U.S. patent application number 14/721379 was filed with the patent office on 2015-12-24 for radial- oder diagonalventilator.
The applicant listed for this patent is ebm-papst Mulfingen GmbH & Co. KG. Invention is credited to Martin Baer, Christian Hammel, Jurgen Schone, Michael Strehle, Michael Sturm.
Application Number | 20150369247 14/721379 |
Document ID | / |
Family ID | 53396195 |
Filed Date | 2015-12-24 |
United States Patent
Application |
20150369247 |
Kind Code |
A1 |
Schone; Jurgen ; et
al. |
December 24, 2015 |
RADIAL- ODER DIAGONALVENTILATOR
Abstract
The invention relates to a radial fan with an impeller (100) and
a cylindrical drive unit (200) that can be rotated around the
longitudinal axis, whereby the impeller (100) consists of a
baseplate and of blades (101) arranged on the baseplate, and
whereby the blades are located on the side facing the main air
flow, and it is characterized in that the impeller (100) can be
operatively connected to the drive unit (200) in two fastening
planes. The impeller consists of a baseplate and blades arranged on
the baseplate, whereby the blades are located on the side of the
baseplate facing the main air flow, and whereby the baseplate is
made up of an upper shell located on the side facing the main air
flow and of a lower shell located on the side facing away from the
main air flow, whereby the upper shell and the lower shell form a
closed cavity with the cylindrical drive unit when in the installed
state, whereby a first fastening plane is located on the upper
shell and a second fastening plane is located on the lower
shell.
Inventors: |
Schone; Jurgen; (Bad
Mergentheim, DE) ; Strehle; Michael; (Ingelfingen,
DE) ; Hammel; Christian; (Pfedelbach-Oberohrn,
DE) ; Sturm; Michael; (Bad Mergentheim, DE) ;
Baer; Martin; (Mulfingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ebm-papst Mulfingen GmbH & Co. KG |
Mulfingen |
|
DE |
|
|
Family ID: |
53396195 |
Appl. No.: |
14/721379 |
Filed: |
May 26, 2015 |
Current U.S.
Class: |
417/423.6 ;
417/423.14 |
Current CPC
Class: |
F04D 29/281 20130101;
F04D 29/263 20130101; F04D 13/06 20130101; F04D 13/021
20130101 |
International
Class: |
F04D 13/02 20060101
F04D013/02; F04D 13/06 20060101 F04D013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Jun 2, 2014 |
DE |
102014210373.8 |
Claims
1. A radial or diagonal fan with an impeller and a prismatic drive
unit that can be rotated around the longitudinal axis,
characterized in that the impeller can be operatively connected to
the drive unit in two fastening planes, whereby the impeller has a
baseplate and blades arranged on the baseplate, and whereby the
blades are located on the side of the baseplate facing the main air
flow, whereby the baseplate is made up of an upper shell located on
the side facing the main air flow and of a lower shell located on
the side facing away from the main air flow, whereby the upper
shell and the lower shell form a closed cavity with the cylindrical
drive unit when in the installed state, whereby a first fastening
plane is located on the upper shell and a second fastening plane is
located on the lower shell.
2. The radial or diagonal fan according to claim 1, characterized
in that on the edge of the upper shell and of the lower shell
facing the drive unit (200), there are fastening means in the
appertaining fastening plane, and the drive unit has two flanges
that are offset in the longitudinal axis, whereby the flanges have
fastening means that can be detachably connected to the fastening
means of the impeller.
3. The radial or diagonal fan according to claim 2, characterized
in that the upper shell and the lower shell are connected by
screwed connections to flanges that are arranged on the cylindrical
drive unit so as to be offset in the longitudinal axis.
4. The radial or diagonal fan according to claim 3, characterized
in that the fastening means in the upper shell, relative to the
longitudinal axis of the rotatable cylindrical drive unit, are
arranged radially offset to the fastening means of the lower
shell.
5. The radial or diagonal fan according to claim 4, characterized
in that there are installation holes in the upper shell and/or in
the lower shell opposite from the fastening means, which are
concealed when in the installed state.
6. The radial or diagonal fan according to claim 5, characterized
in that the installation holes have a larger diameter than the
holes in the lower shell and in the upper shell.
7. The radial or diagonal fan according to claim 5, characterized
in that the fastening means in the upper shell and the fastening
means in the lower shell have holes or threaded bolts that are
operatively connected to holes or threaded bolts of the flanges
when in the installed state.
