U.S. patent number 3,709,104 [Application Number 05/119,558] was granted by the patent office on 1973-01-09 for radial piston hydraulic pump or motor with low loss reaction linkage.
This patent grant is currently assigned to Jaromir Tobias. Invention is credited to Donald L. Culberson.
United States Patent |
3,709,104 |
Culberson |
January 9, 1973 |
RADIAL PISTON HYDRAULIC PUMP OR MOTOR WITH LOW LOSS REACTION
LINKAGE
Abstract
A radial piston hydraulic pump or motor characterized by a new
linkage assembly interposed between the pistons and the reaction
assembly. The linkage assembly, in addition to transmitting forces
between the pistons and the reaction assembly, also stabilizes the
pistons relative to the cylinders. The linkage assembly is
characterized particularly by the incorporation of a parallel pair
of Scott-Russell linkages, some portion of the parallel pair being
guided for linear reciprocal movement by reason of the parallel
nature of the links.
Inventors: |
Culberson; Donald L. (Teaneck,
NJ) |
Assignee: |
Tobias; Jaromir (Rhinebeck,
Dutchess County, NY)
|
Family
ID: |
22385052 |
Appl.
No.: |
05/119,558 |
Filed: |
March 1, 1971 |
Current U.S.
Class: |
91/495;
92/58 |
Current CPC
Class: |
F01B
13/062 (20130101); F16H 21/04 (20130101); F01B
1/0644 (20130101); F01B 1/0655 (20130101) |
Current International
Class: |
F16H
21/04 (20060101); F16H 21/00 (20060101); F01B
1/00 (20060101); F01B 13/00 (20060101); F01B
13/06 (20060101); F01B 1/06 (20060101); F01b
001/06 (); F01b 013/06 () |
Field of
Search: |
;92/56,57,58 ;91/495
;417/273 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schwadron; Martin P.
Assistant Examiner: Cohen; Irwin C.
Claims
Having thus described the invention and illustrated its use, what
is claimed as new and is desired to be secured by Letters Patent
is:
1. In a radial piston pump-motor of the type including a pintle
shaft, a cylinder block rotatably mounted on said shaft and having
cylinders progressively positioned fluid flow communication with
the high and low pressure manifolds of said shaft, piston members
reciprocably mounted in sealing relation of said cylinders, and a
reaction assembly member rotatable about an axis parallel with but
offset from the rotational axis of said block, the improvement
which comprises piston operating linkage means interposed between
said piston members and said reaction assembly for transmitting
forces therebetween, said linkage means each comprising at least
one parallel pair of Scott-Russell linkage assemblies, each member
of each said pair having a link portion pivotally secured to a
piston member, the lines between said pivotal connections to each
piston of each pair being at all times perpendicular to the axis of
rotation of said block.
2. The device of claim 1 wherein said linkages include a common
slide block portion.
3. The device of claim 2 wherein said reaction assembly includes a
slideway and said slide block portion is journalled in said
slideway for movement toward and away from the axis of rotation of
said reaction assembly.
4. The device in accordance with claim 2 and including tandem pairs
of parallel Scott-Russell linkages, said pairs being located at
opposite sides of a plane extending through the axes of said
cylinders.
5. The device of claim 4 wherein said pistons are cup-shaped and
outwardly lap said radial outer ends of said cylinders, at least
one sealing ring being disposed between the lapping portions of
said pistons and cylinders.
6. The device of claim 1 wherein said pistons include guide
portions and said Scott-Russell linkages include slide block
portions reciprocably mounted on said guide portions for movement
axially of said cylinders.
7. The device of claim 2 wherein said Scott-Russell linkages
include long links and short links and the radial outermost ends of
said long links are fixed to the slide block portion of said
linkages, the radial innermost ends of said long links are fixed to
said pistons, and the free ends of said short links are pivotally
connected to said reaction assembly.
8. The device of claim 7 wherein said slide block portion of said
linkages are mounted in guideways formed in said reaction assembly,
said guideways cooperating with said block for limiting movement of
said block to a direction which is radial of said reaction
assembly.
9. The device of claim 8 wherein each said piston is controlled by
two pairs of parallel Scott-Russell linkages arranged in tandem to
opposite sides of said piston, the points of connection of said
pairs to said piston being equally spaced from a plane common with
the axes of said cylinders.
10. The device of claim 1 wherein said pump or motor includes a
drive shaft connected to said reaction assembly.
