U.S. patent application number 14/005501 was filed with the patent office on 2014-01-02 for synchronous electric motor for the operation of a pump and the related motor pump.
This patent application is currently assigned to HYDOR SRL. The applicant listed for this patent is Valerio Bresolin. Invention is credited to Valerio Bresolin.
Application Number | 20140003977 14/005501 |
Document ID | / |
Family ID | 43977571 |
Filed Date | 2014-01-02 |
United States Patent
Application |
20140003977 |
Kind Code |
A1 |
Bresolin; Valerio |
January 2, 2014 |
SYNCHRONOUS ELECTRIC MOTOR FOR THE OPERATION OF A PUMP AND THE
RELATED MOTOR PUMP
Abstract
A synchronous electric motor for operating a pump includes a
motor body, a stator and a rotor coupled to an impeller of the
pump. The motor also comprises a cylindrical element that extends
towards the inside of the motor body from one of its outer walls so
as to define a first cylindrical cavity open to the outside to
insert inside the rotor, wherein the rotor has a circular cross
section essentially corresponding to the inner section of the
cylindrical element so that the rotor is in contact with the
cylindrical element and then there is a friction between the rotor
and the cylindrical element when the rotor rotates, and the rotor
is shaftless and axially and directly coupled to the impeller of
the pump.
Inventors: |
Bresolin; Valerio; (Pove del
Grappa, IT) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bresolin; Valerio |
Pove del Grappa |
|
IT |
|
|
Assignee: |
HYDOR SRL
Bassano del Grappa, Vicenza
IT
|
Family ID: |
43977571 |
Appl. No.: |
14/005501 |
Filed: |
March 13, 2012 |
PCT Filed: |
March 13, 2012 |
PCT NO: |
PCT/IT12/00070 |
371 Date: |
September 16, 2013 |
Current U.S.
Class: |
417/410.1 |
Current CPC
Class: |
F04D 13/064 20130101;
H02K 9/193 20130101; F04D 29/047 20130101; F04D 13/06 20130101 |
Class at
Publication: |
417/410.1 |
International
Class: |
F04D 13/06 20060101
F04D013/06 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 15, 2011 |
IT |
VE2011A000015 |
Claims
1. A motor pump comprising; (a) a first pump; and (b) an electric
motor coupled to the first pump, wherein the electric motor
includes (i) a motor body, a stator and a rotor coupled to an
impeller of the first pump; and (ii) a cylindrical element that
extends towards an inside of the motor body from one of outer walls
of the motor body so as to divide the inside of the motor body in
two cavities, wherein the two cavities include a first cylindrical
cavity arranged inside the cylindrical element that is able to
house the rotor and a second cavity disposed outside the
cylindrical element and able to house the stator, wherein the
cylindrical element has a first open end, opposite to a second end,
positioned at the outer wall of the motor body so that the first
cylindrical cavity is open to the outside so as to insert the rotor
inside the cylindrical element, wherein the rotor, for at least
part of the length of the rotor, has a circular cross section
essentially corresponding to an inner section of the cylindrical
element so that the rotor is in contact with the cylindrical
element and so there is friction between the rotor and the
cylindrical element when the rotor rotates, and wherein the rotor
is shaftless and axially and directly coupled to the impeller of
the first pump.
2. A motor pump according to claim 1, wherein the entire portion of
the rotor housed inside the cylindrical element has a circular
cross section corresponding to the inner section of the cylindrical
element, so that all of the entire portion of the rotor housed
inside the cylindrical element is in contact with the cylindrical
element.
3. A motor pump according to claim 2, wherein the length of the
rotor is equal or higher than the length of the cylindrical
element, so that the rotor essentially fills the entire first
cavity inside the cylindrical element, so that between the
cylindrical element and the rotor there is no space or gap and
frictional contact between the rotor and the cylindrical element
occurs for the entire length of the first cavity of the cylindrical
element.
4. A motor pump according to claim 1, wherein said cylindrical
element is made of self-lubricating and wear-resistant
material.
