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Патент USA US3022751

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Feb. 27, 1962
R. w. BRUNDAGE
3,022,741
VARIABLE VOLUME HYDRAULIC PUMP 0R MOTOR
Filed May 6, 1957
FIG. I
2 Sheets-Sheet 1
I41
ATTORNEY
Feb. 27, 1962
'
Filed May 6, 1957
R. w. BRUNDAGE
3,022,741
VARIABLE VOLUME HYDRAULIC PUMP OR MOTOR
2 Sheets-Sheet 2
INVEN
.
ROBERT W. BRUND
Ww
ATTORNEY
United States Patent ()??ce
3,022,?“
Patented Feb. 27, 1962
2
1
and separated by a pair of lands; one land being adjustable
3,022,741
from a full volume position at one end of the neutral
VLE VOLUME HYDRAULIC PUMP
0R MOTGR
axis through the minimum and maximum volume posi
tions of the chambers toward the opposite end to reduce
Robert ‘W. Brundage, Willoughby, Qhio
(2809 Wakonda Drive, Belnor, St. Louis, Mo.)
Filed May 6, 1957, Ser. No. 657,314
14 Claims. (Cl. 193-120)
the output volume of the pump to zero, the other land
being normally ?xed but so arranged that the movable
land may be adjusted to the minimum or zero volume
position.
This invention pertains to the art of hydraulic pumps
Thus, at the zero volume position, both lands are sym
or motors and more particularly to hydraulic pump or 10 metrically arranged about one end of the neutral axis
which means that the other land is o?set from such neutral
motor of the variable volume type.
The invention is particularly applicable to a. hydraulic
axis. This other land vmay be permanently offset from
pump of the internal gear type and will be described with
the neutral axis or movable therefrom as the adjustable
particular reference thereto although it will be apprecia
' land is moved to the zero volume position.
ated ‘that the invention is equally applicable to internal 15
gear hydraulic motors or to other pumps or motors where-_
Further, in accordance with the invention, the normally
?xed land is of a width wider than the passages leading
from the chambers, and if such land is to be positioned
in the chambers rotate, such as, without limitation, vane
type or rotating-cylinder barrel type pumps or motors.
opposite decreasing volume chambers, it is provided with
_ While the invention will be described and claimed as
a trapping port dividing the land into a pair of auxiliary
directed to a pump, it will be appreciated that the termi 20 lands of a width less than the passage leading from the
nology herein is equally applicable to a motor if the
chambers and means are provided for bleeding such trap
terms “inlet and inlet pressures” are considered as being
ping port to the low pressure manifold when the land is
discharge or discharge pressures and the terms “outlet or
positioned opposite a decreasing volume chamber.
outlet pressures” are considered as inlet or inlet pressures.
Further, in accordance with the invention, the adjust
, Pumps of the type to which this invention pertains 25 able land when adjustable over the arc of decreasing vol
normally comprise a plurality of relatively movable mem
ume chambers or when the increasing volume chambers
bers which de?ne a plurality of closed rotating increasing
leaving the adjustable land come into communication with
and decreasing volume chambers which alternately com
the high pressure manifold, a similar trapping port is
municate through rotating passages with inlet and outlet
provided on the adjustable land in combination with
manifolds sealingly separated by a pair of lands which en 30 means for maintaining the pressure in the trapping port
at approximately one half the high pressure. '1 nus, such
means, when the adjustable land is movable over the arc
of decreasing volume chambers, must bleed ?uid to the
circumferential , width greater than the circumferential
inlet manifold. In the other case when the increasing vol
width of the passages leading from the chambers to the 35 ume chambers leave the adjustable land and come into
gage surfaces on the members between the passages and
prevent ?uid ?ow between the manifolds.
These lands are ordinarily of a carefully controlled
manifolds. Leakage of high pressure ?uid is thus pre
vented around the lands and through the passages when
communication with the high pressure manifold, the means
will supply ?uid under pressure from this manifold to
a passage faces a land.
the trapping port.
