Reversible flow vane pump with improved porting

A reversible flow vane pump having a pump case with a pump chamber in which a rotor is mounted. The rotor has outwardly-opening slots which carry vanes which engage a cam ring and with fluid chambers between vanes. The cam ring can be adjusted to positions at either side of a neutral position to provide reversible flow operation between a pair of ports, with variable volume control. The ports are arranged to increase the length of time in which a port communicates with an intervane fluid chamber which is of decreasing volume for increased utilization of fluid being pressurized. A port which functions as an inlet port in a predominant mode of operation of the pump has an extension effective to increase the length of time in which an intervane fluid chamber of increasing volume can be filled with fluid. This port extension is blocked from communication with the intervane fluid chambers by the cam ring when the pump is operating other than in the predominant mode of operation in order to prevent communication between the ports.

DESCRIPTION 1. Technical Field 
This invention pertains to a reversible flow vane pump having improved 
porting for greater pump efficiency. This is accomplished, in part, by 
rotationally offset porting to increase the length of time a port 
communicates with a vane pump chamber which is of decreasing volume and 
which is most effective in raising pump pressure. This is also achieved by 
increasing the length of time in which a vane pump chamber of increasing 
volume communicates with an inlet port to maximize filling of the pump 
chamber and without cross-communication between the inlet and outlet ports 
of the pump. 
2. Background Art 
A common type of positive displacement pump is a vane pump wherein a rotor 
within a pump chamber carries a series of vanes, in the form of either 
rollers or blades, which, with conventional pump structure, define 
intervane fluid chambers therebetween. A contoured surface controls the 
radial extension of the vanes relative to the rotor to cause intervane 
fluid chambers to increase in volume while filling from an inlet port and 
thereafter decrease in volume when discharging to an outlet port. If the 
vane pump is of variable volume, a movable cam ring can be shifted to 
various positions of eccentricity relative to the rotor to control the 
extent of radial movement of the vanes and, therefore, the variation in 
the size of the fluid chambers between vanes as they travel between the 
inlet and outlet ports. Further, it is known to have the cam ring 
positionable to various positions at either side of a neutral position 
concentric with the rotor, whereby a pair of generally diametrically 
opposite ports can function alternatively as inlet and outlet ports. This 
is a bi-directional vane pump. 
It is conventional in a reversible flow vane pump to have symmetrical 
porting, with the inlet and outlet ports diametrically opposite each 
other, whereby there is the same efficiency of operation in any position 
of the cam ring at either side of the neutral position. 
There are many uses for a vane pump having reversible flow operation 
wherein the predominant mode of operation is with flow in one direction 
and it is desirable to modify the porting for improved efficiency in the 
predominant mode of operation. An example of such a use of a 
bi-directional pump is shown and described in a pending patent application 
of Allan Hutson, Ser. No. 595,167, filed Mar. 30, 1984, owned by the 
assignee of this application. In the Hutson application, a bi-directional 
roller vane pump is in a closed circuit with a fluid motor to provide a 
hydrostatic transmission usable for driving a vehicle, such as a tractor. 
In use of the disclosed reversible flow roller vane pump in such a 
hydrostatic transmission, there are a pair of pump ports, each of which is 
connected by a fluid line to a port of the fluid motor whereby the pump 
ports function one as an inlet port and one as an outlet pressure port and 
with the roller vane pump being bi-directional in operation the function 
of the ports can be reversed to achieve a reversal in the operation of the 
fluid motor. The tractor predominantly operates in a forward direction of 
travel and, thus, the vane pump predominantly operates in what may be 
called a "forward direction" to provide a hydrostatic transmission output 
which will drive the vehicle in the forward direction. The invention 
pertains to unique porting effective in the predominant forward direction 
of pump operation to improve the efficiency of a reversible flow pump when 
so operating. 
DISCLOSURE OF THE INVENTION 
A primary feature of the invention is to provide a reversible flow vane 
pump having porting arranged to provide improved efficiency in a 
predominant direction of operation. 
