U.S. patent application number 13/328060 was filed with the patent office on 2013-06-20 for multi-discharge hydraulic vane pump.
This patent application is currently assigned to Goodrich Pump & Engine Control Systems, Inc.. The applicant listed for this patent is Mihir C. Desai, Xingen Dong, Paul J. Paluszewski. Invention is credited to Mihir C. Desai, Xingen Dong, Paul J. Paluszewski.
Application Number | 20130156564 13/328060 |
Document ID | / |
Family ID | 47504738 |
Filed Date | 2013-06-20 |
United States Patent
Application |
20130156564 |
Kind Code |
A1 |
Dong; Xingen ; et
al. |
June 20, 2013 |
MULTI-DISCHARGE HYDRAULIC VANE PUMP
Abstract
A hydraulic vane pump includes a pump body defining an interior
pumping chamber, an inlet port, and at least one discharge port. A
cam ring is disposed within the interior pumping chamber and
defines a continuous peripheral cam surface. A rotor is mounted for
axial rotation within the interior pumping chamber. A plurality of
vanes are mounted for radial movement within slots formed in the
rotor. The pump includes axially opposed first and second wear
disks disposed within the interior pumping chamber. The first wear
disk is a floating wear disk and has an outer periphery which is
positioned radially inward of the cam surface and is adapted and
configured to slide axially with respect to the cam surface. The
second wear disk is positioned adjacent to a second end surface of
the rotor.
Inventors: |
Dong; Xingen; (Farmington,
CT) ; Paluszewski; Paul J.; (Meriden, CT) ;
Desai; Mihir C.; (Yorba Linda, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Dong; Xingen
Paluszewski; Paul J.
Desai; Mihir C. |
Farmington
Meriden
Yorba Linda |
CT
CT
CA |
US
US
US |
|
|
Assignee: |
Goodrich Pump & Engine Control
Systems, Inc.
|
Family ID: |
47504738 |
Appl. No.: |
13/328060 |
Filed: |
December 16, 2011 |
Current U.S.
Class: |
415/196 |
Current CPC
Class: |
F04C 15/0026 20130101;
F04C 15/0096 20130101; F04C 2240/801 20130101; F04C 11/001
20130101; F04C 2220/24 20130101; F01C 21/0863 20130101; F04C 2/3446
20130101 |
Class at
Publication: |
415/196 |
International
Class: |
F04D 29/40 20060101
F04D029/40 |
Goverment Interests
GOVERNMENT LICENSE RIGHTS
[0001] This invention was made with government support under
contract number AATD W911W6-06-D-0005-0004 awarded by the U.S.
Army. The government has certain rights in the invention.
Claims
1. A hydraulic vane pump, comprising: a) a pump body including an
interior pumping chamber and defining an inlet port for allowing
fluid to be provided to the interior pumping chamber and at least
one discharge port for allowing pressurized fluid to be discharged
from the interior pumping chamber; b) a cam ring disposed within
the interior pumping chamber and defining a continuous peripheral
cam surface; c) rotor mounted for axial rotation within the
interior pumping chamber and defining a pump axis; d) a plurality
of circumferentially spaced apart radially extending vanes mounted
for radial movement within slots formed in the rotor, the plurality
of vanes defining an equal number of circumferentially spaced apart
volume chambers which extend between an outer periphery of the
rotor and the cam surface for carrying pressurized fluid; and e)
axially opposed first and second wear disks disposed within the
interior pumping chamber, the first wear disk having an outer
periphery which is positioned radially inward of the cam surface
and is adapted and configured to slide axially with respect to the
cam surface, so as to provide for thermal expansion of the rotor
and vanes, and the second wear disk being positioned adjacent to a
second end surface of the rotor.
2. A hydraulic vane pump as recited in claim 1, wherein the vane
pump is a multi-discharge hydraulic vane pump and the pump body
defines four radially-oriented discharge ports, each port allowing
pressurized fluid to be discharged from the interior pumping
chamber.
3. A hydraulic vane pump as recited in claim 1, wherein the first
wear disk is biased towards the first end surface of the rotor
using a spring element towards the first end surface of the
rotor.
4. A hydraulic vane pump as recited in claim 1, wherein the first
wear disk is biased towards the first end surface of the rotor
using pressurized fluid discharged from the volume chambers defined
by the vanes.
5. A hydraulic vane pump as recited in claim 1, wherein the pump
body further includes a rear housing plate and the inlet port
extends axially through the rear housing plate to the interior
chamber.
6. A hydraulic vane pump as recited in claim 1, wherein the cam
surface includes four quadrantal cam segments, wherein
diametrically opposed cam segments have identical cam profiles, and
each cam segment defines an inlet arc, a discharge arc and two seal
arcs.
7. A hydraulic vane pump as recited in claim 6, wherein the cam
ring includes a plurality of inlet chambers arranged and configured
to receive fluid from the inlet port and distribute the fluid to
the inlet arc of each cam segment.
8. A hydraulic vane pump as recited in claim 6, wherein the cam
ring includes a plurality of discharge chambers which communicate
with the discharge arc of each cam segment and are arranged and
configured to facilitate the discharge of pressurized fluid from
the interior pumping chamber.
9. A hydraulic vane pump as recited in claim 1, wherein each vane
slot has an under-vane pocket for receiving fluid and the pressure
of the undervane pocket is dependent on an angular position of the
rotor.
10. A hydraulic vane pump as recited in claim 9, wherein the rotor
includes a plurality of axially-extending under-vane passages, each
under-vane passage communicating with an under-vane pocket through
a connector passage.
11. A hydraulic vane pump as recited in claim 10, wherein each wear
disk includes flow passages for communicating fluid into the
under-vane pockets and under-vane passages associated with each
vane slot and the pressure of the undervane pocket is dependent on
an angular position of the rotor.
12. A hydraulic vane pump as recited in claim 9, wherein the
pressure of the fluid in the rotor under-vane passage whilst
positioned in the inlet arc segment is about equal to pump inlet
pressure.
13. A hydraulic vane pump as recited in claim 9, wherein the
pressure of the fluid in the rotor under-vane passage whilst
positioned in the discharge arc segment is about equal to pump
discharge pressure.
14. A hydraulic vane pump as recited in claim 6, further comprising
a fluid metering system for extracting fluid flow from the
discharge arcs of the four cam segments.
