross-section preferably corresponds to 0.8 to 1.2 times the fan blade height h.

Like the fan wheel bottom 6 is the ceiling part 8th with its radial extension 11 and the free end area 12 configured rotationally symmetrical with respect to the axis of rotation x.

Especially the free end area 12 , beyond that also over the fan wheel floor 6 protruding section of the radial extension 11 are in a preferred embodiment in radial overlap to the diffuser 4 arranged, with the diffuser 4 directly also part of the motor housing 5 can be.

The free end area 12 of the ceiling part 8th forms together with one, the radial inside of the free end portion 12 facing surface of the motor housing 5 or diffuser 4 a with respect to the axis of rotation x annular channel 13 , Here, the free end region extends 12 facing surface of the motor housing 5 preferably parallel to the facing inner surface of the free end region 12 which essentially ties the channel 13 extends at an acute angle corresponding to the angle β sloping radially outward.

The resulting gap height in the channel 13 or the hereby given transverse to the longitudinal extent of the free end region 12 considered width b preferably corresponds to about 2% of the largest diameter d of the channel 13 , The in cross section according to 2 considered length of the channel 13 preferably corresponds to the length of the free end region 12 , more preferably about 9% of the diameter d of the channel 13 ,

The channel 13 is both radially inward toward the, the impeller 3 receiving space formed open, as well as circumferentially radially outward. Here joins the canal 13 an annular, correspondingly circumferential receiving space 14 at. Whose receiving space floor extends in a direction transverse to the axis of rotation x extending plane, which is further spaced from the ceiling portion 9 as the circumferential free edge of the free end region 12 ,

The recording room 14 is limited in cross-section on the one hand by the motor housing 5 or an extension of the diffuser 4 , further through the hereby preferably integrally formed and uniform material receiving space floor 15 and more preferably by a foot portion of a more preferably fixed motor housing portion 16 , This motor housing section 16 overflows the impeller like a pot 3 with velvet the ceiling part 8th , He is further preferred with the other motor housing 5 and / or the diffuser 4 and over here with the electric motor 1 rotatably connected.

The motor housing section 16 further preferably extends the free end region 12 , the radial extension 11 as well as the ceiling section 9 each substantially (with respect to the inner wall) extending parallel thereto covering, wherein more preferably in a vertical projection to the inlet opening 10 of the ceiling part 8th also in the motor housing section 16 a corresponding inlet opening 17 is formed.

Further preferred is the inside, ie the impeller 3 facing, surrounding the entrance opening peripheral edge a labyrinthine interaction with the ceiling part 8th reached. For this purpose, the ceiling part engages 8th with preferably two concentric with each other, top part of the upper side formed ribs 18 in appropriately positioned grooves 19 of the motor housing section 16 one.

In the reception room floor 15 is more preferably an outlet opening 20 provided, with a preferably circular edge opening edge.

The outlet opening 20 go, the recording room 14 turned away, in an outlet channel 21 above. This further extends preferably in the direction of the axis of rotation x, according to parallel thereto or along a parallel oriented along.

The outlet channel 21 is open in the representations to the environment. It may continue on the outlet channel 21 connect a hose or the like.

Further assigned to the outlet opening 20 is a stowage wall-shaped Abteilausformung 22 intended. This compartment formation 22 is preferably made of the radially outer wall of the receiving space 14 protrudes with the free end radially inward - with respect to the axis of rotation x - before, so that the free end region occupies a radial distance from the outer wall or to an extension of the outer wall. In a projection on the outlet opening 20 considered the compartment formation ends 22 free-standing in the outlet opening 20 , more preferably approximately in the region of an outlet opening center axis, this at a preferred diameter of the outlet opening 20 at least 1.5 times the radial extent of the receiving space floor 15 equivalent. The radial outer wall of the receiving space 14 here runs correspondingly different from the otherwise concentric orientation to the axis of rotation x (see. 3 ).

Due to the above-described embodiment, a preferably position-independent water separation is achieved in such a blower. This with a low building requirement.

During operation of the electric motor 1 or the blower wheel 3 is through the inlet opening 10 Air tends to be sucked in the axial direction and through the impeller 3 tends to be directed radially outward. Any air-water mixture is here by the impeller 3 set in spin, causing the heavier liquid phase by the resulting centrifugal forces on the co-rotating, cup-shaped ceiling part 8th , in particular in the field of radial expansion 11 reflected.

The liquid phase is from the co-rotating, in the flow direction double conically radially expanded area 11 in the recording room 14 thrown off, wherein the impressed swirl energy is used to the liquid phase at the periphery of the receiving space 14 along the outlet opening 20 to promote.

Here, the liquid phase through the counter to the flow direction within the receiving space 14 directed compartment formation 22 to the outlet opening 20 diverted. A multiple orbiting of the liquid phase within the receiving space 14 is so counteracted. A multiple circling would lead to a reduction of the swirl energy, whereby the desired position independence of the system would be disturbed.

From the outlet opening 20 the liquid phase with a relatively small partial air flow (preferably less than 10% of the total sucked air quantity in the region of the inflow opening 10 ) possibly also carried away against gravity.

In the channel 13 is by the co-rotating ceiling part 8th the swirl is held so high that water flows backwards towards the diffuser 4 along the motor housing side wall of the channel 13 is prevented.

