U.S. patent application number 13/827782 was filed with the patent office on 2014-09-18 for hydraulically balanced stepwise variable displacement vane pump.
This patent application is currently assigned to STEERING SOLUTIONS IP HOLDING CORPORATION. The applicant listed for this patent is John S. Beam, Thomas C. Rytlewski, Albert C. Wong. Invention is credited to John S. Beam, Thomas C. Rytlewski, Albert C. Wong.
Application Number | 20140271299 13/827782 |
Document ID | / |
Family ID | 51501127 |
Filed Date | 2014-09-18 |
United States Patent
Application |
20140271299 |
Kind Code |
A1 |
Wong; Albert C. ; et
al. |
September 18, 2014 |
HYDRAULICALLY BALANCED STEPWISE VARIABLE DISPLACEMENT VANE PUMP
Abstract
A binary vane pump providing a balanced, stepwise variable
displacement is provided. The binary vane pump includes a pressure
plate having first and second discharge ports configured to
discharge fluid from the binary vane pump to a first discharge path
and a thrust plate having third and fourth discharge ports
configured to discharge fluid from the binary vane pump to a second
discharge path. The binary vane pump also includes a ring
positioned axially between the pressure plate and thrust plate, the
ring having an inner cam surface, a rotor rotatably disposed within
the ring, the rotor having a plurality of slots and a plurality of
vanes received and movable within respective slots, and a shaft
extending along an axis through the rotor and configured to rotate
the rotor so that the vanes are rotatable within the ring.
Inventors: |
Wong; Albert C.; (Saginaw,
MI) ; Rytlewski; Thomas C.; (Auburn, MI) ;
Beam; John S.; (Freeland, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Wong; Albert C.
Rytlewski; Thomas C.
Beam; John S. |
Saginaw
Auburn
Freeland |
MI
MI
MI |
US
US
US |
|
|
Assignee: |
STEERING SOLUTIONS IP HOLDING
CORPORATION
Saginaw
MI
|
Family ID: |
51501127 |
Appl. No.: |
13/827782 |
Filed: |
March 14, 2013 |
Current U.S.
Class: |
418/15 |
Current CPC
Class: |
F01C 21/0863 20130101;
F04C 11/001 20130101; F04C 2/3446 20130101; F04C 14/02 20130101;
F04C 15/06 20130101 |
Class at
Publication: |
418/15 |
International
Class: |
F04C 15/06 20060101
F04C015/06; F04C 2/22 20060101 F04C002/22 |
Claims
1. A binary vane pump comprising: a pressure plate including a
first discharge port and a second discharge port configured to
discharge fluid from the binary vane pump to a first discharge
path; a thrust plate including a third discharge port and a fourth
discharge port configured to discharge fluid from the binary vane
pump to a second discharge path; a ring positioned axially between
the pressure plate and thrust plate, the ring having an inner cam
surface; a rotor rotatably disposed within the ring, the rotor
comprising a plurality of slots and a plurality of vanes, vanes of
the plurality vanes corresponding to respective slots of the
plurality of slots and radially movable with the respective slots;
and a shaft extending along an axis through the rotor and
configured to rotate the rotor so the vanes are rotatable within
the ring.
2. The binary vane pump of claim 1, wherein the ring defines an
elongated main chamber having a minor diameter and a major
diameter.
3. The binary vane pump of claim 2, wherein the rotor and vanes are
positioned within the ring to divide the main chamber into a first
pumping chamber at one side of the minor axis and a second pumping
chamber at another side of the minor axis.
4. The binary vane pump of claim 3, wherein the first discharge
port and third discharge port are in fluid communication with the
first pumping chamber and the second discharge port and fourth
discharge port are in fluid communication with the second pumping
chamber.
5. The binary vane pump of claim 4, wherein the first discharge
port and second discharge port are positioned diametrically
opposite to one another.
6. The binary vane pump of claim 5, wherein the third discharge
port and fourth discharge port are positioned diametrically
opposite to one another.
7. The binary vane pump of claim 6, wherein the second discharge
path is selectively separated from the first discharge path by a
check valve.
8. The binary vane pump of claim 7, wherein the second discharge
path is in fluid communication with a low pressure reservoir when
the second discharge path is separated from the first discharge
path by the check valve.
9. The binary vane pump of claim 1, wherein the pressure plate
further comprises at least one first undervane port configured to
supply a first undervane pressure.