15. A hydraulic vane pump as recited in claim 14, wherein the fluid
metering system has a first operating condition in which fluid is
extracted from the discharge arcs of all four cam segments and
combined for delivery to a source of fluid demand.
16. A hydraulic vane pump as recited in claim 14, wherein the fluid
metering system has a second operating condition wherein fluid is
extracted from a first pair of diametrically opposed discharge arcs
for delivery to a source of fluid demand and fluid from a second
pair of diametrically opposed discharge arcs bypasses the source of
fluid demand and returns to the pumping chamber.
17. A multi-discharge hydraulic vane pump, comprising: a) a pump
body including an interior pumping chamber and defining a axially
extending inlet port for allowing fluid to be provided to the
interior pumping chamber and four discharge ports for allowing
pressurized fluid to be discharged from the interior pumping
chamber; b) a cam ring disposed within the interior pumping chamber
and defining a continuous peripheral cam surface; c) rotor mounted
for axial rotation within the interior pumping chamber and defining
a pump axis; d) a plurality of circumferentially spaced apart
radially extending vanes mounted for radial movement within slots
formed in the rotor, the plurality of vanes defining an equal
number of circumferentially spaced apart volume chambers which
extend between an outer periphery of the rotor and the cam surface
for carrying pressurized fluid; and e) axially opposed first and
second wear disks disposed within the interior pumping chamber.
18. A multi-discharge hydraulic vane pump as recited in claim 17,
wherein the first wear disk has an outer periphery which is
positioned radially inward of the cam surface and is mounted for
sliding movement with respect to the cam surface, so as to provide
for thermal expansion of the rotor and vanes, and the second wear
disk being positioned adjacent to a second end surface of the
rotor.
19. A multi-discharge hydraulic vane pump as recited in claim 18,
wherein the first wear disk is biased towards the first end surface
of the rotor using a spring element towards the first end surface
of the rotor.
20. A multi-discharge hydraulic vane pump as recited in claim 18,
wherein the first wear disk is biased towards the first end surface
of the rotor using pressurized fluid discharged from the volume
chambers defined by the vanes.
21. A multi-discharge hydraulic vane pump as recited in claim 17,
wherein the pump body further includes a rear housing plate and the
inlet port extends axially through the side plate towards the
interior chamber.
22. A multi-discharge hydraulic vane pump as recited in claim 17,
wherein the cam surface includes four quadrantal cam segments,
wherein diametrically opposed cam segments have identical cam
profiles, and each cam segment defines an inlet arc, a discharge
arc and two seal arcs.
23. A multi-discharge hydraulic vane pump as recited in claim 17,
wherein the cam ring includes a plurality of inlet chambers
arranged and configured to receive fluid from the inlet port and
distribute the fluid to the inlet arc of each cam segment
24. A multi-discharge hydraulic vane pump as recited in claim 17,
wherein the cam ring includes a plurality of discharge chambers
which communicate with the discharge arc of each cam segment and
are arranged and configured to facilitate the discharge of
pressurized fluid from the interior pumping chamber.
25. A multi-discharge hydraulic vane pump as recited in claim 17,
wherein each vane slot has an under-vane pocket for receiving fluid
and the pressure in the undervane pocket is dependent on an angular
position of the rotor.
26. A multi-discharge hydraulic vane pump as recited in claim 25,
wherein the rotor includes a plurality of axially-extending
under-vane passages, each under-vane passage communicating with an
under-vane pocket through a connector passage.
27. A multi-discharge hydraulic vane pump as recited in claim 26,
wherein each wear disk includes flow passages for communicating
fluid into the under-vane pockets and under-vane passages
associated with each vane slot based and the pressure of the
undervane pocket is dependent on an angular position of the
rotor.
28. A multi-discharge hydraulic vane pump as recited in claim 25,
wherein the pressurized fluid in the rotor under-vane pocket whilst
positioned in the inlet arc segment is about equal to pump inlet
pressure.
29. A multi-discharge hydraulic vane pump as recited in claim 25,
wherein the pressurized fluid in the rotor under-vane pocket whilst
positioned in the discharge arc segment is about equal to pump
discharge pressure.
30. A multi-discharge hydraulic vane pump as recited in claim 22,
further comprising a fluid metering system for extracting fluid
flow from the discharge arcs of the four cam segments.
31. A multi-discharge hydraulic vane pump as recited in claim 30,
wherein the fluid metering system has a first operating condition
in which fluid is extracted from the discharge arcs of all four cam
segments and combined for delivery to a source of fluid demand.
32. A multi-discharge hydraulic vane pump as recited in claim 30,
wherein the fluid metering system has a second operating condition
wherein fluid is extracted from a first pair of diametrically
opposed discharge arcs for delivery to a source of fluid demand and
fluid from a second pair of diametrically opposed discharge arcs
bypasses the source of fluid demand and returns to the pumping
chamber.
33. A hydraulic vane pump, comprising: a) a pump body including an
interior pumping chamber and defining an inlet port for allowing
fluid to be provided to the interior pumping chamber and at least
one discharge port for allowing pressurized fluid to be discharged
from the interior pumping chamber; b) a cam ring disposed within
the interior pumping chamber and defining a continuous peripheral
cam surface, the cam ring also defining a plurality of inlet
chambers and discharge chambers, the inlet chambers being arranged
and configured to receive fluid from the inlet port and to
distribute the fluid to the interior pumping chamber, the discharge
chambers communicating with the interior pumping chamber and are
arranged and configured to facilitate the discharge of pressurized
fluid from the interior pumping chamber; c) a rotor mounted for
axial rotation within the interior pumping chamber and defining a
pump axis; d) a plurality of circumferentially spaced apart
radially extending vanes mounted for radial movement within slots
formed in the rotor, the plurality of vanes defining an equal
number of circumferentially spaced apart volume chambers which
extend between an outer periphery of the rotor and the cam surface
for carrying pressurized fluid, wherein each vane slot has an
under-vane pocket for receiving pressurized fluid based on an
angular position of the rotor; and e) axially opposed first and
second wear disks disposed within the interior pumping chamber, the
first wear disk having an outer periphery which is positioned
radially inward of the cam surface and is axially biased towards a
first end surface of the rotor so as to provide for thermal
expansion of the rotor and vanes and the second wear disk being
positioned adjacent to a second end surface of the rotor.
34. The hydraulic vane pump as recited in claim 33, wherein each
wear disk includes flow passages for feeding fluid into the
under-vane pockets associated with each vane slot and the pressure
of the undervane pocket is dependent on an angular position of the
rotor.