8. The radial or diagonal fan according to claim 1, characterized
in that the upper shell and/or the lower shell have centering means
that cooperate with centering means on the flanges that have been
put in place.
9. The radial or diagonal fan according to claim 8, characterized
in that the centering means are centering projections and centering
indentations that cooperate during the installation of the impeller
on the cylindrical drive unit.
10. The radial or diagonal fan according to claim 1, characterized
in that the upper shell is configured to be rotation-symmetrically
curved in such a way that it curves in the direction of the main
air flow.
11. The radial or diagonal fan according to claim 1, characterized
in that the upper shell has several sections that have at least one
concave section or one convex section or one flat section.
12. The radial or diagonal fan according to claim 1, characterized
in that the lower shell is configured to be flat.
13. The radial or diagonal fan according to claim 1, characterized
in that the cavity has at least one reinforcement that runs as a
round or polygonal ring axially around the cylindrical drive unit
or extends radially relative to the longitudinal axis of the
rotatable cylindrical drive unit.
14. The radial or diagonal fan according to claim 1, characterized
in that the blades arranged on the baseplate are configured with a
shell design.
15. The radial or diagonal fan according to claim 1, characterized
in that the contours of the blades arranged on the baseplate are
configured to be smooth on the side facing the main air flow.
16. The radial or diagonal fan according to claim 2, characterized
in that the flanges of the drive unit extend to differing extents
radially relative to the longitudinal axis.
17. The radial or diagonal fan according to claim 2, characterized
in that installation holes are arranged in the flanges opposite
from the fastening means, which are concealed when in the installed
state.
18. The radial or diagonal fan according to claim 17, characterized
in that the installation holes have a larger diameter than the
holes in the lower flange and in the upper flange.
19. The radial or diagonal fan according to claim 1, characterized
in that the drive unit is a rotor or a shaft connection.
20. The radial or diagonal fan according to claim 1, characterized
in that the impeller has a baseplate as a closure.
Description
[0001] The invention relates to a radial or diagonal fan with an
impeller and a prismatic drive unit that can be rotated around the
longitudinal axis, whereby the impeller consists of a baseplate and
of blades arranged on the baseplate, and of a cover plate as a
closure, and whereby the blades are located on the side facing the
main air flow.
[0002] Nowadays, radial fans with blades that are curved backwards
or diagonal fans are used on a widespread scale. The area of
application ranges from their use in household appliances such as,
for example, exhaust hoods, in air-conditioning units and even in a
wide array of industrial systems. With a radial or diagonal fan,
the air is drawn in parallel or axially relative to the drive axis
of the radial or diagonal fan and is then blown out radially or
diagonally by the rotation of the radial impeller.
[0003] Fundamentally, radial or diagonal fans consist of a drive
unit and an impeller. The drive unit of a radial or diagonal fan
can be configured, for instance, as an asynchronous motor or of a
permanent-magnet synchronous motor (electronically commutated EC
motor). The radial impeller or diagonal impeller is connected to
the rotor of the drive unit and serves to convey air and/or other
gases. The material selection of today's impellers ranges from
plastic versions to metal structures. Nowadays, for
strength-related reasons, impellers with fairly large diameters
(typically 630 mm and larger) are in the form of a simple sheet
metal construction. For strength-related reasons, aluminum or sheet
steel that is relatively thick (typically 5 mm and more) is used.
In the state of the art, impellers with a diameter of 800 mm are
known whose cover plate has a thickness of 4 mm, a blade thickness
of 6 mm and a baseplate thickness of 5 mm. Owing to the relatively
large amount of material employed, this yields impellers that have
a high intrinsic weight and that are thus correspondingly expensive
to produce. Another consequence of the high weight is that the
drive unit and the other components are subject to a high load. In
order to reliably absorb this load and to reliably support the high
intrinsic weight, the drive unit and the other components have to
be solid, which likewise translates into high costs.
[0004] The objective of the invention is to reduce the
above-mentioned drawbacks.
[0005] According to the invention, this objective is achieved by a
radial or diagonal fan according to claim 1. Advantageous
embodiments can be gleaned from the subordinate claims 2 to 20.
[0006] A radial or diagonal fan according to the invention has an
impeller and a prismatic drive unit that can be rotated around the
longitudinal axis, whereby the impeller can be operatively
connected to the drive unit in two fastening planes. Thanks to the
fastening in two planes, the flexural strength is increased,
thereby achieving a greater system strength of the radial or
diagonal fan without increasing the weight.