The recording room 14 is formed spirally with a further preferred embodiment. Next can be distributed over the circumference of the recording room 14 several outlet openings 20 be assigned, so for example, two, three, four or more, which may also be radially aligned with respect to the axis of rotation x, more preferably also tangentially.

The axially behind the fan wheel bottom 6 (viewed in the inflow) provided, bladed diffuser 4 has an axial distance to the ceiling portion 9 which is about 0.2 times the impeller diameter. Also preferred is an overlap of diffuser present in the axial direction 4 and mitdrehendem ceiling part 8th provided, which overlap preferably corresponds to about 0.1 times the impeller diameter.

All disclosed features are essential to the invention. The disclosure of the associated / attached priority documents (copy of the prior application) is hereby also incorporated in full in the disclosure of the application, also for the purpose of including features of these documents in claims of the present application. The subclaims characterize in their optionally sibling version independent inventive developments of the prior art, in particular to make on the basis of these claims divisional applications.

LIST OF REFERENCE NUMBERS

1

electric motor

2

rotor shaft

3

blower

4

diffuser

5

motor housing

6

Gebläseradboden

7

Gebläseradschaufel

8th

cover part

9

ceiling section

10

inflow

11

radial extension

12

free end area

13

channel

14

accommodation space

15

Receiving chamber floor

16

Motor housing portion

17

inlet opening

18

rib

19

groove

20

outlet

21

exhaust port

22

Abteilausformung

b

width

d

diameter

H

height

l

length

x

axis of rotation

α

angle

β

angle

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 102008014642 A1 [0003]

Claims (10)

On the rotor of an electric motor ( 1 ) attached impeller ( 3 ), the impeller ( 3 ) an impeller axis (x) and, by a co-rotating ceiling part ( 8th ) covered impeller blades ( 7 ), wherein further the impeller blades ( 7 ) have an extension in the axial direction, characterized in that the ceiling part ( 8th ) the impeller blades ( 7 ) radially outward in the direction of the axis (x) to half or more of the axial extent of the impeller blades ( 7 ) covered. Fan wheel according to claim 1 or in particular according thereto, characterized in that the ceiling part ( 8th ) the impeller blades ( 7 ) in the inflow direction of the air or in the extension direction of the axis (x) to a given in this direction end of the impeller blades ( 7 ) radially overlapped. Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that the impeller blades ( 7 ) in a radial covering area with the ceiling part ( 8th ) at least over a part of the height (h) in the axial direction with respect to a radially outer end of an impeller ( 7 ) with radial clearance to an inner surface of the ceiling part ( 8th ) are formed and / or, preferably, that in a radial coverage area to the impeller blades ( 7 ) the ceiling part ( 8th ) extends radially outward in the direction of the axis (x). Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that the radial extension ( 11 ) relative to a cross-section, over the length of the axis (x) including different angles (α, β) with the axis (x) is formed and / or, preferably, that a radial free end region ( 12 ) of the ceiling part ( 8th ) includes a larger angle (β) with the axis (x) than a central region. Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that the ceiling part ( 8th ) in the direction of the axis (x) via the impeller blades ( 7 ) extends to an extent that is one half or more of the axial height (h) of the fan blades (FIG. 7 ) and / or, preferably that the ceiling part ( 8th ) in the direction of the axis (x) via the impeller blades ( 7 ) extends to an extent that extends up to a 3 times the axial height (h) of the fan blades ( 7 ) corresponds. Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that a radially free end region ( 12 ) of the ceiling part ( 8th ) in a plane transverse to the axis (x) a motor housing ( 5 ) of the electric motor ( 1 ) and / or, preferably, that a radially free end region ( 12 ) of the ceiling part ( 8th ) of an annular receiving space ( 14 ) is surrounded such that on an inner side of the ceiling part ( 8th ) conveyed liquid into the receiving space ( 14 ) is delivered. Impeller according to one or more of the preceding claims or in particular according thereto, characterized in that the receiving space ( 14 ) In any case, in the direction of the axis (x) extending outlet opening ( 20 ) having. Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that the outlet opening ( 20 ) a compartment formation ( 22 ), which at a distance radially inward to an outer wall of the receiving space ( 14 ) or the outlet opening ( 20 ) and / or, preferably, that the compartment formation ( 22 ) projecting in a projection corresponding to a central axis of the outlet opening in the outlet opening ( 20 ) ends. Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that the ceiling part ( 8th ) from a fixed motor housing section ( 16 ) and / or, preferably, that the ceiling part ( 8th ), at least in a transverse to the axis (x) seen coverage area to the electric motor ( 1 ) or motor housing ( 5 ), in cooperation with the motor housing ( 5 ) a radially directed channel ( 13 ) between an upper side of the motor housing ( 5 ) and a bottom of the ceiling part ( 8th ). Fan wheel according to one or more of the preceding claims or in particular according thereto, characterized in that a direction perpendicular to the flow direction of the channel ( 13 ) given width (b) of the channel ( 13 ) One third or less of the radially outside given free height (h) of the impeller blades ( 7 ) and / or, preferably, that the width (b) of the channel ( 13 ) 0.2 to 1.0 times the radially outside given free height (h) of the impeller blades ( 7 ) and / or that the length (l) of the channel ( 13 ) 0.1 to 0.3 times the diameter of the impeller at the free end of an impeller blade ( 7 ), possibly based on the largest diameter corresponds.

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