10. The binary vane pump of claim 9, wherein the first undervane
pressure urges the plurality of vanes into contact with the inner
cam surface.
11. The binary vane pump of claim 10, wherein the thrust plate
further comprises at least one second undervane port configured to
supply a second undervane pressure.
12. The binary vane pump of claim 11, wherein the second undervane
pressure urges the plurality of vanes into contact with the inner
cam surface.
13. The binary vane pump of claim 1, wherein the thrust plate
further comprises at least one second undervane port configured to
supply a second undervane pressure.
14. The binary vane pump of claim 13, wherein the second undervane
pressure urges the plurality of vanes into contact with the inner
cam surface.
Description
BACKGROUND OF THE INVENTION
[0001] The following description relates to a vane pump, and in
particular, a hydraulically balanced, stepwise variable
displacement binary vane pump.
[0002] A conventional vane pump may include a thrust plate, a ring,
a rotor having vanes connected thereto, a pressure plate and a
drive shaft. The vane pump may be configured as a balanced
cartridge design having two pumping chambers. Each pumping chamber
includes an intake port and a discharge port. The respective intake
ports and discharge ports are symmetrically arranged. Due at least
in part to this arrangement, forces generated at one side of the
pump are counteracted by the other side.
[0003] In the conventional vane pump, two pumping chambers formed
in the ring are connected to a common output circuit. That is, the
two pumping chambers discharge fluid to a common circuit via
respective discharge ports. As a result, the pumping chambers both
push against a common resistance in the common circuit, thereby
providing a high flow rate even when a high flow rate may not be
necessary. The common resistance on the two pumping chambers
requires more mechanical torque/power to drive the pump.
[0004] A binary vane pump having a variable displacement has been
proposed. In such a pump, two pump chambers have a respective
discharge port. Each discharge port flows to a different flow path.
Flow output may be controlled by closing a valve to restrict flow
from one of the discharge ports. However, this configuration may
result in an unbalanced load when the load applied is different for
each pumping chamber. The unbalanced load may lead to excess noise
and/or wear on the parts of the pump, which may reduce the service
life of the pump.
[0005] Accordingly, it is desirable to provide a binary vane pump
that separates the two pumping chambers in a balanced arrangement
and allows for stepwise variable displacement. In such a
configuration, flow output from the pump may be selectively
controlled while balancing the loads in the pump, so that the
mechanical torque/power required to the drive the pump may be
reduced when one pumping chamber is ported to a lower path of
resistance.
SUMMARY OF THE INVENTION
[0006] According to an exemplary embodiment of the present
invention, there is provided a binary vane pump. The binary vane
pump includes a pressure plate having a first discharge port and a
second discharge port configured to discharge fluid from the binary
vane pump to a first discharge path and a thrust plate having a
third discharge port and a fourth discharge port configured to
discharge fluid from the binary vane pump to a second discharge
path. The binary vane pump further includes a ring positioned
axially between the pressure plate and thrust plate, the ring
having an inner cam surface, a rotor rotatably disposed within the
ring, the rotor having a plurality of slots and a plurality of
vanes, vanes of the plurality vanes corresponding to respective
slots of the plurality of slots and radially movable with the
respective slots, and a shaft extending along an axis through the
rotor and configured to rotate the rotor so the vanes are rotatable
within the ring.
[0007] These and other advantages and features will become more
apparent from the following description taken in conjunction with
the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] The subject matter which is regarded as the invention is
particularly pointed out and distinctly claimed in the claims at
the conclusion of the specification. The foregoing and other
features, and advantages of the invention are apparent from the
following detailed description taken in conjunction with the
accompanying drawings in which:
[0009] FIG. 1 is a perspective view of a binary vane pump according
to an exemplary embodiment of the present invention;
[0010] FIG. 2 is an exploded view of a binary vane pump according
to an exemplary embodiment of the present invention;
[0011] FIG. 3 is an axial view of an inner side of a pressure plate
of a binary vane pump according to an exemplary embodiment of the
present invention;
[0012] FIG. 4 is an axial view of an inner side of a thrust plate
of a binary vane pump according to an exemplary embodiment of the
present invention; and
[0013] FIG. 5 is a diagram illustrating flow path through a binary
vane pump according to an exemplary embodiment of the present
invention;
DETAILED DESCRIPTION
[0014] Referring now to the Figures, where the invention will be
described with reference to specific embodiments, without limiting
same, FIGS. 1 and 2 show a binary vane pump 20 in accordance with
an exemplary embodiment of the present invention. Referring to FIG.