11. A hydraulic pump-motor device comprising a pintle shaft, a
cylinder block mounted for rotation on said shaft, a plurality of
piston members mounted on said block for reciprocal movement
radially of said block, said piston members and block defining a
plurality of variable displacement chambers, porting means in said
block for sequentially connecting said chambers with high and low
pressure manifold areas of said pintle as said block rotates about
said shaft, a reaction assembly rotatable relative to said shaft
about an axis displaced from but parallel to the axis of rotation
of said block, Scott-Russell linkage means interposed between each
of said pistons and said reaction assembly, said linkage means each
including a guide member mounted on said reaction ring for
reciprocal movement radially with respect to the axis of rotation
of said reaction assembly, a pair of parallel long links having
their distal ends pivotally connected respectively to a piston
member and a guide member, a pair of parallel short links having
their ends pivotally connected respectively midway between the
pivots of said long links and to said reaction assembly at points
equidistant from the axis of rotation thereof, the effective length
of said short links being one half the effective length of said
long links.
12. The device of claim 11 wherein said linkage comprises two
parallel pairs of said links, said pairs being located in planes
parallel to and equally spaced from a plane extending through the
axes of said cylinders.
13. A hydraulic pump-motor device comprising a pintle shaft, a
cylinder block mounted for rotation on said shaft, a plurality of
piston members mounted for reciprocal movement radially of said
block, said piston members and block defining a plurality of
variable displacement chambers, porting means in said block for
sequentially connecting said chambers with high and low pressure
manifold areas of said pintle as said block rotates about said
shaft, a reaction assembly comprising a spaced pair of reaction
plates one to each side of said block, said plates being mounted
for rotation about a common axis parallel with and displaced from
the axis of said block, said plates each including a plurality of
guideways, in number corresponding to the number of said piston
means, a plurality of stabilizers having their opposed end portions
slidably received in a guideway in both said plates, said
stabilizers being carried in said guideways for reciprocal movement
radially relative to said common axis, a pair of pivot pins
extending from each side of each said piston means, said pins
having their axes parallel with said common axis, a Scott-Russell
linkage means including a pair of parallel long links to each side
of said pistons, said links having their inner ends pivotally
connected to said pins, the outer ends of said parallel long links
being pivotally connected to said stabilizers, a pair of short
parallel links to each side of said piston means, said short links
having their ends pivotally connected respectively midway between
the pivots of said long links and to one of said reaction plates,
the points of connection of said short links to said plates being
equidistant from the axis of rotation of said plates, the effective
length of said short links being one half the effective length of
said long links.
Description
BACKGROUND OF THE INVENTION:
1. Field of the Invention
This invention is in the field of radial piston hydraulic pumps and
motors of the type in which a pintle shaft is provided with
outwardly opening fluid supply manifolds for fluids under high and
low pressure, respectively, the manifolds being separated by land
portions. A block having cylinder bores is rotatably mounted over
the pintle shaft in sealing relation of the manifolds or discharge
areas, the block including passageways extending from a central
bore in the block to the individual cylinder chambers in the block.
By the described arrangement, the cylinder chambers are
sequentially connected to the high and low pressure manifold or
discharge portions of the pintle shaft as the block rotates about
the shaft.
Pistons are sealingly disposed on the cylinder block to define with
the cylinders variable displacement chambers. A reaction assembly
is provided for guiding the pistons in an eccentric path relative
to the axis of rotation of the block, As the pistons proceed in the
eccentric path, they shift axially inwardly and outwardly of the
cylinder bores in the block, thus varying the displacement of the
chambers defined between the pistons and the cylinders.
It will be appreciated that the apparatus may be used either as a
pump or as a motor. When used as a pump, the block is caused to
rotate by a prime mover, whereas when the apparatus is used as a
motor, fluid under pressure is admitted to one of the discharge
areas of the pintle and power is derived from the resultant
rotation.
2. The Prior Art.
Rotary piston pumps and motors operating on the above outlined
principles have long been known and widely used in specific
applications wherein small size and high efficiency are not
significant factors. Although there are many theoretical advantages
which suggest the use of rotary piston pumps and motors as gearless
transmission systems for automobiles, and analogous purposes, the
use of such systems has heretofore been restricted to vehicles of
special types by reason of the deficiencies inhering in all pumps
and motors heretofore known.