Another feature of the invention is to provide a reversible flow vane pump 
having rotationally offset porting to increase the length of time in which 
a port functioning as an outlet port communicates with an intervane fluid 
chamber of decreasing volume to maximize the delivery of pressurized fluid 
to the outlet port. 
Another feature of the invention is to provide a reversible flow vane pump 
with means for increasing the length of one of the ports of the pump when 
functioning as an inlet port when the pump is operating in the predominant 
forward direction to achieve increased filling capability for an intervane 
fluid chamber. When the pump is operating in the other direction of 
operation, the port is of a lesser length to prevent communication between 
the pump ports. 
An object of the invention is to provide a reversible flow vane pump 
comprising, a rotor rotatable about an axis, a plurality of vanes carried 
by said rotor and movable radially of said rotor axis, a cam ring 
surrounding and spaced from said rotor to control the radial movement of 
said vanes, first and second ports at opposite sides of said rotor axis, 
means mounting said cam ring for pivotal movement about an axis parallel 
to and offset from said rotor axis to enable the cam ring to have a 
neutral position or positions at either side of said neutral position with 
positions at one side of neutral providing for pump flow from the first 
port to the second port and the positions at the other side of neutral 
providing for reverse pump flow from the second port to the first port, 
and said ports being constructed and arranged to achieve greater pumping 
efficiency when the pump flow is from the first port to the second port. 
Still another object of the invention is to provide a reversible flow vane 
pump as defined in the preceding paragraph wherein the first port has an 
effectively variable length, dependent upon the orientation of the cam 
ring away from said neutral position. 
Still another object of the invention is to provide a reversible flow vane 
pump as defined in the preceding paragraphs wherein said first port has a 
radially offset extension to increase the effective length thereof and 
said cam ring covers said radially offset extension when in neutral 
position and when in positions to cause pump flow from the second port to 
the first port. 
Still another object of the invention is to provide a reversible flow vane 
pump wherein said second port has an arcuate length and the mid-point of 
said arcuate length is offset in the direction of rotor rotation from a 
line extending between the rotor axis and a pivot axis for the cam ring to 
extend the communication of the second port with the decreasing volume of 
an intervane fluid chamber. 
Still another object of the invention is to provide a reversible flow vane 
pump comprising, a rotor rotatable about an axis, a plurality of vanes 
carried by said rotor and movable radially of said rotor axis, means for 
controlling the radial movement of said vanes, first and second ports at 
opposite sides of said rotor axis, means providing for either forward pump 
flow from the first port to the second port or reverse pump flow from the 
second port to the first port by controlling the volume of the space 
between vanes, and said ports being constructed and arranged to achieve 
greater pumping efficiency when the pump flow is from the first port to 
the second port by offsetting said second port to obtain maximum 
communication with a decreasing space between vanes in forward flow 
operation and having the first port of variable length with the longer 
length operable in forward flow operation.

BEST MODE FOR CARRYING OUT THE INVENTION 
The general construction of the reversible flow roller vane pump 8 is shown 
in FIGS. 1 and 2. The pump case has a center section 10 and a pair of side 
walls 12 and 14 positioned at opposite sides thereof and in sealing 
relation therewith by circumferential grooves 16 and 18 which may 
communicate with a case drain or have O-rings mounted therein. 
The center section 10 is generally annular to provide, with the side walls 
12 and 14, a pump chamber which houses a rotor 20 which is mounted fixedly 
to a driven shaft 22 rotatably supported by bearings 24 and 26 in the pump 
case side walls 12 and 14, respectively, and which defines an axis of 
rotation 30. 
The pump case center section 10 has an internal surface at 28 which defines 
the outer periphery of the pump chamber. 
The rotor 20 has a plurality of circumferentially equally-spaced, 
outwardly-opening slots 32, each of which movably mounts a roller van 34, 
with the movement of the roller vanes 34 outwardly of the slots 32 being 
controlled by the position of a cam ring 40. The cam ring 40 is an annular 
member having an inner peripheral circular surface 42, defining a cam 
surface engageable by the roller vanes 34. The cam ring 40 has a neutral 
position, seen in FIGS. 1 and 3, and has positions to either side of 
neutral, as illustrated in FIGS. 4 and 5. The vanes can be defined by 
means other than rollers, such as blades, in order to provide swept 
volumes of fluid at the periphery of the rotor. 
