U.S. patent application number 16/712169 was filed with the patent office on 2020-06-18 for pump assembly.
The applicant listed for this patent is GRUNDFOS HOLDING A/S. Invention is credited to Jan Caroe AARESTRUP, Therkel DAMM, Klaus Vestergaard KRAGELUND, Jan PLOUGMANN, Erik Bundesen SVARRE, Morten Liengaard SVARRE.
Application Number | 20200191158 16/712169 |
Document ID | / |
Family ID | 64665325 |
Filed Date | 2020-06-18 |
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United States Patent
Application |
20200191158 |
Kind Code |
A1 |
SVARRE; Erik Bundesen ; et
al. |
June 18, 2020 |
PUMP ASSEMBLY
Abstract
A pump assembly includes a rotor axle, an impeller and a pump
housing defining a radial inner reference surface. A drive motor
includes a stator accommodated in stator housing and a rotor
accommodated in a rotor can. A radial bearing ring is in sliding
contact with the rotor axle. A bearing retainer engages the radial
bearing ring and centers it with respect to the radial inner
reference surface. A neck ring is coupled to the pump housing and
has a circumferential wall section. The impeller is located axially
between the bearing retainer and the neck ring. The circumferential
wall section at least partially extends into the impeller or the
impeller at least partially extends into the circumferential wall
section. The circumferential wall section includes a cylindrical
radial outer surface and a cylindrical radial inner surface. The
radial outer surface is eccentric with respect to the radial inner
surface.
Inventors: |
SVARRE; Erik Bundesen;
(Bjerringbro, DK) ; PLOUGMANN; Jan; (Risskov,
DK) ; DAMM; Therkel; (Silkeborg, DK) ;
AARESTRUP; Jan Caroe; (Bjerringbro, DK) ; KRAGELUND;
Klaus Vestergaard; (Risskov, DK) ; SVARRE; Morten
Liengaard; (Bjerringbro, DK) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
GRUNDFOS HOLDING A/S |
Bjerringbro |
|
DK |
|
|
Family ID: |
64665325 |
Appl. No.: |
16/712169 |
Filed: |
December 12, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04D 29/628 20130101;
F04D 29/046 20130101; F04D 13/0606 20130101; F04D 29/20 20130101;
F04D 29/4273 20130101; F04D 29/40 20130101; F04D 29/167 20130101;
F04D 29/4293 20130101 |
International
Class: |
F04D 29/40 20060101
F04D029/40; F04D 29/20 20060101 F04D029/20; F04D 29/046 20060101
F04D029/046 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 13, 2018 |
EP |
18212319.0 |
Claims
1. A pump assembly comprising: a rotor axle extending along a rotor
axis; an impeller fixed to the rotor axle; a pump housing
accommodating the impeller, wherein the pump housing defines a
first radial inner reference surface; a drive motor comprising a
stator and a rotor, wherein the rotor is fixed to the rotor axle
for driving the impeller; a rotor can accommodating the rotor,
wherein the rotor can comprises a rotor can flange; a stator
housing accommodating the stator; a first radial bearing ring in
sliding contact with the rotor axle; a bearing retainer engaging
the first radial bearing ring and centering the first radial
bearing ring with respect to the first radial inner reference
surface of the pump housing; and a neck ring coupled to the pump
housing, wherein: the impeller is located axially between the
bearing retainer and the neck ring; the neck ring comprises a
circumferential wall section; the circumferential wall section at
least partially extends into the impeller or the impeller at least
partially extends into the circumferential wall section; the
circumferential wall section of the neck ring comprises a
cylindrical radial outer surface and a cylindrical radial inner
surface; and the radial outer surface is eccentric with respect to
the radial inner surface.
2. The pump assembly according to claim 1, wherein: the impeller
comprises a radial surface; the radial outer surface or the radial
inner surface of the circumferential wall section has a radial
distance to the radial surface of the impeller defining a gap.
3. The pump assembly according to claim 1, wherein the radial outer
surface or the radial inner surface of the circumferential wall
section of the neck ring is coaxial with the first radial inner
reference surface and the rotor axis.
4. The pump assembly according claim 1, wherein the radial outer
surface or the radial inner surface of the circumferential wall
section of the neck ring is a machined surface with a milling edge
extending along at least a portion of the circumference of the
circumferential wall section of the neck ring.
5. The pump assembly according claim 1, wherein: the rotor can
flange has a radial distance to the pump housing; and the rotor can
comprises a radial inner centering surface, centered by radially
abutting against a radial outer centering surface of the bearing
retainer.
6. The pump assembly according to claim 5, wherein: the radial
inner centering surface of the rotor can has at least three radial
projections; or the radial outer centering surface of the bearing
retainer has at least three radial projections; or the radial inner
centering surface of the rotor can has and the radial outer
centering surface of the bearing retainer have at least three
radial projections.
7. The pump assembly according to claim 5, wherein the bearing
retainer comprises a radial outer bearing retainer surface having
at least three radial projections radially abutting against the
first radial inner reference surface of the pump housing and
centering the bearing retainer with respect to the first radial
inner reference surface of the pump housing
8. The pump assembly according claim 1, wherein: the rotor can
flange forms a circumferential U-shaped groove with a radial inner
section and a radial outer section; and the radial inner section
forms the radial inner centering surface of the rotor can.
9. The pump assembly according claim 1, wherein the rotor can
flange comprises an annular stop surface facing away from the
impeller.
10. The pump assembly according to claim 9, further comprising a
locking ring being secured in a circumferential groove of the pump
housing, wherein the annular stop surface axially abuts against the
locking ring.
11. The pump assembly according claim 1, wherein: the rotor can
flange comprises an annular contact surface facing towards the
impeller; the bearing retainer comprises an annular biasing surface
facing away from the impeller; the bearing retainer is resiliently
preloaded for biasing the annular biasing surface of the bearing
retainer against the annular contact surface of the rotor can
flange.
12. The pump assembly according to claim 11, wherein: the annular
contact surface of the rotor can flange has at least three axial
projections; or the annular biasing surface of the bearing retainer
has at least three axial projections; or the annular contact
surface of the rotor can flange and the annular biasing surface of
the bearing retainer have at least three axial projections.
13. A method of manufacturing a pump assembly comprising a rotor
axle extending along a rotor axis, an impeller fixed to the rotor
axle, a pump housing accommodating the impeller, a drive motor
comprising a stator and a rotor, wherein the rotor is fixed to the
rotor axle for driving the impeller, a rotor can accommodating the
rotor, wherein the rotor can comprises a rotor can flange, a stator
housing accommodating the stator, a first radial bearing ring in
sliding contact with the rotor axle and a bearing retainer engaging
the first radial bearing ring, the method comprising the steps of:
coupling a neck ring to the pump housing; defining a first radial
inner reference surface by machining the pump housing; and defining
a radial outer surface or a radial inner surface by machining a
circumferential wall section of the neck ring so that the radial
outer surface or the radial inner surface is coaxial with the first
radial inner reference surface.
14. The method according to claim 13, wherein the steps of defining
the first radial inner reference surface and defining the radial
outer surface or the radial inner surface are performed after the
step of coupling the neck ring to the pump housing.
15. The method according to claim 13, wherein the steps of defining
the first radial inner reference surface and defining the radial
outer surface or the radial inner surface are performed with the
same machining tool, wherein the fastening of the pump housing in
the machining tool is maintained between these two defining
steps.
16. The method according to claim 13, further comprising a step of
defining a first annular reference surface by machining the pump
housing, wherein all defining steps are performed with the same
machining tool, wherein the fastening of the pump housing in the
machining tool is maintained between the defining steps.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of priority under 35
U.S.C. .sctn. 119 of European Application 18 212 319.0, filed Dec.
13, 2018, the entire contents of which are incorporated herein by
reference.
TECHNICAL FIELD
[0002] The present disclosure relates generally to pump assemblies,
in particular to speed controlled wet rotor pumps. Such pumps in
the power range of 5 W to 3 kW are typically used as circulation
pumps of house heating systems.
