U.S. patent application number 13/387324 was filed with the patent office on 2012-07-26 for vacuum pump system.
This patent application is currently assigned to Oerlikon Leybold Vacuum GmbH. Invention is credited to Thomas Dreifert, Wolfgang Giebmanns.
Application Number | 20120189478 13/387324 |
Document ID | / |
Family ID | 43448219 |
Filed Date | 2012-07-26 |
United States Patent
Application |
20120189478 |
Kind Code |
A1 |
Dreifert; Thomas ; et
al. |
July 26, 2012 |
VACUUM PUMP SYSTEM
Abstract
A vacuum pump system comprises two vacuum pumps which are
connected to each other. In order to create vacuum pump system of a
more compact size, the connection between the two vacuum pumps is
performed via connection elements directly attached to the pump
housing and forming connection sites, and the outlet flange of the
upper pump is placed directly on the inlet flange of the lower pump
without thereby causing a transmission of larger forces or
moments.
Inventors: |
Dreifert; Thomas; (Kerpen,
DE) ; Giebmanns; Wolfgang; (Erftstadt, DE) |
Assignee: |
Oerlikon Leybold Vacuum
GmbH
|
Family ID: |
43448219 |
Appl. No.: |
13/387324 |
Filed: |
July 30, 2010 |
PCT Filed: |
July 30, 2010 |
PCT NO: |
PCT/EP2010/061140 |
371 Date: |
January 26, 2012 |
Current U.S.
Class: |
418/5 |
Current CPC
Class: |
F04C 2230/604 20130101;
F04C 25/02 20130101; F04C 2240/30 20130101; F04C 28/02 20130101;
F04C 2240/805 20130101; F04C 2240/70 20130101; F04C 23/001
20130101; F01C 21/007 20130101; F04B 37/14 20130101 |
Class at
Publication: |
418/5 |
International
Class: |
F04C 29/00 20060101
F04C029/00; F04C 11/00 20060101 F04C011/00 |
Foreign Application Data
Date |
Code |
Application Number |
Aug 11, 2009 |
DE |
10 2009 037 010.2 |
Claims
1. A vacuum pump system, comprising a first vacuum pump comprising
a pump inlet and a pump outlet, a second vacuum pump comprising a
pump inlet and a pump outlet, the pump outlet and/or the pump inlet
of the second vacuum pump being fluidically connected, with the aid
of flanges, to the pump inlet of the first vacuum pump, wherein a
first and a second pump housing are mechanically connected to each
other on at least three connection sites so as to allow for force
transmission, at least two of said connection sites being
flange-independent.
2. The vacuum pump system according to claim 1, wherein each
connection site comprises two mutually confronting connection
elements.
3. The vacuum pump system according to claim 1, wherein at least
two connection sites are arranged outside of the surfaces of said
flanges.
4. The vacuum pump system according to claim 1, wherein at least
two flange-independent connection sites are configured or arranged
in a manner enabling them, in combination, to transfer 25%, and
preferably at least 40%, of the forces and moments occurring in
operation.
5. The vacuum pump system according to claim 1, wherein at least
three connection sites are flange-independent.
6. The vacuum pump system according to claim 5, wherein the
connection of the pump inlet to the pump outlet is substantially
exclusively a fluidic connection.
7. The vacuum pump system according to claim 6, wherein no
force-locking connection, and particularly no screw connection, is
provided between the pump inlet and the pump outlet.
8. The vacuum pump system to according claim 1, wherein the
connection elements comprise projections extending from a housing
wall.
9. The vacuum pump system according to claim 1, wherein mutually
confronting, mutually connected connection elements of a connection
site comprise two mutually plane-parallel support faces.
10. The vacuum pump system according to claim 9, wherein the
support faces of at least two connection elements of a vacuum pump
are arranged in one plane, preferably in the plane of a
flange-abutment face.
11. The vacuum pump system according to claim 1, wherein the
connection sites comprise holding elements, said holding elements
preferably being integrated into said projections or being provided
separately.
12. The vacuum pump system according to claim 2, wherein the
connection elements of at least one connection site are
displaceable relative to each other.