Description
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The subject disclosure is directed to rotary vane pumps, and
more particularly, to a balanced split discharge vane pump that
provides a combined discharge flow for high fluid demand conditions
and a first (primary) discharge flow for low fluid demand
conditions, and still more particularly to a multi-discharge vane
pump that has an inlet port and four discharge ports, includes a
floating side wear disk and a cam ring with internal flow passages,
and a rotor assembly with improved under-vane pumping features.
[0004] 2. Description of Related Art
[0005] Rotary hydraulic vane pumps are well known in the art, as
disclosed for example in U.S. Pat. No. 4,274,817 to Sakamaki et al.
and U.S. Pat. No. 5,064,362 to Hansen. A typical rotary vane pump
includes a circular rotor mounted for rotation within a larger
circular pumping chamber. The centers of these two circles are
typically offset, causing eccentricity. Vanes are mounted to slide
in and out of the rotor to create a plurality of volume chambers or
vane buckets that perform the pumping work. On the intake side of
the pump, the vane buckets increase in volume. These increasing
volume vane buckets are filled with fluid that is forced into the
pumping chamber by an inlet pressure. On the discharge side of the
pump, the vane buckets decrease in volume, forcing pressurized
fluid out of the pumping chamber.
[0006] It is desirable to match the fluid displacement of a vane
pump to the operating characteristics of the system with which the
pump is to be associated. For example, the maximum displacement of
a fuel pump should be coordinated with the maximum fuel
requirements of the associated engine application. However, system
requirements typically vary with operating conditions, so that a
fixed displacement fuel pump that is designed as a function of the
most demanding engine operating conditions may function with less
than desired efficiency under other operating conditions.
[0007] In the case of a fuel pump associated with a gas turbine
engine of an aircraft, fuel flow requirements, as quantified by
pump displacement per rotational speed, under engine starting
conditions greatly exceed fuel flow requirements during other less
demanding engine operating conditions, such as cruise, idle, decent
and taxi. Various attempts have been made to improve fuel pump
efficiency over the operating envelope of a gas turbine engine, by
utilizing different valve arrangements at the pump outlet to meter
a portion of the pump discharge to the engine as a function of
engine demand. However, these prior art arrangements are typically
complex and thus add cost to the pumping system. In other
implementations, variable displacement pumps have been utilized to
match pump output flow to system demand. However, these
implementations are at the expense of pump size/weight and
reliability because of an increase in pump radial/axial loading and
the incorporation of additional moving parts.
[0008] U.S. Patent Application Publication No. 2010/0316507,
entitled Split Discharge Vane Pump and Fluid Metering System
Therefor, discloses a positive displacement vane pump that is
adapted and configured to more closely match the operating
characteristics of the system with which it is associated, as well
as, a valving arrangement for effectively managing the flow of
fluid from the pump depending upon the fluid demand conditions of
the system with which it is associated. The disclosure of U.S.
Patent Application Publication No. 2010/0316507 is hereby
incorporated by reference in its entirety.
[0009] The pump disclosed in U.S. Patent Application Publication
No. 2010/0316507 solves many of the problems noted above with
respect to prior art pump constructions. However, there is need for
a positive displacement vane pump design that further increases
pumping efficiency over the operation range of fuel requirements
and reduces component degradation by more effectively balancing the
forces within the pumping chamber.
SUMMARY OF THE INVENTION
[0010] The present invention is directed to a hydraulic vane pump
that includes, inter alia, a pump body that defines an interior
pumping chamber and an inlet port for allowing fluid to be provided
to the interior pumping chamber and at least one discharge port for
allowing pressurized fluid to be discharged from the interior
pumping chamber. The pump further includes a cam ring that is
disposed within the interior pumping chamber and defines a
continuous peripheral cam surface; and a rotor mounted for axial
rotation within the interior pumping chamber and defining a pump
axis. A plurality of circumferentially spaced apart radially
extending vanes are mounted for radial movement within slots formed
in the rotor, the plurality of vanes define an equal number of
circumferentially spaced apart volume chambers which extend between
an outer periphery of the rotor and the cam surface for carrying
pressurized fluid. Still further, the pump includes axially opposed
first and second wear disks disposed within the interior pumping
chamber. The first wear disk has an outer periphery which is
positioned radially inward of the cam surface and is adapted and
configured to slide axially with respect to the cam surface, so as
to provide for thermal expansion of the rotor and vanes. The second
wear disk is fixedly positioned adjacent to a second end surface of
the rotor. However, as will be discussed below, the second wear
disk can also be a floating disk (i.e., adapted for sliding in the
axial direction).
[0011] In a preferred embodiment, the pump is a multi-discharge
hydraulic vane pump and the pump body defines four
radially-oriented discharge ports, each discharge port allowing
pressurized fluid to be discharged from the interior pumping
chamber.
[0012] It is envisioned that the first wear disk is biased towards
the first end surface of the rotor using a spring element.
Moreover, the first wear disk can be biased towards the first end
surface of the rotor using pressurized fluid discharged from the
volume chambers defined by the vanes.
[0013] In certain constructions of the present invention, the pump
body further includes a rear side plate and the inlet port extends
axially through the rear side plate to the interior chamber.
[0014] Preferably, the cam surface includes four quadrantal cam
segments, wherein diametrically opposed cam segments have identical
cam profiles, and each cam segment defines an inlet arc, a
discharge arc and two seal arcs.
[0015] In a preferred embodiment, the cam ring includes a plurality
of inlet chambers arranged and configured to receive fluid from the
inlet port and distribute the fluid to the inlet arc of each cam
segment. The cam ring can also includes a plurality of discharge
chambers which communicate with the discharge arc of each cam
segment and are arranged and configured to facilitate the discharge
of pressurized fluid from the interior pumping chamber.
[0016] It is presently preferred that each vane slot has an
under-vane pocket for receiving pressurized fluid based on an
angular position of the rotor. Additionally, in certain
embodiments, the rotor includes a plurality of axially-extending
under-vane passages, each under-vane passage communicating with an
under-vane pocket through a connector passage.
[0017] Preferably, each wear disk includes flow passages for
communicating fluid into the under-vane pockets and under-vane
passages associated with each vane slot. The pressure of the
undervane pocket is dependent on an angular position of the rotor.