5. A motor pump according to claim 4, wherein said self-lubricating
and wear-resistant material is a polymeric material.
6. A motor pump according to claim 1, wherein said cylindrical
element comprises a collar at a first end of said cylindrical
element, and said motor body has an opening provided with a shape
and dimensions corresponding to that of said collar, so that by
inserting said cylindrical element inside said motor body said
collar closes said opening of said motor body.
7. A motor pump according to claim 1, wherein said rotor comprises
at least one permanent magnet.
8. A motor pump according to claim 1, wherein said stator comprises
at least one statoric pack defining at least two pole pieces faced
to said cylindrical element and at least one electric winding to
generate a magnetic field and then at least two magnetic poles at
said at least two pole pieces.
9. A motor pump according to claim 1, further comprising: (c) a
duct placed on the side of said cylindrical element, wherein the
duct defines a longitudinal slot of communication between said
cylindrical element (224) and the duct, wherein the duct is in
communication with said first pump so that the fluid pumped by said
first pump may enter into the duct and lubricate, or cool, or
lubricate and cool, contact area between said rotor and said
cylindrical element.
10. A motor pump according to claim 9, wherein said duct also
communicates with an area interposed between the rotor and a bottom
of the cylindrical element, and the rotor is also provided with a
through hole so that the fluid that arrives between the bottom of
the cylindrical element and the rotor passes through the rotor and
then comes out of the rotor.
11. A motor pump according to claim 1, wherein said first pump
comprises a pump body inside which the impeller of said first pump
is housed, wherein the pump body is provided with a suction intake
through which the liquid to be pumped is sucked and an outlet
through which the pumped liquid goes out, and inside the pump body
is defined a passage that connects the suction intake to the
outlet, wherein the passage has a dimension equal or greater than
the dimension of the suction intake and of the outlet, so that any
foreign body that penetrates inside the pump body through the
suction intake may pass through the passage and go out from the
outlet.
12. A motor pump according to claim 2, wherein said cylindrical
element is made of self-lubricating and wear-resistant
material.
13. A motor pump according to claim 12, wherein said
self-lubricating and wear-resistant material is a polymeric
material.
14. A motor pump according to claim 3, wherein said cylindrical
element is made of self-lubricating and wear-resistant
material.
15. A motor pump according to claim 14, wherein said
self-lubricating and wear-resistant material is a polymeric
material.
Description
[0001] This is a National Phase Application in the United States of
International Patent Application No. PCT/IT2012/000070 filed Mar.
13, 2012, which claims priority on Italian Patent Application No.
VE2011A000015, filed Mar. 15, 2011. The entire disclosures of the
above patent applications are hereby incorporated by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to a synchronous electric
motor for the operation of a pump. The invention also relates to a
motor pump comprising a synchronous electric motor coupled to a
pump.
BACKGROUND OF THE INVENTION
[0003] It is well known to use synchronous motors for the operation
of pumps, such as pumps for aquariums, pumps for household
appliances as, for example, washing machines, dishwashers and more.
Synchronous motors comprise a motor body inside which a stator and
a rotor are housed. The stator comprises a statoric pack, usually a
stack of magnetic laminations, on which one or more electrical
windings are wound. The statoric pack has at least two pole pieces
inside which a rotor is positioned. Then, the stator forms the
inductor of the electric motor.
[0004] The rotor usually consists of a permanent magnet of
cylindrical shape and constitutes the armature of the electric
motor. By feeding the electric windings, a magnetic flux is
generated in the statoric pack and, therefore, magnetic poles are
generated at the pole pieces that interact with the magnetic field
of the rotor, thus causing the rotation of the rotor. The rotor
usually is holed in the centre, and inside a shaft is rigidly
inserted and fixed. The shaft is supported at its two ends by
respective bushes, which are rigidly secured inside cavities formed
in the motor body. The impeller of the pump is fixed to one of the
two ends of the shaft.
[0005] In some motors of the prior art, as shown in FIG. 1, a
cylindrical element is used for insulating the statoric part from
the rotoric part and, thus, prevents the electric windings of the
stator from coming into contact with the liquid to be pumped. In
this FIG. 1, a motor pump 10 of the prior art comprising a motor 20
coupled to a pump 50 is shown.
