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BACKGROUND OF THE INVENTION
The present invention relates to rotary vane pumps, and more particularly
to improvements in rotary vane pumps whereby an auxiliary pressure outlet
may be provided.
Rotary vane pumps are generally known in the prior art. For example, U.S.
Pat. No. 2,544,987, issued Mar. 13, 1951, describes a rotary vane pump of
the type generally applicable to the present invention having intake and
discharge passages interspersed at approximately 90.degree. intervals
about the path of rotation of a rotor. U.S. Pat. No. 2,544,988, issued
Mar. 13, 1951 discloses a rotary vane pump having a floating cheek plate
and utilizing liquid pressure from the discharge side of the pump against
the cheek plate to adjust the clearance between the rotor and vane
surfaces and the cheek plate. According to the teachings of this patent
the intake passages to the pump are located completely on one side of the
rotor of the pumping unit while the discharge passages are completely on
the other side of the rotor. The cheek plate is provided with a dual
function, providing liquid distributing ports in connecting the discharge
side of the pumping unit to the outlet and also directing liquid pressure
to the discharge chamber. U.S. Pat. No. 3,007,419, issued Nov. 7, 1961,
discloses a rotary vane pump having an accumulator reservoir maintained at
a pressure approaching the pump discharge pressure, and valve means
operated in phase relation with the pump rotor to bleed small amounts of
liquid out of the pump's discharge in a manner to offset pulsations caused
by the pump.
U.S. Pat. No. 1,468,889, issued Sept. 25, 1923, discloses a multistage
rotary pump having two concentric ported cylinders and an eccentric rotor
or rotating member. This patent discloses a plurality of radial vanes
confined between two concentric cylinders in a rotor which is
eccentrically mounted relative to the cylinders. As the rotor is rotated
the vanes are also rotated within the confines of the two concentric
cylinders, and the eccentric motion of the rotor creates a relative
reciprocation between the rotor and the vanes, so as to provide an inner
and outer series of expansible chambers. Passages may interconnect the
inner and outer ported cylinders to develop a multistage pumping effect,
or liquid may be delivered from the first stage to a comparatively low
pressure and from the second stage at a higher pressure. Dual pressure
operation is therefore achieved by driving an eccentric rotor within two
concentric chambers, and providing complex interrelating passages.
There is a need to provide a pump of relatively simple construction wherein
two separate liquid pressures may be delivered from a single pump,
particularly where the secondary pump output pressure is independent of
the primary pump output pressure. It is preferable to provide such a pump
with as simple a design as possible in order that the costs of providing
two such pressures may be significantly lower than the cost of merely
providing two pumps operating at different pressures and coupled into the
same flow system.
SUMMARY OF THE INVENTION
The invention comprises a novel utilization of operating principles of
conventional rotary vane pumps, and specifically utilization of the
pumping effects of the individual vanes within a rotary vane pump, to
develop an auxiliary pump output pressure. As the rotor of a rotary vane
pump rotates the vanes within the rotor follow the surface contour of an
eccentric outer chamber surrounding the rotor, and therefore the vanes
slide radially in and out of the rotor slots. Each vane, within its radial
slot, functions as a small piston pump, creating an intake at its inner
radius point as the vane slides outwardly and creating a discharge
pressure at its inner radius point as the vane slides inwardly. In
conventional rotary vane pumps passages are provided between the pump
discharge chamber and the inner vane ends during the pump intake phase to
develop pressure forces against the inner vane ends, and to thereby force
the vanes outwardly against the eccentric chamber wall within which the
rotor rotates. These pressure forces assist in maintaining an oil tight
seal between the eccentric chamber surface and the ends of the respective
vanes. Conventional rotary vane pumps bleed off this pressure during the
pump discharge phase through passages feeding into the pressure discharge
chamber of the pump.
The present invention utilizes the pressurized liquid developed by the
vanes during their radial inward movement, by coupling this pressurized
liquid through independent passages to an auxiliary outlet from the pump,
and thereby to provide an auxiliary pressurized liquid outlet for the pump
.
