U.S. patent application number 16/507972 was filed with the patent office on 2020-01-23 for vacuum pumping system having an oil-lubricated vacuum pump.
The applicant listed for this patent is Agilent Technologies, Inc.. Invention is credited to Andrea Bertallot, Roberto Carboneri, Giovanni Iannucci, Andrea Lepore.
Application Number | 20200025203 16/507972 |
Document ID | / |
Family ID | 63012958 |
Filed Date | 2020-01-23 |
United States Patent
Application |
20200025203 |
Kind Code |
A1 |
Carboneri; Roberto ; et
al. |
January 23, 2020 |
VACUUM PUMPING SYSTEM HAVING AN OIL-LUBRICATED VACUUM PUMP
Abstract
A vacuum pumping system includes an oil-lubricated vacuum pump,
including a stationary pump stator and a rotatable pump rotor, and
a motor, including a stationary motor stator and a rotatable motor
rotor cooperating with each other for driving in rotation the pump
rotor. The motor further includes an oil-tight unit including a
metal jacket enclosing the motor rotor and forming a container
intended to collect and keep inside the motor any oil leaking from
the pump.
Inventors: |
Carboneri; Roberto; (Torino,
IT) ; Lepore; Andrea; (Cassino, IT) ;
Bertallot; Andrea; (Cavour, IT) ; Iannucci;
Giovanni; (Caserta, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Agilent Technologies, Inc. |
Santa Clara |
CA |
US |
|
|
Family ID: |
63012958 |
Appl. No.: |
16/507972 |
Filed: |
July 10, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
F04C 25/02 20130101;
H02K 5/18 20130101; H02K 9/19 20130101; H02K 5/128 20130101; F04C
29/0085 20130101; F04C 18/344 20130101; F04C 23/008 20130101; H02K
7/14 20130101; F04C 2240/40 20130101; F04C 29/02 20130101 |
International
Class: |
F04C 29/02 20060101
F04C029/02; F04C 25/02 20060101 F04C025/02 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 19, 2018 |
EP |
18184580.1 |
Claims
1. A vacuum pumping system, comprising: a vacuum pump, comprising a
pump casing defining a stationary pump stator and housing a
rotatable pump rotor, said pump stator and said pump rotor
cooperating with each other for pumping a fluid from a pump inlet
to a pump outlet; and a motor, comprising a motor casing in which a
stationary motor stator and a rotatable motor rotor are received,
said motor stator and said motor rotor cooperating with each other
for driving in rotation said pump rotor by means of a drive shaft,
wherein: said vacuum pump is an oil-lubricated vacuum pump; and the
vacuum pumping system further comprises an oil-tight unit arranged
to enclose at least a portion of the motor rotor and forming at
least part of a container configured to collect and keep inside the
motor any oil leaking from the pump.
2. The vacuum pumping system sample according to claim 1, wherein
said unit comprises at least a portion clamped between the motor
casing and the pump casing.
3. The vacuum pumping system according to claim 2, wherein said
unit comprises a substantially cylindrical jacket enclosing the
whole of the motor rotor and forming said container, and wherein
said jacket: comprises a side wall located in an air gap separating
the motor rotor from the motor stator; is open at a first end,
where it is clamped between the motor casing and the pump casing;
and is closed, at a second end opposite the first end, by a base
accommodated at least partly inside the motor casing.
4. The vacuum pumping system according to claim 3, wherein the open
end of said jacket has a rim that projects radially outwards and
forms the portion clamped between the motor casing and the pump
casing, and wherein a static seal is provided between a surface of
said rim facing the pump casing and a confronting surface of the
pump casing.
5. The vacuum pumping system according to claim 3, wherein said
jacket is made of sheet metal.
6. The vacuum pumping system according to claim 3, wherein said
jacket is provided, at both the first and second end, with bases
having a larger diameter than the side wall and protruding radially
outwards from the side wall, and wherein, in the base provided at
the first, open end of the jacket, the surface turned towards the
pump casing is configured so as to engage in oil-tight manner a
complementarily shaped axial recess formed in the pump casing.
7. The vacuum pumping system according to claim 6, wherein, in the
radially protruding portions of said bases, the surfaces turned
towards each other are shaped so as to define annular
circumferential axial recesses accommodating opposite axial ends of
the motor stator, and wherein each of said circumferential axial
recesses is radially delimited towards the outside of the motor by
an axially projecting edge located between the motor stator and the
motor casing and, towards the inside of the motor, by a thickened
end portion of the side wall.