[0006] The motor 20 comprises a motor body 22 delimited by walls.
By starting from an upper wall 22A of the motor body 22, a
cylindrical element 24 extends towards the inside having two ends:
a first end 24a facing the wall 22A and open towards the outside,
and a second end 24b facing the inside of the motor body 22 and
closed by a bottom 26. The cylindrical element 24 thus defines two
cavities: a first cavity 28 inside the cylindrical element 24 and a
second cavity 30 outside the cylindrical element 24, but contained
inside the motor body 22.
[0007] A rotor 32 containing a magnet is housed in the first cavity
28, while the stator is housed in the second cavity 30, wherein the
pole pieces 34 of the stator have been represented in FIG. 1. The
rotor 32 comprises a shaft 36, which is inserted and fixed inside a
hole made in the centre of the rotor 32. The shaft 36 has two ends:
a first end 36a on which the impeller 52 of the pump 50 is fixed,
and a second end 36b housed inside a seat 26a formed on the bottom
26 of the cylindrical element 24. A portion of the shaft 36 between
the rotor 32 and the impeller 52 is inserted into a bush 38 wherein
the shaft 36 is free to rotate. The bush 38 is fixed by a gasket
40, for example an O-ring, inside the cylindrical element 24.
[0008] The pump 50 comprises a pump body 54 mounted onto the motor
body 22, and inside the pump body 54 the impeller 52 is housed. By
feeding the electric windings of the stator, magnetic poles are
generated at the pole pieces 34 which, by interacting with the
magnetic field of the rotor magnet 32, put the rotor 32 in rotation
and, therefore, also the impeller 52. As can be seen, thanks to the
cylindrical element 24, the second cavity 30 that houses the stator
is completely closed and, therefore, the electrical windings are
completely insulated.
[0009] However, this embodiment of the prior art just described has
several drawbacks. First of all, the embodiment is quite complex
since it is necessary to construct a shaft for transmitting motion
from the rotor to the impeller, and it is also necessary to
construct a rotor with a hole inside where the shaft is inserted
and fixed, and a bush to support one end of the shaft and a housing
seat for supporting the other end of the shaft. In addition, once
all these elements are constructed, it is necessary to mount them
to each other. Then, both the production costs for obtaining the
individual pieces, and their assembly, are high. Then, with time
and due to wear, it is inevitable that some components may fail and
interrupt the correct operation of the motor pump, and also making
necessary a cost for the intervention by specialized personnel.
[0010] In particular, since the gasket 40 is in contact with the
pump body, it is also in contact with the fluid to be pumped, which
in some cases is dirty or even aggressive. In fact, the water waste
of a washing machine contains chemically aggressive detergents that
easily attack and erode the gaskets; therefore, they must be
frequently replaced causing evident inconveniences. Moreover,
spaces or air chambers are defined between the first cylindrical
cavity 28 and the rotor 32, and, more precisely, a first air
chamber between the rotor 32 and the bottom 26 of the cylindrical
element 24 and a second air chamber between the rotor 32 and the
bush 38. Then, the two air chambers are in communication with each
other through the space defined between the cylindrical element 24
and the rotor 32.
[0011] It was established by the applicant that these air chambers
due to (a)the constant starting and stopping of the motor, and (b)
the variation of the temperature of the liquid to be pumped (for
example, in case of a motor pump for washing machines or
dishwashers, the liquid can be either at room temperature or
heated), function as minipumps, which suck the liquid contained in
the impeller body. But, despite the fact gasket 40 is used, these
air chambers are able to suck the liquid contained in the impeller
body especially if, as indicated above, it has to be considered
that the seals are worn and attacked by the liquid to be
pumped.
