OBJECT OF THE INVENTION
[0001] The present invention, as stated in the title of this specification, refers to some
improvements in centrifugal pumps which are specifically made in a characteristic
sealing ring that prevents part of the pumped fluid from passing through an undue
area from the discharge chamber to the suction chamber, thereby achieving an increase
of the driven flow rate of around 10%, as well as an increase in the hydraulic performance
of the pump of around 8%.
[0002] Thus, the typical sealing ring made of a polyamide material, prevents leakage of
fluid from the discharge chamber with higher pressure to the suction chamber at a
lower pressure, through an undue area corresponding to the support of the front face
of the turbine coupled within a housing attached by its axis to a rear support.
BACKGROUND OF THE INVENTION
[0003] Centrifugal pumps generally include a pump housing or body (static part) and a centrifugal
turbine or runner (rotating part), so that the better the fit between both elements,
the better the performance of the pump will be.
[0004] On this basis, the mixed-flow centrifugal pumps traditionally, due to the difficulty
of mechanically adjusting the turbine with respect to the housing, have been mounting
these two elements with the use of an intermediate element, such as a tow material
or wear ring inside of the suction mouth of the pump housing.
[0005] This intermediate element provided a seal between the suction chamber and the discharge
chamber by maintaining a constant radial friction in the suction mouth of the turbine.
[0006] This friction, in addition to needing a much comprehensive maintenance in exchange
for a better sealing of the suction chamber to the discharge chamber, resulted in
a loss of engine power, thereby it should be oversized.
[0007] More recently, due to the inclusion of numerical control machine tools and machining
centers, a better adjustment between the turbine and the pump housing was achieved;
thereby the use of intermediate elements such as a tow material or wear ring was abandoned.
[0008] The tolerance of the mentioned adjustment existing between the neck of the turbine
and the pump housing, is now usually in the order of about 0.2 mm.
DESCRIPTION OF THE INVENTION
[0009] In order to achieve the objectives and avoid the drawbacks mentioned in the preceding
paragraphs, the invention proposes some improvements in centrifugal pumps that are
of the type having a turbine placed inside a housing having a inlet mouth for a fluid
and an outlet mouth for the same fluid, in an front support that separates a suction
chamber corresponding to the inlet mouth and a discharge chamber corresponding to
an internal hole of the body pump wherein the turbine is located, and by a rear support
through the motor shaft.
[0010] The improvements are characterized in that they comprise an axial fluid-tight sealing
ring with an angular profile that provides a perimeter sealing between said chambers,
while such sealing ring is located in an angular hole established in correspondence
with the front support of the turbine.
[0011] That angular hole is defined between the suction mouth of the turbine and an angular
recess of the housing, with the sealing ring being coupled with a certain tightening
in the suction mouth of the turbine that rotates dragging the mentioned sealing ring,
front section of which axially contacts by its outer flat face against a flat front
section of the angular recess of the housing.
[0012] This axial contact provides the perimeter sealing between the suction chamber and
the discharge chamber, such sealing ring being placed into the angular hole of the
front support of the turbine with an axial clearance and with a radial clearance as
well.
[0013] The radial clearance of the sealing ring will be delimited between the outer face
of its annular path radial section and the curved surface, having also an annular
path, of the angular recess of the housing corresponding to the front support of the
turbine.
[0014] The radial clearance of the sealing ring will be between 0.1 mm and 0.8 mm. While
the axial clearance of the sealing ring being higher, because of the pressure differences
between the two chambers, it is axially moved against the flat front section of the
angular recess of the pump housing getting smaller adjustments at 0.1 mm.
[0015] Another feature of the invention is that the sealing ring, includes in one of its
second embodiments, an axial driving spring device that is integral with said sealing
ring itself, pushing the same at all times against the flat front section of the angular
recess in the pump housing.
[0016] The referred spring device is characterized in that it comprises several cantilever
elastic wings arranged in the same annular plane of the radial section of the sealing
ring, such elastic wings being joined by their ends to some angular extensions starting
from the radial section radial of the sealing ring, such elastic wings contacting
at all times a front seat that outside limits the terminal portion of the turbine.
[0017] Another feature of the invention is that the elastic wings of the spring device comprise
pairs of sections that converge on common raised areas by one end, with this areas
being elastically deformed in their support on the front seat of the turbine.
[0018] The sealing ring is made in all its embodiments of a polyamide material.
[0019] Thus, the mentioned improvements of the invention achieve an increase of the driven
flow rate of around 10%, as well as an increase in the pump hydraulic performance
of around 8%, because undue leakage of fluid is prevented from the discharge chamber
with a higher pressure to the suction chamber with a lower pressure of the fluid.