8. The vacuum pumping system according to claim 6, wherein the base
provided at the second end of the jacket is wholly received inside
the motor casing.
9. The vacuum pumping system according to claim 6, wherein the
surface of the base provided at the second end of the jacket turned
away from the motor has a conical profile at least partially
projecting outside the motor casing, and wherein said surface
projecting outside the motor casing is provided with cooling
fins.
10. The vacuum pumping system according to claim 6, wherein said
jacket is made of an oil-resistant, electrically insulating
thermosetting or thermoplastic resin.
11. The vacuum pumping system according to claim 2, wherein said
unit comprises a first disc-shaped component and a second
disc-shaped component accommodating opposite axial end portions of
both the motor stator and the motor rotor and forming, together
with the motor stator, the container, the first disc-shaped
component forming the portion of the unit clamped between the motor
casing and the pump casing, and engaging in oil-tight manner a
complementarily shaped axial recess formed in the pump casing.
12. The vacuum pumping system according to claim 11, wherein the
first disc-shaped component and the second disc-shaped component
have, on their faces turned towards each other, respective
circumferential axial recesses accommodating opposite axial ends of
the motor stator, and wherein said circumferential axial recesses
are radially delimited towards the outside of the motor by a
respective first annular axial projection located between the motor
stator and the motor casing, and are radially delimited, towards
the inside of the motor, by a respective second annular axial
projection located between the motor stator and the motor
rotor.
13. The vacuum pumping system according to claim 11, wherein the
second disc-shaped component is wholly received inside the motor
casing.
14. The vacuum pumping system according to claim 11, wherein the
surface of the second disc-shaped component turned away from the
motor has a conical profile at least partially projecting outside
the motor casing, and wherein the surface of the second disc-shaped
component projecting outside the motor casing is provided with
cooling fins.
15. The vacuum pumping system according to claim 11, wherein said
first and second disc-shaped components are made of an
oil-resistant, electrically insulating thermosetting or
thermoplastic resin.
Description
RELATED APPLICATIONS
[0001] This application claims priority to European Patent
Application No. EP 18184580.1, filed Jul. 19, 2018, titled "VACUUM
PUMPING SYSTEM HAVING AN OIL-LUBRICATED VACUUM PUMP," the content
of which is incorporated by reference herein in its entirety.
TECHNICAL FIELD
[0002] The present invention relates to vacuum pumping systems and,
more particularly, it concerns a vacuum pumping system having an
oil-lubricated vacuum pump.
BACKGROUND
[0003] Vacuum pumps are used to achieve vacuum conditions, i.e. for
evacuating a chamber (so-called "vacuum chamber") and establishing
sub-atmospheric pressure conditions in said chamber. Many different
kinds of vacuum pumps, having different structures and operating
principles, are known and each time a specific vacuum pump is to be
selected according to the needs of a specific application, namely
according to the degree of vacuum that is to be attained in the
corresponding vacuum chamber.
[0004] In general, a vacuum pump comprises a pump casing, in which
one or more pump inlets and one or more pump outlets are provided,
and pumping elements, arranged in said pump casing and configured
for pumping a gas from said pump inlet(s) to said pump outlet(s):
by connecting the pump inlet(s) to the vacuum chamber, the vacuum
pump allows the gas in the vacuum chamber to be evacuated, thus
creating vacuum conditions in said chamber.
[0005] More specifically, in a kind of vacuum pumps, the pumping
elements comprise a stator defining a pumping chamber and a rotor
rotatable in said pumping chamber, and the stator and the rotor
cooperate with each other for pumping the gas from the pump
inlet(s) to the pump outlet(s). In such vacuum pumps, the rotor is
generally mounted to a rotating shaft which is driven by a motor,
namely by an electric motor.
[0006] Even more specifically, vacuum pumping systems are known in
which the vacuum pump is connected to an oil tank, whereby oil can
be transferred from the oil tank to the vacuum pump, and in
particular to the pumping chamber, for acting as coolant and
lubricating fluid and for sealing the chamber. Among such systems,
those using rotary vane vacuum pumps can be mentioned, and the
following description will refer to a system of that kind.