[0012] Therefore, the impurities contained in the liquid, such as
detergents, cleansing agents and various impurities in case of
motor pumps for washing machines or dishwashers, penetrate inside
the cavity, which houses the rotor and, with time, they accumulate
and prevent the correct rotation of the rotor inside the cavity,
thus causing jamming or irreparable damages to the rotor. This
causes issues due to the stopping of the motor and, then, generates
a high cost for maintenance or even replacement of the damaged
motor pump.
[0013] The aim of the present invention is to obviate the drawbacks
mentioned above with reference to the cited prior art and, in
particular, to avoid a rapid wear of the various components that
form the electric motor. Especially, an aim of the present
invention is to prevent the rotor functioning incorrectly, or even
jamming or failing due to impurities that could penetrate into the
cavity.
SUMMARY OF THE INVENTION
[0014] These aims, discussed above, are achieved by a motor pump
according to a first non-limiting illustrative embodiment of the
present invention, in which a motor pump (100) comprises an
electric motor (120) coupled to a pump (150), wherein the electric
motor (120) includes a motor body (122), a stator (140) and a rotor
(132,232) coupled to an impeller (152) of the pump (150), wherein
the motor (120) further comprises a cylindrical element (124,224)
that extends towards the inside of the motor body (122) from one of
its outer walls (122A) so as to divide the inside of the motor body
(122) in two cavities, namely, a first cylindrical cavity (128)
inside the cylindrical element (124,224) that is able to house the
rotor (132,232) and a second cavity (130) outside the cylindrical
element (124,224) that is able to house the stator (140), wherein
the cylindrical element (124,224) has a first open end (125a),
opposite to a second end (125b), positioned at the outer wall
(122A) of the motor body (122) so that the first cylindrical cavity
(128) is open to the outside so as to insert the rotor (132,232)
inside the cylindrical element (124,224), characterized in that the
rotor (132,232), for at least part of its length, has a circular
cross section essentially corresponding to the inner section of the
cylindrical element (124,224) so that the rotor (132,232) is in
contact with the cylindrical element (124,224), and then there is a
friction between the rotor (132,232) and the cylindrical element
(124,224) when the rotor (132,232) rotates, and the rotor (132,232)
is shaftless and axially and directly coupled to the impeller (152)
of the pump (150).
[0015] In accordance with a second non-limiting illustrative
embodiment of the present invention, the first embodiment is
modified so that the entire portion of the rotor (132,232) housed
inside the cylindrical element (124,224) has a circular cross
section corresponding to the inner section of the cylindrical
element (124,224), so that all the portion of the rotor housed
inside the cylindrical element (124,224) is in contact with the
cylindrical element (124,224). In accordance with a third
non-limiting, illustrative embodiment of the present invention, the
second non-limiting embodiment is further modified so that the
rotor (132,232) has a length equal or higher than the length of the
cylindrical element (124,224), so that the rotor essentially fills
the entire first cavity (128) inside the cylindrical element
(124,224), so that between the cylindrical element (124,224) and
the rotor (132,232) there is no space or gap and the frictional
contact between the rotor (132,232) and the cylindrical element
(124,224) occurs for the entire length of the first cavity (128) of
the cylindrical element (124,224). In accordance with fourth
non-limiting, illustrative embodiment of the present invention, the
first, second and third non-limiting embodiments are further
modified so that the cylindrical element (124,224) is made of
self-lubricating and wear-resistant material. In accordance with a
fifth non-limiting, illustrative embodiment of the present
invention, the fourth non-limiting embodiment is further modified
so that the self-lubricating and wear-resistant material is a
polymeric material.
[0016] In accordance with a seventh non-limiting illustrative
embodiment of the present invention, the first, second, third,
fourth, fifth and sixth non-limiting embodiments are further
modified so that the cylindrical element (124,224) comprises a
collar (127) at its first end, and the motor body (122) has an
opening (123) with the shape and dimensions corresponding to that
of the collar (127), so that by inserting the cylindrical element
(124,224) inside the motor body (122) the collar (127) closes the
opening (123) of the motor body (122). In accordance with an eighth
non-limiting, illustrative embodiment of the present invention, the
first, second, third, fourth, fifth, sixth and seventh non-limiting
embodiments are further modified so that the rotor (132,232)
comprises at least one permanent magnet (134). In accordance with a
ninth non-limiting illustrative embodiment of the present
invention, the first, second, third, fourth, fifth, sixth, seventh
and eighth non-limiting embodiments are further modified so that
the stator (140) comprises at least one statoric pack (142)
defining at least two pole pieces (142A, 142B) faced to the
cylindrical element (124,224) and at least one electric winding
(144) to generate a magnetic field and then at least two magnetic
poles at the at least two pole pieces (142A, 142B).