Among the advantages of utilizing rotary piston hydraulic pumps or
motors in a vehicle, such as an automobile, there may be mentioned
the possibility of permitting the pump to be driven by an engine
operating within a relatively restricted torque-speed range, such
as an internal combustion engine, and varying the drive speed by
varying the displacement of the pump and/or motor or motors, rather
than by varying the speed. By avoiding the necessity of increasing
and decreasing the speed of the multiple parts of the prime mover
which, as will be understood, have substantial inertia, it will be
appreciated that better vehicle acceleration may be obtained since
the inertia of the components of the transmission assembly is far
less than that of the prime mover.
It is well understood that internal combustion engines may be
operated highly efficiently if they are permitted to rotate at a
fixed speed or in accordance with a predetermined speed-torque
program, resulting not only in better fuel economies but also in
discharge of less partly burned by-products. The importance of the
latter characteristic will be readily understood in view of the
present emphasis on exhaust emission controls, and recognition that
automotive exhausts are considered to be the largest single source
of air pollutants.
In certain types of internal combustion engines, the so-called
"Wankel" engine being a prime example, difficulties other than
efficiency losses result from the engine being operated outside
predetermined optimum speed ranges. The Wankel engine, for
instance, by reason of its unusual design, involves great
difficulties in sealing the various combustion chambers to prevent
"blow-by" or leakage from one chamber to an adjacent chamber, which
difficulties are largely relieved so long as the engine operates
within a designated speed range.
No attempt has been made herein to catalog all of the various
theoretical advantages inhering in the use of radial piston pumps
or motors as hydrostatic transmission for automobiles. However,
limitations in the performance capabilities of available pumps or
motors have precluded such use. In general, the performance
deficiencies of hydraulic radial piston pumps and motors may be
classified in two categories, namely:
1. flow restrictions, i.e. the ability of a radial piston pump or
motor of limited size to permit high volumetric flow rates of
hydraulic fluid, and
2. mechanical losses inherent in the design of known pumps and
motors.
The problems of flow restriction have, by and large, been solved in
accordance with U.S. Pat. Nos. 3345,916 and 3548,719. Thus, the
drawbacks in the use of radial piston pumps and motors are now of
the second above enumerated type.
Broadly stated, it is a principal objective of the present
invention to provide a radial piston pump or motor having an
improved force transmitting linkage between the pistons and the
reaction assembly whereby losses and deficiencies inhering in
reaction ring-piston connections heretofore known are overcome,
resulting in the provision of a pump-motor having high efficiency,
relative freedom from wear and long life characteristics.
SUMMARY OF THE INVENTION
The invention may be summarized as directed to an improved linkage
for communicating forces between the pistons of a radial piston
pump or motor and the reaction assembly thereof. The improved
linkage comprises at least one pair of Scott-Russell straight line
motion linkages, which linkages are arranged in parallel and within
a common plane extending through the axis of rotation of the block.
The linkages may be oriented in any one of a series of different
positions, functioning in each case to relieve the pistons of
cocking and/or lateral force moments relative to the cylinders.
In the preferred embodiments, the connection between the pistons
and the reaction assemblies is made by the use of two separate
pairs of Scott-Russell linkages, the pairs being disposed in
parallel planes perpendicular to the axis of rotation of the block
and the connections between the pistons and the opposed pair of
linkages being symmetrical with respect to the axis of the
pistons.
It is accordingly an object of the invention to provide an improved
radial piston pump or motor device.
A further object of the invention is the provision of a radial
piston pump or motor device wherein mechanical losses are
minimized.
Still a further object of the invention is the provision of a
device of the type described in which parallel pairs of
Scott-Russell linkages are employed as the force transmitting agent
between the reaction assembly and the piston members, thereby to
relieve the latter of cocking forces or stabilizing functions,
whereby efficient use of piston rings may be made.
Still a further object of the invention is the provision of a pump
or motor of the type described wherein sliding movement between
components subjected to forces normal or substantially normal to
the direction of sliding movement is eliminated.
A further object of the invention is the provision of a device of
the type described wherein fluid side forces are minimized and
wherein balanced dynamic forces are exerted.
Still a further object of the invention is the provision of a
device of the type described wherein the provision of accurately
machined parts, such as the polygonal reaction plates heretofore
required in certain types of apparatuses is obviated, the
clearances required being maintained within limits readily achieved
and satisfactorily met in such industries as the automobile
industry in the manufacture of automotive engines.