1, the binary vane pump 20 includes a thrust plate 22, a ring 24, a
rotor 26, a pressure plate 28 positioned about an axis `A`.
[0015] FIG. 2 shows an exploded view of the binary vane pump 20
according to an exemplary embodiment of the present invention. A
shaft 30 extends through the thrust plate 22, ring 24, and rotor 26
along the axis `A` and is configured to rotate to drive the binary
vane pump 20. In an exemplary embodiment, the shaft 30 also extends
at least partly into the pressure plate 28.
[0016] The thrust plate 22 includes a central opening 32,
positioned about the axis `A`, through which the shaft 30 extends.
The thrust plate 22 includes a flange configured so that the thrust
plate 22 may be non-rotatably fastened to an adjacent vehicle
component. Thus, the shaft 30 may rotate within the central opening
23 of the thrust plate 22.
[0017] In an exemplary embodiment, the ring 24 includes a plurality
of intakes 34. In one example, the ring 24 may include four intakes
34. A first two intakes may be positioned on axially opposite sides
of the ring 24. A second two intakes may be positioned on a
diametrically opposite side of the ring 24 from the first two
intakes, and may be positioned on axially opposite sides of the
ring 24 from one another. It is understood, however, that a
different number of intakes may be included, and the intakes may be
positioned on adjacent components, such as the thrust plate 22 or
the pressure plate 28.
[0018] An inner circumferential surface of the ring 24 presents an
inner cam surface 36. The inner cam surface 36 defines a generally
oblong or elongated shape such that ring 24 includes a generally
oblong or elongated main chamber 38 radially bounded by the inner
cam surface 36. The main chamber 38 has a minor diameter and a
major diameter.
[0019] The rotor 26 is positioned in the main chamber 38 of the
ring 24. The rotor 26 includes an opening 40 configured to receive
the shaft 30. The shaft 30 is rotatable and the rotor 26 is
connected to the shaft 30 at the opening 40 so that the rotor 26
rotates with the shaft 30. Thus, the rotor 26 may rotate about the
axis `A` together with the shaft 30. In an exemplary embodiment,
the rotor 26 is positioned on a splined section of the shaft 30,
and the rotor 26 includes a plurality of splines within the opening
40 to rotationally secure the rotor 26 to the shaft 30. It is
understood, however, that other mechanisms may be used to
rotationally secure the rotor 26 to the shaft 30 such that the
rotor 26 rotates with the shaft 30.
[0020] The rotor 26 includes a plurality of radially extending
slots 42 configured to receive respective vanes 44. The vanes 44
are movable in a radial direction of the rotor 26 within respective
slots 42 so that the vanes 44 may contact the inner cam surface 36
during rotation of the rotor 26.
[0021] The rotor 26 is positioned within the main chamber 38 such
that a variable clearance is formed between the rotor 26 and inner
cam surface 36. The vanes 44 extend across the variable clearance
and are movable with respect slots 42 to accommodate variances in
the clearance. In an exemplary embodiment, the variable clearance
is at a minimum value along the minor diameter. The variable
clearance increases toward the major diameter and is at a maximum
along the major diameter. The variable clearance decreases moving
from the major diameter toward to the minor diameter.
[0022] The rotor 26 and the vanes 44 divide the main chamber 38
into a first pumping chamber 46 and a second pumping chamber 48 at
the minor diameter. That is, the first pumping chamber 46 is formed
on one side of the minor diameter and the second pumping chamber 48
is formed on another side of the minor diameter, separated from the
first pumping chamber 46 by the rotor 26 and vanes 44. Accordingly,
in an exemplary embodiment, the first pumping chamber 46 is
positioned diametrically opposite from the second pumping chamber
48 in the ring 24. In an exemplary embodiment, a pumping chamber
refers to a volume between the rotor 26 and the inner cam surface
36 of the ring 24 which includes at least one intake 34 and at
least one discharge port in communication therewith, as described
further below. In an exemplary embodiment, the thrust plate 22 and
pressure plate 28 provide axial boundaries of the first pumping
chamber 46 and second pumping chamber 48.
[0023] FIG. 3 illustrates an inner side of the pressure plate 28
according to an exemplary embodiment of the present invention.