BRIEF DESCRIPTION OF THE DRAWINGS
An understanding of the scope and advantages of the present invention will
become apparent from the following specification, and with reference to
the appended drawings, in which:
FIG. 1 shows an isometric view of the invention; and
FIG. 2 shows the invention in cross section, taken along the lines 2--2 of
FIG. 1; and
FIG. 3 shows a cross-sectional view of the invention taken along the lines
3--3 of FIG. 1; and
FIG. 4 shows a symbolic diagram of the operation of a conventional rotary
vane pump; and
FIG. 5 shows a symbolic diagram of the operation of the invention; and
FIG. 6A shows a pressure plate utilized in a rotary vane pump according to
the teachings of the invention; and
FIG. 6B shows a cross section view taken along the lines 6B--6B of FIG. 6A;
and
FIG. 6C shows a cross section view taken along the lines 6C--6C of FIG. 6A.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Referring first to FIG. 1 there is shown a rotary vane pump 10
incorporating the present invention. Pump 10 is comprised of an intake
chamber casting 22, a pumping chamber casting 20, and a discharge chamber
casting 24, all of which are secured together by bolts or other fasteners.
A drive shaft 18 projects from casting 22, and is preferably retained on
ball bearings within casting 22. An inlet 12 is tapped into casting 22 and
is adaptable for connection to a source of inlet liquid. A primary outlet
14 passes through casing 24 and is adaptable for connection to an external
pressurized flow communication path. A secondary outlet 16 passes through
casting 24 and is adaptable for connection to a secondary pressurized flow
communication path.
Referring next to FIG. 2, there is shown a cross-sectional view taken along
the lines 2--2 of FIG. 1. Shaft 18 passes through bearings seated in
casting 22, the end of shaft 18 being formed into a splined end which is
slidably securely attached to rotor 26. Rotor 26 is positioned in pumping
chamber 21, which is an eccentrically shaped chamber. An intake chamber 23
is in flow communication with inlet 12.
A pressure plate, or cheek plate 32 closes one end of pumping chamber 21.
Passages through pressure plate 32 create a flow communication path
between pumping chamber 21 and primary discharge chamber 25. A secondary
discharge chamber 34 is created within a tube 35, the ends of which are
seated respectively into casting 24 and pressure plate 32. Liquid sealing
O-rings 36 and 37 seal the respective ends of tube 35 from leakage. A
compression spring 30 is seated between casting 24 and pressure plate 32,
and serves to urge pressure plate 32 toward casting 20 and rotor 26.
Compression spring 30 serves to improve the liquid seal between pressure
plate 32 and casting 20 and rotor 26.
The primary discharge chamber 25 communicates with pumping chamber 21 via
passages 27 and 28 through pressure plate 32. Secondary discharge chamber
34 is in flow communication with passages 39 and 40, which open into
grooves 41 and 42 on the face of pressure plate 32. Secondary discharge
chamber 34 is also in flow communication with secondary outlet 16.
FIG. 3 shows a cross-sectional view taken along lines 3--3 of FIG. 1.
Intake chamber 23 is in flow communication with inlet 12, and also is in
flow communication with pumping chamber 21. Discharge chamber 25 is in
flow communication with primary outlet 14. Discharge chamber 25 is also in
flow communication with the inner radius of some of the rotor vanes
through passages 29 and 31, which open through pressure plate 32 into
grooves 47 and 48 respectively. Grooves 47 and 48 are arcuate grooves
which are in flow communication with the inner radii of a plurality of
rotor vane slots, and liquid flow through this path pressurizes the rotor
vane slots in flow communication therewith, thereby creating pressure
forces which tend to urge the vanes outwardly in sealing contact against
the inner surface contour of pumping chamber 21.