TECHNICAL BACKGROUND
[0003] Wet rotor pumps usually comprise a rotor can separating a
permanent magnet rotor from a stator. The rotor drives an impeller
located in a pump housing. Typically, a motor housing is fastened
to the pump housing, wherein the rotor can and the stator are
attached to the pump housing by the fastener of the motor
housing.
[0004] EP 2 072 828 A1 describes a wet rotor centrifugal pump as a
circulation pump for house heating systems. The pump disclosed
therein has a compact design by locating motor electronics at least
partially radially around the stator. The motor housing of that
pump is attached to the pump housing via a rotor can flange so that
the motor housing can be removed without releasing any wet parts.
However, the pump disclosed therein uses circumferentially
distributed trunnions 26 of a large rotor can flange for rotation
prevention and axial alignment of the components. The large rotor
can require significant lateral space.
[0005] For an even more compact design with a smaller rotor can
flange, other solutions for an exact coaxial alignment of the rotor
axis with the respect to the pump housing are needed.
SUMMARY
[0006] In contrast to such known pumps, embodiments of the present
disclosure provide a pump assembly with a more compact design.
[0007] In accordance with a first aspect of the present disclosure,
a pump assembly is provided comprising [0008] a rotor axle
extending along a rotor axis, [0009] an impeller fixed to the rotor
axle, [0010] a pump housing accommodating the impeller, wherein the
pump housing defines a first radial inner reference surface, [0011]
a drive motor comprising a stator and a rotor, wherein the rotor is
fixed to the rotor axle for driving the impeller, [0012] a rotor
can accommodating the rotor, wherein the rotor can comprises a
rotor can flange, [0013] a stator housing accommodating the stator,
[0014] a first radial bearing ring being in sliding contact with
the rotor axle, and [0015] a bearing retainer embracing (engaging)
the first radial bearing ring and cantering the first radial
bearing ring with respect to the first radial inner reference
surface of the pump housing and [0016] a neck ring coupled to the
pump housing, wherein the impeller is located axially between the
bearing retainer and the neck ring, wherein the neck ring comprises
a circumferential wall section, wherein the circumferential wall
section at least partially extends into the impeller or the
impeller at least partially extends into the circumferential wall
section. [0017] The circumferential wall section of the neck ring
comprises a cylindrical radial outer surface and a cylindrical
radial inner surface, wherein the radial outer surface is eccentric
with respect to the radial inner surface. Preferably, the
circumferential wall section at least partially extends into the
impeller, because the fluids flow is from the neck ring into the
impeller. However, alternatively, the impeller may at least
partially extend into the cylindrical section of the neck ring.
[0018] The gap between the impeller and the neck ring must be large
enough for low-friction rotation of the impeller, wherein the gap
must account for any eccentricity of the rotor axis with respect to
the neck ring of the pump housing due to manufacturing tolerances.
However, the larger the gap between the impeller and the neck ring
is, the more fluid escapes from the high-pressure chamber directly
back through the gap to the low-pressure chamber, which costs
pumping efficiency.
[0019] The pump assembly disclosed herein provides a smaller gap
and thus a higher pump efficiency, because manufacturing tolerances
between different pump parts, which are typically independently
manufactured in separate manufacturing steps, do not lead to an
eccentricity of the rotor axis with respect to the neck ring of the
pump housing. In case the circumferential wall section at least
partially extends into the impeller, the eccentric radial outer
surface of the circumferential wall section of the neck ring can be
better coaxially aligned with respect to the first radial inner
reference surface, which maybe used to define the position of the
rotor axis by means of the bearing retainer and the rotor can. The
radial outer surface may also be tilted with respect to the radial
inner surface in order to be better aligned perpendicular to a
first annular reference surface of the pump housing determining the
angular orientation of the rotor axis by means of a stator housing.
In case the impeller at least partially extends into the
cylindrical section of the neck ring, it is the radial inner
surface of the circumferential wall section that is coaxially
aligned to the rotor axis.
[0020] Optionally, the impeller may comprise a radial inner or
outer surface, wherein the radial outer or inner surface of the
circumferential wall section have a radial distance to the radial
inner or outer surface of the impeller defining a gap. As stated
above, this gap can be designed much smaller with the pump assembly
according to this disclosure. Optionally, the radial outer or inner
surface of the circumferential wall section of the neck ring is
coaxial with the first radial inner reference surface and the rotor
axis.
[0021] Optionally, in case the circumferential wall section at
least partially extends into the impeller, the radial outer surface
of the circumferential wall section of the neck ring may be a
machined surface with a milling edge extending along at least a
portion of the circumference of the circumferential wall section of
the neck ring. In case the impeller at least partially extends into
the cylindrical section of the neck ring, it is preferably the
radial inner surface of the circumferential wall section of the
neck ring that is a machined surface with a milling edge extending
along at least a portion of the circumference of the
circumferential wall section of the neck ring. Preferably, in
either case, the milling edge may extend along the full
circumference of the circumferential wall section of the neck
ring.
[0022] Optionally, the rotor can flange may have a radial distance
to the pump housing and the rotor can may comprise a radial inner
cantering surface being centered by radially abutting against a
radial outer cantering surface of the bearing retainer.
[0023] Optionally, the radial inner cantering surface of the rotor
can and/or the radial outer cantering surface of the bearing
retainer may have at least three, preferably four, radial
projections. The radial projections facilitate an exact concentric
alignment between the rotor can and the bearing retainer.
[0024] Optionally, the bearing retainer may comprise a radial outer
bearing retainer surface having at least three radial projections
radially abutting against the first radial inner reference surface
of the pump housing and cantering the bearing retainer with respect
to the first radial inner reference surface of the pump housing.
These radial projections facilitate an exact concentric alignment
of the bearing retainer with respect to the pump housing. The first
radial inner reference surface of the pump housing may be defined
in the same manufacturing step of the pump housing when the neck
ring position is defined to minimize manufacturing tolerances.
[0025] Optionally, the rotor can flange may form a circumferential
U-shaped groove with a radial inner section and a radial outer
section, wherein the radial inner section forms the radial inner
cantering surface of the rotor can. Thereby, the rotor can flange
is stiffened and stabilized. It should be noted that the rotor can
may not even be in direct contact with the pump housing.
[0026] Optionally, the rotor can flange may comprise a annular stop
surface facing away from the impeller. This stop surface may define
an exact positioning of the rotor can in axial direction. In
contrast to wet rotor centrifugal pumps known in the prior art, the
rotor can is axially not limited by the pump housing directly. The
rotor can may thus be more resilient to withstand pressure shocks.
The annular stop surface may be conical, wherein the radially
outward end of the annular stop surface is located further away
from the impeller than the radially inward end of the annular stop
surface. The rotor can flange may thus deform resiliently for an
axial movement to resiliently withstand pressure shocks.
[0027] Optionally, a locking ring may be secured in a
circumferential groove of the pump housing, wherein the annular
stop surface axially abuts against the locking ring. When the pump
assembly is assembled, the locking ring may be placed into the
groove after the rotor can flange has been placed into position
within the pump housing. If the end of the rotor axle to which the
impeller is fixed is denoted as the "lower" end and the rotor axle
extends "upward" from the impeller into the rotor can, the rotor
can is secured against an "upward" movement. This is fundamentally
different to the pumps known in the prior art, wherein the rotor
can is fixed "downwardly" to the pump housing by screws. Thus, the
pump assembly disclosed herein allows for a much more compact
design.
[0028] Optionally, the rotor can flange may comprise an annular
contact surface facing towards the impeller and the bearing
retainer flange comprises an annular biasing surface facing away
from the impeller, wherein the bearing retainer is resiliently
preloaded for biasing the annular biasing surface of the bearing
retainer flange against the annular contact surface of the rotor
can flange. The bearing retainer may thus not only be used for
cantering the rotor can, but also for axial positioning of the
rotor can with respect to the pump housing. The bearing retainer
may comprise a conical bearing retainer flange section, wherein the
radially outward end of the bearing retainer flange section is
located closer to the impeller than the radially inward end of the
bearing retainer flange section. The radially outward end of the
bearing retainer flange section may rest on an axial stop surface
of the pump housing. The annular biasing surface may be formed by a
radially inward portion of the conical bearing retainer flange
section. The annular contact surface of the rotor can flange and/or
the annular biasing surface of the bearing retainer flange may
comprise at least three axial projections.