Using the present invention, substantial increases in
The lands are ordinarily located on the neutral axis
through the points of maximum and minimum volume of 40 volumetric e?iciency over all ranges of output volume can
the chambers. It is known that the output volume of a
hydraulic pump or the speed of a motor may be varied by
adjusting the lands away from this neutral axis.
be obtained over the use of a straight bypass to control
the output volume and substantial increases in volumetric
ef?ciency at low volume outputs can be obtained over that
described in my copending application, Serial No. 548,022,
In my co-pending application, Serial No. 497,779, ?led
March 29, 1955, now US. Patent No. 2,898,862, issued 45 filed November 21, 1955, now US. Patent No. 2,956,506,
issued October 18, 1960.
August 11, 1959, an arrangement is described wherein the
The principal object of the invention is the provision
output volume of a pump may be varied by rotating only
of a new and improved hydraulic pump (or motor) which
the land disposed opposite the point of minimum volume
overcomes all the di?iculties of the prior art, provides for
of the chambers for full volume past the increasing vol
ume chambers. Such an arrangement o?ers substantial 50 ready adjustment of the output volume, has a high volu
metric e?iciency, and a high mechanical e?iciency.
advantages over moving both lands. As now appears,
Another object of the invention is the provision of a
one disadvantage is present, namely that because of inter
ference with the other land (which was ?xed), the mova
ble land could not be adjusted to zero output volume.
The present invention contemplates a pump (or motor)
new and improved hydraulic pump wherein one of the
lands only may be adjusted to control the output volume
55 and the other lands arranged to move from its normally
?xed position where it would interfere with adjustment
which overcomes the above di?iculties and enables the out
of the ?rst stop.
put volume of the pump with one adjustable stop to be
Another object of the invention‘is the provision of a
readily varied from a maximum to zero.
new and improved hydraulic pump which is relatively sim
In accordance with the present invention, a hydraulic 60
ple in construction, economical to manufacture, and has
pump (or motor) is comprised of: a plurality of members
provision for providing a desired pressure gradient across
de?ning a plurality of revolving, increasing and decreas
ing volume chambers; input and outlet manifolds com
municating alternately with such chambers as they revolve
the sealing faces of the stops.
The invention may take physical form in certain parts
and arrangement of parts, preferred embodiments of‘
‘3,022,741
4
which will be described in this speci?cation and illustrated
in the accompanying drawing which is a part hereof and
wherein:
FIGURE 1 is a side cross-sectional view of a variable
volume hydraulic pump illustrating a preferred embodi
ment of the invention.
FIGURE 2 is a cross-sectional view of FIGURE 1
taken on the line 2-2 thereof with the gear members
pressure (as will appear) in the cavity 8 may exert an
axial force to the right to hold the right hand surface of
the sleeve 26 in sealing engagement with the disc 12. The
sleeve 26 is reciprocably mounted in a counterbore 29
in the left hand of the housing “A” and an O-ring 30
seals its outer surface. A compression spring 31 bears
against the base of the counterbore 29 and against the left
hand of the sleeve 27 to provide an initial sealing force
forming the pump shown in phantom thereover. The
of the sleeve 26 on the sealing disc 12. The area of the
pump is shown as adjusted to the full volume position.
10 surface 28 is so proportioned that the sealing force be
FIGURE 3 is a view similar to FIGURE 2 but without
tween the surfaces is sui?cient to prevent the leakage of
the phantom gears showing the pump adjusted to zero
hydraulic ?uid from the cavity 8 between the surfaces
‘
and thus outwardly along the shaft 11. The construction
FIGURE 4 is a View similar to FIGURE 2 but showing
and operation of the sleeve 26 is described and claimed
an alternative embodiment of the invention adjusted to the 15 in my co-pending application, Serial No, 613,235, ?led
full volume position.
October 1, 1956, and will not be described further herein.
FIGURE 5 is a view similar to FIGURE 4, but show
Su?ce it to say, that the pump cavity 8 is closed and under
ing the pump adjusted to the zero volume position.
hydraulic pressure.