[0007] The impeller has a baseplate and blades arranged on the
baseplate as well as, optionally, a cover plate as a closure,
whereby the blades are located on the side of the baseplate facing
the main air flow, and whereby the baseplate is made up of an upper
shell located on the side facing the main air flow and a lower
shell located on the side facing away from the main air flow,
whereby the upper shell and the lower shell form a closed cavity
with the cylindrical drive unit when in the installed state,
whereby a first fastening plane is located on the upper shell and a
second fastening plane is located on the lower shell. The wall
thickness of the material employed can be reduced by the shell
construction, as a result of which the weight of the radial or
diagonal fan is reduced even further. Thanks to the fastening in
the two planes, the stiffness of the radial or diagonal fan is
nevertheless retained.
[0008] Advantageously, on the edge of the upper shell and of the
lower shell facing the drive unit, there are fastening means that
create a detachable connection together with fastening means on the
cylindrical drive unit when in the installed state. Consequently,
the impeller can be installed on or removed from the drive
unit.
[0009] Advantageously, the upper shell and the lower shell are
connected by screwed connections to flanges that are arranged on
the cylindrical drive unit so as to be offset in the longitudinal
axis. Since the flanges are offset, they can connect the upper
shell and the lower shell to the drive unit in such an offset
manner that a particularly stable connection is created between the
drive unit and the impeller.
[0010] Advantageously, the fastening means in the upper shell,
relative to the longitudinal axis of the rotatable cylindrical
drive unit, are arranged radially offset to the fastening means of
the lower shell. The radially offset arrangement allows a simpler
installation of the impeller on the flanges of the drive unit.
[0011] Advantageously, there are installation holes in the upper
shell or in the lower shell opposite from the fastening means,
which are concealed when in the installed state. Thus, it is
possible to access the fastening means without removing the
impeller from the drive unit.
[0012] In an especially advantageous embodiment, the installation
holes have a larger diameter than the holes in the lower shell and
in the upper shell. As a result, a tool, for example, a socket
wrench, can be inserted through the installation hole. For the
installation, it has proven to be especially advantageous to use
fastening means in the form of nuts that are screwed onto threaded
bolts. In particular, staked nuts can be used that have an outer
diameter widening, for example, in the form of a permanently
attached washer. These staked nuts can be picked up, for instance,
with the magnetizable socket of a socket wrench and installed. As a
result, the nut can be screwed onto a threaded bolt that is
concealed and that ends in the cavity, without the possibility that
the nut might be lost during the installation. As a result, a
reliable installation and, in particular, a reliable automatic
installation, is possible. A nut that is lost during the
installation severely disrupts the installation process. If the nut
is lost in the cavity, it has to be retrieved from there with a
great deal of effort. It would not be possible to use the radial
fan with a loose nut in the cavity.
[0013] Advantageously, the fastening means in the upper shell and
the fastening means in the lower shell have holes or threaded bolts
that are operatively connected to holes or threaded bolts of the
flanges when in the installed state. This allows a simple
installation of the impeller on the drive unit via the threaded
bolts that can be inserted into the holes. Subsequently, the
threaded bolts can be screwed with fitting nuts.
[0014] Advantageously, the upper shell and/or the lower shell have
centering means that cooperate with centering means on the flanges
that have been put in place. The centering means simplify the
correct installation of the impeller on the drive unit.
Advantageously, the centering means are centering projections and
centering indentations that cooperate during the installation of
the impeller on the cylindrical drive unit.
[0015] Advantageously, the upper shell is configured to be
rotation-symmetrically curved in such a way that it curves in the
direction of the main air flow. As a result, flow separations are
avoided. At the same time, this shape enhances the efficiency.
[0016] Advantageously, the upper shell has several sections that
have at least one concave section or one convex section or one flat
section.
[0017] Advantageously, the lower shell is configured to be flat,
which leads to a reduction of the costs for tools and parts.
[0018] Advantageously, the cavity has at least one reinforcement
that runs as a round or polygonal ring axially around the
cylindrical drive unit. This reinforcement makes it possible to use
thin materials, even under high loads.
[0019] Advantageously, the cavity has at least one reinforcement
that extends radially relative to the longitudinal axis of the
rotatable cylindrical drive unit. This ensures a flux of force from
the flanges to the blades.