[0029] During assembly of the pump assembly, the bearing retainer
may be placed into the pump housing to rest of the axial stop
surface of the pump housing. The rotor can may be pressed downwards
with its lower annular contact surface onto the upper annular
biasing surface of the bearing retainer to resiliently deform the
conical bearing retainer flange section. The locking ring is placed
into the groove to secure the rotor can axially while the rotor can
is pressed down against the bearing retainer. Thus, the bearing
retainer is resiliently preloaded to bias the rotor can upward
against the locking ring. The impeller, the rotor axle, the rotor,
the bearings, the bearing retainer and the rotor can may be placed
into the pump housing as a pre-assembled unit being secured
downwards by the locking ring, wherein the bearing retainer acts as
an upwardly biasing spring.
[0030] Optionally, the pump housing may define a first annular
reference surface facing away from the impeller and the stator
housing defines a second annular reference surface facing towards
the impeller, wherein the second annular reference surface is
biased against the first annular reference surface. Preferably, the
first annular reference surface of the pump housing is defined in
the same machining step as the first radial inner reference
surface, preferably with the same drilling head, to minimize
manufacturing tolerances. The first annular reference surface may
thus extend in a plane exactly orthogonal to the center axis of the
first radial inner reference surface. Therefore, the first annular
reference surface may allow for an exact angular alignment of the
stator housing with respect to the pump housing.
[0031] Optionally, the stator may define a second radial inner
reference surface and the rotor can may comprise a radial outer
alignment surface being aligned perpendicular to the first annular
reference surface of the pump housing by radially abutting against
the second radial inner reference surface of the stator. Thereby,
the rotor can may be angularly aligned with respect to the pump
housing by means of the stator housing. For instance, the stator
may comprise a plurality of stator teeth around each of which a
stator coil in form of windings is spooled, wherein the second
radial inner reference surface are defined by the radial inner
surface of the plurality of stator teeth.
[0032] Optionally, the first annular reference surface may be
located radially more outward than the first radial inner reference
surface and/or the first annular reference surface is located
axially further away from the impeller than the first radial inner
reference surface. Thereby, the pump housing provides a good
leverage for the stator housing to angularly align the rotor can
with respect to the pump housing.
[0033] Optionally, the second radial inner reference surface is
located radially more inward than the second annular reference
surface and/or the second radial inner reference surface is located
axially further away from the impeller than the second annular
reference surface. Thereby, the stator housing has a good leverage
to angularly align the rotor can with respect to the pump
housing.
[0034] Optionally, the second annular reference surface may extend
in a plane essentially orthogonal to the center axis of the second
radial inner reference surface. Therefore, the second annular
reference surface may allow for an exact angular alignment of the
rotor can with respect to the pump housing.
[0035] Optionally, the pump assembly may comprise a bayonet ring
for securing the stator housing to the pump housing, wherein the
bayonet ring is resiliently preloaded for axially biasing the
stator housing against the pump housing towards the impeller. The
second annular reference surface of the stator housing is thus
pressed downwards onto the first annular reference surface of the
pump housing by means of the bayonet ring. The bayonet ring allows
for securing the stator housing to the pump housing in a very
compact way. Furthermore, the bayonet ring secures the stator
housing against rotation around the rotor axis in well-defined
angular position. The bayonet ring may be a metal wire with
circular cross-section. The bayonet ring may comprise
circumferential first sections with a first radius and
circumferential second sections with a second radius, wherein the
second radius is smaller than the first radius. The second sections
may be formed as radially inward projections cooperating with
bayonet grooves in a radially outer surface of the stator housing.
The first sections of the bayonet ring may be secured in a
circumferential groove of the pump housing. The bayonet grooves in
the stator housing may comprise a first "vertical" section through
which the second sections of the bayonet ring pass when the stator
housing is placed downwards onto the first annular reference
surface of the pump housing. The bayonet grooves in the stator
housing may comprise a second "upwardly sloped" circumferential
section with a first end at the first "vertical" section and a
second end circumferentially distanced from the first end, wherein
the first end of the second section is located closer to the second
annular reference surface of the stator housing than the second end
of the second section. Upon manual rotation of the stator housing
by a pre-defined angle for the second sections of the bayonet ring
to be guided along the second sections of the bayonet grooves from
the first end to the second end, the second sections of the bayonet
ring are pushed upward by the slope while the first sections of the
bayonet ring remain secured in the pump housing. Thereby, the
bayonet ring resiliently twists between the first sections and the
second sections. The second sections of the bayonet ring may click
into a horizontal or "downwardly sloped" end section at the second
end of the second section of the grooves. The resilient twist of
the bayonet ring biases the second annular reference surface of the
stator housing downward onto the first annular reference surface of
the pump housing.
[0036] In accordance with a second aspect of the present
disclosure, a method of manufacturing a pump assembly is provided
comprising the steps: [0037] coupling a neck ring to a pump
housing, [0038] defining a first radial inner reference surface by
machining the pump housing, and [0039] defining a radial outer
surface or radial inner surface by machining a circumferential wall
section of the neck ring so that the radial outer surface or radial
inner surface is coaxial with the first radial inner reference
surface.
[0040] This manufacturing method allows for a smaller nominal gap
between the impeller and the neck ring, because smaller tolerances
can be achieved.
[0041] Optionally, the steps of defining the first radial inner
reference surface and defining the radial outer surface or radial
inner surface are performed after the step of coupling the neck
ring to the pump housing. So, the pump housing and the neck ring
may be machined together as a first preassembled unit.
[0042] Optionally, the steps of defining the first radial inner
reference surface and defining the radial outer surface or radial
inner surface are performed with the same machining tool, wherein
the fastening of the pump housing in the machining tool is
maintained between these two defining steps. In other words, the
pump housing is not unclamped from the machining tool between these
two defining steps. This further reduces manufacturing
tolerances.
[0043] Optionally, the method may further comprise a step of
defining a first annular reference surface by machining the pump
housing, wherein all defining steps are performed with the same
machining tool, wherein the fastening of the pump housing in the
machining tool is maintained between the defining steps. In other
words, the pump housing is not unclamped from the machining tool
between these two defining steps. This is useful to not only reduce
the tolerances for the concentric positioning, but also to reduce
the tolerances for the coaxial angular alignment, i.e. non-tilting.
In fact, the radial outer surface may thus be tilted with respect
to the radial inner surface.