13. The vacuum pump system according to claim 2, wherein a spacer
element is provided to compensate for level differences between
mutually confronting connection elements, particularly between
their abutment faces.
14. The vacuum pump system according to claim 2, wherein the
connection elements are at least partially arranged in the region
of side walls of the pump housing and/or in the region of support
flanges.
15. The vacuum pump system according to claim 2, wherein an adapter
element arranged between two vacuum pumps connected to each other,
for connection of connection elements which are not confronting
each other, one of said vacuum pumps optionally comprising only one
connection site which is formed as a flange.
16. The vacuum pump system according to claim 15, wherein, for
receiving the weight of an upper vacuum pump, said adapter element
comprises at least two adapter feet.
17. The vacuum pump system according to claim 15, wherein, for
receiving the weight of an upper vacuum pump, said adapter element
comprises at least three, preferably four adapter feet, to the
effect that the inlet flange preferably remains stress-free.
18. The vacuum pump system according to claim 1, comprising more
than two vacuum pumps.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The present disclosure relates to a vacuum pump system
comprising a plurality of vacuum pumps which are connected to each
other.
[0003] 2. Discussion of the Background Art
[0004] Vacuum pump systems of the above type comprise two or more
vacuum pumps, which usually are arranged in series. The medium to
be conveyed, usually gas, will thus be sucked in by a first pump
via the inlet of said pump and will then be conveyed, via the pump
outlet, to the adjacent second vacuum pump. Normally, in a system
comprising two vacuum pumps, the second vacuum pump will perform
the conveying process against the ambient pressure. Optionally, it
is also possible to arrange a plurality of vacuum pumps in series
or also partly parallel to each other, wherein, usually, the last
vacuum pump in the direction of conveyance will carry out the
compression against the ambient pressure. In such an arrangement,
fore vacuum pumps for compression against the ambient pressure are
frequently provided in the form of rotary vane vacuum pumps,
sliding vane vacuum pumps, claw vacuum pumps, multi-stage Roots
vacuum pumps and screw vacuum pumps. In such pump systems, the
first pump in the conveying direction, at whose inlet the lowest
pressure is generated, is frequently provided as a Roots pump.
[0005] Known vacuum pump systems comprise a supporting rack or
frame on which the individual vacuum pumps are arranged. Mounting
the vacuum pumps on said rack can be performed e.g. with the aid of
the feet provided on the pump housing. Then, the inlets and the
outlets of the vacuum pumps will be connected to each other by
rigid or flexible conduits or by special adapters. The weight
forces and gas forces occurring during pump operation will largely
be taken up by said rack. In such pump systems, the rack can be
lifted and moved by use of a forklift, i.e. from below, or by use
of a crane with the aid of crane eyelets. On the one hand, such
vacuum pump systems of the type comprising a rack for support of
the individual pumps have the advantage that, in most cases, the
individual pumps can be exchanged independently from each other. An
essential disadvantage of such systems, however, resides in the
considerable space requirement for the rack. Further, the rack as
well as the required connection elements will incur additional
expenses.
[0006] In another type of known vacuum pump systems, vacuum
pumps--usually two pumps--are directly connected to each other. In
this case, no separate rack is provided. Connection of the two
vacuum pumps is effected by connecting the outlet flange of the
first vacuum pump, directly or via an adapter, to the inlet flange
of the second vacuum pump. In this embodiment, the weight and gas
forces occurring during operation have to be taken up by the
flanges and to be transmitted to the pump housings. Here, it is
normally not possible to provide crane eyelets for transport of the
vacuum pump system because, during transport, the flanges would be
subjected to massive stresses and thus would run a high risk of
damage. Further, connecting two pumps via inlet and outlet flanges
has the disadvantage that the flanges and the adapter,
respectively, must be very solid and be provided with free areas
for screw connections, to make it possible to take up and transmit
the corresponding forces and, first of all, to assemble the
arrangement. This will cause additional costs. Further still, it
often happens that the outlines of the two interconnected vacuum
pumps are not congruent, with one pump thus projecting beyond the
outline of the other one. This will lead to considerable space
requirements.
[0007] It is an object of the disclosure to provide a compact
vacuum pump system which merely has a minimum space
requirement.