FIGURE 6 is a cross-sectional view of FIGURE 1 on
In accordance with the present invention, the pump
the line 2—2 showing an alternative embodiment of the
also includes arcuately extending inlet and outlet mani
volume.
invention; and
folds 35, 36 opening toward the ported plate 14 and each
FIGURE 7 is a similar view showing the invention ap
plied to a motor.
'
>
Referring now to the drawings wherein the showings
adapted to be simultaneously in communication with one
or more of the passages 25, the number being variable
so that the output volume of the pump may also be varied.
are for the purpose of illustrating a preferred embodi 25
The inlet and outlet manifolds are sealingly separated
ment of the invention only and not for the purposes of
at the arcuate ends by what may be termed‘ a “?xed” land
limiting same, the ?gures show a hydraulic pump com
38 and an adjustable land 39 both having their left hand‘
prised. of a housing “A” made up of two cup-shaped fac
surface in sealing engagement with the right hand‘ sur
ing. members 9, 10 de?ning a closed pump cavity 8 in
face of the ported plate 14. Thus the chambers 17, 18
which the various members of the pump are mounted. 30 each have a passage 25' opening through a rotating seal
A drive shaft 11 driven from an external power source,
ing surface and the manifolds open through sealing sur
not shown, extends into the interior of the housing “A”
faces, both of which surfaces are in sealing engagement.
and has mounted thereon for rotation therewith, reading
The inlet manifold 35. extends axially and communi
from left to right, a sealing disc 12, an externally toothed
cates with a passage 40 in the right hand base of the hous
gear 13, and a ported plate 14. The sealing disc 12 is 35 ing “A” which communicates with radially outward ex
rigidly mounted on the shaft 11 as by an interference ?t
tending passage 41 to the outside of the housing “A,”
and is supported‘ for rotation in the housing as by a roller
The outlet manifold 36 also extends axially of the hous
bearing 16 axially slidable in interior of the housing and
ing “A” and communicates with an outlet or discharge
held in position on the disc 12 by means of a snap ring 5.
passage 43 in the right hand base of the housing “A"
In like manner, vthe ported plate 14 is rotatably sup 40 which in turn communicates with a radially outward ex
ported in a roller bearing 6 held in place in the housing by
tending passage 44 to the external surface of the housing.
means of a snap ring 7. The ported plate 14 is axially
As will be seen from FIGURE 2, the discharge passage
movable within the roller bearing 6.
43 is located adjacent to the point of minimum volume of
An internally toothed ring gear 15 having one, or more,
the chambers. 17, 18, but spaced therefrom slightly oppo
teeth than the teeth of the gear 13 is meshed with the 45 site to the direction of rotation.
externally toothed gear 13 and de?nes therebetween a plu
'In a like manner, the inlet passage 40 is located adja
rality of rotating progressively increasing and decreasing
cent to the point of maximum volume of the chambers
volume chambers 17, 18. The gear 15 is mounted. for ro
17, 18 and spaced slightly therefrom in a direction oppo
tation on an axis spaced from the axis of] the shaft 11 by
site to the direction of rotation. The total diameter of
means of a roller bearing 21 mounted in a counterbore in 50 passage 40 is so adjusted that when the lands 38, 39 are
the housing “ ” having an axis spaced from the axis of
the shaft 11 the desired amount... The ring gear 15 is
axially siidable in the bearing 21.
The gear 13 and the ported plate 1'4v are keyed to rotate
with the. shaft 11' as by means of the key 22 and the pin '
23 but both members are axially‘ slidable on the shaft 11..
in the position as shown in either FIGURES 2 or 3, the
passage 40 will not be, in communication with the out
let manifold 36.