A further object is the provision of a device of the class
described which eliminates the use of return springs or their
equivalent, as is required in certain hydraulic pumps and motors
heretofore known.
It is a further object of the invention to provide a device of the
class described which lends itself well to the use of non-tilting
hydrostatic bearings.
A still further object of the invention is the provision of a
device of the class described wherein reaction loads are
transmitted to the reaction assembly at portions which are closer
to the axis of the pintle shaft than any constructions heretofore
known, thereby reducing the over-all diameter of the pump-motor
mechanism.
To attain these objects and such further objects as may appear
herein or be hereinafter pointed out, reference is made to the
accompanying drawings, forming a part hereof, in which:
FIG. 1 is a horizontal sectional view through a radial piston pump
or motor of the type described;
FIG. 2 is a section taken on the line 2--2 of FIG. 1, wherein
repetitive details of construction of the linkage and cylinder
assemblies have been omitted for purposes of clarity;
FIG. 3 is an exploded perspective view of a piston, elements of the
reaction assembly, and elements of a linkage assembly;
FIGS. 4 and 5 are diagrammatic views of a linkage assembly
embodying the principles of the pump or motor illustrated in FIGS.
1 to 3, in varying positions in the course of the piston
stroke;
FIGS. 6 and 7 constitute diagrammatic views of an alternate form of
connection between the linkage, reaction assembly and piston, the
figures depicting the parts in varying positions during the
stroke;
FIGS. 8 and 9 are diagrammatic views showing a still further
modification of the manner in which the linkages are interconnected
between the pistons and the reaction assembly, the figures
depicting the parts in varying positions during the stroke;
FIGS. 10 and 11 are diagrammatic views showing a still further
modification in the manner of interposing the linkages between the
pistons and the reaction assembly, the figures depicting the parts
in varying positions during the stroke;
FIG. 12 is a sectional view taken on the line 12--12 of FIG. 1.
Referring now to the drawings, 10 is a housing within which is
mounted a radial piston pump or motor assembly in accordance with
the invention, it being understood that the housing will normally
incorporate mounting means wherein the same may be fixed in some
predetermined relation relative to the apparatus with which it is
being used, such as, by way of example, an automobile or other
vehicle.
The housing desirably includes an outer shell 11 of cylindrical
configuration, closed at one end by a cover plate 12, mounted in
position by closure bolts 13. A circular opening 14 is formed at
the other end of the shell 11, the outer race 15 of a shaft bearing
16 being supported within an annular bearing support boss 17
secured by bolts 18 within the opening 14. The inner race 19 of the
bearing 16 supports the input-output shaft 20 which, in the
illustrated embodiment as will be more fully set forth hereinafter,
is fixed to the reaction assembly.
The pintle assembly 21 is supported by the housing so as to be
laterally movable with respect thereto. The outer or left hand end
22 of the pintle assembly 21 is slidably mounted in a slide block
support assembly 23, secured to the end plate 12 of the
housing.
The slide block support assembly includes a laterally extending
guideway 24, having parallel upper and lower guide wall portions
which define the guideway proper.
The the pintle includes an enlarged collar25, the upper and lower
surfaces 25', 25' of which are elongated in the lateral direction
and intimately engage with the upper and lower parallel walls
defining the guideway 24. The guideway 24 is provided with an
opening which is elongated in the lateral direction, to provide
clearance for the side to side movement of the pintle, while
maintaining the pintle axis against tilting in any direction.
It will be readily understood that alternate means of providing
lateral movement between the pintle and the housing may be
employed.
Optionally, the clearance defining the guideway 24 may be provided
through the use of a spacer plate 26, the opening in which is
oversized as compared with the complemental openings formed in
inner slide plate 27 and outer slide plate 28, respectively forming
the inner and outer boundaries of the slideway referred to
generally as 24. The plates 26, 27, 28 may be interconnected by
bolts 29 or other suitable means.