The cam ring 40 is mounted for pivotal movement on a pin 44 extending 
through an ear 46 on the cam ring and fitted on openings in the pump case 
side walls 12 and 14. The position of the cam ring 40 is set by the 
positioning of a block 50 mounted within a slot 55 in the control shaft 57 
which is housed in the pump case side wall 12 for transverse movement, as 
viewed in FIG. 1, and which has a pin 52 secured thereto which extends 
through an ear 54 at the lower end of the cam ring, as viewed in FIGS. 1 
and 2. A slot 56 is provided in pump case side wall 14 to prevent 
overstroking of the cam ring 40 by limiting the travel of pin 52. A 
plurality of Belleville springs 58 surround the pin 52 to take up 
tolerances and prevent rattling of the actuation structure. 
The structure is more particularly disclosed and described in the Hutson 
application, previously referred to, and reference may be made thereto for 
a more detailed understanding of this structure. With the cam ring 40 
concentric with the axis of rotation 30, the cam ring is in the neutral 
position shown in FIG. 3, wherein the pin 52 is centered relative to the 
slot 56. In FIG. 4, pin 52 is shown at the right-hand end of the slot 56 
to position the cam ring 40 to achieve flow in a "forward direction" 
between the pump ports to be described. In FIG. 5, the pin 52 is 
positioned at the left-hand end of the slot 56 to achieve a reversal in 
the direction of flow from that achieved with the pump components as 
positioned in FIG. 4 and which will be subsequently described as "reverse 
direction" operation. 
The pump 8 has a plurality of intervane fluid chambers with a fluid chamber 
defined between a pair of adjacent roller vanes 34, the cam surface 42 of 
the cam ring 40, the exterior surface of the rotor 20 between the roller 
vanes and the interior surfaces of the pump case side walls 12 and 14. 
Each of these fluid chambers transports a swept volume of fluid between an 
inlet port and an outlet port. Additionally, there are undervane pumping 
chambers defined between the base of the outwardly-opening slots 32 which 
carry the roller vanes 34 and the under surface of the roller vanes. 
The porting is provided in each of the pump case side walls 12 and 14 and 
the porting in one pump case side wall is the mirror image of the other. 
The porting for the pump case side wall 14 is shown particularly in FIGS. 
3 to 5. There are a pair of outer arcuate ports generally diametrically 
opposite each other, including a first port 60 and a second port 62, with 
these ports communicating with passageways 64 and 66, respectively, which, 
by suitable connections 67 and 68 can be connected to a source of fluid 
and a pressure utilization device which, in a use such as shown in the 
Hutson application previously referred to, would be the outlet and inlet 
ports, respectively, of a fluid motor 69 (FIG. 6). The ports 60 and 62 at 
the face of the pump case side wall 14 are of increased dimension, as 
indicated by the respective broken lines 70 and 72. The passageways 64 and 
66 also communicate, respectively, with a pair of inner arcuate ports, 
with an inner arcuate port 76 communicating with the undervane pumping 
chambers defined by the rotor slots 32 beneath a plurality of roller vanes 
34 and the inner arcuate port 78 communicating with a number of undervane 
pumping chambers which are adjacent the second port 62. The cam ring 40 
has side grooves 40a and 40b which coact with the ports 60, 62, 80 and 82 
to facilitate fluid flow. 
As seen in FIG. 2, pump case side wall 12 has the same porting, with outer 
arcuate ports 80 and 82 corresponding to second and first ports 62 and 60 
communicating with the connecting passages 84 and 86 associated with the 
respective connecting passages 64 and 66. Inner arcuate ports 88 and 90 
connect to the connecting passages 84 and 86, respectively, and operate 
similarly to the inner arcuate ports 76 and 78 to communicate with the 
undervane pumping chambers. 