[0017] In accordance with a tenth non-limiting illustrative
embodiment of the present invention, the first, second, third,
fourth, fifth, sixth, seventh, eighth and ninth non-limiting
embodiments are further modified so that the motor pump comprises a
duct (229) placed on the side of the cylindrical element (224) and
that defines a longitudinal slot (228) of communication between the
cylindrical element (224) and the duct (229), wherein the duct
(229) is in communication with the pump (150) so that the fluid
pumped by the pump (150) can enter into the duct (229) and
lubricate and/or cool the contact area between the rotor (232) and
the cylindrical element (224). In accordance with an eleventh
non-limiting, illustrative embodiment of the present invention, the
first, second, third, fourth, fifth, sixth, seventh, eighth, ninth
and tenth non-limiting embodiments are further modified so that the
duct (229) also communicates with the area interposed between the
rotor (232) and the bottom (226) of the cylindrical element (224),
wherein the rotor (232) is also provided with a through hole (237)
so that the fluid that arrives between the bottom (226) of the
cylindrical element (224) and the rotor (232) can pass through the
rotor (232) and then comes out. In accordance with a twelfth
non-limiting illustrative embodiment of the present invention, the
first, second, third, fourth, fifth, sixth, seventh, eighth, ninth,
tenth and eleventh non-limiting embodiments are further modified so
that the pump (150) comprises a pump body (154) inside which the
impeller (152) of the pump (150) is housed, wherein the pump body
(154) is provided with a suction intake (156) through which the
liquid to be pumped is sucked and an outlet (158) through which the
pumped liquid goes out, wherein inside the pump body (154) is
defined a passage (162) that connects the suction intake (156) to
the outlet (158) and that has a dimension equal or greater than the
dimension of the suction intake (156) and of the outlet (158), so
that any foreign body that penetrates inside the pump body (154)
through the suction intake (156) can pass through the passage (162)
and go out from the outlet (158).
[0018] In this way, the construction design of the motor is
considerably simplified since, compared to the motors of the prior
art, there is no drive shaft, and it is not necessary to drill the
rotor in order to insert the shaft, and it is not necessary to
construct the bushes, or other supports, inside which the ends of
the shaft rotate. It is simply necessary to realize only a rotor
and coupled it axially and directly to the impeller. In fact,
bearing in mind that the rotor, for at least a portion of its
length, has a section corresponding to the cylindrical cavity of
the cylindrical element inside which it is housed, there is no need
of any support as the rotor is directly supported by the
cylindrical element inside which it is inserted. In other words,
the rotor itself operates as a shaft and the bushes are replaced by
the cylindrical element inside which the rotor rotates.
[0019] Thanks to the simplicity of this construction, the
production time of such a motor is considerably reduced and the
manufacturing cost is significantly limited. Moreover, the diameter
of contact between the rotor and the cylindrical element is much
higher than the diameter of contact between the drive shaft and the
bushes of the prior art motors and, therefore, the contact surface
is much wider. Consequently, the contact pressures are very
limited, so there is a significant reduction of the wear. In this
way, the service life of the motor significantly extends.
[0020] Furthermore, due to the fact that there is a direct contact
between the rotor and the cylindrical element for at least a
portion of the length of the rotor, the fluid is not able to
penetrate inside the cavity housing the rotor. Therefore, there is
no risk that the rotor can be subject to malfunctions or jammings
due to the impurities contained in the fluid to be pumped.