The elliptical shape of pumping chamber 21 can be noted from a comparison
of FIGS. 2 and 3. In FIG. 3, pumping chamber 21 is shown as a relatively
large and open chamber, corresponding generally to the late intake or
early pressure discharge phases of rotor rotation. By comparison, FIG. 2
shows vane chamber 21 as a relatively small chamber, corresponding
generally to the late pressure or early intake phases of rotor rotation.
Specifically, FIG. 3 shows a cross-sectional view corresponding to the
position of rotor 26 at or near the end of an intake phase of its
rotation; FIG. 2 shows a cross-sectional view of rotor 26 at or near the
end of a pressure discharge phase of rotation.
FIG. 6A shows a top view of pressure plate 32. Passages 27 and 28 form the
main pressure passages between the pumping chamber 21 and primary
discharge chamber 25. Arcuate grooves or slots 41 and 42 communicate with
passages 39 and 40 respectively. Arcuate grooves 45 and 46 form intake
cavities in the pumping chamber during the intake phase of rotor position.
Arcuate grooves 47 and 48 form shallow segmented grooves to aid in
distribution of liquid from passages 29 and 31. FIG. 6B shows a
cross-sectional view of pressure plate 32 taken along the line 6B--6B of
FIG. 6A. Passages 29 and 31 are drilled through to the bottom side of
pressure plate 32, and therefore provide a flow communication path between
discharge chamber 25 and arcuate grooves 47 and 48. Arcuate grooves 47 and
48 are in flow communication with the inner radial ends of the vanes that
sweep past the arcuate angle defined by grooves 47 and 48 during the
intake phase of rotor position. FIG. 6C shows a cross-sectional view of
pressure plate 32 taken along the lines 6C--6C of FIG. 6A. Passages 39 and
40 are in flow communication through a cross passage, which in turn
communicates with secondary discharge chamber 34. Passages 39 and 40 are
also in flow communication respectively with arcuate grooves 41 and 42,
and are therefore in flow communication with the inner radial ends of the
vanes as they sweep past the angle subtended by arcuate grooves 41 and 42
during the pressure discharge phase of rotor rotation. In summary, the
grooves and passages in pressure plate 32 provide a pressurized liquid
flow path from the discharge chamber to the inner vane ends during the
intake phase of rotation, which pressurized liquid acts to create a
radially outward force against the vanes; during the pressure discharge
phase of rotor rotation the inward radial movement of the vanes causes
delivery of pressurized liquid via the grooves and passages to the
secondary discharge chamber of pressure plate 32. In this manner,
pressurized liquid is relieved from the inner radius ends of the vanes
during the pressure discharge portion of rotor rotation, by feeding it
into a secondary discharge outlet which may be utilized as a secondary
pressure outlet from the pump. The source of liquid for this secondary
pressure outlet is the discharge chamber forming a part of the primary
pressure discharge of the pump. The volume of liquid which flows to the
secondary pressure outlet is considerably less than the volume of liquid
flowing from the primary pressure outlet, as may be seen from the relative
sizes of the flow passages herein described. Thus, the pressurized liquid
flow through the secondary outlet provides relatively low degradation and
bleed off from the primary liquid outlet.
FIG. 4 shows a symbolic diagram illustrating the construction of a
conventional rotary vane pump. The overall principles of operation of this
pump are similar to the pump of the present invention, with the exception
that the secondary outlet is not present. A pair of inlet passages 50, 51
communicate with the pumping chambers 53, 54 respectively, which pumping
chambers are formed by the elliptical shape of the contour surrounding the
rotor 52. A plurality of vanes 60, 61, 62 . . . 71, are equally spaced
about rotor 52 and are radially slidable in slots in rotor 52. A pair of
outlet passages 55, 56 are in flow communication with portions of pumping
chambers 53, 54.