With the lands positioned as shown in FIGURE 2, i.e.',
at the points of minimum andmaximum chamber volume,
the pump will have full volume output. These points of
minimum and maximum volume de?ne what may be
Means, as will appear hereinafter, holds these members,
in side by side engagement so that the sealing disc 12'
termed as the neutral axis- of the pump. With the lands
sealingly engages the left hand surfaces of the gears 13,
adjusted as shown in FIGURE 3, the pump will have zero‘
15 to close the left hand end of the chambers 17, 18 while 60 volume output. To obtain such variation in volume, the
land 39 is adjustable from the position in FIGURE 2 that
the ported plate 14 is in sealing engagement with the
is from the neutral axis adjacent the point of zero cham
right hand end of the gears 13, 15.
ber volume over the increasing volume chambers thus
The ported plate 14 has a plurality of passages 25 which
exposing the increasing volume chambers 17 to the pres-,
when considered in a direction toward the chambers 17,.
sures in the outlet manifold. The result is that the pres
1'8 slope outwardly and away from the direction of rota
sures in the outlet manifold exert a motor action on the
tion. One passage 25 is provided for each chamber 17,
increasing volume chambers 17 and the energy of this
18 and ?uid going to and from the chambers 17, 18.
?uid is recovered.
'
passes through the passages 25. The use of the ported
Because of the “?xed” land 38, it was impossible here
plate 14 and the function of the sloping‘ of the passages
tofore to move the land 39 to a position so that the pump
25 is more fuliy described in my co-pending application,
would have zero volume. In accordance with the pres
Serial No. 613,235, ?led October 1, 1956 and will not be
further detailed herein.
‘a
A sleeve 26 surrounds the shaft 11 to the left of the
ent invention, the land 38, while normally being desig
nated as; a “?xed”- land, is mounted for movement a slight.
distance. clockwise as viewed in FIGURE 3 so that the
sealing disc 12 and has a radially outwardly extending
?ange 27 to provide; a pressure surface 28 on which ?uidv 75 output volume. of. the. pump can bereduced to zero.
‘3,022,741
5
While the mounting and arrangements of the lands 38,
39 to permit this may be as desired, in the embodiments
shown, the land 39 is in the form of a lug extending axial
ly on a shaft 45. Any cavitation which might occur as
the increasing volume chamber approaches the maximum
volume point is low or any that does occur is offset by
the decrease in volume of the chambers after it passes the
6
the high-pressure manifold urges the land 38 in the same
direction that the adjustable land would move it when
it moved to the zero volume position. In this embodi
ment of the invention, the ?xed land 38 is permanently
positioned offset from the neutral axis in the direction of
rotation from the point of minimum volume of the cham
bers. Some cavitation will occur underneath the land
38, as so positioned in FIGURE 6, but as previously in
point of maximum volume.
~
dicated, the chamber with the cavitation will subse
However, with the ?xed land being movable away from
the point of maximum volume, means must be provided to 10 quently come into communication with the low pressure
prevent trapping. Such means comprise a trapping port
manifold, and no harm will result.
It is to be noted that in FIGURE 6, the trapping port
65, centrally located in the face of the land 38, extend
ing radially inwardly to the inner surface of the land 38.
65 has been omitted as unnecessary.
The trapping port 65 communicates with a groove or pas
However, the adjustable land 39 must have the trap
sage 66 on the outer surface of the shaft 45 adjacent to 15 ping port 74) provided therein, and meansare provided
for maintaining the pressure in this trapping port at ap
the adjustable land 39 on the side in the direction or ro
tation and communicating with the inlet manifold. As
proximately one-half the high pressure. However, in the
embodiment shown in FIGURE 6, ?uid will be supplied
the land 39 comes into contact with the land 38, the trap
to the trapping port, and the pressure regulating valve
ping port 65 is communicated to the inlet manifold 35.
Trapping is prevented.
20 shown is similar to that shown in FIGURES 1, 4 and 5
with the exception that the valve seat 75 is at the base of
The trapping port 65 in e?ect divides the ?xed land 38
the valve chamber so that ?uid may be bled from the
into two auxiliary lands 38a and 38b both of which have
trapping port 70 to the low pressure manifold.
a circumferential width just less than the circumferential
FIGURE 7 shows the invention applied to a variable
width of the passages 25.
In the embodiments shown in FIGURES 2 and 3, the 25 speed hydraulic motor wherein the output speed of the
motor is adjusted by positioning one of the lands. In
adjustable land 39 moves from a maximum volume posi
the case of a motor for'the same direction of rotation,
tion opposite the point of zero volume of the chambers
the inlet manifold becomes the high pressure manifold.