SUMMARY
[0008] The vacuum pump system of the disclosure comprises at least
two vacuum pumps. In a first case, a pump outlet of a first vacuum
pump is arranged in fluid connection to the pump inlet of a second
vacuum pump arranged downstream in the flow direction. The
connection is effected by connecting the outlet flange to the inlet
flange. Preferably, said connection is established directly via the
flanges. Alternatively, also an indirect connection is possible via
tube conduits or other intermediate elements. The disclosure
provides that, on both pump housings, at least three connection
sites are mechanically connected to each other for force
transmission and/or moment transmission. According to the
disclosure, at least two of said connection sites are
flange-independent.
[0009] It can also be provided that the pump inlet of the second
vacuum pump is connected to the pump inlet of the first vacuum
pump. In such an embodiment, two identical vacuum pumps, arranged
parallel to each other, are connected to each other in such a
manner that one pump will suck fluid from the suction region of the
other pump so that both pumps will be running under identical
operating conditions, while the free suction flange of the other
pump can be used for mounting thereon a still further vacuum pump,
optionally a vacuum pump of a different type. Instead of using a
direct flange connection, both suction regions of said identical
pumps can also be connected via an external tube conduit.
[0010] Thus, according to a first preferred embodiment, there is
effected--in accordance with the state of the art--a first
mechanical connection via said two interconnected flanges, so that
the connection of the outlet flange to the inlet flange will form a
first connection site for transmitting a part of the occurring
forces and/or moments. Additionally, in accordance with the
disclosure, at least two further connection sites are provided on
the two pump housings. Herein, said two connection sites preferably
comprise respectively one connection element on both pump housings
wherein, according to a preferred embodiment, the two connection
elements of a connection site are arranged confronting each other.
Also on said at least two further connection sites, a transmission
of forces and/or moments will occur. As compared to the direct
connection of two vacuum pumps via said pump flanges, the
additional provision of at least two further connection sites has
the advantage that only a part of the forces and moments has to be
taken up by the flange connection. This in turn offers the
advantage that the flanges themselves are allowed to be less
robust. Particularly, it is possible to arrange the three
connection sites at a largest possible distance from each other so
as to achieve an advantageous transmission of forces and/or
moments. Thus, according to a particularly preferred embodiment, at
least two connection sites are located outside the flange surfaces,
i.e. those surfaces where the two flanges are lying against each
other and where they are optionally connected to each other by
screw connections or the like. Preferably, at least two of said
connection sites are arranged outside the flange surfaces defined
by standards. In large flange systems, it may be sufficient to
provide just one additional connection site for achieving a
sufficient distribution of forces and moments.
[0011] With particular preference, said at least two
flange-independent connection sites are able to take up and
respectively transfer at least 25%, and more preferably 40%, of the
forces and moments occurring during operation. Thereby, the flanges
on the pump inlet and the pump outlet connected thereto can be
given a less massive and thus a correspondingly less expensive
design.
[0012] According to a further preferred embodiment, at least three
flange-independent connection sites are provided. Particularly,
this has the advantage that the fluid connection via the inlet
flange and the outlet flange can be given a more simple
configuration. Particularly, it is made possible to design the
flange connection to the effect that it will substantially serve
only as a fluid connection and that there will be substantially no
force transmission. Such a design is advantageous particularly in
cases where the flange connection is accessible only with
difficulties. In this embodiment, for instance, the flange
connection between the pump outlet and the pump inlet can be
designed in such a manner that only a sealing function is effected
and, if required, there is additionally provided a positioning via
register pins or the like (e.g. housing sealings with centering
rings). This has the advantage that the mechanical connection
between the two vacuum pumps can be provided at more-conveniently
accessible sites.
[0013] Thus, in this embodiment, the pump outlet and the pump inlet
are particularly not connected to each other in a force-locking
manner. Particularly, no screw connections are provided.