The pump structure thus far described, except for porting details to be 
described, is generally known in the art wherein rotation of the driven 
shaft 22 causes rotation of the rotor 20 to successively carry roller 
vanes 34 past the first port 60 and the second port 62 communicating with 
the pump chambers between roller vanes and also to carry the undervane 
pumping chambers between the ports 76 and 78. 
The pump is disclosed as a reversible flow, variable volume structure 
dependent upon the position of the cam ring 40. As seen in the neutral 
position of FIG. 3, the fluid chambers between roller vanes as well as the 
undervane pumping chambers do not change their swept volume, so that there 
is no pump flow. 
In the operating mode shown in FIG. 4, which is referred to as "forward 
direction" operation, the cam ring 40 has been pivoted about the pin 44 to 
cause a variation in the volume of the intervane pump chambers, as well as 
the undervane pump chambers as the rotor rotates and there is "forward" 
pump flow from the first ports 60 and 82 to the second ports 62 and 80 and 
from the inner arcuate ports 76 and 90 to the inner arcuate ports 78 and 
88. In the operating mode illustrated in FIG. 5, which is referred to as 
"reverse direction" operation, the cam ring 40 has been pivoted in a 
clockwise direction about the pin 44 whereby there is "reverse" pump flow 
from the second ports 62 and 80 to the first ports 60 and 82 and from the 
inner arcuate ports 78 and 88 to the inner arcuate ports 76 and 90. 
With the foregoing general description of a pump having swept volumes at 
the perimeter of the rotor and, more particularly, a vane pump having 
reversible variable volume flow, the improvements may be more particularly 
described. With the cam ring 40 positioned at either side of the neutral 
position, shown in FIG. 3 and as illustrated in FIGS. 4 and 5, the cam 
ring is out of concentricity with the rotor 20 and a pair of cross-overs 
are defined. 
At a first cross-over, a fluid chamber between a pair of vanes changes from 
a fluid chamber of decreasing volume to one of increasing volume, while at 
the second cross-over, the fluid chamber changes from one of increasing 
volume to one of decreasing volume. These cross-overs are defined at 
locations wherein the cam surface 42 of the cam ring is at minimum and 
maximum distances from the surface of the rotor 20, respectively. The 
first cross-over, in FIG. 4, lies slightly above a transverse line passing 
through the axis of rotation 30 and to the left thereof. The second 
cross-over, wherein the distance between the rotor and the cam ring is 
maximum, lies below a transverse line through the axis of rotation 30 of 
the rotor and to the right thereof. Referring to FIG. 5, the first 
cross-over lies to the right of the axis of rotation 30 and slightly above 
a transverse line therethrough. The second cross-over lies to the left of 
the axis of rotation 30 and slightly below a transverse line therethrough. 
In the forward operation illustrated in FIG. 4, the maximum pumping 
efficiency is achieved by increasing the communication time of the pump 
outlet port, the second port 62, with a pump chamber of decreasing volume 
which is pressurizing the fluid and by increasing the length of time in 
which a fluid chamber of increasing volume is in communication with the 
inlet port, the first port 60. The increased time of communication with 
the outlet port is achieved by rotationally offsetting the parts of the 
second ports 62 and 80 which open to the intervane fluid chambers between 
the roller vanes and as illustrated by broken line 70 in FIG. 4. A line 
passing through the center of the cam ring mounting pin 44 and the axis of 
rotation 30 passes through top dead center of the pump and, as seen in 
FIG. 3. The second port 62 is generally symmetrical with this line but the 
opening 70 thereof is rotationally offset in a counterclockwise direction 
whereby there is increased communication time with a fluid chamber between 
roller vanes 34, identified at A and B. In FIG. 4, the roller vane B has 
just reached a position to block off communication with the trailing edge 
of the port opening 70 with the rotor 20 rotating in the direction of the 
arrow shown in FIG. 4. This permits the utilization of additional 
pressurized fluid which is in a decreasing swept volume between roller 
vanes and which is approaching the minimum distance cross-over. The inner 
arcuate ports 76,84 and 78,86 are rotationally offset similarly to the 
outer arcuate ports 60,80 and 62,82, respectively. 