[0021] Preferably, the entire part of the rotor housed within the
cylindrical element has a circular cross-section corresponding to
the inner section of the cylindrical element, so that the whole
part of the rotor housed inside the cylindrical element is in
contact with the cylindrical element. In particular, the rotor has
a length equal or higher than the length of the cylindrical element
so that the rotor substantially engages the entire inner cavity of
the cylindrical element, so that between the cylindrical element
and the rotor there are no spaces or voids, and the friction
contact between the rotor and the cylindrical element occurs for
the entire length of the first inner cavity of the cylindrical
element.
[0022] It is evident that if the rotor completely engages the
cavity wherein it is housed, first of all, the contact occurs on a
very extensive surface increasing the benefits described
previously, but above all there is no possibility that impurities
penetrate inside the cavity. This is due not only because the
entire cavity is engaged by the rotor, but above all because there
are no air chambers between the rotor and the cavity, and the pump
effect is no longer originated, as previously described, the effect
which could draw back the fluid with impurities to be pumped into
the cavity. Since the fluid is no longer drawn back inside, there
is no deposit of impurities between the rotor and the cavity that
houses it. The motor no longer gets damaged or experiences no
further malfunctions, and the service life is considerably
extended.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] These and other advantageous characteristics of the present
invention will become more apparent from the following description
of an embodiment provided only by the way of example, with no
limitation, and which refer to the following drawings wherein:
[0024] FIG. 1 illustrates a motor pump of the prior art;
[0025] FIG. 2 is a cross section of a motor pump according to the
present invention;
[0026] FIGS. 3, 4 and 5 are cross sections showing, in exploded
views, the motor pump of FIG. 2 and, in particular, respectively
illustrate the pump body, the rotor with impeller housed inside a
cylindrical element, and the motor body;
[0027] FIGS. 6 and 7 are cross sections showing details of FIG. 4,
i.e., the rotor with impeller and the cylindrical element able to
contain the rotor;
[0028] FIG. 8 is a perspective view of the rotor with impeller
housed in the stator of the motor pump of FIG. 2;
[0029] FIGS. 9, 10 and 11 are perspective views that illustrate, in
exploded views, what components collectively illustrated in FIG. 8,
in particular, respectively the rotor with the impeller, the
cylindrical element, and the stator;
[0030] FIG. 12 is a perspective view illustrating a variant of the
invention relating to the cylindrical element and the rotor
contained therein;
[0031] FIGS. 13 and 14 are perspective views of the cylindrical
element of FIG. 12 respectively shown in full and partially
sectioned views;
[0032] FIGS. 15 and 16 are perspective views of the rotor of FIG.
12, respectively shown in full and partially sectioned views.
DETAILED DESCRIPTION OF THE INVENTION
[0033] In FIG. 2, generally indicated with 100 is a motor pump
comprising a synchronous electric motor 120 coupled to a pump 150,
such as a pump for aquariums or a pump for household appliances,
such as washing machines and dishwashers. The motor 120 comprises a
motor body 122, which, as better illustrated in FIG. 5, is
delimited by walls, in particular an upper wall 122A where a
circular opening 123 is formed.
[0034] FIGS. 7 and 10 show in detail a cylindrical element 124
inserted inside the motor body 122, wherein the cylindrical element
is formed by a tubular element 125 having two opposite ends: a
first open end 125a and a second end 125b closed by a bottom 126. A
collar 127 is mounted on the first end 125a of the tubular element
125 with dimensions corresponding to the circular opening 123 made
in the upper wall 122A, so by inserting the cylindrical element 124
into the motor body 122, the collar 127 closes the circular opening
123. A circumferential recess 129 is made on the collar 127, whose
function will be described below.
[0035] The cylindrical element 124, inside the pump body 122, thus
defines two cavities: a first cavity 128 inside the cylindrical
element 124, and a second cavity 130 outside the cylindrical
element 124 but inside the motor body 122. The rotor 132 is housed
inside the first cavity 128 (see FIG. 4), while a stator 140 is
housed in the second cavity 130 (see FIG. 8). The rotor 132, as
better illustrated in FIGS. 4 and 6, has a shape corresponding to
that of the cylindrical element 124 so that it is possible to
insert the rotor 132 inside the cylindrical element 124, completely
filling the first cavity 128. Thus, the rotor 132 is supported
during its rotation along its entire outer cylindrical surface by
the cylindrical element 124.