[0020] Hereinafter to provide a better understanding of this specification and being an
integral part thereof, some figures in which with an illustrative and not limitative
manner the object of the invention has been represented, are attached.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021]
Figure 1.- Shows a perspective view of a centrifugal pump that includes the improvements
object of the invention. These basically consist of the inclusion of a characteristic
sealing ring that prevents that part of the pumped fluid from flowing from the discharge
chamber with a higher pressure to the suction chamber with a lower pressure of the
fluid, thus achieving a higher performance of the pump.
Figure 2.- Shows a sectional view of a centrifugal pump wherein the location of the
sealing ring in a first embodiment is shown in detail.
Figure 3.- Shows a detailed partial sectional view of a second embodiment of the sealing
ring.
Figure 4.- Shows a perspective view of a first embodiment of the sealing ring.
Figure 5.- Shows a sectional view of the sealing ring in a first embodiment shown
in the figure above.
Figure 6.- Shows a perspective view of a second embodiment of the sealing ring.
Figure 7.- Shows a sectional view of the sealing ring in a second embodiment shown
in the figure above.
DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] Considering the numbering adopted in the figures, a centrifugal pump 1 comprises
in principle a housing 2 as a static element, and a turbine 3 as a dynamic element
that rotates by a driving element not shown in the figures, with the interposition
of an intermediate shaft 4, so that the housing 2 is closed on the rear side corresponding
to the intermediate shaft 4 via a rear cover 5, while on the front side of the housing
2 is located the inlet mouth 6 for the fluid. An outlet mouth 7 for the fluid is radially
placed in the housing 2.
[0023] On this basis, the turbine is located in an inner hole of the housing 2 establishing
the discharge chamber 8, setting the turbine 3 on a rear support 9 of the rear cover
5 and on a front support 10 of the housing 2 with the interposition of a sealing ring
11-12, which as stated earlier, prevents some of the fluid from perimeter passing
from the discharge chamber 8 with a higher pressure of the fluid to a suction chamber
13 with a lower pressure of the fluid, with the discharge chamber 8 corresponding
with the inner hole of the housing 2 wherein the turbine 3 is located. It should be
also note that the inlet mouth 6 for the fluid is continued by the suction chamber
13.
[0024] The front support 10, wherein the characteristic sealing ring 11-12 is located, includes
an annular recess 14 faced with a terminal portion 15 of the turbine 3, generating
between said annular recess 14 of the housing 2 and the terminal portion 15 of the
turbine 3, a small angular hole 16 wherein the sealing ring 11-12 is set with an undetermined
axial clearance and with a radial clearance of about 0.5 mm, existing between the
annular outer face of the sealing ring 11-12 and the annular surface of the angular
recess 14 of the housing 2. The radial clearance can be as large as desired, within
reasonable limits, since the sealing ring 11-12 does not generate any radial sealing,
but axial, as will be described in detail below.
[0025] The obstruction on the front support 10 is achieved by the axial pressure exerted
by the sealing ring 11-12 against a flat front section 18 of the angular recess 14
made inside the housing 2.
[0026] The sealing ring 11-12 is freely coupled with some adjustment to the terminal portion
15 of the turbine 3, so that it partially draws on its rotation at all times the sealing
ring 11-12.
[0027] In a first embodiment, the sealing ring 11 comprises an angular profile consisting
of a radial section and a front section. The axial adjustment of the sealing ring
11 against the flat front section 18 of the angular recess 14 of the housing 2 is
produced as a result of the pressure differences between the two discharge and suction
chambers.
[0028] In a second more effectively embodiment, the sealing ring 12 comprises an angular
structure formed in principle by a radial section and a front section, combined with
the addition of an axial driving spring device 17 that is part of the sealing ring
12 itself, such spring device 17 section from the radial section.
[0029] The spring device 17 always tends to axially the sealing ring 12 against the flat
front section 18 of the angular recess 14 of the housing 2 in the centrifugal pump
1, even when it is inactive, thus also avoiding in this position undue leakage of
the fluid.
[0030] The spring device 17 abuts against a front seat 19 which externally defines the terminal
portion 15 of the turbine 3.
[0031] In turn, the said spring device 17 comprises several cantilevered elastic wings 20
arranged in the same annular plane as the radial section of the sealing ring 12, such
wings being joined by their ends to angular extensions 21 that also start from the
radial section of the sealing ring 12.
[0032] The cantilevered elastic wings 20 comprise pairs of sections that converge on common
raised areas by one of their ends, with these areas being elastically deformed on
their support against the front seat 19 of the turbine 3, thereby the support of the
elastic wings 20 against the front seat 19 axially pushes the sealing ring 12 against
the flat front section 18 of the angular recess 14 in the housing 2, thereby producing
a more effective seal between the suction chamber 13 with a lower pressure and the
discharge chamber 8 with a higher pressure.
[0033] The sealing ring 11-12 is made of polyamide by using an injection molding process,
without excluding other plastic materials.