17 over the arc of the increasing volume chambers.
In this embodiment of the invention, the ?xed land 38
The arcuate width of the land 39 is wider than the
width of the passages 25. Thus, as a passage 25 moves 30 is offset from the neutral axis opposite the point where
the chambers of the maximum volume in a direction op
under the land 39, cavitation in the corresponding increas
posite to the rotation. Thus, the increasing volume
ing volume chamber will occur. However, as this cham
chambers as they leave the ?xed land 33 come into com
ber with the cavitation moves from under the land, it
r'nunication with the low pressure. Cavitation is not a
comes into communication with the inlet manifold and
35 problem. The adjustable land 39 is adjustable over the
no, problems are presented. '
arc of the decreasing volume chambers to a point ad
In the embodiments shown in FIGURES 4 and 5, how
jacent the neutral axis where the chambers of a maximum
ever, the land 39 is adjustable from a full volume position
volume for zero speed of rotation of the motor. In this
opposite the point of maximum volume of the chambers
case, the adjustable land 39 moving over a decreasing
(see FIGURE 4) over the arc of the increasing volume
chambers to the zero volume position (see FIGURE 5). 40 volume chamber must have the pressure relief valve so
arranged as to bleed fluid from the trapping port 70 to
In this embodiment, cavitation will also occur within the
the low pressure manifold.
I
chambers, but here the chambers with the cavitation move
It will be seen that to change the embodiment of FIG
into communication with the high pressure manifold.
URE 6 from a pump to a motor, as shown in FIGURE
This is undesirable. Thus in accordance with the in
vention, the land 39 is provided with a trapping port 70 45 7, the ?xed land has been shifted from an offset in the
direction of rotation from the point of minimum volume
which divides the land 39 into two auxiliary lands of a
to an offset opposite the direction of rotation from the
width less than the width of the passages 25 so that cavi
point of maximum volume.
tation will not occur. Means have been provided for sup
If the embodiment of FIGURE 3 is to be employed as
plying hydraulic ?uid to the trapping port 70 at a pres
a motor, the land 38 would be shifted so as to be opposite
sure equal approximately to one-half the high pressure
the decreasing volume chambers, but oifset from the neu
?uid. In the embodiment of the invention shown, the
tral axis adjacent the point of minimum volume of the
trapping port 70 communicates with the high pressure
chambers against the direction of rotation.
manifold through passage 71 and a pressure valve con
sisting of a chamber 72 in the member 45, a valve seat 75
Thus, it will be seen that in accordance with the in
screwed into this chamber, and a ball 73 held in engage 55 vention, a hydraulic pump or motor of the variable vol
time or speed type has been provided wherein one of the
ment with the valve seat by a spring 74. The tension of
the spring 74 is so adjusted as to maintain a pressure in
lands is adjustable to vary the volume or speed, and the
the trapping port 70 generally equal to one-half the pres
other land is so arranged relative to the neutral axis of
the pump that the adjustable stop may be moved to
sure in the high pressure manifold.
The trapping port 70 is also shown in connection with 60 either the zero volume or speed position. Further, it will
be seen that in some instances it is possible to position
the embodiment in FIGURE 3, although for the reasons
a land in a permanently offset position, While in other
above indicated, namely that cavitation is not a problem
cases, it is possible to arrange the ?xed land so that it‘
in this embodiment, the trapping port 70 and pressure
may move to this position from a normal position on the
valve may be conveniently omitted.
'
In the embodiments of the invention described, it will 65 neutral axis.
The invention has been described with reference to
be appreciated that the pressure in the high pressure
preferred embodiments. Obviously, modi?cations and
manifold on the sides of the ?xed land 38 normally urges
alterations will occur to others upon a reading and un
the ?xed land to a position on the neutral axis through
derstanding of this speci?cation, and it is my intention
the chambers, and the adjustable land moves over the
arc of the increasing volume chambers, and when it 70 to include all such modi?cations and alterations insofar
as they come within the scope of the appended claims.
reaches the ?xed land, it moves the ?xed land from this
position.