[0036] The rotor 132 contains a magnet 134 and it is coupled at its
one end 132a directly and axially to the impeller 152 of the pump
150. At the end 132a coupled to the impeller 152, the rotor 132 has
a circumferential projection 136 of dimensions corresponding to
that of the circumferential recess 129 formed on the cylindrical
element 124. By inserting the rotor 132 within the cylindrical
element 124, the circumferential projection 136 enters into the
circumferential recess 129, which, therefore, acts as a guide for
the relative rotation between the rotor 132 and the cylindrical
element 124. The stator 140, as shown in FIG. 11, comprises a
statoric pack 142 of ferromagnetic material having two pole pieces
142A, 142B and an electric winding 144 wound also.
[0037] The pump 150 comprises a pump body 154 inside which the
impeller 152 is housed. As can be seen more clearly in FIG. 3, the
pump body 154 includes an inlet or a suction intake 156 through
which the liquid to be pumped is sucked and an outlet 158 through
which the pumped liquid comes out. The pump body 154 also includes
a circular opening 160 having dimensions corresponding of the
collar 127 of the cylindrical element 124 so, by mounting the pump
body 154 onto the motor body 122, the circular opening 160 is
closed by the collar 127. Inside the pump body 154, when the
impeller 152 is inserted inside, a passage 162 (see FIG. 2) of the
liquid is defined that connects the suction intake 156 to the
outlet 158, and which has dimensions equal or higher than the
dimensions of the suction intake 156 and the outlet 158. This way,
any foreign body that may penetrate inside the pump body 154
through the suction intake 156 is able to cross the passage 162 and
comes out from the outlet 158.
[0038] For the assembling of the motor pump, it is sufficient to
perform the following steps: (a) insert the stator 140 into the
motor body 122; (b) insert the cylindrical element 124 into the
motor body 122 so that the collar 127 closes the circular opening
123 of the motor body 122; (c) insert the rotor 132 with the
impeller 152 inside the cylindrical element 124 so that the
circumferential projection 136 is inserted inside the
circumferential recess 129; and (d) mount the pump body 154 onto
the motor body 122 so that the circular opening 160 of the pump
body 154 is closed by the collar 127 of the cylindrical element
124. As can be noted, the stator 140 with the electric winding 144
is housed inside the second cavity 130 of the motor body 122, which
is completely insulated, so that there is no possibility that
liquid can penetrate and come into contact with the electric
winding 144.
[0039] By feeding the electric winding 144 of the stator 140 with
electricity, magnetic poles are generated at the pole pieces 142A,
142B, which interacts with the magnetic field of the magnet 134 of
the rotor 132 putting the rotor 132 in rotation and, therefore,
putting the impeller 152 in motion. The rotor 132 rotates inside
the cylindrical element 124, which acts as a plain bearing. The
cylindrical element 124 is preferably made with self-lubricating
and anti-wear material, such as a polymeric material. The
construction of such a motor is very simple due to the reduced
number of components necessary for its realization. The time and
the cost of construction are, therefore, considerably reduced.
[0040] It can be noted that the rotor 132 fully engages the first
cavity 128 of the cylindrical element 124, whereby the contact
surface between the rotor 132 and the cylindrical element 124 is
remarkable, and then the rotor is suitably supported inside the
cylindrical element 124. Thanks to this feature, the operation of
the rotor is more regular and also wear is reduced. Moreover, the
following very important characteristic has to be noted: between
the cylindrical element 124 and the rotor 132 there is no space or
air chambers so that the above pump effect is not created, thus
avoiding that impurities contained in the liquid to be pumped,
which as already explained is a source of malfunctionings and
failure, penetrate into the cylindrical element 124.