[0007] A conventional vacuum pumping system using a rotary vane
vacuum pump is shown in FIG. 1 and is generally denoted 10.
[0008] Pumping system 10 essentially comprises a rotary vane vacuum
pump 20 and an electric motor 30 for driving pump 20.
[0009] Pump 20 comprises a pump casing 21 in which one or more pump
inlets and one or more pump outlets (not shown in the Figure) are
defined. Pump casing 21, which is refined so as to act also as pump
stator, internally defines a pumping chamber in which a pump rotor
23 eccentrically rotates. Rotor 23 is fastened to or integral with
a pump shaft 24 driven in rotation by motor 30 and is provided with
one or more radially slidable vanes 25 (only one being visible in
the drawing) that, during rotation of the rotor 23, move in contact
with the inner walls of the pumping chamber. As known, in such kind
of pump, oil is introduced into the pumping chamber for lubricating
and cooling the pump and separating the regions at different
pressures.
[0010] Motor 30 in turn comprises a casing 31, fastened to pump
casing 21 and enclosing a motor stator 32 and a motor rotor 33.
Motor stator 32 and motor rotor 33 cooperate with each other so as
to drive pump rotor 23 into rotation by means of a drive shaft 34,
associated with motor rotor 33. Drive shaft 34 can be coupled to
pump shaft 24 or it can be made as an integral unit with pump shaft
24 and pump rotor 23, as shown in the Figure. End walls 35, 36
close a chamber housing motor rotor 33 and rotatably support, in
association with suitable rolling bearings, the end portions of
shaft 34.
[0011] To prevent oil and possibly toxic gases present in the
pumping chamber from passing to motor 30 and escaping in the
environment through the motor casing 31, a dynamic seal 40,
typically a lip seal, is provided around shaft 34 between motor
casing 31 and pump casing 21. The dynamic seal 40 is also to
prevent dust inlet into the pumping chamber.
[0012] U.S. Pat. No. 6,644,942 discloses a pumping system in which
the motor rotor and stator are accommodated in a resin jacket
preventing lubricant present in a chamber adjacent to the motor
module from leaking into the motor module itself. Yet, the prior
art is concerned with a dry vacuum pump, in particular a dual-rotor
pump with two parallel rotors coupled via a gear assembly located
in a casing containing oil, and the chamber containing oil is not
the pumping chamber, but is the casing housing the gear assembly.
This pumping system still needs the provision of a lip seal around
the shaft, at the wall separating the two chambers to be
isolated.
[0013] Dynamic seals are rather expensive. Moreover, in the case of
vacuum pumping systems comprising a rotary vane vacuum pump, these
dynamic seals are the main cause of oil leaks during operation of
the pump.
SUMMARY
[0014] To address the foregoing needs, in whole or in part, and/or
other needs that may have been observed by persons skilled in the
art, the present disclosure provides methods, processes, systems,
apparatus, instruments, and/or devices, as described by way of
example in implementations set forth below.
[0015] It is an object of the invention to provide a pumping system
using an oil-lubricated vacuum pump, which has a more effective
sealing system for preventing oil leaks from the pumping
chamber.
[0016] It is another object of the invention to provide a pumping
system using an oil-lubricated vacuum pump, which does not require
dynamic seals between the vacuum pump and the motor, and thus can
be made in a more cost-effective manner than the prior art
systems.
[0017] These objects may be attained by a pumping system as
disclosed herein.
[0018] More particularly, the invention provides a vacuum pumping
system comprising an oil-lubricated vacuum pump and an electric
motor driving the pump, in which the system further comprises an
oil-tight unit arranged to enclose at least a portion of the motor
rotor and forming at least part of a container intended to collect
and keep inside the motor any oil leaking from the pump.
[0019] Advantageously, the oil-tight unit has at least a portion
clamped between a motor casing and a pump casing.
[0020] In a first embodiment of the invention, said unit comprises
a substantially cylindrical jacket made of sheet metal, enclosing
the whole of the rotor and forming said container.
[0021] According to a preferred feature of the first embodiment of
the invention, the jacket has a side wall located in an air gap
separating the motor rotor from the motor stator, is open at a
first end, where it is clamped between the motor casing and the
pump casing, and is closed, at a second end opposite the first end,
by a bottom wall accommodated inside the motor casing.