[0020] Advantageously, the blades arranged on the baseplate are
configured with a shell design. This further reduces the weight of
the impeller.
[0021] Advantageously, the contours of the blades arranged on the
baseplate are configured to be smooth on the side facing the main
air flow, as a result of which better efficiency can be achieved
and flow-related disturbances can be reduced.
[0022] In another advantageous embodiment, the flanges of the drive
unit extend to differing extents radially relative to the
longitudinal axis. This simplifies the installation of the radial
fan in the axial direction.
[0023] Moreover, it has proven to be advantageous for installation
holes to be arranged in the flanges opposite from the fastening
means, which are concealed when in the installed state.
[0024] In addition, it is advantageous for the installation holes
to have a larger diameter than the holes in the lower flange and in
the upper flange. The advantages of this are analogous to those
indicated above for the diameter of the installation holes of the
upper shell and lower shell.
[0025] The drive unit of the radial fan can be a rotor or a shaft
connection.
[0026] The structural design of the fastening in conjunction with
the lightweight construction of the impeller allows a higher motor
utilization and has positive effects in terms of the service life
of the motor.
[0027] Additional advantages, special features and practical
refinements of the invention can be gleaned from the subordinate
claims and from the presentation below of preferred embodiments
making reference to the drawings.
[0028] The drawings show the following:
[0029] FIG. 1 an exploded view of a radial fan with a section
through the impeller in a first embodiment,
[0030] FIG. 2 a three-dimensional view of the radial fan in the
installed state according to FIG. 1,
[0031] FIG. 3 a section through a radial fan according to another
embodiment,
[0032] FIGS. 4a-f schematic views of the connection of the impeller
to the drive unit according to another embodiment,
[0033] FIGS. 5a-e sectional views through a radial fan according to
another embodiment,
[0034] FIG. 6 two three-dimensional views of drive units according
to other embodiments.
[0035] In the various figures of the drawing, the same parts are
always designated with the same reference numerals and
consequently, as a rule, are only described once.
[0036] As FIGS. 1 and 2 illustrate, a radial fan according to the
invention consists of an impeller 100 and a cylindrical drive unit
200. The impeller 100 is connected to the drive unit 200 by means
of fastening means that will still be explained in greater detail
below. Here, FIG. 1 shows an exploded drawing of the radial fan and
FIG. 2 shows the radial fan in the assembled or installed state.
The radial fan serves to convey a gas or a liquid by means of
blades 101 that are located on the impeller and that are arranged
on a baseplate of the impeller 100. The impeller 100 rotates with
the cylindrical drive unit 200 around a longitudinal axis that runs
through the center in the lengthwise direction of the drive unit
200.
[0037] According to the invention, the baseplate consists of an
upper shell 102 and a lower shell 103, whereby the upper shell 102
faces the main air flow and conveys the gas or liquid with the
blades 101. The gas or the liquid is drawn in parallel or axially
relative to the drive axis of the radial fan, and is then blown out
radially or diagonally by the rotation of the radial impeller. For
the sake of clarity, only the application case involving
transporting air will be mentioned below, whereby the transport of
other gases can always be meant here as well. The main air flow
could thus also be a main flow of any gas. Thus, the term "main air
flow" also includes the main gas flow. The space of the main air
flow is defined by the blades 101 in conjunction with the upper
shell 102 of the baseplate and with the wall (e.g. the rotor 201)
of the drive unit 200, since the main portion of the transported
medium is moved here. The upper shell 102, together with the lower
shell 103, forms a cavity 104 that, in the installed state, is
closed off with the rotor 201. The upper shell 102 and the lower
shell 103 are arranged rotation-symmetrically around the drive unit
200, which can be rotated around the longitudinal axis. The two
shells can be joined by riveted connections, screwed connections,
welded connections, stamped connections, pressed connections, or
adhesive connections. It is also possible to combine the impeller
with a baseplate or cover plate that is not
rotation-symmetrical.
[0038] In order to increase the stability of the baseplate,
reinforcement ribs 105, 106 can be arranged in the cavity 104
between the upper shell 102 and the lower shell 103, and these
reinforcement ribs 105, 106 can further subdivide the cavity 104.
The reinforcement 105 can be configured in the form of at least one
ring that is arranged axially around the longitudinal axis and that
is configured to be either round or polygonal. This ensures a
uniform distribution of the weight on the rotating baseplate. The
reinforcement 106, however, can also run radially relative to the
longitudinal axis, as is shown in FIG. 3. This arrangement of the
reinforcement 106 ensures a flux of force from the drive unit 200
all the way to the blades 101.