[0044] The various features of novelty which characterize the
invention are pointed out with particularity in the claims annexed
to and forming a part of this disclosure. For a better
understanding of the invention, its operating advantages and
specific objects attained by its uses, reference is made to the
accompanying drawings and descriptive matter in which preferred
embodiments of the invention are illustrated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0045] In the drawings:
[0046] FIG. 1 is a perspective view of an example of a pump
assembly disclosed herein;
[0047] FIG. 2 is a top view of an example of a pump assembly
disclosed herein;
[0048] FIG. 3 is a longitudinal cut view along cut A-A as outlined
in FIG. 2 of an example of a pump assembly disclosed herein;
[0049] FIG. 4 is a partly exploded view of an example of a pump
assembly disclosed herein;
[0050] FIG. 5a is a perspective exploded view of a pump housing
plus bayonet ring according to an example of a pump assembly
disclosed herein;
[0051] FIG. 5b is a perspective view of a pump housing plus bayonet
ring according to an example of a pump assembly disclosed
herein;
[0052] FIG. 6 is a perspective view of a pump housing plus bayonet
ring and rotor can according to an example of a pump assembly
disclosed herein;
[0053] FIG. 7 is a top view of a pump housing with an inserted
bayonet ring, rotor can and locking ring according to an example of
a pump assembly disclosed herein;
[0054] FIG. 8a is a longitudinal cut view along cut A-A as outlined
in FIG. 7 of an example of a pump assembly disclosed herein;
[0055] FIG. 8b is a longitudinal cut view along cut A-A as outlined
in FIG. 7 of an example of a pump assembly disclosed herein;
[0056] FIG. 9 is a partly exploded view of a pump housing plus a
bayonet ring, a rotor can and a locking ring according to an
example of a pump assembly disclosed herein;
[0057] FIG. 10 is a top view of an example of a pump assembly
disclosed herein;
[0058] FIG. 11 is a longitudinal cut view with a detailed view
along cut A-A as outlined in FIG. 10 of an example of a pump
assembly disclosed herein;
[0059] FIG. 12 is a perspective view of a pump housing plus bayonet
ring and stator housing according to an example of a pump assembly
disclosed herein;
[0060] FIG. 13 is a longitudinal cut view with a detailed view of a
pump housing with an installed bearing retainer and, prior to their
installation, a rotor can and a locking ring according to an
example of a pump assembly disclosed herein;
[0061] FIG. 14 is a longitudinal cut view with a detailed view of a
pump housing with an installed bearing retainer and, after their
installation, a rotor can and a locking ring according to an
example of a pump assembly disclosed herein;
[0062] FIG. 15 is a longitudinal cut view with a top view and with
a detailed top view of a bearing retainer and a rotor can according
to an example of a pump assembly disclosed herein;
[0063] FIG. 16a is a cut view with a detailed cut view of a pump
housing with an installed neck ring before being machined according
to an example of a pump assembly disclosed herein;
[0064] FIG. 16b is a top view of a neck ring before being machined
according to an example of a pump assembly disclosed herein;
[0065] FIG. 17a is a cut view and a detailed cut view of a pump
housing with an installed neck ring after being machined according
to an example of a pump assembly disclosed herein;
[0066] FIG. 17b is a top view of a neck ring after being
asymmetrically machined according to an example of a pump assembly
disclosed herein;
[0067] FIG. 18a is a perspective view of a stator housing and a
stator former as part of the stator housing according to an example
of a pump assembly disclosed herein;
[0068] FIG. 18b is a perspective view of a stator housing and a
stator former as part of the stator housing according to an example
of a pump assembly disclosed herein;
[0069] FIG. 19a is a bottom view of a cap of a stator housing
according to an example of a pump assembly disclosed herein;
[0070] FIG. 19b is a sectional view along cut K-K of the cap as
outlined in FIG. 19a; and
[0071] FIG. 19c is a detailed view O-O, as outlined in FIG. 19b, of
the cap.
DESCRIPTION OF PREFERRED EMBODIMENTS
[0072] Referring to the drawings, FIGS. 1 to 19 show embodiments of
a pump assembly 1 with a centrifugal pump unit 2, an input port 3
and an output port 5, wherein the input port 3 and an output port 5
are coaxially arranged on a pipe axis F on opposing sides of the
pump unit 2.
[0073] The input port 3 and the output port 5 comprise connector
flanges 7, 9 for a connection to pipes (not shown). The pump unit 2
comprises a rotor axis R essentially perpendicular to the pipe axis
F. It should be noted that the terms "radial", "circumferential",
"angular" and "axial" throughout this disclosure are to be
understood with reference to the rotor axis R. A pump housing 11 of
the pump unit 2 is arranged between the input port 3 and the output
port 5. The pump housing 11 comprises an impeller 12 (see FIGS. 3,
4 and 8a,b) for rotating counter-clockwise around the rotor axis R
and pumping fluid from the input port 3 to the output port 5. The
impeller 12 is driven counter-clockwise by a three-phase
synchronous permanent magnet drive motor having a stator 17 located
in a stator housing 13 around the rotor axis R. The electronics are
also accommodated by the stator housing 13, so that the stator
housing 13 may be denoted as electronics housing 13. The stator
housing 13 is mounted to the pump housing 11 by means of a
bayonet-like mount (see FIGS. 4 and 12).
[0074] The stator housing 13 comprises motor control electronics on
a printed circuit board (PCB) 15 extending in a plane essentially
perpendicular to the rotor axis R below a front face 19 of a cap 21
of the stator housing 13. The stator housing 13 is not rotationally
symmetric, but provides more room at one lateral side for
electronics controlling the motor (see FIG. 2). The motor and motor
electronics are power supplied via a low DC voltage connector (not
shown). The pump assembly 1 may comprise an external power supply
module (not shown) for connection with the low DC voltage
connector. The external power supply module may transform an AC
line voltage of 110-240V to a low DC voltage of 30-60V. The
external power supply may comprise a line filter against
electromagnetic interference (EMI) and a voltage converter, which
is located on the motor electronics PCB. Thus, the motor
electronics PCB 15 and the stator housing 13 may have a more
compact configuration. The front face 19 of the cap 21 of the
stator housing 13 may comprise a user interface, such as a button,
a light-emitting diode (LED) and/or a display (not shown). A button
may for instance be an on/off-button. One or more LEDs and/or a
display may signal an operating parameter or status, e.g. for
indicating a normal operation, a failure mode, a motor speed, a
successful/unsuccessful wireless connection, a power consumption, a
flow, a head and/or a pressure.
[0075] The top view of FIG. 2 shows the cut A-A, the view of which
is shown in FIG. 3. The non-rotationally-symmetric shape of the
stator housing 13 is clearly visible in FIG. 2. The cut view of
FIG. 3 displays the very compact pump configuration achieved by the
pump assembly disclosed herein. The inlet port 3 curls from the
pipe axis F in a fluid-mechanically efficient way to lead from
below coaxially with the rotor axis R into an impeller chamber 23
of the pump housing 11. The impeller chamber 23 has a concentric
bottom entry 25 in fluidic connection with the inlet port 3 and a
tangential exit 27 in fluidic connection with the outlet port 5. A
neck ring 29 fixed to the pump housing 11 comprises a
circumferential wall section 30 extending partially into the
impeller 12 and thereby separating the impeller chamber 23 into a
low-pressure chamber including the bottom entry 25 (fluid input)
from a high-pressure chamber including the tangential exit 27
(fluid output). There is a gap G between the impeller 12 and the
circumferential wall section 30 of the neck ring 29 that must be
large enough for low-friction rotation of the impeller 12, wherein
the gap G must account for any eccentricity of the rotor axis R
with respect to the neck ring 29 due to manufacturing tolerances.
However, the gap G should be minimal to minimize the amount of
fluid escaping from the high-pressure chamber directly back through
the gap G to the low-pressure chamber, which costs pumping
efficiency. The impeller 12 comprises inner spiral vanes 31 and at
its bottom side an impeller plate 33 for forming fluid-mechanically
efficient impeller channels for accelerating fluid radially outward
and tangentially in counter-clockwise direction by a centrifugal
force when the impeller 12 rotates. Such a radially outward and
tangentially flow creates a central suction of fluid from the inlet
port 3.
[0076] The pump housing 11 has an upper circular opening 35 through
which the impeller 12 can be placed into the impeller chamber 23
during manufacturing of the pump unit 2. In order to achieve a most
compact pump configuration, the circular opening 35 may have a just
slightly larger diameter than the impeller 12. The end of the
circular opening 35 is formed by a radially inward projection 37.
The radially inward projection 37 forms an axial annular surface 39
on which a bearing retainer 41 resides with a radial outer section
of a bearing retainer flange 43. A rotor axle 45 extends along the
rotor axis R through the bearing retainer 41 and is rotationally
fixed with a lower end portion to the impeller 12. The bearing
retainer 41 centers a first radial bearing ring 47 with a radially
inner ceramic surface being in radial sliding contact with an outer
ceramic surface of the rotor axle 45. The rotor axle 45 and the
first radial bearing ring 47 may comprise ceramic low friction
radial contact surfaces. A very thin lubricating film of the pumped
fluid in the range of microns may establish between the rotor axle
45 and the first radial bearing ring 47 when the rotor axle 45
rotates relative to the fixed first radial bearing ring 47. An
axial bearing plate 49 is placed on top of the first radial bearing
ring 47 to provide a low friction annular bottom carbon surface.