Preferably, the fluid in the rotor under-vane passage whilst
positioned in the inlet arc segment is about equal to pump inlet
pressure and the fluid in the rotor under-vane passage whilst
positioned in the discharge arc segment is about equal to pump
discharge pressure.
[0018] Certain constructions of the vane pump of present invention
include a fluid metering system for extracting fluid flow from the
discharge arcs of the four cam segments. It is envisioned that the
metering system has a first operating condition in which fluid is
extracted from the discharge arcs of all four cam segments and
combined for delivery to a source of fluid demand. The fluid
metering system can also include a second operating condition
wherein fluid is extracted from a first (primary) pair of
diametrically opposed discharge arcs for delivery to a source of
fluid demand and fluid from a second pair of diametrically opposed
discharge arcs bypasses the source of fluid demand and returns to
the pumping chamber.
[0019] The present invention is also directed to a multi-discharge
hydraulic vane pump that includes, among other elements, a pump
body that has an interior pumping chamber and defines a axially
extending inlet port for allowing fluid to be provided to the
interior pumping chamber and four radially-extending discharge
ports for allowing pressurized fluid to be discharged from the
interior pumping chamber. The vane pump further includes a cam ring
disposed within the interior pumping chamber that defines a
continuous peripheral cam surface and a rotor mounted for axial
rotation within the interior pumping chamber that defines a pump
axis. A plurality of circumferentially spaced apart and radially
extending vanes are mounted for radial movement within slots formed
in the rotor. The plurality of vanes define an equal number of
circumferentially spaced apart volume chambers which extend between
an outer periphery of the rotor and the cam surface for carrying
pressurized fluid. The pump further includes axially opposed first
and second wear disks which are disposed within the interior
pumping chamber.
[0020] In a preferred embodiment, the first wear disk has an outer
periphery which is positioned radially inward of the cam surface
and is mounted for sliding movement with respect to the cam
surface, so as to provide for thermal expansion of the rotor and
vanes. The second wear disk is positioned adjacent to a second end
surface of the rotor.
[0021] It is envisioned that the first wear disk is biased towards
the first end surface of the rotor using a spring element.
Moreover, the first wear disk can be biased towards the first end
surface of the rotor using pressurized fluid discharged from the
volume chambers defined by the vanes.
[0022] In certain constructions of the present invention, the pump
body further includes a rear housing with an inlet port that
extends axially through the rear side plate to the interior
chamber.
[0023] Preferably, the cam surface includes four quadrantal cam
segments, wherein diametrically opposed cam segments have identical
cam profiles, and each cam segment defines an inlet arc, a
discharge arc and two seal arcs.
[0024] In a preferred embodiment, the cam ring includes a plurality
of inlet chambers arranged and configured to receive fluid from the
inlet port and distribute the fluid to the inlet arc of each cam
segment. The cam ring also includes a plurality of discharge
chambers which communicate with the discharge arc of each cam
segment and are arranged and configured to facilitate the discharge
of pressurized fluid from the interior pumping chamber.
[0025] It is presently preferred that each vane slot has an
under-vane pocket for receiving either low inlet or discharging
high outlet pressurized fluid based on an angular position of the
rotor. Additionally, in certain embodiments, the rotor includes a
plurality of axially-extending under-vane passages, each under-vane
passage communicating with an under-vane pocket through a connector
passage.
[0026] It is envisioned that each wear disk can includes flow
passages for communicating fluid into the under-vane pockets and
under-vane passages associated with each vane slot. The pressure of
the undervane pocket in dependent on an angular position of the
rotor. Preferably, the pressurized fluid in the rotor under-vane
passage whilst positioned in the inlet arc segment is about equal
to pump inlet pressure and the fluid in the rotor under-vane
passage whilst positioned in the discharge arc segment is about
equal to pump discharge pressure.
[0027] Certain constructions of the vane pump of present invention
include a fluid metering system for extracting fluid flow from the
discharge arcs of the four cam segments. It is envisioned that the
metering system has a first operating condition in which fluid is
extracted from the discharge arcs of all four cam segments and
combined for delivery to a source of fluid demand. The fluid
metering system can also include a second operating condition
wherein fluid is extracted from a first pair of diametrically
opposed discharge arcs for delivery to a source of fluid demand and
fluid from a second pair of diametrically opposed discharge arcs
bypasses the source of fluid demand and returns to the pumping
chamber.
[0028] The present invention is further directed to a hydraulic
vane pump that includes, inter alia, a pump body that defines an
interior pumping chamber, an inlet port for allowing fluid to be
provided to the interior pumping chamber and at least one discharge
port for allowing pressurized fluid to be discharged from the
interior pumping chamber. The hydraulic vane pump further includes
a cam ring disposed within the interior pumping chamber that
defines a continuous peripheral cam surface, the cam ring also
defining a plurality of inlet chambers and discharge chambers. The
inlet chambers are arranged and configured to receive fluid from
the inlet port and to distribute the fluid to the interior pumping
chamber and the discharge chambers communicate with the interior
pumping chamber and are arranged and configured to facilitate the
discharge of pressurized fluid from the interior pumping
chamber.
[0029] A rotor is mounted for axial rotation within the interior
pumping chamber and defines a pump axis. A plurality of
circumferentially spaced apart and radially extending vanes are
mounted for radial movement within slots formed in the rotor. The
plurality of vanes define an equal number of circumferentially
spaced apart volume chambers which extend between an outer
periphery of the rotor and the cam surface for carrying pressurized
fluid. Each vane slot has an under-vane pocket for communicating
fluid. The pressure in the undervane pockets are dependent on an
angular position of the rotor.
[0030] Axially opposed first and second wear disks are disposed
within the interior pumping chamber, the first wear disk has an
outer periphery which is positioned radially inward of the cam
surface and is axially biased towards a first end surface of the
rotor, so as to provide for thermal expansion of the rotor and
vanes. The second wear disk is positioned adjacent to a second end
surface of the rotor. Preferably, each wear disk includes flow
passages for communicating fluid into the under-vane pockets
associated with each vane slot. The pressure of the undervane
pockets is dependant on an angular position of the rotor.