[0034] Thus, in summary, the sealing between the suction chamber 13 and the discharge chamber
8 is the result of the axial friction between the outer side of the front section
of the sealing ring 11-12 and flat front section 18 of the angular recess 14 made
in the casing 2 of the pump 1.
[0035] Indeed, by the effect of centrifugal speed of the turbine 3, in the suction chamber
13 a suction or pressure drop is produced, while in the discharge chamber 8 an increase
of pressure is produced. This pressure difference makes the sealing ring 11-12 to
suffer a thrust out with a force equal to the result of multiplying the difference
of the axial front surface of the sealing ring 11-12 by the pressure of the discharge
chamber, minus the same axial surface of the sealing ring by the pressure of the suction
chamber, so that as the surface is the same, it is clear that the result will be positive.
[0036] As indicated above, the sealing ring has a sliding fit with the outer area of the
mouth of the centrifugal turbine or runner 15, so that the sealing ring will be axially
moved until axially rubbing against the flat front section of the angular recess 14
in the housing 2 of the pump 1, resulting in the sealing or hydraulic separation of
the suction and discharge chambers.
[0037] Inasmuch as the centrifugal pump start and because the sealing ring is at rest (no
thrusting force by the pressure difference of the suction and discharge chambers),
there could be the fact that the sealing ring is not in its normal working position,
that is, rubbing against the flat front section 18 of the angular recess 14 in the
housing 2 of the pump 1, which would cause a hydraulic leak from the discharge chamber
to the suction chamber, resulting in an equal pressure between the two opposite axial
faces of the hoop or sealing ring, and consequently it would not produce the axial
thrusting force described above.
[0038] In order to avoid this problem, the sealing ring includes into its most advantageous
embodiment the spring device 17, so even when the pump at rest, the axial contact
between the sealing ring 12 and the flat front section 18 of the angular recess 14
in the housing of the pump is guaranteed.
[0039] Finally it should be noted that the initial tightness in the absence of pressure
difference (pump off) between the two chambers 8-13, such initial tightness is caused
by the spring device 17 of the sealing ring 12.
1. Improvements in centrifugal pumps, these pumps (1) being of the type having a turbine
(3) placed inside a housing (2) having a inlet mouth (6) for a fluid and an outlet
mouth (7) for the same fluid, said turbine (3) being coupled to a rear support (9)
and to a front support (10) that separates a suction chamber (13) corresponding to
the inlet mouth (6) and a discharge chamber (8) corresponding to an internal hole
wherein the turbine (3) is located, characterized in that they comprise an axial fluid-tight sealing ring with an angular profile that provides
a perimeter sealing between said chambers (8-13), while said ring is located in an
angular hole (16) established in correspondence with the front support (10) of the
turbine (3), angular hole (16) defined between a terminal portion (15) of the turbine
(3) and an angular recess (14) of the housing (2), with the sealing ring being coupled
with a certain tightening in the terminal portion (15) of the turbine (3) that rotates
dragging the mentioned sealing ring, front section of which axially contacts by its
outer flat face against a flat front section (18) of the angular recess (14) in the
housing (2), with this axial contact providing the perimeter sealing between the suction
chamber (13) and the discharge chamber (8), with the sealing ring being placed into
the angular hole (16) of the front support (10) with an axial clearance and with a
radial clearance as well.
2. Improvements in centrifugal pumps, according to claim 1, characterized in that the radial clearance of the sealing ring is delimited between the outer face of its
annular path radial section and the curved surface, also with an annular path, of
the angular recess (14) in the housing (2).
3. Improvements in centrifugal pumps, according to claim 2, characterized by the radial clearance of the sealing ring is between 0.1 mm and 0.8 mm.
4. Improvements in centrifugal pumps according to claim 1, characterized in that the sealing ring (12) includes an axial driving spring device (17) integral with
the sealing ring (12) itself, pushing the same all times against the flat front section
(18) of the angular recess (14) in the housing (2) of the pump (1).
5. Improvements in centrifugal pumps, according to claim 4, characterized in that the spring device (17) comprises several cantilevered elastic wings (20) arranged
in the same annular plane as the annular section of the radial section of the sealing
ring (12), said elastic wings (20) being joined by their ends to angular extensions
(21) that start from the radial section of the sealing ring (12), said elastic wings
(20) contacting at any time against a front seat (19) which externally defines the
terminal portion (15) of the turbine (3).
6. Improvements in centrifugal pumps, according to claim 5, characterized in that the elastic wings (20) of the spring device (17) comprise pairs of sections that
converge on common raised areas by one of their ends, with these areas being elastically
deformed on their support over the front seat (19) of the turbine (3).
7. Improvements in centrifugal pumps, according to claim 1, characterized in that the sealing ring comprises a polyamide material.