As rotor 52 is engaged in the direction of rotation shown by the arrow, the
vanes are centrifugally forced outwardly into sliding contact with the
contour of the pumping chambers. The volume between adjacent vanes entraps
a quantity of liquid, and this quantity of liquid is moved rotationally
along with the vanes. As the vanes move past an inlet, such as vanes 61,
62 moving past inlet passage 50, they tend to create an opening of
increasing size with rotational angle. This increasing-volume opening acts
as a suction volume, drawing liquid from the inlet into the volume between
vanes 61 and 62. The volume of liquid entrapped between adjacent vanes is
increased until the rotor brings the vanes to the position shown for vanes
62, 63, wherein the maximum amount of liquid has been entrapped and vane
63 is beginning to be forced radially inward by the decreasing elliptical
contour of the pumping chamber 53. This decreasing volume acts to build up
liquid pressure for the volume of liquid entrapped between the adjacent
vanes 62, 63, and this pressurized liquid is ultimately coupled into
outlet passage 55 for flow communication with an outlet from the pump.
When the rotor has moved to a position as shown by vane 65, a segment of
chamber contour is traversed wherein no liquid may be entrapped between
adjacent vanes. Shortly thereafter, the vanes once again encounter a
region of contour of increasing elliptical size and the cycle is repeated.
In the example shown, two elliptical pumping chamber sections are
illustrated, although rotary vane pumps may be constructed with greater or
lesser numbers of chamber sections depending upon particular applications.
Considering the operation of the individual vanes, is can be seen that any
particular vane will radially move relative to the radial direction of its
slot, depending upon the contour of the pumping chamber at any given
instant. Thus, vane 60 is shown at a radially inwardmost position, and
vane 62 is shown at a radially outward position. In conventional rotary
vane pumps, it is typical to provide passages from the pressurized outlet
of the pump back to the inside radii of the respective vane slot ends.
During the intake phase of rotor position such pressurized liquid directed
at the inner ends of the vanes serves to assist in forcing the vanes
outwardly against the chamber contour, thereby improving the liquid seal
which may be found between the vane end and the chamber contour. During
the pressure discharge phase of rotation of the rotor the vanes are forced
back inwardly and the pressurized liquid found along the inner radius of
the vane slots is forced into the discharge chamber to be included with
the discharge liquid. Suitable passages and bleed holes are provided,
usually in conjunction with arcuate slots or grooves along the inner vane
circumference 58, to ensure flow communication between the discharge
chamber and the respective vane slots at all points of rotation.
FIG. 5 shows a symbolic diagram illustrating the construction of the
present invention, as an improvement in rotary vane pumps of the type
known in the prior art. Reference numbers of FIG. 5 are identical to the
previous disclosure herein to the extent identical or similar features are
shown. The description of the operation of FIG. 5 is identical, both in
construction and operational details, as that of FIG. 4, with the
exception of the following. The bleed holes and/or passages provided
between the discharge chamber and the respective vane slots during the
respective pressure discharge phases of rotor rotation are eliminated.
Instead, grooves 41 and 42 are constructed between the slots along the
inner vane radii 58 associated with the pressure discharge phase of rotor
position to common passages 39 and 40. Passages 39 and 40 are connected to
a passage which connects to secondary outlet 34. These arcuate grooves 41
and 42 provide a liquid flow path from the inner vane slots associated
with the pressure discharge phase of operation to passages 39 and 40,
chamber 34, and secondary outlet 16.
An alternative form of the invention may be provided in rotary vane pumps
wherein the pressure plate or cheek plate is not an independent structural
member, but is formed as a part of either the pumping chamber casting or
the discharge chamber casting. The inventive principles described herein
are equally applicable to pumps of this construction.
A further alternative form of the invention may be provided by expanding or
contracting the arcuate length of the slots and passages described herein,
with respect to the flow coupling of liquid from the inner vane radii to
auxiliary discharge chambers. The inventive scope of the present invention
will permit flow coupling of any one or more vane passages with one or
more auxiliary pressure outlets, and therefore multiple auxiliary pressure
outlets may be provided for certain applications.
The present invention may be embodied in other specific forms without
departing from the spirit or essential attributes thereof, and it is
therefore desired that the present embodiment be considered in all
respects as illustrative and not restrictive, reference being made to the
appended claims rather than to the foregoing description to indicate the
scope of the invention.
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