[0031] These and other features and benefits of the subject
invention and the manner in which it is assembled and employed will
become more readily apparent to those having ordinary skill in the
art from the following enabling description of the preferred
embodiments of the subject invention taken in conjunction with the
several drawings described below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] So that those skilled in the art to which the subject
invention appertains will readily understand how to make and use
the methods, devices and systems of the subject invention without
undue experimentation, preferred embodiments thereof will be
described in detail hereinbelow with reference to certain figures,
wherein:
[0033] FIG. 1 is a perspective view of a multi-discharge pump
assembly which has been constructed in accordance with a preferred
embodiment of the present invention;
[0034] FIG. 2 is a partially exploded perspective view of the pump
assembly of FIG. 1 in which a front side plate has been removed for
ease of illustration;
[0035] FIG. 3 is an exploded perspective view of the cam ring, the
rotor assembly, the annular spacer and the rear side plate used in
the pump assembly of FIG. 1;
[0036] FIGS. 4 provides a end view of a rear side plate used in the
pump assembly of FIG. 1;
[0037] FIG. 5 provides a cross-sectional view of the rear side
plate shown in FIG. 4 taken along cut line 5-5;
[0038] FIG. 6 provides a cross-sectional view of the rear side
plate shown in FIG. 4 taken along cut line 6-6;
[0039] FIG. 7 is an exploded view of a portion of the pump assembly
of FIG. 1 which illustrates the front side fixed wear plate, the
rotor assembly, the cam ring and the rear side sliding wear
plate;
[0040] FIG. 8 is a perspective view of the rotor assembly used in
the pump assembly of FIG. 1;
[0041] FIG. 9 is a cross-sectional view of the rotor assembly of
FIG. 8 taken along cut line 9-9;
[0042] FIG. 10 is a perspective view of the cam ring used in the
pump assembly of FIG. 1;
[0043] FIG. 11 is an end view of the cam ring of FIG. 10;
[0044] FIG. 12 provides a perspective view of the rear side
floating disk used in the pump assembly of FIG. 1;
[0045] FIG. 13 is a front end view of the floating wear disk of
FIG. 12;
[0046] FIG. 14 is a rear end view of the floating wear disk of FIG.
12;
[0047] FIG. 15 is a cross-sectional view taken along cut line 15-15
of the floating wear disk of FIG. 12;
[0048] FIG. 16 provides a perspective view of the front side fixed
wear disk used in the pump assembly of FIG. 7;
[0049] FIG. 17 is a front end view of the fixed wear disk of FIG.
16;
[0050] FIG. 18 is a rear end view of the fixed wear disk of FIG.
16;
[0051] FIG. 19 is sectional view of the pump assembly shown in FIG.
1 which illustrates that when the vanes are within the seal arc,
the under-vane cavities are connected to pump discharge
passages;
[0052] FIG. 20 is a cross-sectional view of the pump assembly shown
in FIG. 1 taken along cut line 20-20 in FIG. 19;
[0053] FIG. 21 is sectional view of the pump assembly shown in FIG.
1 taken along cut line 21-21 which illustrates that when the vanes
are within the discharge ramp/arc, the over-vane and under-vane
cavities are connected to pump discharge passages;
[0054] FIG. 22 is sectional view of the pump assembly shown in FIG.
1 taken along cut line 22-22 which illustrates that when the vanes
are within the inlet ramp/arc, the over-vane and under-vane
cavities are connected to pump inlet passages; and
[0055] FIG. 23 provides a cross-sectional view of the rotor
assembly and a portion of the cam ring.
[0056] These and other aspects of the subject invention will become
more readily apparent to those having ordinary skill in the art
from the following detailed description of the invention taken in
conjunction with the drawings.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0057] Disclosed herein are detailed descriptions of specific
embodiments of the devices, systems and methods of the present
invention. It will be understood that the disclosed embodiments are
merely examples of the way in which certain aspects of the
invention can be implemented and do not represent an exhaustive
list of all of the ways the invention may be embodied. Indeed, it
will be understood that the systems, devices, and methods described
herein may be embodied in various and alternative forms. The
figures are not necessarily to scale and some features may be
exaggerated or minimized to show details of particular components.
Well-known components, materials or methods are not necessarily
described in great detail in order to avoid obscuring the present
disclosure. Any specific structural and functional details
disclosed herein are not to be interpreted as limiting, but merely
as a basis for the claims and as a representative basis for
teaching one skilled in the art to variously employ the
invention.
[0058] For ease of description, the components of this invention
are described in an upright operating position, and terms such as
upper, lower, front, rear, horizontal, etc., are used with
reference to this position. It will be understood, however, that
the components of this invention may be manufactured, stored,
transported, used, and sold in an orientation other than the
position described.
[0059] Figures illustrating the components show some mechanical
elements that are known and will be recognized by one skilled in
the art. The detailed descriptions of such elements are not
necessary to an understanding of the invention, and accordingly,
are herein presented only to the degree necessary to facilitate an
understanding of the novel features of the present invention.
[0060] Referring now to the drawings wherein like reference
numerals identify similar structural features or elements of the
subject invention, there are illustrated in FIG. 1 an embodiment of
the hydrostatically-balance, multi-discharge hydraulic vane pump of
the present invention designated generally by reference numeral 10
which includes a cartridge assembly pumping element (item 90 in
FIG. 7) . The cartridge assembly 90 is configured to fit within a
reusable housing (annular space 16). In other words, the pump
element 90 can be readily replaced when worn or in need of repair.
FIGS. 2 through 18 provide views of the various component parts
that form the pump element 90 and FIGS. 19 through 23 provide
cross-sectional and elevational views for pump assembly 10 in a
variety of operating configurations.
[0061] Pump assembly 10 includes a single inlet port 24 (see FIGS.
19-22) for admitting low pressure fluid into the pump assembly 10.
Pump assembly 10 also includes four discharge ports 30a-d for
discharging pressurized fluid from the pump assembly 10. Discharge
ports 30a and 30c diametrically oppose each other. Similarly,
discharge ports 30b and 30d diametrically oppose each other.
Normally, 30a/30c or 30b/30d for one of two pumps.
[0062] By passing through the pump assembly 10, the low pressure
fluid becomes high pressure fluid and exits the pump assembly
through either two diametrically opposed discharge ports 30a-d or
through all of the discharge ports. The manner in which the low
pressure fluid proceeds from the inlet port 24 into the interior
pump chamber 42, is pressurized and is supplied to the discharge
ports 30a-d will be discussed in detail herein below. By having
diametrically opposed discharge ports 30a-d, the forces generated
in the pumping process thereby effectively cancel to provide a
balanced pump assembly 10.
[0063] The pump assembly 10 also includes fixed front and rear side
plates 80a, 80b, which are separated from one another by an annular
spacer 16. The inlet port 24 is formed in the rear side plate 80b.