There is a thin lubricating film of the pumped fluid between the
low friction annular bottom carbon surface and an annular top
ceramic face of the first radial bearing ring 47 for a low-friction
axial sliding contact. A permanent magnet rotor 51 embraces the
rotor axle 45 and is rotationally fixed to it. A second radial
bearing ring 53 is in low-friction radial sliding contact with an
upper end of the rotor axle 45. The second radial bearing ring 47
is centered by a bearing bushing 55 with radial extensions and
axial channels for allowing an axial fluid flow. As the impeller 12
sucks itself together with the rotor axle 45 and the permanent
magnet rotor 51 downwards during rotation, only one axial bearing
plate 49 is necessary.
[0077] The neck ring 29, the impeller 12, the rotor axle 45, the
first radial bearing ring 47, the axial bearing plate 49, the
permanent magnet rotor 51, the second radial bearing ring 53 and
the bearing bushing 55 are so-called "wet parts" which are all
immersed in the fluid to be pumped. The rotating ones of the wet
parts, i.e. the impeller 12, the rotor axle 45 and the permanent
magnet rotor 51 are so-called "wet-running" using the fluid to be
pumped for providing lubricant films for reducing friction at two
radial surfaces and one axial contact surface. The fluid to be
pumped is preferably water.
[0078] The wet parts are enclosed by a pot-shaped rotor can 57 such
that fluid can flow between the impeller chamber 23 and the inner
volume of the rotor can 57. The rotor can 57 comprises a lower
first axial end, i.e. the axial end facing the impeller 12, and an
upper second axial end, i.e. the axial end facing away from the
impeller 12. The first axial end is open and defines a rotor can
flange 63. The second axial end is closed. The second axial end of
the rotor can 57 may comprise a pot-shaped coaxial appendix with a
smaller radius than the main body of the rotor can 57 as shown in
the embodiment according to FIGS. 1 to 9. Alternatively, the second
axial end of the rotor can 57 may be an essentially flat end of
main body of the rotor can 57 as shown in the embodiment according
to FIGS. 10 to 19.
[0079] In order to achieve a compact configuration of the pump unit
2, the rotor can flange 63 is relatively small compared to the
prior art, I.e. not much larger in diameter than the impeller 12
and fitting into the circular opening 35 of the pump housing 11.
However, such a compact configuration comes with a challenge to
precisely coaxially align the rotor axis with respect to the neck
ring 29 of the pump housing 11. The coaxial alignment may be needed
radially, axially and/or angularly. Preferred embodiments of the
pump assembly disclosed herein provide for a radial, an axial
and/or angular alignment of the rotor axis R, i.e. centering the
rotor axis R with respect to the neck ring 29 of the pump housing
11.
[0080] In order to center the rotor axis R with respect to the neck
ring 29 of the pump housing 11, the rotor can flange 63 has a
radial distance to the pump housing 11. A radial gap H around the
rotor can flange 63 provides for some radial wiggle room to
coaxially align the rotor can 57 with respect to the pump housing
11. The rotor can 57 is centered by means of the bearing retainer
41 instead of the pump housing 11. Therefore, the rotor can 57
comprises a radial inner centering surface 65 being centered by
radially abutting against a radial outer centering surface 67 of
the bearing retainer 41. The bearing retainer 41 itself is centered
by the bearing retainer flange 43 comprising a radial outer bearing
retainer surface 69 radially abutting against a first radial inner
reference surface 71 of the pump housing 11.
[0081] The radial outer bearing retainer surface 69 comprises at
least three radial projections 70 radially abutting against the
first radial inner reference surface 71 of the pump 0housing 11 and
centering the bearing retainer 41 with respect to the first radial
inner reference surface 71 of the pump housing 11. Similarly, the
radial inner centering surface 65 of the rotor can 57 and/or the
radial outer centering surface 67 of the bearing retainer 41 may
have at least three radial projections 72 for centering the rotor
can 57 with respect to the bearing retainer 41. In the example
shown (best visible in FIG. 15), the radial outer centering surface
67 of the bearing retainer 41 comprises the radial projections 72,
which project radially outward to contact the radial inner
centering surface 65 of the rotor can 57. In case of radial
projections at the radial inner centering surface 65 of the rotor
can 57, the radial projections would project radially inward to
contact the radial outer centering surface 67 of the bearing
retainer 41.
[0082] As can be seen in FIGS. 3, 11, 13 and 14, the rotor can
flange 63 forms a circumferential U-shaped groove 73 with a radial
inner section 75 and a radial outer section 77, wherein the radial
inner section 75 forms the radial inner centering surface 65 of the
rotor can 57.
[0083] Thereby, the rotor can flange 63 is stiffened and
stabilized. The rotor can flange 63 further comprises an annular
stop surface 79 facing away from the impeller 12. This annular stop
surface 79 defines an exact positioning of the rotor can 57 in
axial direction. The annular stop surface 79 may be slightly
conical, wherein the radially outward end 81 of the annular stop
surface 79 is located further away from the impeller 12 than the
radially inward end 83 of the annular stop surface 79. The rotor
can flange 63 may thus deform resiliently for an axial movement to
resiliently withstand pressure shocks. A sealing ring 84 (only
visible in the embodiment shown in FIGS. 11, 13 and 14), here in
form of an O-ring with essentially circular cross-section, is
arranged between the bearing retainer flange 43 and the rotor can
flange 63. It seals a radial distance between the radial outer
section 77 of the rotor can flange 63 and the first radial inner
reference surface 71 of the pump housing 11.
[0084] As can be seen best in FIG. 14, the annular stop surface 79
abuts axially from below against a locking ring 85 being secured in
a circumferential groove 87 of the pump housing 11. When the pump
assembly is being assembled (see FIG. 13), the locking ring 85 may
be placed into the groove 87 after the rotor can flange 63 has been
placed into position within the pump housing 11. The rotor can 57
is thus secured against an upward movement out of the pump housing
11. The rotor can flange 63 comprises an annular contact surface 89
facing towards the impeller 12 and the bearing retainer flange 43
comprises an annular biasing surface 91 facing away from the
impeller 12, wherein the bearing retainer 41 is resiliently
spring-loaded for biasing the annular biasing surface 91 of the
bearing retainer flange 43 against the annular contact surface 89
of the rotor can flange 63. The rotor can 57 is thus pressed upward
against the locking ring 85 by means of the bearing retainer
41.
[0085] The bearing retainer flange 43 comprises a conical bearing
retainer flange section 93, wherein a radially outward end 94 of
the bearing retainer flange section 93, i.e. the radial outer
bearing retainer surface 69, is located axially closer to the
impeller 12 than a radially inward end 95 of the bearing retainer
flange section 93. The radially most outward section of the bearing
retainer flange section 93 rests on the axial annular stop surface
39 of the pump housing 11. The annular biasing surface 91 is formed
by an upper radially inward portion of the conical bearing retainer
flange section 93. The annular biasing surface 91 comprises n 3
axial projections 94 towards the rotor can flange 63, wherein the
axial projections 94 may be circumferentially distributed in an
n-fold symmetry on the upper radially inward portion of the conical
bearing retainer flange section 93. Preferably, the annular biasing
surface 91 comprises n =4 dot-shaped projections 94. The
projections 94 serve as well-defined points of axial contact
between the rotor can flange 63 and the bearing retainer flange
43.
[0086] FIG. 13 shows a situation during assembly of the pump
assembly 1 before the rotor can 57 is secured in position by means
of the locking ring 85. FIG. 14 shows a situation after the rotor
can 57 is secured in position by means of the locking ring 85.
During assembly of the pump assembly 1, the bearing retainer 41 is
placed into the pump housing 11 to rest on the axial annular stop
surface 39 of the pump housing 11. The rotor can 57 is then pressed
downwards with its lower annular contact surface 89 onto the axial
protrusions 94 of the upper annular biasing surface 91 of the
bearing retainer flange 43 to resiliently deform the conical
bearing retainer flange section 93. The locking ring 85 is placed
into the groove 87 to secure the rotor can 57 axially while the
rotor can 57 is held pressed down against the bearing retainer
flange 43. Thus, the bearing retainer 41 is resiliently
spring-loaded to bias the rotor can 57 upward against the locking
ring 85. The impeller 12, the rotor axle 45, the rotor 51, the
bearings 47, 53, the bearing retainer 41 and the rotor can 57 are
placed into the pump housing 11 as a first pre-assembled unit 99
(see. FIG. 4) being secured downwards by the locking ring 85,
wherein the bearing retainer 41 acts as an upwardly biasing spring.