[0014] It is especially preferred that the connection elements are
at least partly formed as outward projections of a housing wall of
the corresponding vacuum pump. Advantageously, such projections are
more easily accessible and, particularly, they can also be
processed more easily. Thereby, especially, it is rendered possible
to process the contact faces of the projections in an easy manner
and to give them the most planar shape possible. Preferably, in
this regard, two mutually confronting connection elements comprise,
at a connection site, two mutually plane-parallel contact faces. In
this manner, particularly, it is avoided that tensions might be
introduced into the housings of the individual vacuum pumps as a
result of the assembly process of the vacuum pump system. Further,
in this regard, it is particularly preferable that at least
two--and, more preferably, all--contact faces of a vacuum pump are
arranged in one plane. Preferably, this plane corresponds to a
flange contact face, this being preferred particularly in
embodiments wherein the flange connection also serves for
transmission of forces and moments. When using three or more
connection sites, it may be advantageous to keep the flange faces
of the outlet and inlet flanges at a distance of about 0.1 mm,
provided that the sealing system allows for such a measure, so that
the flange system will not have to take up any connection forces or
moments. It can thus be avoided that a pump housing might be
deformed due to connection forces, with the possible consequence of
reduced running gaps for the pump rotors.
[0015] Preferably, the individual connection sites are additionally
provided with holding elements. The holding elements comprise e.g.
screws, clamping elements or the like for safeguarding a mechanical
connection of the individual vacuum pumps of the vacuum pump
system. The individual holding elements are e.g. integrated into
said projections forming the connection elements. For instance, a
holding site can be configured in such a manner that one of the two
vacuum pumps to be connected to each other comprises a cylindrical
projection, with a foot-shaped projection resting thereon which
relative to the second pump housing extends laterally outward. It
is then possible to use a screw as a holding element, which will be
screwed through the foot-shaped projection of the upper pump into
the cylindrical projection of the lower pump. It is also possible
to provide separate holding elements; in this case, there are
provided e.g. two projections arranged cylindrically confronting
each other and being in abutment with each other while, however,
not being mechanically connected to each other. With the aid of a
claw-like connection, an eyelet connection or the like, the two
housings of the vacuum pump can then be connected to each other,
preferably outside on their sidewalls.
[0016] According to a further preferred embodiment, at least one
connection element of a connection site is configured to allow for
displacement of the two connection elements relative to each other
at this connection site. Preferably, in this case, one of the two
connection elements is of a rail-like type so that the second
connection element of this connection site can be displaced within
the first, rail-like connection element. With particular
preference, two connection sites are configured in this manner,
wherein the two displacement means are parallel to each other. This
has the advantage, for instance, that manufacturing tolerances can
be easily compensated for, and that an occurrence of tensions due
to the assembly process is avoided. Further, this makes it possible
to connect vacuum pumps of different sizes to each other. By the
provision of such rail-like connection elements, also the assembly
and disassembly processes are facilitated, especially under
conditions of narrow space. In case that said rail-like connection
elements are suitably configured, also a compensation of different
thermal expansions of the two pumps is possible.
[0017] Further, it is possible to provide spacer elements between
connection elements for level equalization. Such a provision is
particularly advantageous since it offers the possibility to
connect different pumps to each other, thus making it possible to
compile a modular system. The corresponding spacer elements can be
rigid or elastic.
[0018] According to a particularly preferred embodiment, the
position of the individual connection elements is at least
partially selected to the effect that the connection elements are
arranged in the region of the side walls of the pump housing and/or
in the region of support flanges. Advantageously, this allows for a
good introduction of forces and/or moments into the pump housing.
Thereby, it is safeguarded that the introduced forces and/or
moments will cause only a slightest possible deformation of the
pump housings. This is advantageous particularly because of the
very narrow play between the pump housings and the pump elements
such as e.g. the rotors.
[0019] According to a further preferred embodiment of the
disclosure, or a possible modification of the above described
embodiments, an adapter element is provided between the two vacuum
pumps which are to be connected. This makes it possible, e.g., to
connect very different vacuum pumps to each other. Particularly,
thereby, a vacuum pump which does not comprise separate connection
elements can be connected, via the outlet flange, to a further
vacuum pump comprising a plurality of connection elements. For this
purpose, the adapter element preferably comprises at least two
adapter feet. A connection of the above type is possible
particularly if the flange of the upper pump is sufficiently
dimensioned for taking up forces and/or moments. The lower pump in
turn would be stressed in such a manner that at least two
flange-independent connection sites would take up and respectively
transfer at least 25% and preferably at least 40% of the forces
occurring during operation.