[0022] According to another preferred feature of this embodiment,
the open end of said jacket has a rim that projects radially
outwards and forms the jacket portion clamped between the motor
casing and the pump casing. In this case, a static seal is provided
between a surface of said rim facing the pump casing and the
confronting surface of the pump casing.
[0023] In a second embodiment of the invention, said unit still
comprises a substantially cylindrical jacket forming said
container. Like in the first embodiment, the jacket encloses the
whole of the rotor, has a side wall located in an air gap
separating the motor rotor from the motor stator, and is open at a
first end, where it is clamped between the motor casing and the
pump casing. In this second embodiment the jacket is made of a
non-metallic material, preferably an oil-resistant, electrically
insulating thermosetting or thermoplastic resin, and the side wall
is a very thin layer of the resin.
[0024] According to a preferred feature of the second embodiment of
the invention, the jacket is provided, at both ends, with bases
having a larger diameter than the side wall and protruding radially
outwards from the side wall, and the base provided at the open end
engages in oil-tight manner a complementarily shaped axial recess
formed in the pump casing.
[0025] According to another preferred feature of this embodiment,
in the radially protruding portions of said bases, the surfaces
turned towards each other are shaped so as to define annular
circumferential axial recesses accommodating opposite axial ends of
the motor stator.
[0026] Advantageously, the circumferential axial recesses are
radially delimited towards the outside of the motor by a respective
annular axial projection located between the motor stator and the
motor casing and, towards the inside of the motor, by a thickened
end portion of the side wall of the jacket.
[0027] Thanks to the use of a jacket made of resin and having a
very thin side wall, there is no need of increasing the air gap
between the stator and the rotor of the motor in order to
accommodate a metal jacket like that used in the first embodiment
and to take into account its thermal expansion.
[0028] In a third embodiment of the invention, said unit comprises
first and second disc-shaped components accommodating opposite
axial end portions of both the motor rotor and the motor stator and
forming, together with the motor stator, the container intended to
collect and keep inside the motor any oil leaking from the pump.
The first component forms the portion of the unit clamped between
the motor casing and the pump casing and engages in oil-tight
manner a complementarily shaped axial recess formed in the pump
casing.
[0029] The two components are made of a non-metallic material,
preferably an oil-resistant, electrically insulating thermosetting
or thermoplastic resin.
[0030] According to a preferred feature of this second embodiment,
both the first and the second component have, on their face turned
towards the other component, a circumferential axial recess
accommodating a respective axial end of the motor stator.
[0031] Advantageously, the circumferential axial recesses are
radially delimited towards the outside of the motor by a respective
first annular axial projection located between the motor stator and
the motor casing and, towards the inside of the motor, by a
respective second annular axial projection located between the
motor stator and the motor rotor.
[0032] Having a "container" that is located between the motor
stator and the motor casing solves the problems of noise and
vibrations that can affect, during operation, a pumping system
having a metal jacket located in the air gap between the motor
stator and the rotor. Moreover, there is no need to increase the
radial size of the air gap in order to allow the insertion of the
jacket and to take into account the thermal expansion thereof.
[0033] In the second and third embodiments, the base of the jacket
opposite the open end and the second disc-shaped component,
respectively, can be wholly accommodated inside the motor casing.
In the alternative, their surfaces turned away from the motor can
have a conical profile at least partially projecting outside the
motor casing. Such conical surface can then be provided with
cooling fins.
[0034] The embodiments in which the jacket base or the second
component partly come out from the motor casing allow a better
thermal dissipation than the embodiments in which said elements are
wholly accommodated inside the motor casing, since the jacket base
or the second component can directly receive the air flow created
by an external cooling system of the pumping system. Moreover, the
provision of the cooling fins allows increasing the cooling surface
and having a more effective circulation of the external flow of
cooling air.
[0035] Other devices, apparatus, systems, methods, features and
advantages of the invention will be or will become apparent to one
with skill in the art upon examination of the following figures and
detailed description. It is intended that all such additional
systems, methods, features and advantages be included within this
description, be within the scope of the invention, and be protected
by the accompanying claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] The invention can be better understood by referring to the
following figures. The components in the figures are not
necessarily to scale, emphasis instead being placed upon
illustrating the principles of the invention. In the figures, like
reference numerals designate corresponding parts throughout the
different views.