Means for effecting the lateral shifting movement between the
pintle and the housing are interposed between the noted parts. For
purposes of simplicity, in the illustrated embodiment the lateral
shifting assembly 30 has been shown to comprise a threaded member
31 having an inner end 32 rotatably secured to the pintle in such
manner that axial shifting of the threaded member relative to the
pintle is prevented. The threaded member 31 passes through a
threaded post 33 affixed at 34 to the housing, an adjustment knob
35 being provided for rotation of the screw and consequent lateral
shifting movement of the pintle. It will be appreciated that in
actual practice such lateral movement may be effected by any of a
series of hydraulic, manual or automatic adjustment control
mechanisms. Similarly, it will be appreciated that in certain
instances where variable displacement is not required, the pintle
may be locked permanently with its axis displaced a fixed distance
from the axis of the reaction assembly, in which case no adjustment
mechanism and, indeed, no slide mechanism need be provided.
The inner end 36 of the pintle assembly includes a pair of axially
directed stabilizer pins 37, 38, which function, by sliding
engagement within a complemental, transversely extending slot 39
formed in floating bearing block 40, to limit upward and downward
relative movement between the pintle and the block 40, when viewed
in the orientation of FIGS. 1 and 2. The block 40 is disposed
within an annular recess 41 formed within the right handmost
reaction plate 42.
The inner end 36 of the pintle assembly is stabilized against
displacement from the plane of the section of FIG. 1 by engagement
of the pins 37, 38 in the slideway 39 formed in the block 40 and
against transverse movement by a lateral stabilization assembly
which is the subject of a patent application filed on even date
herewith and entitled Radial Pump or Motor with Stabilized Pintle
and, hence, a full description thereof is beyond the scope of the
present description.
Briefly stated, the stabilizer includes a flexible cable or cables
43 of fixed over-all length, the distal ends 44, 45 of which are
fixed with relation to the housing. The cable includes transversely
extending portions adjacent the ends, turning gradually to axially
extending branches 46, 47 slidably extending within slots 48, 49
within the body of the pintle and in line with the land defining
bridge portion 50 thereof -- see FIG. 2. The cable includes a
transversely extending central branch portion 51 which is made fast
at 52 to the block 40, the cable junction between the axially
directed branches 46, 47 and the laterally directed portion 51
being passed over rollers 53, 54 or like anti-friction members
carried by the innermost end of the pintle.
It will be recognized from the foregoing that, in view of the fixed
length of the cable, a lateral shifting movement of the pintle will
result in extension of one branch of the cable and a concomitant
diminution of the length of the other branch, the end result of
which cable arrangement is to stabilize the inner end of the pintle
relative to the housing in an improved manner as contrasted with a
purely cantilevered arrangement. It will be appreciated that a
cantilevered structure will operate satisfactorily and that the
stabilizing arrangement described need not be employed to realize
the advantages of the present invention.
A cylinder block assembly 55, in accordance with known practice, is
rotatably mounted on the pintle shaft. The cylinder block assembly
of the present apparatus includes a spoke-like series of cylinder
bosses 56 projecting radially from a central hub portion 57, which
hub is provided with the usual axial bore 58. As is conventional in
radial piston pumps and motors, the bore 58 intimately engages and
surrounds the radial, outwardly open manifold or discharge area 59,
60 of the pintle shaft, to provide communicating passageways
between the discharge areas and the cylinder bores 61.
Optionally but preferably, the passages or transition areas 62 in
the cylinder block which adjoin the pintle shaft and lead or
conduct fluid from the shaft to the bore portions 61 of the
cylinders proper are elongated in their axial dimension and reduced
in their angular dimension, in accordance with the teachings of
U.S. Pat. Nos. 3,345,916 and 3,548,719 so as to provide an improved
flow path between the cylinders and the pintle.
It will be further appreciated that the conventional configuration
of passageway may be employed, while still retaining certain of the
benefits of the present invention.
In accordance with conventional practice, the land areas 63, which
are shown in dot and dash lines in FIG. 2, have their peripheral
portions of a somewhat greater arcuate extent than the arcuate
extent of the passages 62 at the bore 58 of the block so that as
the passages traverse the lands, the passages are sealed by the
lands and there is no possibility of a bridging of the passage
between the charge and discharge areas of the pintle shaft.
In the embodiment illustrated in FIGS. 1 and 2, the seal between
the pistons and cylinders is effected between the external surface
of the cylinder and the internal bore portions of the piston
assemblies 64 which are essentially cup-like. However, it will be
appreciated that the apparatus of the present invention is fully
usable with conventional pistons riding on and sealing the internal
surfaces of the cylinders.