Referring to FIGS. 2 and 3, the pressure plate 28 includes an
opening 50 centered on the axis `A`. The shaft 30 may extend
through the opening 50. The inner side of the pressure plate 28
faces the ring 24, main chamber 38, first pumping chamber 46,
second pumping chamber 48, rotor 26 and vanes 44. The pressure
plate 28 is substantially rotationally fixed relative to the ring
24 and serves as an axial boundary for the first and second pumping
chambers 46, 48 (FIG. 2). A high system pressure is applied on an
outer surface of the pressure plate 28 to compress the pressure
plate 28 and ring 24 together to minimize leakage paths.
[0024] In an exemplary embodiment, the pressure plate 28 includes a
first discharge port 52 and a second discharge port 54. The first
discharge port 52 is in fluid communication with the first pumping
chamber 46 and discharges to a first discharge path 56 outside of
the first pumping chamber 46. The second discharge port 54 is in
fluid communication with the second pumping chamber 48 and also
discharges to the first discharge path 56 outside of the second
pumping chamber 48. Thus, the first and second discharge ports 52,
54 allow fluid to flow from the first pumping chamber 46 and second
pumping chamber 48 to the first discharge path 56. The first
discharge path 56 flows to a hydraulic load downstream from the
binary vane pump 20. A high system pressure from the hydraulic load
acts against the binary vane pump 20 in via the first discharge
path 56.
[0025] In an exemplary embodiment, the first and second discharge
ports 52, 54 may be formed as openings extending axially through an
axial face of the pressure plate 28. However, it is understood the
present invention is not limited to this example, and that other
configurations of the first and second discharge ports 52, 54 are
envisioned. For example, the first and second discharge ports 52,
54 may extend radially through a radial wall or extend through a
combination of an axial wall and radial wall.
[0026] FIG. 4 illustrates an inner side of the thrust plate 22
according to an exemplary embodiment of the present invention. In
an exemplary embodiment, the thrust plate 22 includes a third
discharge port 58 and a fourth discharge port 60. The third
discharge port 58 is in fluid communication with the first pumping
chamber 46 and discharges to a second discharge path 62 outside of
the first pumping chamber 46. The fourth discharge port 60 is in
fluid communication with the second pumping chamber 48 and
discharges to the second discharge path 62 outside of the second
pumping chamber 48. In the exemplary embodiments above, the third
and fourth discharge ports 58, 60 allow fluid to flow from the
first pump chamber 46 and second pump chamber 48 to the second
discharge path 62.
[0027] In an exemplary embodiment, the third and fourth discharge
ports 58, 60 may both include an inlet 64 formed in an axial face
of the thrust plate 22 and extend partially through the thrust
plate 22 to an outlet 66 formed in an outer radial wall of the
thrust plate 22. Thus, fluid flowing from the first and second
pumping chambers 46, 48 may flow through respective inlets 64 of
the third and fourth discharge ports 58, 60 formed on an axial
face, and be discharged from the thrust plate through respective
outlets 66 on an outer radial wall. It is understood the present
invention is not limited to this example, and that other
configurations of the third and fourth discharge ports 58, 60 are
envisioned. For example, the third and fourth discharge ports 58,
60 may extend axially through an axial wall, or radially through a
radial wall.
[0028] In an exemplary embodiment, the first discharge port 52 and
the second discharge port 54 are positioned diametrically opposite,
i.e., 180 degrees apart, from one another on the pressure plate 28.
In addition, the third discharge port 58 and the fourth discharge
port 60 are positioned diametrically opposite, i.e., 180 degrees
apart, from one another on the thrust plate 22. Due to this
positioning of the discharge ports, fluid discharge loads on the
pump 20 may be balanced, and stresses on various pump components
may be minimized. It is understood however that the present
invention is not limited to this specific configuration. For
example, the first and second discharge ports 52, 54 may be
positioned at non-180 degree angles relative to one another, so
long as fluid discharge loads, and in turn, stresses on the pump
are maintained at a suitable level. Likewise, the third and fourth
discharge ports 58, 60 may also be positioned at non-180 degree
angles relative to one another.
[0029] While the first and second discharge ports 52, 54 are
described as being positioned in the pressure plate 28 and the
third and fourth discharge ports 58, 60 are described as being
positioned in the thrust plate 22 in the exemplary embodiments
above, it is understood that the first, second, third and fourth
discharge ports 52, 54, 58, 60 may all be positioned either the
pressure plate 28 or the thrust plate, or some combination
thereof.