Having this described my invention, I claim:
1. A positive displacement hydraulic device comprised
In some cases, it is desirable to move the adjustable
of a plurality of members movable relatively to each
land over the arc of the decreasing volume chambers, as
shown in FIGURE 6. In such a case, the pressure in 75 other and, de?ning a plurality of chambers revolving in av
8..
?xed closed path of movement, said chambers gradually
increasing in volume after they pass a ?xed point of mini
ate pressure approximately equal to. one half the pres
mum volume on said path of movement until they reach
a ?xed point of maximum volume on said path of move
sure in. the high pressure, manifold.
8. The improvement of claim 7 wherein said, ?rst land
is adjustable along the line of movement of the increas
ment and then gradually decreasing in volume until they
reach said ?xed point of minimum volume, means de?n
ing volume chambers and said means consist of a pres
sure valve arranged to admit ?uid from, the high pres
ing an arcuate inlet and an arcuate outlet manifold in
sure manifold to said trapping port!
9. The improvement of claim 7 wherein said ?rst land
of said manifolds and sealingly separating said manifolds
is adjustable along the line of movement of said decreas
one fom the other, an opening for each chamber revolv 10 ing volume chambers and said means consist vof a pres
ing therewith, each of said openings moving past said
sure relief valve arranged to, bleed fluid from said trap
lands to alternately communicate its associated chamber
ping port to‘the low pressure manifold.
cluding ?rst and second lands, one at each arcuate end
with either said inlet or said outlet manifold, said ?rst
land being normally located at the point of maximum
volume so that as each chamber reaches and passes
10. A variable volume or speed hydraulic pump or
motor respectively comprised of: a housing; a plurality
of rotatable‘ members de?ning a plurality of chambers
through maximum volume, its opening shifts from com
which revolve in a ?xed closed path of movement, said
munication with one manifold to the other manifold,
chambers gradually increasing in volume after they have
said second land being adjustable independently of said
passed a ?xed point of minimum volume on said path
?rst land along the path of movement of said chambers
of movement until they reach a ?xed point of maximum
from the point of minimum volume to the point of maxi 20 volume on said path of movement and then gradually
mum volume so as to change the point in the path of
movement in which each opening moves past said second
land and shifts communication of its chamber from one
manifold to the other, the improvement which comprises
said ?rst land is movable from the point of maximum
decreasing in volume until they reach said ?xed point
of minimum volume, means de?ning an arcuate inlet
and an arcuate outlet manifold including ?rst and sec
ond lands, one on each arcuate end of said manifold and
provided for biasing said ?rst land towards said point of
sealing separating said manifolds, an opening for each
chamber revolving therewith, each of said openings mov
ing past said lands to alternately communicate its asso
ciated chamber with either said inlet or said outlet mani
fold, one of said manifolds being at high ?uid pressure,
maximum volume.
said points of minimum and maximum volume de?ning
volume to allow said second land to be adjusted to a
point adjacent the point of maximum volume.
2. The improvement of claim 1 wherein means are
.
3. The combination of claim 1 wherein hydraulic pres
sure in the output manifold urges said ?rst land toward
the point of maximum volume.
4. The improvement of claim 1 wherein said ?rst land
has a trapping port dividing said land into two auxiliary 35
lands and means are providedrfor communicating said
a neutral axis, said second land being adjustable along
the path of movement of said decreasing volume cham
hers, the improvement which comprises: said ?rst land
being spaced from said neutral axis along the path of
movement.
.
trapping port with one of said manifolds as said ?rst land
11. The improvement of claim 10 wherein the spacing
of said ?rst land is in the direction of rotationvof said
is adjusted from said point of maximum volume.
5. The improvement of claim I wherein said second
pump.
rotating members and said device is being used as a
12. The improvement of claim 10 wherein said spacing
land has a pressure groove which communicates with 40
each opening as said opening moves past said second land
is counter to the direction of rotation of said rotating
and means are provided for maintaining said groove at
members and said device is being used as a motor.