The increased fill time for a fluid chamber of increasing volume is 
achieved by varying the effective length of the first port 60 only when in 
the forward direction operation, illustrated by positioning of the 
components as shown in FIG. 4. This increased effective length is achieved 
by the use of a radially offset arcuate extension 100 of the first port 60 
which extends from the first port in the direction of rotor rotation and 
is at a greater radial distance from the rotor axis 30 than the first port 
60. The selective variation of the length of the first port 60 is 
illustrated by comparison of FIGS. 3, 4 and 5. When the cam ring 40 is in 
neutral position, the radially inward edge of the extension 100 is blocked 
from communication with the fluid chambers between vanes by the cam ring 
40. There is also blockage of the extension 100 when the cam ring 40 is 
positioned for reverse direction operation, as shown in FIG. 5. The 
extension 100 only communicates with intervane fluid chambers when in the 
forward direction operation for maximum pumping volume, as illustrated in 
FIG. 4, or when the cam ring 40 is positioned to a lesser pivoted position 
but still for forward direction operation. The normal length of the first 
port 60 as exposed to the fluid chambers is shown by the broken line 102 
and with the extension 100 extending beyond an end 104 thereof. This 
increases the time of communication of a fluid chamber with the first port 
60 when the latter port is functioning as an inlet port for maximum 
filling of a fluid chamber as it approaches the maximum cross-over and is 
of increasing volume. 
In the reverse direction operation of FIG. 5, the second port 62 is the 
inlet port and it supplies fluid chambers of increasing volume and, as a 
fluid chamber travels past the maximum cross-over, the fluid is 
pressurized and delivered to the first port 60 which is the outlet port. 
The first port 60 terminates at the trailing edge 104, since the extension 
100 thereof is blocked by the cam ring 40. 
The extension 100 is radially offset to be utilized only in the forward 
operation illustrated in FIG. 4 in order to be blocked by the cam ring 40 
when the pump is in neutral or in the reverse direction operation 
illustrated in FIG. 5. When in reverse direction operation, the first port 
60 is the pressure outlet port and, if the extension 100 communicated with 
an intervane fluid chamber between vanes, there could be communication at 
the minimum cross-over, seen in FIG. 5, between the first port 60 and 
second port 62 whereby pressure would not be maintained at the first port 
60. The radial positioning of the extension 100 relative to the 
positioning of the cam ring 40 is selected whereby when the pump operation 
is shifted from forward direction to reverse direction, the cam ring 40 
will block the extension 100 from communication with an intervane fluid 
chamber slightly before the cam ring 40 reaches the neutral position of 
FIG. 3 to avoid cross-communication between the first port 60 and the 
second port 62. 
In the use of the pump, as in the previously described hydrostatic 
transmission for a vehicle, the predominant time of operation is in the 
described forward direction. Therefore, the extension 100 can be 
associated with the first port 60 and rendered effective by positioning of 
the cam ring 40 when in forward direction operation and removed from the 
system by positioning of the cam ring 40 when in reverse direction 
operation. 
The pump also has means to prevent cavitation and to prevent blow-by 
resulting from a trapped swept volume under compression causing movement 
of a vane away from the cam surface of the cam ring and resulting noise by 
rattling contact between vanes and the cam ring. 
This means embodies the use of a pair of auxiliary ports 110 and 112 
located generally one at each of the cross-overs of the pump. These 
auxiliary ports 110 and 112 each have an arcuate length sufficient to be 
effective in preventing blow-by and cavitation and are effective in many 
types of pump including the bi-directional pump disclosed herein. 
In the forward direction operation of FIG. 4, the auxiliary port 110 is 
located in the area of minimum cross-over and there is an intervane fluid 
chamber between roller vanes A and B of decreasing volume and which is out 
of communication with the second port 62 which is the pressure port. This 
results in a trapped volume of fluid in a decreasing volume intervane 
fluid chamber which, without the auxiliary port 110, could result in a 
pressure build-up sufficient to force the roller vane A away from the cam 
surface 42 of the cam ring, with resulting loss of pressure because of 
blow-by of pressure to the inlet port 60. The blow-by also results in a 
rattle caused by movement of the roller vane A toward and away from the 
surface of the cam ring which is a common source of noise in a vane pump. 