[0037] FIG. 1 is a longitudinal sectional view of part of a pumping
system of the prior art.
[0038] FIG. 2 is a longitudinal sectional view, similar to FIG. 1,
of part of a pumping system according to a first embodiment of the
invention.
[0039] FIG. 3 is a longitudinal sectional view of a pumping system
according to a second embodiment of the invention.
[0040] FIG. 4 is a longitudinal sectional view, similar to FIG. 2,
of part of a pumping system according to a variant of the
embodiment shown in FIG. 3.
[0041] FIG. 5 is a longitudinal sectional view, similar to FIG. 3,
of a pumping system according to a third embodiment of the
invention.
[0042] FIG. 6 is a longitudinal sectional view, similar to FIG. 4,
of part of a pumping system according to a variant of the
embodiment shown in FIG. 5.
[0043] In FIGS. 2 to 6, the same reference numerals as in FIG. 1
have been used to denote the parts of the pump and the motor.
DETAILED DESCRIPTION
[0044] FIG. 2 shows a first embodiment of a pumping system 100
according to the invention. In order to provide a more efficient
sealing of motor 30 against oil leakage from the pumping chamber, a
sheet-metal jacket 50 is provided which encloses motor rotor 32 and
is clamped at one end between motor casing 31 and pump casing
21.
[0045] Jacket 50 is a substantially glass-shaped element, i.e. a
substantially cylindrical element open at one end (the end clamped
between motor casing 31 and pump casing 21), and has a side wall 51
located in the air gap between stator 32 and rotor 33 of motor 30.
The open end surrounds the corresponding end wall 35 of the rotor
chamber, and bottom wall (or base) 52 opposite the open end is
arranged internally of motor casing 31. The open end of jacket 50
has a rim 53 projecting radially outwards, and such rim 53 is the
portion of jacket 50 clamped between motor casing 31 and pump
casing 21. In order to ensure oil tightness between pump 20 and
motor 30, a sealing gasket 54, in particular an O-ring, is provided
between rim 53 and the confronting surface of pump casing 21.
[0046] The provision of jacket 50 and O-ring 54 results in any oil
leaking from the pump environment being collected within jacket 50.
As it can be readily appreciated by the skilled in the art, a
static seal like O-ring 54 is much less prone to failures than
dynamic seal 40 of the prior art. The provision of a jacket 50
collecting any possible oil leak moreover prevents escape of oil
(or any other unwanted substance, like gases etc. developed or
present for some reason in the pump 20) and dispersion thereof in
the environment.
[0047] The provision of sheet-metal jacket 50 and the associated
O-ring 54 overcomes the problems connected with using a lip seal,
but it is open to improvements as far as some aspects are
concerned, in particular:
[0048] since metal jacket 50 is located between stator 32 and rotor
33 of motor 30, it can originate noise and vibrations during
operation of pumping system 100;
[0049] an increase of the radial size of the air gap may be
required, to allow insertion of jacket 50 itself and to take into
account the thermal expansion thereof, thus entailing an increase
of the radial size of the whole pumping system 100.
[0050] Such improvements are achieved by system 200 shown in FIGS.
3 and 4.
[0051] More specifically, in the embodiment of FIG. 3, a pair of
disc-shaped components 60, 70 are provided, which are made of a
non-metallic material, in particular a leak-proof, oil-resistant
and electrically insulating thermoplastic or thermosetting resin,
and are configured so as to accommodate opposite axial ends of
motor stator 32 and motor rotor 33. With such an arrangement,
components 60, 70 form, together with motor stator 32, a sort of
"container" collecting any oil leaking from pump 20 and keeping
such oil within motor 30.
[0052] Component 60 is clamped between pump casing 21 and motor
casing 31 and fits in oil-tight manner in a complementarily shaped
recess 26 provided in the confronting surface of pump casing 21. A
central opening 65 in component 60 accommodates end wall 35 of the
rotor chamber. On its surface turned towards component 70,
component 60 has two substantially parallel annular axial
projections 61, 62 defining an annular axial recess 63 intended to
receive one end of stator 32. Outer annular projection 61 is
clamped between motor stator 32 and motor casing 31, and inner
annular projection 62 is clamped between motor stator 32 on the one
side and motor rotor 33 and end wall 35 on the other side.