13. The device of claim 10 including the further im
a pressure approximately one half the pressure in the
high pressure manifold.
provement wherein said second land is divided into two
6. The improvement of claim 5 wherein said second
land is. adjustable along the path of movement of said
increasing volume chambers and said means include a
pressure reducing valve communicating the high pres
auxiliary lands with a trapping groove therebetween, said
groove communicating with each opening as said open
ing moves past said second land and means are provided
to communicate said trapping groove with the low pres
sure manifold of said device with said groove.
sure manifold, said means including a pressure relief
7. A hydraulic device comprised of a plurality of 59 valve.
members movable relatively to each other and de?ning
a plurality of chambers revolving in a ?xed closed path
of movement, said chambers gradually increasing in vol
ume after they pass a ?xed point of minimum volume
on said path of movement until they reach a ?xed point
of maximum volume on said path of movement and then
gradually decreasing in volume until they reach said
14. A positive displacement hydraulic device com
prised of a plurality .of members movable relativelvto
each other and de?ning a plurality of chambers revolving
in a?xed closed path of movement, said chambers gradu
ally increasing in volume after they pass a ?xed point of
minimum volume on said path of movement until they
reach a ?xed point of maximum volume on said path of
movement and then gradually decreasing in volume until
they reach vsaid ?xed point of minimum volume, means
?xed point of minimum volume, means de?ning an arm
ate inlet and an arcuate outlet manifold including ?rst
and second lands, one at each arcuate end of said mani 60 de?ning an arcuate inlet and an arcuate outlet manifold
including ?rst and second lands, one at each arcuate end
fold and sealingly separating said manifolds one from
of said manifolds and sealingly separating said manifolds
the other, an opening for each chamber revolving there-.
one from the other, an opening for each chamber revolving
with, each of said openings moving past said lands to
alternately communicate its associated chamber with
therewith, each of said openings moving past said lands
either said inlet or said outlet manifold, one of said mani 65 to alternately communicate its associated chamber with
either said inlet or said outlet manifold, said second land
folds being at high hydraulic pressure, the improvement
which comprises: said ?rst land being adjustable along
being adjustable independently of said ?rst land along the
the path of movement of said chambers and having a
path of movement of said chambers from the point of
minimum volume to the point of maximum volume so as
line of movement width greater than said openings, said
first land having a trapping port communicating with 70 to change the point in the path of movement in which‘
each opening moves past said second land and shifts
each opening as said opening moves past said ?rst land,
communication of its chamber from one manifold to the
‘said trapping port dividing said ?rst land into a pair of
other, the improvement which comprises: said ?rst land
auxiliary lands, each having a line of movement width
being ‘permanently ?xed at a point close to but spaced
equal to or less than the line of movement width of said
openings, and means for maintaining said trapping ports
from said point of maximum volume whereby said second
3,022,741
10
9
land can be adjusted to a point at the point of maximum
2,509,321
2,628,567
2,688,927
2,728,297
volume.
References Cited in the ?le of this patent
UNITED STATES PATENTS
Re. 23,086
724,994
1,482,807
1,486,835
1,603,395
1,799,237
7
5
H011 ________________ __ Feb. 22, 1949
Cooley _______________ __ Apr. 7, 1903
Newberg ____________ __ Feb. 5,
Hill ________________ .. Mar. 11,
Mohl ________________ __ Oct. 19,
Jensen ________________ -_ Apr. 7,
1924
1924
1926 10
1931
2,749,843 I
2,785,637
2,898,862 _
Topanelian ___________ .... May 30, 1950
De Lancey __________ __ Feb. 17, 1953
Nuebling ____________ .... Sept. 14, 1954
Cilley ______________ __ Dec.
Nubling ____________ __ June
Nubling ____________ __ Mar.
Brundage ___-_________ __ Aug.
27,
12,
19,
11,
1955
1956
1957
1959
FOREIGN PATENTS
331,054
Great Britain __________ __ July 3, 1930
501.409
France ______________ .... Jan. 24, 1920 r
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