The auxiliary port 110 is connected to a source of fluid at ambient 
pressure, such as case pressure within the pump chamber externally of the 
cam ring 40 whereby fluid between roller vanes A and B can flow to the 
pump chamber and blow-by is prevented. 
The spacing between the trailing edge of the second port opening 70 and the 
leading edge of the auxiliary port 110 is slightly less than the distance 
between the lines of contact of two adjacent roller vanes with the cam 
surface 42 of the cam ring whereby the fluid chamber between the vanes A 
and B will communicate with the auxiliary port 110 slightly before vane B 
closes off communication with the second port 62. This is only a temporary 
transient condition with some slight loss of pressure by flow through the 
auxiliary port 110. However, this slight loss is offset by the avoidance 
of blow-by and creation of noise. As seen in FIG. 4, communication with 
the second port 62 is blocked; however, roller vane A is in a position to 
have placed the trailing fluid chamber already in communication with the 
auxiliary port 110. 
During the forward direction operation shown in FIG. 4, the auxiliary port 
112 has a leading edge 114 rotationally in advance of the maximum 
cross-over whereby the connection thereof to the source of fluid at 
ambient pressure enables filling of an expanding intervane fluid chamber 
to prevent cavitation which would otherwise result from a lack of fluid to 
fill the fluid chamber, since roller vane E has blocked off communication 
with the first port 60. 
The auxiliary port 110 has a finger 116 extending beyond the trailing edge 
thereof which enables supply of fluid at case pressure to an expanding 
fluid chamber between roller vanes A and C prior to the time at which that 
fluid chamber reaches communication with the first port 60. Thus, the 
auxiliary ports avoid cavitation problems throughout the extent of rotor 
rotation by providing a source of fluid to expanding intervane fluid 
chambers in the forward direction of operation. 
In the reverse direction operation as illustrated in FIG. 5, the auxiliary 
port 112 prevents blow-by and rattling noise by having the leading edge 
114 thereof rotationally in advance of the minimum cross-over position. A 
fluid chamber between roller vanes D and E, which is of decreasing volume, 
may communicate with the auxiliary port 112 to prevent a pressure build-up 
in a trapped volume and thus avoid blow-by and the erratic movement of the 
roller vane D. 
The roller vanes D and E, as positioned in FIG. 5, have moved past the 
locations at which the fluid chamber therebetween first communicates with 
the auxiliary port 112 and is out of communication with the first port 60. 
The extension 100 of the first port 60 is not effective to prevent blow-by 
since the cam ring 40 is positioned to block the extension 100 from 
communication with the fluid chamber between vanes. The blocking of the 
extension 100 is necessary to assure that pressure at the first port 60 
cannot communicate with the ambient pressure at the auxiliary port 112. 
The auxiliary port 112 has its trailing edge 120 located beyond the 
minimum cross-over whereby fluid at ambient pressure can reach a fluid 
chamber between the roller vanes D and F which is of increasing volume to 
prevent cavitation. 
In the reverse direction operation of FIG. 5, the auxiliary port 110 
assists to prevent cavitation by having a leading edge 122 thereof located 
in advance of the maximum cross-over, whereby a fluid chamber between 
roller vanes A and B which is of increasing volume can be supplied with 
fluid from the auxiliary port 110 after passing out of communication with 
the second port 62 which is the inlet port. 
As stated previously, the embodiment of the inventions in a reversible flow 
roller vane pump is for illustrative purposes only, with it being 
understood that the invention with respect to the improved porting 
efficiency could be used with other types of vane pumps and the 
improvements relating to prevention of cavitation and blow-by could be 
utilized with any type of pump having swept volumes carried around the 
periphery of a rotor and without structure for achieving reversible 
variable volume flow.