Optionally but preferably, the interior surfaces 65 of the pistons
may be provided with an annular groove or grooves 66, within which
may be seated one or more piston rings 67. It will further be
evident that while the rings are shown as mounted in grooves formed
in the pistons, it is equally practicable to form the ring
retaining grooves on the external surfaces of the cylinders, or
rings may be mounted on both the pistons and the cylinders.
It will further be appreciated that fluid is conducted to and from
the chambers 59 and 60 through input and output conduits (not
shown) which are preferably flexible, to facilitate displacement of
the pintle, and which are led to the chambers through the outer end
32 of the pintle shaft assembly 21.
Operating forces in the pump-motor are exerted between the pistons
and the reaction assembly 68 next to be described.
The reaction assembly includes the previously mentioned inner
reaction plate 42 which is fixed by bolts 69 to the shaft 20, outer
reaction plate 70, and a cylindrical reaction shell 71 which
interconnects plates 42 and 70. The plate 70 is mounted, as by
bearing 72, on a cylindrical shaft extension portion 73 of the
slide block support assembly 23. A series of machine screws 74
extending through apertures in the plates and into complementally
tapped apertures in the shell 71 may be employed to interconnect
these parts.
It will be appreciated that the radial piston reaction pump-motor
device as heretofore described is essentially conventional in its
construction with the exception of the pintle stabilizing mechanism
hereinabove generally described.
The essential novelty of the present invention lies in the linkage
mechanism which is employed to interconnect the pistons with the
reaction assembly 68 in a manner which will be hereinafter
described in detail.
The linkage in each instance comprises two or more straight line
mechanisms of the type known as Scott-Russell linkages. To
facilitate an understanding of the detailed showing of the
linkages, reference will initially be made to the diagrammatic
showings of FIGS. 4 and 5.
In each such view there is shown a pair of Scott-Russell linkages 1
and 2, each of which linkages is comprised generally of a long link
L, a short link S, and a slide block B. The effective length of the
short link is one half the effective length of the long link. The
distal ends of the long link L are pivotally connected to the slide
block and to the piston assembly 64. One end of the short link S is
pivotally connected to the reaction assembly at point P and the
other end to the center point C of the long link L.
It is a property of a Scott-Russell linkage that when the pivotal
connection point A of the long link L is moved toward or away from
the point P in the direction of the line D, that the opposite end E
of the long link L will be shifted precisely along a linear locus
represented by the line F. It will thus be apparent that with two
Scott-Russell linkages 1 and 2 disposed in parallelism, as the
slide block B is moved within the guideway provided therefor, in
the direction of the line D, the free ends E, E' will always remain
on the line F. In view of the fact that the pistons 64 have two
points of connection, E and E', to the linkages, it will be
apparent that the pistons will be supported against tilting and
will be stabilized in space and their axes will at all times be
perpendicular to the line F.
As hereinafter used in the application and claims, the term
"Scott-Russell linkage" is intended to refer to a linkage assembly
as shown at 1 and 2 of FIG. 4, comprising, as noted, a long link
and a short link, the effective length of the short link, e.g. the
distance between pivots, being one half of the effective length of
the long link, e.g. the distance between pivots.
Reference to a "pair" or "parallel pair" of such linkages is
intended to refer to two such linkages which lie in a common plane
or act as if they lay in a common plane perpendicular to the axis
of rotation of the cylinder block, the linkage of the pair being
offset angularly within such plane. An example of such a "pair" of
linkages is shown in FIGS. 4 and 5 wherein the arcuate segment Z
indicates the directions of rotation of the block and reaction
assembly.
While it is feasible to connect the pistons to the reaction
assembly through the use of a single parallel pair of Scott-Russell
linkages, which linkages might lie in a plane extending through the
common axes of the cylinders and projecting outwardly to a
surrounding reaction assembly, it has been determined to be
preferable to employ two parallel pairs of Scott-Russell linkages
for controlling each piston, one pair being disposed adjacent each
side of the piston.
In the light of the foregoing general description, reference will
be made especially to FIGS. 1 to 3 for details of the specific
linkage constructions herein employed.
As best seen from FIG. 3, each piston assembly 64 includes four
integral, outwardly extending stub shafts 75, 76, 77, 78. The stub
shafts 75, 77, and the stub shafts 76, 78 are coaxial, all of the
shafts being parallel to the axis of rotation of the cylinder
block.
It will be appreciated from a comparison of FIGS. 3 and 4 that the
axes of the shafts 75, 77 correspond with the pivot point E in FIG.