The discharge ports 30a-30d are formed in the annular spacer
16.
[0064] An end plate 22 is fixed to the front side plate 80a using a
series of bolts 27a-f and defines an axial passageway 26 through
which a drive shaft 28a passes to attach to a rotor assembly 70.
The front and rear side plates 80a, 80b, along with the annular
spacer 16, combine to form an interior or pumping chamber 42 that
houses a cam ring 90, a floating side wear disk 50, a fixed side
wear disk 60 and the rotor assembly 70 (see FIG. 3).
[0065] Referring to FIG. 2, a perspective view of the pump assembly
10 is shown with the front side plate 80a removed to illustrate the
rotor assembly 70 and the cam ring 90 housed in the pumping chamber
42 and having a front end abutting the fixed side wear disk 60.
FIG. 3 provides an additional exploded perspective view in which
the cam ring 90, fixed side wear disk 60, floating wear disk 50 and
the rotor assembly 70 have been removed from within the interior
pumping chamber 42.
[0066] The rotor assembly 70, which is best viewed in FIGS. 8 and
9, is mounted on a drive shaft 28b for axial rotation within the
pumping chamber 42. The rotor assembly is supported for rotation
within the pumping chamber 42 by two journal bearings which are
associated with the side wear disks 50/60. As shown in FIG. 19,
rotor drive shaft 28b engages with drive shaft 28a which extends
outside of the front side plate 80a.
[0067] Rotor assembly 70 includes a rotor body 71, which fits
within a pumping chamber surface 35 defined by cam ring 90 (best
shown in FIG. 11). The rotor body 71 includes a plurality of
radially outwardly acting vane elements 36 which normally contact
the elliptical pumping chamber surface 35. As described in more
detail below, a plurality of circumferential vane buckets or volume
chambers 44 are formed between the rotor body 71, the elliptical
pumping chamber surface 35, the vane assemblies 36 and the wear
disks 50/60 (see FIG. 20).
[0068] For each vane element 36, rotor body 71 includes a vane slot
38 into which the vane element is slidably received, an axially
extending under-vane pumping pocket 73 and an axially extending
under-vane pumping passage 75. Radially extending, but angled,
connector passages 77, allow fluid to communicate between the
under-vane pumping pocket 73 and under-vane pumping passage 75. The
manner in which the under-vane pumping occurs and the benefits
associated with the configuration of the under-vane pumping of the
present invention will also be described below.
[0069] Referring now to FIGS. 4 through 6, which provide several
views of rear housing plate 80b. Eight through holes 82 are
provided in the outer flanges of the front and rear housing plates
80a/80b which allow the rear housing plate 80b and the front
housing plate 80a to be secured to the annular spacer 16 using
through bolts and associated nuts (see FIG. 1). As discussed above,
the axial inlet port 24 for the pump assembly 10 is formed in the
rear side plate 80b and branches off into four diametrically
opposed angled inlet channels 84. These inlet channels 84 can also
been viewed in FIG. 3 and as will be discussed below are arranged
and configured so as to distribute the incoming fluid into four
axially extending inlet chambers 92 formed in cam ring 90.
[0070] Referring now to FIGS. 10 and 11, in addition to the axially
extending inlet chambers 92, cam ring 90 also defines axially
extending discharge chambers 94. Still further, the outer periphery
96 of the cam ring 90 also includes a plurality of access slots 108
which are used to enable the formation of radially extending ports
104/106 which extend through the inner wall 102 of the cam ring 90
to the pumping chamber surface 35. Ports 104 extend radially inward
from the inlet chambers 92 and ports 106 extend radially inward
from the discharge chambers 94. The purpose of the flow ports
104/106 will also be discussed below.
[0071] The cam ring 90 is also provided with a number of seal
grooves. For example, the outer periphery 96 of the cam ring 12
includes a plurality of seal grooves 98 which are adapted and
configured for receiving linear sealing elements. Each end of the
cam ring 90 also includes a circular seal groove 99 and the pumping
chamber surface 35 includes front and rear circumferential seal
grooves 97. Those skilled in the art will readily appreciate the
seals inserted into the seal grooves 97/98/99 are designed to
prevent cross port leakage throughout the pump assembly 10.
[0072] Referring now to FIGS. 12 through 15 where there is
illustrated floating wear disk 50. As shown in FIG. 19, unlike
prior art wear disks, which are fixedly positioned outside and
adjacent to the end of the cam ring, floating wear disk 50 is
positioned entirely within the inside profile of the cam ring 90
and is adapted for sliding in an axial direction to allow for
thermal expansion of the rotor assembly during operation. However,
unlike prior art devices wherein the axial gap between the wear
disk and the rotor must be minimized in order to prevent cross port
leakage, in pump assembly 10 it is the circumferential gap between
the floating wear disk 50 and the pumping chamber surface which
must be sealed. Since the circumferential gap is much less impacted
by thermal expansion during operation of the pump, it is easier to
maintain the seal in this location.
[0073] Like cam ring 90, floating wear disk 50 includes a plurality
of fluid ports which allow fluid to communicate with pump assembly
10. For example, eight radial holes 52 are provided which extend
from the outer periphery of the floating wear disk 50. Four of the
radial holes 52 connect with four axially extending discharge fluid
ports 54 and the other four radial holes 52 connect with four
axially extending inlet fluid ports 56. As will be discussed in
detail below, the discharge fluid ports 54 are used to allow
pressurized discharge fluid to be provided to the under-vane slots
and under-vane passages to used for under-vane pumping and the
inlet fluid ports 56 are used to allow low pressure inlet fluid to
be provided to the under-vane slots and under-vane passages to be
used for under-vane pumping.
[0074] The floating wear disk 50 is also provided with a journal
bearing 58 which supports one end of the rotor assembly 70 within
the pumping chamber 52. Four seal grooves 53 are provided on the
rear face of the floating wear disk 50 and are adapted for
receiving a face seal. Additionally, eight spring cavities 55 are
formed in the rear face of the floating wear disk 50 and contain a
spring element or biasing mechanism for urging the floating wear
disk 50 in the direction of the rotor assembly 70. Moreover, a
small hole 59 extends from each of the discharge fluid ports 54 to
the rear face of the floating wear disk 50. As a result,
pressurized discharge fluid is supplied to the back side of the
floating wear disk 50 and further urges/biases the floating wear
disk 50 in the direction of the rotor assembly 70. The
configuration and location of the seal grooves 53 defines a load
area against which the pressurized discharge fluid works in order
to urge the floating wear disk 50 towards the rotor assembly 70. As
a result, the amount of pressure applied to the back side of the
wear disk 50 can be adjusted by adjusting the load area upon which
the discharge fluid works.