[0053] Component 70 has a central hollow 75 (or possibly a central
opening, like component 60) accommodating end wall 36 of the rotor
chamber. On its surface turned towards component 60, component 70
has two substantially parallel annular axial projections 71, 72
defining an axial annular recess 73 intended to receive the other
end of stator 31. Similarly to projections 61, 62, outer annular
projection 71 is clamped between motor stator 32 and motor casing
31, and inner annular projection 72 is clamped between motor stator
32 on the one side and motor rotor 33 and end wall 36 on the other
side. Reference 74 denotes the outer surface (i.e. the surface
turned away from the motor) or base of component 70, which, in the
embodiment shown in FIG. 3, is flat so that component 70 is wholly
housed within motor casing 31.
[0054] The Figure also shows gas inlet and outlet 27, 28, as well
as some details of the external body of pumping system 200.
[0055] The shape of components 60 and 70 and the engagement of
component 60 within recess 26 in pump casing 21 ensure oil
tightness without the need to use a sealing gasket like O-ring 54.
Moreover, the components are clamped between stator 32 and casing
31 of motor 30, thus no problems of vibrations and noise arise
because of the rotation of rotor 33. At the same time, there is no
need to increase the air gap between stator 32 and rotor 33 of
motor 30, as required in the embodiment shown in FIG. 2 in order to
accommodate metal jacket 50 and to take into account its thermal
expansion. A proper choice of the resin also allows improving the
thermal dissipation characteristics not only over the prior art,
but also over the solution with metal jacket shown in FIG. 2.
[0056] A further improvement is obtained by the configuration of
system 200 shown in FIG. 4. Like in the embodiment of FIG. 3, a
pair of disc-shaped components 80, 90 are provided, which are made
of a non-metallic material, in particular a leak-proof,
oil-resistant and electrically insulating thermoplastic or
thermosetting resin, and are configured so as to accommodate
opposite axial ends of motor stator 32 and motor rotor 33. Thus,
also components 80, 90 form, together with motor stator 32, a sort
of container collecting any oil leaking from pump 20 and keeping
such oil within motor 30.
[0057] The first disc-shaped component 80 is identical to component
60 shown in FIG. 3 and its elements are denoted by reference
numerals corresponding to those used in FIG. 3, yet beginning with
digit 8 instead of with digit 6. The second disc-shaped component
90 differs from component 70 shown in FIG. 3 only in respect of the
configuration of its base 94, which, instead of being flat like
base 74 of component 70, has a surface with conical profile (more
particularly, shaped as a frustum of a cone) on its side turned
away from motor 30, such that base 94 projects outside motor casing
31. Cooling fins 96 are formed on the portion of base 94 located
outside casing 31. The remaining elements of component 90 are
identical to those of component 70 and they are denoted by
reference numerals corresponding to those used in FIG. 3, yet
beginning with digit 9 instead of with digit 7.
[0058] Component 90 having a base 94 partly coming out from motor
casing 31 allows a better thermal dissipation than component 70
wholly accommodated inside motor casing 31, since base 94 can
directly receive the air flow created by the external cooling
system (not shown) of pumping system 200. The provision of cooling
fins 96 in the portion of base 94 projecting outside motor casing
31 allows increasing the cooling surface and having a more
effective circulation of the external cooling air flow.
[0059] FIGS. 5 and 6 show a pumping system 300 according to a third
embodiment of the invention. In FIGS. 5 and 6, elements
corresponding or functionally equivalent to elements depicted in
FIGS. 3 and 4, respectively, are denoted by the same reference
numerals preceded by digit 1.
[0060] More specifically, in the embodiment of FIG. 5, the
container intended to collect and keep inside motor 30 any oil
leaking from pump 20 includes a glass-shaped jacket 150, configured
so as to accommodate both rotor 33 and the axial ends of stator 32
of motor 30 and made, like the components of system 200, of a
non-metallic material, in particular a leak-proof, oil-resistant
and electrically insulating thermoplastic or thermosetting
resin.