[0039] Preferably, the blades 101 have a hollow profile, that is to
say, they are designed to be hollow. This distributes the
introduction of force into the baseplate and the cover plate,
thereby leading to reduced peak stresses and thus reducing the
metal plate thicknesses as well as the weight of the impeller 100.
Moreover, the side of the blades 101 facing the main air flow is
preferably configured to be smooth in order to avoid swirling.
[0040] The cylindrical drive unit 200 can be a rotor 201 of an
asynchronous motor or of a permanent-magnet synchronous motor as is
shown in FIGS. 1 to 6. However, it is also possible for the drive
unit 200 to be a shaft that is driven by a motor.
[0041] Around the rotor 201, there are two ring-shaped flanges 202,
203 that project radially outwards and that have fastening means to
fasten the impeller to the rotor 201 of the drive unit 200. The
flanges 202, 203 are arranged in two planes that are offset axially
relative to the longitudinal axis, whereby the distance between the
flanges is approximately the same as the distance between the upper
shell 102 and the lower shell 103 on the side facing the rotor 201.
Therefore, in the installed state, the upper shell 102 is connected
to the flange 202 that is closest in the main air flow, and the
lower shell 103 is connected to the second flange 203. Thus, the
baseplate of the impeller 100 is connected via two ring-shaped
fastening means to the rotor 201 of the cylindrical drive unit 200,
as is shown in a sectional view in FIG. 3.
[0042] FIG. 3 shows a section through the impeller 100 and through
parts of the rotor 201. The impeller 100 has a largely flat lower
shell 103 as well as a curved upper shell 102, which together form
a cavity 104. According to this embodiment, a reinforcement rib 106
is arranged in the cavity 104 radially relative to the longitudinal
axis of the drive unit 200. Two flanges 202, 203 are arranged on
the rotor 201 of the drive unit 200, whereby the one flange 202 is
connected to the upper shell 102 while the other flange 203 is
connected to the lower shell 103 by fastening means.
[0043] FIGS. 4a-f show various embodiments of upper shells 401a-d
and lower shells 402a-d that can be connected to various flanges
403a-d, 404a-d. The upper shells 401a-d and the lower shells 402a-d
have different diameters and different fastening means. The
individual embodiments will be described below. FIG. 4a shows an
upper shell 401a that has a larger diameter than that of the lower
shell 402a. This means that, during the installation onto the rotor
201, the upper shell 401a is closer to the rotor 201 than the lower
shell 402a is. The flanges 403a, 404a have to be configured in such
a way that, during the installation of the impeller 100 onto the
rotor 201, the lower shell 402a can slide past the flange 403a for
the upper shell 401a axially relative to the longitudinal axis of
the drive unit 200. In the embodiment of FIG. 4a, the impeller is
installed from above, that is to say, axially from the direction of
the main air flow, so that the lower shell 402a can slide past the
flange 403a for the upper shell 401a. Consequently, the flange 403a
for the upper shell 401 projects radially to a lesser extent from
the rotor than the flange 404a for the lower shell 402a does. This
geometric arrangement of the upper and lower shells as well as of
the flanges is also present in the embodiments of FIGS. 4c and 4e.
In the embodiments of FIGS. 4b, 4d and 4f, the geometry of the
shells and flanges is reversed, so that the impeller 100 has to be
installed from below (the side facing away from the main air flow).
The upper shell 401a and the lower shell 402a are provided with
threaded bolts 407, 408 that are accommodated in corresponding
holes 406a, 409a. Thus the holes 406a, 409a and the threaded bolts
407, 408 are fastening means for fastening the impeller 100 onto
the rotor 201. For the sake of clarity, additionally needed nuts or
locknuts are not shown in FIGS. 4a-f. The flange 404a in FIG. 4a
additionally has an installation hole 405a that makes it possible
to access the threaded bolt 408 of the upper shell 401a for
installation purposes. FIG. 4b shows a reversed arrangement, so
that the upper shell 401b can be installed with its threaded bolt
408 in the hole 409b of the upper flange 403b. The lower shell 402b
is installed via the threaded bolt 407 onto the lower flange 404b
via the hole 406b, whereby there is an installation hole 405b in
the upper flange. FIGS. 4c and 4d show two embodiments by way of
example in which the threaded bolts 410, 411 are arranged on the
flanges 403c, 403d, 404c, 404d, which can engage into the holes
409c, 409d of the upper shell 401c, 401d and into the holes 406c,
406d of the lower shell 402c, 402d. No nuts are shown here either.