It should be noted in FIG. 13 that the bearing retainer flange 43
has initially some lateral wiggle room between the radial outer
bearing retainer surface 69 and the first radial inner reference
surface 71 of the pump housing 11. This facilitates the insertion
of the bearing retainer 41 into the pump housing 11 during
assembly. As shown in FIG. 14, the axial pressure exerted by the
rotor can flange 63 onto the bearing retainer flange 43 slightly
flattens the conical bearing retainer flange section 93, whereby
the lateral wiggle room between the radial outer bearing retainer
surface 69 and the first radial inner reference surface 71 of the
pump housing 11 is closed. The radial outer bearing retainer
surface 69 is radially pressed outward against the first radial
inner reference surface 71 of the pump housing 11. The flattening
of the bearing retainer flange 43 between a first relaxed state
shown in FIG. 13 and a second spring-loaded state shown in FIG. 14
can be seen by comparing the angle .beta. in FIGS. 13 and 14. The
angle .beta. may be denoted as a base angle of the conical bearing
retainer flange section 93 with an apex angle
.alpha.=180.degree.-2.beta.. The apex angle a is not explicitly
shown in FIGS. 13 and 14, but it can be inferred that the apex
angle .alpha. is larger in the second spring-loaded state shown in
FIG. 14 than in the first relaxed state shown in FIG. 13.
[0087] As shown in FIG. 15, the radial outer bearing retainer
surface 69 may comprise at least three, preferably four, radial
projections 70 radially abutting against the first radial inner
reference surface 71 of the pump housing 11 and centering the
bearing retainer 41 with respect to the first radial inner
reference surface 71 of the pump housing 11. It should be noted in
FIG. 14 that a radial gap H remains between the rotor can flange 63
and the pump housing 11, so that the rotor can 57 can effectively
be centered by the contact between the radial inner centering
surface 65 of the rotor can 57 and the radial outer centering
surface 67 of the bearing retainer 41.
[0088] The neck ring 29, as shown in FIGS. 16a,b and 17a,b, is
coupled to the pump housing 11 by a several tons strong press-fit
so that the neck ring 29 and the pump housing 11 constitute a
second pre-assembled unit 101 as opposed to the first preassembled
unit 99 as shown in FIG. 4. When the pump assembly 1 is fully
assembled, the impeller 12 is located axially between the bearing
retainer 41 and the neck ring 29, wherein the neck ring 29
comprises the circumferential wall section 30 at least partially
extending into the impeller 12. The circumferential wall section 30
comprises a radial outer surface 105 and the impeller 12 comprises
a radial inner surface 107, wherein the radial outer surface 105 of
the circumferential wall section 30 and the radial inner surface
107 of the impeller 12 have a radial distance defining the gap G
(see FIG. 4). The indirect centering of the rotor can 57 by means
of the bearing retainer 41 rather than the pump housing 11 directly
reduces manufacturing tolerances and thus allows for a smaller gap
G, which increases the pumping efficiency.
[0089] The gap G is minimized by an asymmetrically machined neck
ring 29 as shown in FIG. 17a,b. When the neck ring 29 is coupled to
the pump housing 11 by press-fitting, the neck ring 29 may be
initially rotationally symmetric as shown in FIG. 16b. However, the
lateral position and/or the axial alignment of the neck ring 29 may
not be exact and comprises some tolerances. If the neck ring 29 is
not asymmetrically machined neck ring 29 as shown in FIG. 16b after
being press-fitted into the pump housing 11, the gap G must be
large enough to accommodate such tolerances. As shown in FIG. 17b,
the neck ring 29 is asymmetrically machined with the same tool and
in the same machining processing which generates, at the pump
housing 11, the first radial inner reference surface 71 and the
first annular reference surface 109. As a result, as shown in FIGS.
17a,b, the circumferential wall section 30 of the neck ring 29 may
get a machined cylindrical radial outer surface 105 that is exactly
coaxially aligned with the first radial inner reference surface 71
and a first annular reference surface 109, and thus with the rotor
axis R. After machining, the radial outer surface 105 of the
circumferential wall section 30 of the neck ring 29 is eccentric
with respect to a radial inner surface 110 of the circumferential
wall section 30. In the detail view of FIG. 17a, a milling edge 112
extending along at least a portion of the circumference of the
circumferential wall section 30 of the neck ring 29 is visible on
the left-hand side, where more material was milled away from the
circumferential wall section 30 of the neck ring 29 than on the
right-hand side. Thereby, the radial outer surface 105 is better
aligned with the rotor axis (R) so that the gap G can be configured
smaller, which increases the pumping efficiency. It should be noted
that the machined asymmetry of the circumferential wall section 30
of the neck ring 29 may be in the range of tens of microns or even
less. In an alternative embodiment, the impeller 12 may at least
partially extend into the circumferential wall section 30 of the
neck ring 29, so that it is the radial inner surface 110 of the
circumferential wall section 30 which is preferably eccentrically
machined with respect to the radial outer surface 105 of the
circumferential wall section 30 in order to reduce the gap G.
[0090] The stator housing 13 may be used to angularly align the
rotor axis R with respect to the pump housing 11 as shown in FIG.
11. In order to achieve this, the pump housing 11 has a machined
first annular reference surface 109 facing away from the impeller
12 and the stator housing 13 has a second annular reference surface
111 facing towards the impeller 12, wherein the second annular
reference surface 111 rests on the first annular reference surface
109, biased downwards my means of a bayonet ring 113. Thus, the
angular orientation of the stator housing 13 with respect to the
pump housing 11 is well-defined. As explained above, the first
annular reference surface 109 is machined with the same tool and in
the same machining processing which generates the first radial
inner reference surface 71 and the outer surface 105 of the neck
ring 29.
[0091] The stator 17, as shown in FIGS. 18a,b, comprises windings
(not shown) wound around a stator core 114, for instance
essentially comprised of a stack of ferrite or iron laminates,
wherein the stator core 114 is formed as a stator ring 118 with
radially inwardly projecting stator teeth 120. For the stator
housing 13 to align the rotor can 57 angularly, as shown in FIG.
11, the stator teeth 120 of the stator 17 in the stator housing 13
define a second radial inner reference surface 115 for a
heat-conductive contact with the rotor can 57. Correspondingly, the
rotor can 57 comprises a radial outer alignment surface 117
abutting radially against the second radial inner reference surface
115. Thereby, the rotor can 57 is angularly aligned essentially
perpendicular to the first annular reference surface 109 of the
pump housing 11. It should be noted in FIG. 11 that the stator
housing 13 has some lateral wiggle room in the pump housing 11 so
that the rotor can 57 is able to center the stator housing 57 while
the stator housing 13 keeps the rotor axis R essentially
perpendicular to the first annular reference surface 109.
[0092] The second annular reference surface 111 of the stator
housing 13 is defined by injection overmolding a surface portion of
the stator core 114, wherein an injection mandrel contacts the
second radial inner reference surface 115 and holds the stator core
114 in a well-defined position during overmolding. Thereby, the
second annular reference surface 111 of the stator housing 13 is
essentially perpendicular to the second radial inner reference
surface 115 with minimal manufacturing tolerances. As shown in
FIGS. 18a, b, the stator 17 comprises a first material 122 as an
electrically insulating layer between the stator windings and the
stator core 114. The first material 122 effectively covers a first
surface portion of the stator core 114 that serves as a bobbin
former for the stator windings to be spooled on. The layer of the
first material 122 is preferably as thin as possible to allow for
good heat-dissipation between the stator windings and the stator
core 114 and thick enough to be sufficiently electrically
insulating. As high thermal conductivity is mostly accompanied by
low dielectric strength, the heat dissipation is effectively
maximized by overmolding the first surface portion of the stator
core 114 with a thin layer of the first material 122 having a high
dielectric strength and/or a high comparative tracking index (CTI),
for instance above 175. Irrespective of whether the pump assembly 1
is used as a medical equipment or not, the first material 122 may
belong to the material group IIIa according to the International
Electronic Commission Standard IEC 60601-1:2005 with a CTI in the
range of 175 to 400. The first material 122 may be a moldable
plastic such as a polyamide (PA), a polyethylene terephthalate
(PET), or a liquid crystal polymer (LCP). The first material 122
may further form bobbin webs 130 projecting axially from both axial
ends of the stator core 114 to keep the windings laterally in place
(see FIGS. 18a, b).