[0075] Referring now to FIGS. 16 through 18 which illustrate the
fixed side wear disk 60 used in the pump assembly 10 of the present
invention Like the floating wear disk 50, the fixed side wear disk
60 includes a journal bearing 68 and a plurality of radial holes
62. Four axially extending discharge fluid ports 64 communicate
with four of the radial holes 62 and four radially extending inlet
fluid ports 66 communicate with the remaining four radial holes 62.
Similar to the floating wear disk 50, discharge fluid ports 64 and
inlet fluid ports 66 are used to provide fluid in support of
under-vane pumping.
[0076] The back side of the fixed side wear disk 60 includes
circular pressure relief groves 67a/67b and four radially extending
pressure relief grooves 69a-d. It should be noted that both the
floating side wear disk and the fixed side wear disk include slots
for receiving a pin which prevents the disks 50/60 from rotating
with respect to the cam ring 90.
[0077] Referring now to FIGS. 19 through 23 which illustrate the
arrangement of the component parts used in pump assembly 10 and the
manner in which the pump assembly operates to increase the pressure
of the inlet fluid. In operation, fluid is received in inlet port
24 and is diverted into the four inlet channels 84. The four inlet
channels 84 provide the fluid to the four axially extending inlet
chambers 92 formed in the cam ring 90. From the inlet chambers 92
the fluid is directed radially inward through the radially
extending inlet ports 104. The end two ports 104 provide fluid to
four radial holes 52/62 formed in the wear disks 50 and 60
respectively, and this fluid is used for under-vane pumping. The
fluid proceeding through the remaining ports 104 formed in the cam
ring 90 is supplied into vane buckets 44 which are in the four
inlet arc regions "I" shown in FIG. 23. As the rotor assembly 70
rotates the fluid is displaced and exits the vane buckets 44 in the
discharge arc region "D" through the interior-most ports 106 formed
in the cam ring 90 and is received into the four axially extending
discharge chambers 94. A portion of the pressurized fluid contained
in the discharge chamber 94 is provided to the discharge fluid
ports 54/64 of the wear disks 50/60 via radial holes 52/62 and is
used for under-vane pumping. The remaining pressurized fluid
contained with the four axially extending discharge chambers 94
formed in the cam ring 90 is provided to the four discharge ports
30a-d of the pump assembly 10.
[0078] FIG. 19 is sectional view of the pump assembly shown in FIG.
1 which illustrates that when the vanes 36 are within the seal arc
"S", the under-vane slot 75 and the under-vane passage 73 are
connected to pump discharge passages which are formed in the wear
disks 50/60 and the cam ring 90. FIG. 20 is a cross-sectional view
of the pump assembly shown in FIG. 1 taken along cut line 20-20 in
FIG. 19.
[0079] FIG. 21 is sectional view of the pump assembly shown in FIG.
1 which illustrates that when the vanes 36 are within the discharge
ramp/arc "D", the over-vane 44 and under-vane cavities 73/75/77 are
connected to pump discharge passages which are formed in the wear
disks 50/60 and the cam ring 90.
[0080] Lastly, FIG. 22 is sectional view of the pump assembly shown
in FIG. 1 which illustrates that when the vanes 36 are within the
inlet ramp/arc "I", the over-vane and under-vane cavities are
connected to pump inlet passages which are formed in the wear disks
50/60 and the cam ring 90.
[0081] Typically, in prior art vane pumps, the wear disks are
fixedly mounted within the interior pumping chamber and abut the
axial ends of the cam ring and rotor blade. As shown in these
figures, the front side wear disk 50 is a floating wear disk which
is located radially inside of the pumping chamber surface 35
defined by the cam ring 90.
[0082] Previously disclosed vane pump designs usually have a fixed
axial clearance between the wear disk and the rotor. Moreover, the
wear plates/disks at both side of the rotor/vane are fixed. For a
fixed axial clearance design, the longer the rotor, the more axial
clearance is needed considering free thermal expansion of the rotor
and vanes. At high operating temperatures, the amount of available
clearance between the rotor and wear disks could be significantly
reduced due to rotor/vane expansion. As a result, mechanical
galling and premature wear could occur at rotor ends if the axial
clearance is not sufficient.
[0083] Moreover, as discussed previously, cross-port leakage occurs
due to above described fixed axial clearance. Excessive leakage
could then take place at high pump operating pressures. This
leakage could have significant effect on the minimum allowable
operation speed of the pump, in addition to significant energy loss
of the pump. In other terms, the pump could have little or no
discharge flow due to its excessive internal re-circulated
cross-port leakage at a low input speed.
[0084] Therefore, it is preferred to have a vane pump with at least
one pressure compensated side wear disk. In the present invention,
during pump operation, the pressure over-balanced side wear disk 50
is subject to a net clamping force that pushes the wear disk
against the rotor/vanes (rotating group) tightly. This net force
comes from mechanical spring force and/or hydraulic pressure acting
on the back side of the floating wear disk 50 at the side opposite
to the rotor 70. Usually, the higher the operating pressure, the
higher the net clamping force. In a pump of good design, the
clamping force closes the axial gap and squeezes the oil film
between rotor and the wear disk to a minimum film thickness without
mechanical contact between two parts that rotate close to each
other.
[0085] To allow the floating wear disk 50 to move freely inside the
cam ring 90 as a result of the above described net biased force,
the outer shape of the wear disk 50 generally has the same shape
(with adequate radial clearance for free relative movement) as the
inner pumping chamber surface 35 of the cam ring 90. Thus, the
floating wear disk 50 requires precision manufacturing similar to
the cam ring inner diameter 35.
[0086] Typically, the inner pumping chamber surface of a cam ring
has an elliptical shape for a single balance (dual action) fixed
displacement vane pump. As shown in FIG. 23, in the present
invention, the cross-section of the inner pumping chamber surface
35 is close to a circle because it has two balanced pumps in a same
pumping element. Alignment pins could be used to ensure proper
orientation of the wear disk and the cam profile.
[0087] Those skilled in the art will readily appreciate that the
fixed side wear disk 60 could also be a floating wear disk if cost
is not a concern. Preferably, both disks 50/60 are made of steel,
aluminum, or other light weight materials for weight reduction and
have hard coated layers applied on the wear surfaces (rotor side).