[0030] In an exemplary embodiment, the first and second discharge
ports 52, 54 are formed of a similar size, shape and configuration,
as each other so that similar quantities of fluid may flow
therethrough. Accordingly, a balanced fluid discharge load may be
achieved. Likewise, the third and fourth discharge ports 58, 60 may
be formed similarly as well.
[0031] A pumping volume is defined between two adjacent vanes 44,
the rotor 26, the inner cam surface 36, the thrust plate 22 and the
pressure plate 28. In operation, the pumping volume increases as
adjacent vanes 44 rotate from the minor diameter toward the major
diameter. The pumping volume becomes at least partially filled with
the fluid during rotation. The pumping volume then decreases as the
rotor 26 rotates and the adjacent vanes 44 move from the major
diameter toward the minor diameter. The decrease in pumping volume
causes an increase in pressure on the fluid. The increased pressure
causes the fluid to flow from the pumping volume out through a
discharge port 52, 54, 58, 60. For example, the first discharge
port 52 is positioned in fluid communication with the first pumping
chamber 46 at a location where pressure within the pumping volume
is sufficient to force the fluid to flow from the first pumping
chamber 46 through the first discharge port 52 to the first
discharge path 56. Likewise, the second discharge port 54 is
positioned in fluid communication with the second pumping chamber
48 at a location where pressure within the pumping volume is
sufficient to force the fluid to flow from the second pumping
chamber 48 through the second discharge port 54 to the first
discharge path 56.
[0032] Referring again to FIG. 3, the inner side of the pressure
plate 28 may further include at least one first undervane port 57.
In an exemplary embodiment, the first undervane port 57 may be
formed as an opening extending through the pressure plate 28. The
first undervane port 57 is configured to communicate the high
system pressure applied on an outer or back surface of the pressure
plate 28 to the vanes 44 as a first undervane pressure, to urge the
vanes 44 radially outward from the rotor 26 and into contact with
the inner cam surface 36. That is, high system pressure from
outside the main chamber 38 may be exerted on the vanes 44 as an
undervane pressure to act behind the vanes (i.e., on a radially
inner side) and urge the vanes 44 into contact with the inner cam
surface 36 in one of, or both of the first pumping chamber 46 and
second pumping chamber 48. The vanes 44 may also be urged into
contact with the inner cam surface 36 due a centripetal force
resulting from rotation of the rotor 26. The first undervane port,
or ports, 57 may be in fluid communication with a respective first
and/or second discharge port 52, 54. For example, a channel may
extend along the inner axial surface of the pressure plate from the
undervane port 57 to the respective discharge port 52, 54.
[0033] Referring again to FIG. 4, the inner side of the thrust
plate 22 may include at least one second undervane port 68. In an
exemplary embodiment, the second undervane port 68 may be formed as
an opening extending through the thrust plate 22. The second
undervane port 68 is configured to communicate high system pressure
to the vanes 44 as a second undervane pressure, to urge the vanes
44 radially outward from the rotor 26 and into contact with the
inner cam surface 36. As noted above, the vanes 44 may also be
urged into contact with the inner cam surface 36 due a centripetal
force resulting from rotation of the rotor 26. The second undervane
port, or ports, 68 may be in fluid communication with a respective
third and/or fourth discharge port 58, 60. For example, a channel
may extend along the inner axial surface of the thrust plate 22
from the second undervane port 68 to the respective discharge port
58, 60. The channel may also be formed within the thrust plate 22
itself, so that the channel is not open to directly to a pumping
chamber 46, 48.
[0034] It is understood that the undervane ports 57, 68 are not
limited to the configurations described above. For example, the
undervane ports may be formed on only one of the pressure plate 28
and thrust plate 22.
[0035] FIG. 5 is a diagram of a flow path through a binary vane
pump 20 according to an exemplary embodiment of the present
invention. The first and second discharge ports 52, 54 are fluidly
coupled to and discharge fluid to the first discharge path 56. The
first discharge path 56 acts on a high system pressure to drive a
hydraulic load H.