[0093] It should be noted that the overmolding of the first surface
portion of the stator core 114 with the first material 122 is
performed in a first overmolding step, at a relatively high
temperature of the stator core 114 for decreasing the viscosity of
the first material 122 and thereby achieving a comprehensive thin
insulating coating layer. After that first overmolding step, at a
lower temperature of the stator core 114, a second surface portion
of the stator core 114 is overmolded in a separate second
overmolding step with a second material 124 for forming walls of
the stator housing 13. Thereby, the risk of cracking of the second
material 124 is reduced, because the thermal expansion/contraction
of the stator core 114 during and after overmolding can be better
controlled. The second annular reference surface 111 of the stator
housing 13 is defined in the second overmolding step, wherein an
injection mandrel contacts the second radial inner reference
surface 115 defined by the stator teeth 120 and holds the stator
core 114 in a well-defined position during injection overmolding.
The second material 124 fulfils different requirements than the
first material 122 and may have different physical and/or chemical
properties. For instance, the second material 124 may have
particularly low flammability, which is less of an issue for the
first material 122, which may thus have a higher flammability than
the second material 124. The second material 124 may be classified
with the highest flame-retarding rating 5VA according to the UL 94
Standard for Safety of Flammability of Plastic Materials. The
second material 124 may be a moldable plastic such as a polyamide
(PA), a polyphenylene sulphide (PPS), or a polyether ether ketone
(PEEK). The second material 124 may comprise a certain glass fibre
content, for instance 10% to 50%, preferably about 30%, depending
on the requirements.
[0094] A radially inner surface 126 of the stator ring 118 forms
part of the first surface portion of the stator core 114 that is
coated with the first material 122 having a first thickness
d.sub.1. A radially outer surface 128 of the stator ring 118 forms
part of the second surface portion of the stator core 114 that is
coated with the second material 124 having a second thickness
d.sub.2. In order to achieve a thin insulation coating made of the
first material 122 and stable integrity of the walls of the stator
housing 13 made of the second material 124, the first thickness
d.sub.1 is lower than the second thickness d.sub.2. The different
thicknesses d.sub.1, d.sub.2 may be best seen in FIG. 11. In case
the thicknesses vary, e.g. in axial direction as shown for the
second thickness d.sub.2 in FIG. 11, the minimal second thickness
d.sub.2 is higher than the minimal first thickness d.sub.1.
Preferably, the second thickness d.sub.2 is at least 2 mm.
[0095] For providing a good leverage to the stator housing 13 to
align the rotor can 57 angularly, the pump housing 11 is configured
such that the first annular reference surface 109 is located
radially more outward than the first radial inner reference surface
71 and/or the first annular reference surface 109 is located
axially further away from the impeller 12 than the first radial
inner reference surface 71.
[0096] Likewise, for having a good leverage to align the rotor can
57 angularly, the stator housing 13 is configured such that the
second radial inner reference surface 115 is located radially more
inward than the second annular reference surface 111 and/or the
second radial inner reference surface 115 is located axially
further away from the impeller 12 than the second annular reference
surface 111.
[0097] The embodiments of the pump assembly 1 shown in FIGS. 1 to
19 have a very compact bayonet-like mount of the stator housing 13
to the pump housing 11 (see in particular FIGS. 4 and 12). As part
of the bayonet-like mount, the bayonet ring 113 secures the stator
housing 13 to the pump housing 11, wherein the bayonet ring 113 is
resiliently spring-loaded for axially biasing the stator housing 13
downwards against the pump housing 11 towards the impeller 12. The
second annular reference surface 111 of the stator housing 13 is
thus pressed downwards onto the first annular reference surface 109
of the pump housing 11 by means of the bayonet ring 113. The
bayonet ring secures 113 the stator housing against rotation around
the rotor axis R in a well-defined angular position. The bayonet
ring 113 is a metal wire with circular cross-section. The bayonet
ring 113 comprises circumferential first sections 119 with a first
radius R.sub.a and circumferential second sections 121 with a
second radius wherein the second radius R.sub.i, is smaller than
the first radius R.sub.a, i.e. R.sub.i<R.sub.a. The second
sections 121 may be formed as radially inward projections
cooperating with bayonet grooves 123 in a radially outer surface
125 of the stator housing 13. The first sections 119 of the bayonet
ring 113 are secured in a circumferential groove 127 of the pump
housing 11. The bayonet grooves 123 in the stator housing 13 may
comprise a first "vertical" section 129 through which the second
sections 121 of the bayonet ring 113 pass when the stator housing
13 is placed downwards onto the first annular reference surface 109
of the pump housing 11. The bayonet grooves 123 in the stator
housing 13 may comprise a second "upwardly sloped" circumferential
section 131 with a first end 133 at the first "vertical" section
129 and a second end 135 circumferentially distanced from the first
end 133, wherein the first end 133 of the second section 131 is
located closer to the second annular reference surface 111 of the
stator housing 13 than the second end 135 of the second section
131. Upon manual rotation of the stator housing 13 by a pre-defined
angle for the second sections 121 of the bayonet ring 113 to be
guided along the second sections 131 of the bayonet grooves 123
from the first end 133 to the second end 135, the second sections
121 of the bayonet ring 113 are pushed upward by the slope while
the first sections 119 of the bayonet ring 113 remain secured in
the pump housing 11. Thereby, the bayonet ring 113 resiliently
twists between the first sections 119 and the second sections 121.
The second sections 121 of the bayonet ring 113 may click into a
horizontal or "downwardly sloped" end section 137 at the second end
135 of the second section 131 of the grooves 123. The resilient
twist of the bayonet ring 113 biases the second annular reference
surface 111 of the stator housing 13 downward onto the first
annular reference surface 109 of the pump housing 11.
[0098] FIGS. 19a-c show the lid or cap 21 of the stator housing 13
in different views. The cap 21 comprises two materials, a first
electrically insulating material 139 at the outer side of the cap
21 and a heat-conductive second material 141 at the inner side of
the cap 21. The first material 139 of the cap 21 may be the same as
the second material 124 of the stator 17. The heat-conductive
material 141 may comprise a metal or a plastic with heat-conductive
additives such as graphite carbon fibers and/or ceramics like boron
nitride. As the heat-conductive material 141 is usually less
suitable for electric insulation, the first heat-conductive
material 141 is only at the inside of the cap 21 and not at the
outside. The inner side of the first material 139 may be at least
partially overmolded with the heat-conductive material 141. The
heat-conductive material 141 is useful to dissipate heat from the
PCB 15 which extends in a plane essentially perpendicular to the
rotor axis R close to the inner side of the cap 21. It is
particularly advantageous that the cap 21 comprises a front face 19
that extends essentially parallel to the PCB 15, i.e. essentially
perpendicular to the rotor axis R, and a radially outer wall 143
extending essentially parallel to the rotor axis R. Thereby, the
heat-conductive material 141 can not only extend essentially
parallel to the front face 19 at the inner side of the cap 21, but
also essentially parallel to the radially outer wall 143 at the
inner side of the cap 21. This has the advantage that the heat from
the PCB 15 is effectively dissipated when the pump assembly 1 is
installed in a horizontal as well as in a vertical rotor axis
orientation. This is, because the heat-conductive material 141 is
most efficient when a convection hot air stream is able to flow
along the outer side of the first material 139 to cool down. As the
convection hot air stream is mainly vertical, it is advantageous to
have the heat-conductive material 141 close to the PCB 15 extending
in a vertical direction irrespective of the installation
orientation of the rotor axis R of the pump assembly 1. The surface
of the heat-conductive material 141 that is facing the PCB 15 is
terraced corresponding to the layout of the PCB, so that a direct
contact or only a minimal gap between the electronic components on
the PCB 15 and the heat-conductive material 141 is achieved over
most of the area of the PCB 15 to facilitate a most efficient heat
transfer from the components of the PCB 15 to the heat-conductive
material 141, preferably indirectly conveyed by a heat-conductive
paste arranged between the heat-conductive material 141 and the
electronic components on the PCB 15.