[0020] The above described individual embodiments of the inventive
vacuum pump system with at least two vacuum pumps have the special
advantage that, by corresponding adaptation of the positions of the
inlet and outlet flanges and of the connection sites, a very
compact vacuum pump system can be realized. Particularly, this
vacuum pump system has a short constructional length since it is
possible, for instance, to arrange the smaller one of the two
vacuum pumps within the outline of the larger vacuum pump so that
the smaller pump does not project beyond the larger pump.
Particularly in case of Roots pumps, the position of the outlet
flange can be freely selected in the axial direction, at least
within certain limits. Consequently, there can be performed a
corresponding geometric adaptation and, thus, the position of the
pumps relative to each other can be improved so as to create a
compact vacuum pump system.
[0021] Particularly, the inventive provision of connection elements
on the individual vacuum pumps makes it possible to provide a
modular system including different vacuum pumps, particularly fore
vacuum pumps and high-vacuum pumps. Different pumps of different
performance levels can be combined with each other in a simple
manner, thus making it easily possible to realize vacuum pump
systems with very different performance spectra. Thereby, the
system costs can be kept very low. Further, the various embodiments
of the disclosure have the advantage of allowing for a compact
vacuum pump system which additionally is highly robust. Further,
the assembly process can be significantly simplified. By said
preferred modular system, high flexibility can be achieved, it
being possible to realize a scalable modular system. Further, it is
of course possible to combine more than two pumps with each other
in a vacuum pump system. Further, as a result of the advantageous
force and/or moment transmission, it is rendered possible to
transport the entire vacuum pump system with the aid of a crane or
a floor conveyer system (e.g. a forklift).
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The disclosure will be described hereunder in greater detail
with reference to the accompanying drawings.
[0023] In the drawings, the following is shown:
[0024] FIGS. 1 to 5 plan views of different embodiments of a vacuum
pump of a vacuum pump system;
[0025] FIG. 6 an enlarged sectional view as seen in the direction
of arrow VI in FIG. 5;
[0026] FIG. 7 a schematic plan view of a preferred configuration of
a connection site;
[0027] FIG. 8 a schematic sectional view taken along line VIII in
FIG. 7;
[0028] FIGS. 9 and 10 schematic lateral views of preferred
embodiments of connection sites;
[0029] FIG. 11 a schematic lateral view of an embodiment of a
vacuum pump system;
[0030] FIG. 12 a view of the bottom side of the upper vacuum pump
shown FIG. 11, as seen in the direction of arrow XII in FIG.
11;
[0031] FIG. 13 a schematic sectional view of an embodiment of the
flange connection; and
[0032] FIG. 14 a schematic lateral view of a further embodiment of
a vacuum pump system, provided with an adapter element.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0033] Each of FIGS. 1 to 5 is a strongly schematic plan view of a
vacuum pump such as e.g. a screw-type vacuum pump. Onto the
respective upper side 10 of the respective vacuum pump housing,
there will be mounted the second vacuum pump (not shown in the
Figures) of the vacuum pump system and be connected to the first
vacuum pump 12 (which is shown). In all vacuum pumps 12 depicted in
FIGS. 1 to 5, the upper side 10 is illustrated with an inlet flange
14 surrounding an inlet opening 16. Said inlet flange 14, which in
the illustrated embodiment has a quadrangular cross section, can of
course also be circular. In the illustrated embodiment, inlet
flange 14 is provided with four fastening bores 18. In cooperation
with corresponding fastening bores on the outlet flange of the
second pump placed thereon, which pump is to be connected to the
first pump 12, the two flanges can be mechanically fastened to each
other by screws. Further, the vacuum pumps 12 shown in FIGS. 1 to 5
comprise a lateral outlet 20.
[0034] For creating connection sites, the embodiment shown in FIG.