[0041] Thanks to the simplicity of construction, the large contact
surface between the rotor and the cylindrical element is realized,
and because there are no air chambers in the cavity that houses the
rotor, the motor is extremely reliable and its service life is
considerably increased with respect to the motors of prior art. It
should also be considered that due to the contact between the rotor
132 and the cylindrical element 124, the air gap existing between
the stator 140 and the rotor 132 is reduced to the minimum possible
and, in such condition, the magnetic field of the stator 140 and
that of the rotor 132 are closely linked. Consequently, between the
voltage that feeds the electric winding of the stator 140 and the
electric current passing through there, there is a very little
phase angle .phi. that is very close to zero, and then the
so-called power factor Cos .phi. is essentially equal to 1. This
way, the electric current in the winding 144 is the minimum
possible and, therefore, the electrical losses due to the Joule
effect are reduced to a minimum. In so doing, the efficiency of the
electric motor is high and, with the same electric power of known
motors, it is able to operate a pump that absorbs more power.
[0042] FIG. 12 shows a variant of the invention and, in particular,
a rotor 232 inserted inside a cylindrical element 224. As better
seen from FIGS. 13 and 14, the cylindrical element 224 is similar
to the cylindrical element 124, i.e., it has a tubular element 225
provided with a collar 227. A tubular duct 229 is placed beside the
tubular element 225 and it has the same length but of smaller
section. A longitudinal slot 228 is formed in the area of contact
between the tubular element 225 and the duct 229 for the entire
length of the two elements, which puts in contact the inside of the
tubular element 225 with the inside of the duct 229. As will be
seen from FIGS. 12, 15 and 16, the rotor 232 is provided with a
central pin 233 on which a magnet 234 is mounted, while the
impeller 152 is mounted at the free end 233A of the pin 233. The
pin 233 has an axial through hole 237. As noted in FIG. 12, the
length of the rotor 232 is less than the length of the tubular
element 225 and, therefore, the rotor 232 is spaced apart from the
bottom 226 of the tubular element 225. In FIG. 12, a stator 240 is
represented, which externally surrounds the cylindrical element
224.
[0043] When the pump is operated, the rotor 232 rotates inside the
tubular element 225, and the impeller 152 coupled to the rotor 232
thrusts the liquid to be pumped into the duct 229 and, thanks to
the longitudinal slot 228, the liquid comes into contact with the
rotor 232 enabling both the cooling and lubrication of the contact
area between the rotor 232 and the tubular element 225. Because the
rotor 232 is spaced apart from the bottom of the tubular element
225, the liquid thrust through the slot 228 goes inside the tubular
element 225 in the area below the rotor 232 and then goes up along
the through hole 237 of the rotor 232 and, finally, comes out from
the free end 233A of the pin 233. This way, a forced circulation of
liquid is created that considerably increases the amount of liquid
that enters into the longitudinal slot 228 and, then, in the
contact area between the rotor 232 and the tubular element 225.
This effectively cools and lubricates the area where there is
friction between the rotor and the tubular element.
[0044] Finally, it is evident that any variation or modification,
functionally or conceptually equivalent, falls under the scope of
the present invention. For example, it is possible to have a stator
with a different number of pole pieces, or having more electric
windings, or having stator packs with a different shape.
[0045] Generally, however, the invention encompasses in scope a
synchronous electric motor (120) for operating a pump (150). The
motor (120) comprises a motor body (122), a stator (140) and a
rotor (132,232) coupled to an impeller (152) of the pump (150). The
motor (120) also comprises a cylindrical element (124,224) that
extends towards the inside of the motor body (122) from one of its
outer walls (122A) so as to define a first cylindrical cavity (128)
open to the outside to insert inside the rotor (132,232), wherein
the rotor (132,232) has a circular cross section essentially
corresponding to the inner section of the cylindrical element
(124,224) so that the rotor (132,232) is in contact with the
cylindrical element (124,224), and then there is friction between
the rotor (132,232) and the cylindrical element (124,224) when the
rotor (132,232) rotates, and the rotor (132,232) is shaftless and
axially and directly coupled to the impeller (152) of the pump
(150).
* * * * *