It also should be appreciated that the back side of the floating
wear disk 50 is connected to corresponding pump discharge pressure
all the time.
[0088] When a rotor rotates, vanes are expected to maintain contact
with the inner surface of the cam ring. Since the inner surface of
the cam ring has a varying radius at different angular positions,
each vane, which behaves as a piston, will slide into and out of
the rotor inside the rotor vane slot. This radial movement of the
vane stokes fluid into and out the cavity beneath it. To let each
vane work as a positive displacement piston pump, a porting device
is needed. The porting device assures that when the cavity volume
increases, the under-vane pumping passages are linked to a pump
inlet pressure; and conversely, when the bucket volume is reduced,
the under-vane pumping passages are linked to its corresponding
pump discharge line.
[0089] Conventional vane pumps usually incorporate flow passages
that directly connect an under-vane cavity to corresponding
over-vane volume chambers. Thus, under-vane cavities can be linked
to the inlet and discharge ports of the pump at the same time as
their corresponding over-vane volume chambers. Those flow passages
could be inside the rotor or use the interface between rotor and
the side wear plate. The disadvantage of the conventional design is
that there are significant dynamic pressure losses along and
through the flow passages and cavitation damage could result in
these areas when the pump is operated at very high speed.
[0090] Vane pump assembly 10 provides a separate porting mechanism
to link inlet and discharge ports of each pump (over-vane) to its
corresponding under-vane cavities. When a cavity volume increases,
it is linked to pump inlet pressure. When the cavity is reduced, it
is linked to a corresponding discharge line.
[0091] Over vane volume chambers (16 total for pump assembly 10)
are separated by vane/cam sealing. As shown in FIG. 19 when a vane
36 is sweeping on the seal arc "S" (the constant radius portion of
the cam ring profile located between inlet and discharge ports),
its under-vane passage 73 and under-vane slot/pocket 75 are linked
to a pump discharge pressure port to assure that the vane 36 can be
pushed out by under-vane hydraulic pressure forces. When a vane 36
is sweeping on the inlet ramp "I", as shown in FIG. 22, its
under-vane passage 73 and under-vane slot 75 are connected to inlet
pressure. When a vane 36 is sweeping the discharge ramp, as shown
in FIG. 21, its under-vane passage 73 and under-vane slot 75 are
connected to its corresponding discharge line. As a result, the
pressure ports on the wear disks are longer in the circumferential
direction in the discharge ports 54/64 than the inlet ports
56/66.
[0092] As discussed previously, there are radial holes 52/62 on the
outer surfaces of the wear disks 50/60. Those radial holes 52/62
are used to connect the under-vane passage 73 and under-vane slot
75 (for under-vane pump porting) to pump inlet lines 92 and
discharge lines 94, which are integrated into the cam ring 90.
[0093] Vanes pump under-vane cavity fluid at very rapid speed. To
avoid excessive pressure build up or de-compression due to
resistance of the under-vane cavities and flow passages, unlike a
conventional design, which has only one axial slot to connect
under-vane cavity to pump system ports or over-vane volume chamber,
the pump assembly 10 has both an under-vane passage 73 and an
under-vane slot 75 for a single under-vane pumping element. This
arrangement reduces the pressure loss inside the under-vane cavity
and flow passages.
[0094] The outer axial slot 75 is a primary one and the inner axial
passage 73 is the second link to under-vane cavities and pump
ports. The second passage 73 is linked to the primary slot inside
the rotor via a number of radial connector passages 77. Those
radial connector passages 77 are slanted with an angle to reduce
the energy loss of merging flow.
[0095] As will be readily appreciated, pump assembly 10 is a split
discharge pump and is essentially a main fuel pump that consists of
four separate pumps. Each pump can discharge flow both from
over-vane volume chambers and under-vane volume chambers. All
volume chambers need separate timely porting to assure volume
chambers are connected to an inlet line when their volume is
expanding and connected to a pump discharge line when its volume is
contracting.
[0096] As discussed above, the cam ring 90 is designed to receive
fluid from a common pump inlet 24 (four pumps share the same pump
inlet) and it ports it to the inlet ports 56/66 of the wear disk,
along with performing porting for the over-vane volume chambers. In
addition, it receives discharge flow from the wear plates 56/60 and
combines the flow with corresponding over-vane discharge flow and
then provides for discharge from one of the four corresponding
discharge ports 94 in the cam ring.
[0097] To assure the minimum timing error for over-vane porting,
the angular location of the ports on the inner surface of the cam
ring is very critical and requires precision manufacturing. To
reduce the manufacturing cost, these ports are machined from the
outer surface of the cam ring 90. When the cam ring is inserted
into its housing/annular space 16, some construction openings on
the outer surface will be covered by the inner surface of the
annular spacer 16. As discussed previously, multiple seal cords are
used to seal circumferential cross-port leakage between the cam
ring and the housing.
[0098] Those skilled in the art will readily appreciate that the
cam ring 90 could have been designed differently with multiple
pieces for ease of manufacturing. For instance, a hardened
sleeve/ring could be used as vane running wear surface and inserted
into a separate block inclusive of the flow ports, thereby
simplifying manufacturing of the cam running surface and the flow
passages.
[0099] Moreover, unlike prior vane pump constructions, vane pump
assembly 10 includes single inlet port 24 oriented in the axial
direction and multiple discharge ports 30a-30d oriented in the
radial direction. There are a total four vane pumps for this
split-discharge vane pump. All four pumps share the same pump inlet
volume. For each pump, the over-vane volume chamber discharges flow
into the cam ring. There, flow merges with the discharge flow from
its corresponding under-vane cavity. Then, the total flow is
expended from the pump from a pump discharge port. There are total
of four discharge ports, one for each pump.
[0100] To form two balanced dual action vane pumps, the flow from
two diagonally opposite discharge ports of the main pump could be
combined by external plumbing. Alternatively the two ports could be
linked internally inside a main pump housing by design, along with
necessary control valves, as illustrated in U.S. Patent Application
Publication No. 2010/0316507, the disclosure of which is
incorporated by reference.
[0101] While the subject invention has been described with respect
to preferred embodiments, those skilled in the art will readily
appreciate that changes and modifications may be made thereto
without departing from the spirit and scope of the subject
invention as defined by the appended claims.
* * * * *