In FIG. 4c, the upper shell has an installation hole 405c. In FIG.
4d, the installation hole 405d has been made in the lower shell
402d.
[0044] Instead of the permanently attached threaded bolts 407, 408,
it is also possible to use open threaded bolts or threaded rods
412, which are shown accordingly in FIGS. 4e and 4f. In FIG. 4e,
installation holes 405c, 405a are arranged in the upper shell 401c
and in the lower flange 404a. The embodiment according to FIG. 4f
has the corresponding installation holes 405b, 405d in the upper
flange 403b and in the lower shell 402d. For all of the embodiments
of FIGS. 4a-f, it applies that multiple fastening means can be
attached around the rotor 201.
[0045] The embodiments of FIGS. 5a-e show different configurations
of the upper shell 102 in sectional views. Thanks to these
different embodiments, depending on the medium, flow-related losses
can be diminished and the noise emissions can be reduced. FIG. 5a
shows an upper shell 102 that is divided into several sections,
whereby the sections are configured to be concave, convex or
rectilinear or else conical. FIG. 5b shows a curvature of the upper
shell 102 in the direction of the lower shell 103. As shown in FIG.
5c, the upper shell 102 can be curved in the direction of the main
air flow. FIG. 5d shows a rectilinear configuration of the upper
shell 102. FIG. 5e summarizes these different configurations once
more. Due to the shape of the upper shell, which can be altogether
described as pot-like, the efficiency and the sound level that is
created can be improved by 0.5% to 5%. When thin sheet metal
(approximately 0.5 mm to 2 mm) is used, the division of the
baseplate into an upper shell 102 and a lower shell 103 can lead to
a drastic weight reduction by more than 50%. The lower weight of
the impeller according to the invention results in high
eigenfrequencies and high critical rotational speeds. The lower
shell 103 is preferably configured to be flat.
[0046] FIG. 6 shows two embodiments of rotors. The rotor 601 has no
cooling ribs, whereas the rotor 201 has cooling ribs. If the
cooling elements or cooling ribs are situated in the main air flow,
swirling can occur. In contrast, cooling elements are needed in
order to cool the motor. This cooling is particularly important in
the area around which air flows. In the embodiment of the rotor 601
without cooling ribs, FIG. 6 also shows that, on the flanges 602,
603, there can be centering projections 605 or centering holes 606
that cooperate with corresponding centering projections and the
centering holes in the upper shell and in the lower shell, thereby
simplifying the installation of the impeller. Owing to the
centering projections 605 and centering holes 606, the basic
unbalance of the impeller 100 can be improved, thereby resulting in
a reduction in the number of balancing cycles during the production
of the impeller 100. Since a flange 603 projects further radially
outwards, a stiffening step 607 can be attached to this flange 603
in order to increase the stability, so that the flange is cranked.
Moreover, FIG. 6 shows threaded bolts 604 that are configured as
press-in threaded bolts 604. The press-in threaded bolts 604 can
also have additional centering projections, thereby facilitating
the installation. With the press-in threaded bolts 604, one can
also use locknuts instead of simple nuts. This allows a better hold
and centering by means of a socket wrench. In this way, the nuts or
screws can be largely prevented from being tilted or lost.
LIST OF REFERENCE NUMERALS
[0047] 100 impeller [0048] 101 blade [0049] 102, 401a-d upper shell
[0050] 103, 402a-d lower shell [0051] 104 cavity [0052] 105, 106
reinforcement rib [0053] 200 drive unit [0054] 201, 601 rotor
[0055] 202, 403a-d, 602 upper flange [0056] 203, 404a-d, 603 lower
flange [0057] 405a-d installation hole [0058] 406a-b hole in the
lower flange [0059] 406c-d hole in the lower shell [0060] 407
threaded bolt on the lower shell [0061] 408 threaded bolt on the
upper shell [0062] 409a-b hole in the upper flange [0063] 409c-d
hole in the upper shell [0064] 410 threaded bolt on the lower
flange [0065] 411 threaded bolt on the upper flange [0066] 412 open
threaded bolt [0067] 604 press-in threaded bolt [0068] 605
centering projection [0069] 606 centering hole [0070] 607
stiffening step
* * * * *