1 is provided with six cylindrical connection elements 22 extending
upward from said housing side 10. Via these cylindrical, columnar
connection elements 22, a connection to the second, or upper,
vacuum pump can be established by use of various connection
options, as will still be explained with reference to FIGS. 6 to
10. In the embodiment shown in FIG. 1, there are thus provided,
outside said flange 14, six flange-independent connection elements
22 for forming up to six connection sites. The connection of first
pump 12 with the second pump thereabove can thus be mechanically
effected already by said connection sites alone. This has the
advantage that only small forces and/or moments have to be
transmitted via flange 14. Therefore, it will not be necessary to
design the flange 14 in an especially robust or stable manner.
[0035] Particularly in small vacuum pumps, it may be sufficient to
provide only two connection elements 22 (FIG. 2). The connection
with the second vacuum pump arranged thereabove will then be
performed by the two connection elements 22 as well as by flange
14.
[0036] According to a further possible embodiment, three
flange-independent connection sites 22 (FIG. 3) are provided. Thus,
there exists a three-point connection via three connection elements
22. In this embodiment, flange 14 does not need to be capable of
taking up forces and/or moments.
[0037] In the embodiments illustrated in FIGS. 1 to 3, the
individual cylindrical connection sites 22 comprise threaded bores
24 for receiving fastening screws. Also in these embodiments, a
different connection of the two pumps can be provided, as described
hereunder with reference to FIGS. 7 to 10.
[0038] One such alternative connection is schematically shown in
FIG. 4. In this embodiment, the connection is not performed via the
connection elements 22. Here, the connection sites 22 are of a
cylindrical shape and comprise a planar surface 26 for placing
thereon cylindrical foot-shaped elements of the vacuum pump
arranged thereabove, said elements e.g. corresponding to the
connection elements 22. Thus, in this embodiment, the connection
elements 22 serve only for support but not for establishing a
mechanically fixed connection. The mechanical connection is
performed via separate holding elements 28. In the illustrated
embodiment, there is provided, for each connection element 22, one
respective holding element 28 arranged on an outer wall 30 of the
pump housing. These holding elements are designed as projections
with U-shaped recesses, thus allowing for attachment to a
corresponding holding element located on the second vacuum pump by
use of a threaded bar or the like (in this regard, cf. FIG. 9 to be
discussed later on).
[0039] According to a further preferred embodiment (FIG. 5),
rail-like connection elements 32 are provided instead of said
cylindrical connection elements 22. The connection elements 32
comprise a rail 33 having a rectangular cross section and being
fixedly connected to the housing of the lower pump 12. On said rail
33, a carriage 37 fixedly connected to the housing of the upper
pump, is guided for displacement in the longitudinal direction 39
of the pump housing. For adjustment, there can further be provided
a lateral guidance 33a. Thereby, the upper pump can be easily
adjusted relative to the lower pump. Particularly, in this manner,
it is safeguarded that no tension can be introduced into flange 14
due to the assembly process. For mechanical connection of the two
pumps, also this embodiment is provided with holding elements 28 on
the lateral walls 30 of the lower pump as well as on the upper pump
(said upper pump being not shown).
[0040] The connection between two or more pumps of a vacuum pump
system can be provided in the manner explained hereunder with
reference to FIGS. 7 to 10.
[0041] In a first embodiment of a connection site 34 (FIGS. 7, 8),
the upper side 10 of lower pump 12 is provided with the cylindrical
connection element 22. A housing 36 of an upper pump comprises a
lateral eyelet-like projection 38. This projection is supported by
its underside on the plane upper side 26 of connection element 22.
Further, said connection element 38 of said upper pump housing 36
is formed with a bore 40 which is in alignment with the threaded
bore 24 of lower connection element 22. Thus, the fixation can be
performed by a screw 42 (FIG. 8), not shown in FIG. 7.
[0042] Further, it is possible to realize a connection site 34 by
connecting two lug-like connection elements 38 (FIG. 9) to each
other. In the embodiment shown in FIG. 9, the two lug-like
connection elements 38 are not in immediate abutment with each
other but are provided with an intermediate spacer element 44. Said
element 44 can be rigid or elastic. Depending on the configuration
of the connection elements, it can also be omitted.