[0061] Jacket 150 has a side wall 151 consisting of a thin resin
layer located in the air gap between stator 31 and rotor 32 of
motor 30, and two bases 160, 170, having a larger diameter than
side wall 151, so that said bases 160, 170 protrude radially
outwards from side wall 151. Base 160 at the open end of jacket 150
has a central opening 165 accommodating the corresponding closing
wall 35 of the rotor chamber, is clamped between pump casing 21 and
motor casing 31 and its surface turned towards pump casing 21 is
configured so as to fit in oil-tight manner in a complementarily
shaped recess 26 provided in the confronting surface of pump casing
21. The other base 170 has a central hollow 175 (or possibly a
central opening, like base 160) accommodating end wall 36 of the
rotor chamber.
[0062] In the radially protruding portions of bases 160, 170, the
surfaces turned towards each other are shaped so as to define
annular axial recesses 163, 173, respectively, intended to
accommodate the opposite axial ends of motor stator 32. More
particularly, recess 163 is defined between an edge 161 of base
160, axially projecting towards base 170 and clamped between motor
stator 32 and motor casing 31, and a thickened end portion 162 of
side wall 161. Similarly, recess 173 is defined between an edge 171
of base 170, axially projecting towards base 160 and clamped
between motor stator 32 and motor casing 31, and a thickened end
portion 172 of side wall 151. Reference 174 denotes the outer
surface (i.e. the surface turned away from the motor) of base 170.
In the embodiment shown in FIG. 5, said surface 174 is flat and
base 170 is wholly housed within motor casing 31.
[0063] The shape of jacket 150, with base 160 engaging recess 26 in
pump casing 21, ensures oil tightness without the need to use a
sealing gasket like O-ring 54. Moreover, since jacket 150 is made
of resin and its side wall 151 is very thin, there is no need of
increasing the air gap between stator 31 and rotor 32 of motor 30
to accommodate a metal jacket like jacket 50 (FIG. 2) and to take
into account its thermal expansion. Moreover, no problems of
vibrations and noise exist. At the same time, like in the
embodiment of FIGS. 3 and 4, a proper choice of the resin also
allows improving the thermal dissipation characteristics not only
over the prior art but also over the solution with metal jacket
shown in FIG. 2.
[0064] Referring now to FIG. 6, the container intended to collect
and keep inside motor 30 any oil leaking from pump 20 includes a
glass-shaped jacket 250, similar to jacket 150 and intended to
provide, over jacket 150 shown in FIG. 5, the same improvement as
provided by the use of component 90 in pumping system 200 shown in
FIG. 4.
[0065] Like jacket 150, jacket 250 has a side wall 251 consisting
of a thin resin layer located in the air gap between stator 31 and
rotor 32 of motor 30, and two bases 180, 190, having a larger
diameter than side wall 251, so that said bases protrude radially
outwards from side wall 251. Jacket 250 differs from jacket 150
shown in FIG. 5 only in respect of the configuration of base 190,
which, instead of having a flat external surface, like base 170 of
jacket 150, has an external surface 194 with conical profile (more
particularly, shaped as a frustum of a cone), such that surface 194
projects outside motor casing 31. Moreover, cooling fins 196 are
formed on the portion of surface 194 located outside casing 31.
[0066] Base 190 having a surface 194 partly coming out from motor
casing 31 allows a better thermal dissipation than base 170 wholly
accommodated inside motor casing 31, since base 190 can directly
receive the air flow created by the external cooling system (not
shown) of pumping system 300. The provision of cooling fins 196 in
the portion of surface 194 outside motor casing 31 allows
increasing the cooling surface and having a more effective
circulation of the external cooling air flow.
[0067] It is to be appreciated that, when pouring the resin for
forming the first and second components 60, 70 and 80, 90 of FIGS.
3 and 4 or jackets 150 and 250 of FIGS. 5 and 6, some resin could
become incorporated between the magnets of motor stator 32. In view
of this fact, the embodiment shown in FIGS. 3 and 4 could even be
interpreted as a limit case of the embodiment shown in FIGS. 5 and
6, where the resin layer forming side walls 151, 251 of jackets
150, 250 has a substantially zero thickness.
[0068] Of course, while leaving the principle of the invention
unchanged, the embodiments and the construction details can be
widely changed with respect to what has been described and shown by
way of non-limiting example only, without thereby departing from
the scope of the invention as defined in the following claims.
[0069] It will be understood that various aspects or details of the
invention may be changed without departing from the scope of the
invention. Furthermore, the foregoing description is for the
purpose of illustration only, and not for the purpose of
limitation--the invention being defined by the claims.
* * * * *