[0099] FIG. 19c indicates by dashes in the second material 141 that
the second material 141 is not fully homogeneous, but has an inner
structure defining a certain spatial orientation of the second
material 141. The spatial orientation of the inner structure of the
second material 141 basically follows a flow path that the second
material 141 took during the overmolding of the inner side of the
cap 21. Therefore, the second material 141 comprises at least one
first area 145, where the spatial orientation is predominantly
parallel to the rotor axis (R), and at least one second area 147,
where the spatial orientation is predominantly perpendicular to the
rotor axis (R). The first area(s) 145 mark the area(s) at or around
injection point(s) of the second material 141 during overmolding.
The second area(s) 147 mark the area(s) where the second material
141 flows along the inner side of the front face 19. It was found
that the spatial orientation of the inner structure of the second
material 141 has a significant influence on the heat-conducting
properties. Heat conduction along the spatial orientation of the
inner structure of the second material 141 is better than
perpendicular to it. Therefore, the first area 145 of the second
material 141 has a first direction 149 of predominant
heat-conduction perpendicular to the front face 19, whereas the
second area 147 of the second material 141 has a second direction
151 of predominant heat-conduction parallel to the front face 19 or
the radially outer wall 143 of the cap 21. The lateral location of
the injection point(s) of the second material 141 during
overmolding may thus be wisely chosen to define the first area(s)
145, where the hottest electronic components are located on the PCB
15. This facilitates the heat dissipation from the components on
the PCB 15 into the second material 141, which spreads the heat
laterally via the second area(s) 147. The first material 139 may
act as a heat sink that is cooled by an ambient convection air
stream along the front face 19 and/or the radially outer wall 143
of the cap 21.
[0100] Where, in the foregoing description, integers or elements
are mentioned which have known, obvious or foreseeable equivalents,
then such equivalents are herein incorporated as if individually
set forth. Reference should be made to the claims for determining
the true scope of the present disclosure, which should be construed
so as to encompass any such equivalents. It will also be
appreciated by the reader that integers or features of the
disclosure that are described as optional, preferable,
advantageous, convenient or the like are optional and do not limit
the scope of the independent claims.
[0101] The above embodiments are to be understood as illustrative
examples of the disclosure. It is to be understood that any feature
described in relation to any one embodiment may be used alone, or
in combination with other features described, and may also be used
in combination with one or more features of any other of the
embodiments, or any combination of any other of the embodiments.
While at least one exemplary embodiment has been shown and
described, it should be understood that other modifications,
substitutions and alternatives are apparent to one of ordinary
skill in the art and may be changed without departing from the
scope of the subject matter described herein, and this application
is intended to cover any adaptations or variations of the specific
embodiments discussed herein.
[0102] In addition, "comprising" does not exclude other elements or
steps, and "a" or "one" does not exclude a plural number.
Furthermore, characteristics or steps which have been described
with reference to one of the above exemplary embodiments may also
be used in combination with other characteristics or steps of other
exemplary embodiments described above. Method steps may be applied
in any order or in parallel or may constitute a part or a more
detailed version of another method step. It should be understood
that there should be embodied within the scope of the patent
warranted hereon all such modifications as reasonably and properly
come within the scope of the contribution to the art. Such
modifications, substitutions and alternatives can be made without
departing from the spirit and scope of the disclosure, which should
be determined from the appended claims and their legal
equivalents.
[0103] While specific embodiments of the invention have been shown
and described in detail to illustrate the application of the
principles of the invention, it will be understood that the
invention may be embodied otherwise without departing from such
principles.
LIST OF REFERENCE DESIGNATIONS
[0104] 1 pump assembly [0105] 2 pump unit [0106] 3 input port
[0107] 5 output port [0108] 7 connector flange [0109] 9 connector
flange [0110] 11 pump housing [0111] 12 impeller [0112] 13 stator
and/or electronics housing [0113] 15 printed circuit board (PCB)
[0114] 17 stator [0115] 19 front face of the cap of the stator
housing [0116] 21 cap of the stator housing [0117] 23 impeller
chamber [0118] 25 concentric bottom entry [0119] 27 tangential exit
[0120] 29 neck ring [0121] 31 inner spiral vanes [0122] 33 impeller
plate [0123] 35 circular opening [0124] 37 inward projection [0125]
39 axial annular stop surface of the pump housing [0126] 41 bearing
retainer [0127] 43 bearing retainer flange [0128] 45 rotor axle
[0129] 47 first radial bearing ring [0130] 49 axial bearing plate
[0131] 51 rotor [0132] 53 second radial bearing ring [0133] 55
bearing bushing [0134] 57 rotor can [0135] 63 rotor can flange
[0136] 65 radial inner centering surface [0137] 67 radial outer
centering surface [0138] 69 radial outer bearing retainer surface
[0139] 70 radial projections of the radial outer bearing retainer
surface [0140] 71 first radial inner reference surface [0141] 72
radial projections of the radial outer centering surface [0142] 73
circumferential groove of the rotor can flange [0143] 75 radial
inner section of the rotor can flange [0144] 77 radial outer
section of the rotor can flange [0145] 79 annular stop surface of
the rotor can flange [0146] 81 radially outward end of the annular
stop surface of the rotor can flange [0147] 83 radially inward end
of the annular stop surface of the rotor can flange [0148] 84
sealing ring [0149] 85 locking ring [0150] 87 circumferential
groove of the pump housing [0151] 89 annular contact surface of the
rotor can flange [0152] 91 annular biasing surface of the bearing
retainer flange [0153] 93 bearing retainer flange section [0154] 94
axial projections [0155] 95 radially inward end of the bearing
retainer flange section [0156] 99 first pre-assembled unit [0157]
101 second pre-assembled unit [0158] 105 radial outer surface
[0159] 107 radial inner surface [0160] 109 first annular reference
surface [0161] 110 radial inner surface [0162] 111 second annular
reference surface [0163] 112 milling edge [0164] 113 bayonet ring
[0165] 114 stator core [0166] 115 second radial inner reference
surface [0167] 117 radial outer alignment surface [0168] 118 stator
ring [0169] 119 circumferential first sections of the bayonet ring
[0170] 120 stator teeth [0171] 121 circumferential second sections
of the bayonet ring [0172] 122 first material of the stator [0173]
123 bayonet grooves [0174] 124 second material of the stator [0175]
125 radially outer surface of the stator housing [0176] 126
radially inner surface of the stator ring [0177] 127
circumferential groove of the pump housing [0178] 128 radially
outer surface of the stator ring [0179] 129 first section of a
bayonet groove [0180] 130 bobbin webs [0181] 131 second section of
a bayonet groove [0182] 133 first end of the second section of a
bayonet groove [0183] 135 second end of the second section of a
bayonet groove [0184] 137 end section of a bayonet groove [0185]
139 first material of the cap of the stator housing [0186] 141
second material of the cap of the stator housing [0187] 143
radially outer wall of the cap of the stator housing [0188] 145
first area of the first material of the cap of the stator housing
[0189] 147 second area of the first material of the cap of the
stator housing [0190] 149 first direction of predominant heat
dissipation [0191] 151 second direction of predominant heat
dissipation [0192] R rotor axis [0193] H radial gap of the rotor
can [0194] G radial gap of the neck ring [0195] .alpha. apex angle
of conical bearing retainer flange section
[0195] .beta. = 180 .degree. - .alpha. 2 ##EQU00001##
* * * * *