[0043] The two lug-like connection elements 38, preferably arranged
on an outer wall of the pump housing, can also serve as holding
elements. These holding elements will thus effect a substantially
mechanical connection of the two pumps, as described above in the
context of said holding elements 28 (FIGS. 4 and 5). Additionally,
connection elements are provided, on which the two pumps are in
abutment above each other, however without a mechanical connection.
These connection elements can be designed e.g. as already described
with reference to FIGS. 4 and 5.
[0044] Further, a connection site 34 can also be designed in the
manner illustrated in FIG. 10. Optionally, herein, a spacer element
44 is arranged between a lug-like connection element 38 and a
cylindrical connection element 22, said elements 38 and 22 being
again fastened to each other by a screw 42.
[0045] FIG. 11 is a lateral view of an embodiment of a pump system
according to the disclosure. In this pump system, the lower, first
pump 12 is provided e.g. in the form of a screw-type vacuum pump.
The second, or upper, pump 35 is provided in the form of a Roots
vacuum pump. The connection of the two pumps 12,35 is provided in
such mutual adjustment that the vacuum pump system will be of the
most compact design possible. Particularly, when seen in lateral
view, the upper pump 35 does not laterally project beyond the lower
pump 12. As depicted on the right-hand side in FIG. 11, the
connection of the two pumps 12,35 is performed via two connection
sites 34 arranged behind each other. These connection sites 34 are
designed as illustrated in FIGS. 9 and 10, with a spacer element 44
being provided for height adjustment. Provided on the left side in
FIG. 11 are two further connection sites 34, again arranged behind
each other, wherein these connection sites are designed as shown in
FIGS. 7 and 8. Here, no spacer element is provided.
[0046] Thus, in a bottom view of said Roots vacuum pump 35 (FIG.
12), the four connection elements 38 of the four connection sites
34 are visible. Further shown in this view is an outlet flange 46
connected to the inlet flange 14 of lower pump 12. The connection
can be performed via screws in corresponding bores 18 provided for
this purpose. Since, however, it is not absolutely required to
bring about a transmission of forces and/or moments via said
flanges 46,14, it is also possible to provide a purely fluidic
connection with corresponding sealing elements. This has the
advantage that, on the flanges 14,46 which possibly are accessible
only with difficulties, no attachment needs to be performed by
screws.
[0047] A flange connection between two flanges 14,46 is illustrated
by way of example in FIG. 13. In such a flange connection,
substantially no transmission of forces and/or moments takes place
between the two flanges 14,46. The present connection is a purely
fluidic connection between the two flanges 14,46. For this purpose,
flange 14 is provided with an annular groove 48 surrounding the
inlet 16 of lower pump 12. On said annular groove 48, a sealing
element 52 is arranged, generating a sealing effect against the
upper flange 46. The two housings will be connected to each other
by screws 42 on connection sites 34 and will be aligned with each
other. Thus alignment can also be performed via register pins.
[0048] According to a further embodiment of a pump system, an upper
or second pump 56 (FIG. 14) is fastened to the lower pump 12
exclusively via its outlet flange 46. In order to realize a good
reception of the occurring forces and/or moments, outlet flange 46
is not connected directly to inlet flange 14. Instead, an adapter
element 58 is provided. Said adapter element is configured to
realize a mechanic and fluidic connection between the two flanges
46,14 and, further, it comprises two adapter feet 60. Thus, when
seen in plan view, the adapter element 58 of the illustrated
embodiment is substantially Y-shaped so that the adapter feet 60
are arranged behind each other. The two adapter feet 60 are
connected to connection elements 22 of lower pump 12 wherein,
according to the disclosure, this connection can be provided in the
manner described in the various examples herein.
[0049] In order to mount the upper vacuum pump, which possibly has
a heavy weight, to the pump housing of the lower pump, and to do so
preferably without transmission of forces and moments, it is
particularly advantageous to design said adapter element 58 in such
a manner that it can be fixed in an X-shaped configuration over the
four connection sites 22 and that the inlet flange 14 of lower pump
12 will remain nearly unstressed.
[0050] Of course, pump systems of the disclosure may comprise not
only two pumps but also more than two pumps.
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