[0036] The third and fourth discharge ports 58, 60 are fluidly
coupled to and discharge fluid to the second discharge path 62. The
second discharge path 62 is selectively separated from the first
discharge path 56 by a check valve 70 positioned in the second
discharge path 62. With the check valve 70 in a closed position,
the second discharge path 62 is isolated from the high system
pressure and hydraulic load H. Thus, the binary vane pump 20 does
not require an increased amount of force to pump the fluid against
the high system pressure out of the third and fourth and discharge
ports 58, 60. When the check valve 70 is closed, a reservoir valve
is opened so that fluid from the second discharge path 62 may flow
to the low pressure reservoir 72 fluidly coupled to the second
discharge path. That is, the pump 20 pumps against a low pressure
rather than a high pressure through the third and fourth discharge
ports 58, 60 when the check valve 70 is closed, thereby requiring
less power/torque.
[0037] In operation, the binary vane pump 20 may operate to provide
a stepwise variable displace to account for "high load" and "low
load" scenarios. In a high load scenario, the check valve 70 is
controlled to move to an open position and the reservoir valve is
closed. With the check valve 70 in the open position, both the
first discharge path 56 and second discharge path 62 are exposed to
the high system pressure. Thus, in the high load scenario, the
binary vane pump 20 pumps fluid through the first and second
discharge ports 52, 54 into the first discharge path 56 and through
the third and fourth discharge ports 58, 60 into the second
discharge path 62 to act against the hydraulic load H. Accordingly,
in the high load scenario, the binary vane pump 20 has an increased
fluid output to the hydraulic load.
[0038] In the low load scenario, the check valve 70 is moved to a
closed position, thereby restricting flow from the second discharge
path 62 to the hydraulic load and the reservoir valve is opened.
Thus, in this scenario, only fluid discharged through the first and
second discharge ports 52, 54 acts against the hydraulic load. The
second discharge path 62 is connected to a lower pressure reservoir
72. Thus, the pump 20 is pumping against a low resistance through
the third and fourth discharge ports 58, 60. Accordingly, the
binary vane pump 20 requires less power to operate.
[0039] It is understood that addition discharge ports may be
provided in the pressure plate and/or thrust plate which have a
check valve positioned between them and the hydraulic load, such
that additional load may be output from the pump 20 upon opening of
the check valve, and the output of the pump 20 maybe more
accurately controlled.
[0040] With further reference to FIG. 5, the binary vane pump 20
may also include a series of grooves and sealing devices installed
in the grooves along an outer periphery. In an exemplary
embodiment, the thrust plate 22 may include two circumferential
grooves 74, with an O-ring 76 positioned in each groove. Further,
the pressure plate 28 may include a groove 78 having an O-ring 80
positioned therein.
[0041] The integration of the features above may be utilized to
effectively achieve better control over flow and pressure, and
thus, provide a more efficient use of mechanical torque/power. In
addition, the configurations described in the exemplary embodiments
above may provide a balanced output from the binary vane pump,
which may reduces stresses within the pump and surrounding
components. The binary vane pump 20 of the exemplary embodiments
above may be used together with, for example, an automatic
transmission system to power or lubricate the system, or engine oil
pumps. It is understood that the binary vane pump 20 of the
exemplary embodiments above may be used together with other
hydraulic systems as well, and in particular, hydraulic systems
where it may be advantageous to selectively control the flow from
the pump.
[0042] In the exemplary embodiments above, the first and second
pumping chambers 46, 48 discharge fluid primarily through the first
and second discharge ports 52, 54 to work against high system
pressure in a low load scenario. Where higher output is required
from the pump 20 to act against a higher hydraulic load, the check
valve 70 may be opened, while the reservoir valve is closed.
Accordingly, the first and second pumping chambers 46, 48 discharge
fluid through the first and second discharge ports 52, 54 and the
third and fourth discharge ports 58, 60 to work against the high
system pressure from the hydraulic load H. In addition, because the
first and second discharge ports may be positioned diametrically
opposite from another, and the third and fourth discharge ports may
be positioned diametrically opposite one another, output from the
pump is balanced and stresses resulting from imbalanced discharge
may be reduced or eliminated.
[0043] While the invention has been described in detail in
connection with only a limited number of embodiments, it should be
readily understood that the invention is not limited to such
disclosed embodiments. Rather, the invention can be modified to
incorporate any number of variations, alterations, substitutions or
equivalent arrangements not heretofore described, but which are
commensurate with the spirit and scope of the invention.
Additionally, while various embodiments of the invention have been
described, it is to be understood that aspects of the invention may
include only some of the described embodiments. Accordingly, the
invention is not to be seen as limited by the foregoing
description.
* * * * *