4, and the axes of the shafts 76, 78 with the pivot point E'.
The reaction plates 42 and 70 are integrally formed with a
plurality of truncated segments 79, 79'. The opposed or facing wall
portions 80 and 80' of each adjacent pair of segments are parallel
with each other and with a line 81 extending from the axis of
rotation 82 of the reaction assembly-- see FIG. 2. It will thus be
seen that the opposed faces or walls 80, 80' define guideways
corresponding to the guideways shown in FIGS. 4 and 5, which assure
radial movement of the center point of the slide block B relative
to the axis of rotation 82 of the reaction assembly.
The structures corresponding to the slide block B in the
diagrammatic view, FIG. 4, are shown at 83, 83. As best appreciated
from an inspection of FIG. 3, the slide blocks 83, 83 include
parallel end walls 84, 85 which slidably engage against opposed
walls 80, 80' defining the slideways, the described interfit
assuring that the center point of the slide blocks 83, 83 is
constrained to move in a purely radial direction relative to the
axis 82 of the reaction assembly.
The reaction plates 42 and 70 form the anchor points for reaction
pins 86, 86', which pins correspond to the points P as shown in
FIG. 4. For this purpose, the plates in juxtaposition to each
linkage assembly are provided with a pair of parallel apertures 87,
87'.
The reaction pins 86 include an inwardly directed bearing portion
88, a locating shoulder or collar 89, and a threaded outer end
portion 90. It will be understood that the pins are mounted by
insertion through the apertures 87, 87' and are locked in position
by the pin retainer nuts 91.
For purposes of clarity, only one pin of each pair of linkages is
shown in FIG. 3.
Short links corresponding to the links S of the diagrammatic view,
FIG. 4, are shown at 92 in FIGS. 1 to 3. The links 92 are provided
with internal outer and inner bores 93, 94, the axes of the bores
93, 94 being parallel, the radius of the bores being such as to
intersect and leave therebetween internal divider segments 95,
96.
The inner bores 94 of the short links 92 are mounted on the bearing
portions or trunnions 88 and the reaction pins 86, a thrust washer
97 being preferably interposed between the links 92 and the collars
89 of the reaction pins. The link 92 is secured against inward
movement relative to the right hand reaction plate 42 by annular
retainer member 130, held in place by machine screws 131. In
similar fashion, the links 92 are secured against movement away
from the left hand reaction plate 70 by annular retainer member 132
which is recessed at angularly spaced positions to provide
clearance for pivotal movement of the links 92, the member being
secured to the plate 70 by machine screws or like means (not
shown).
The long links corresponding to the links L are comprised of a
multi-part construction including an inner link component 98, a
transversely extending cross link 99 and a connector sleeve 100. It
will be appreciated from an inspection particularly of FIG. 3 that
the length of a cross link 99 is such as to enable both of its end
portions 101 and 102 to be utilized in conjunction with a different
Scott-Russell linkage.
Hereinafter in the specification and claims, the two Scott-Russell
linkages which are secured to the opposite sides of a cross link 99
will be referred to as "tandem linkages." It will be understood
that the two linkages forming a tandem operate about coaxial pivot
points, to move in displaced planes, as opposed to a "pair" or
"parallel pair" of linkages, which operate in common planes but
about parallel displaced axes.
The common axis 103 of the cylindrical ends 101, 102 of the cross
links 99 corresponds with the pivot point C in the diagrammatic
view, FIG. 4. It will be appreciated that the outer bores 93 of a
tandem of short links 92 are pivotally mounted on the portions 101
and 102 of the cross link 99.
The connection between the long link 99 and the stub shafts 75, 77
and the stub shafts 76, 78, respectively, are effected through the
use of the inner links 98 previously described. In this connection,
each inner link 98 includes a bearing aperture 104, the apertures
104, 104 of a tandem pair of inner links 98, 98 being mounted on
the opposed stub shafts 75, 77, respectively.
The outer ends 105 of the inner links 98 are provided with
semi-circular recesses 106 defined by opposed legs 107, 108. A
retainer cross bore 109 extends through both legs 107, 108. The
cross link 99, inwardly adjacent its end portions 101, 102, is
provided with reduced diameter portions 110, 111. It will be
appreciated that the inner links 98 are connected to the cross link
99 by placing the legs 107, 108 in straddling position of the
reduced diameter portions 110, 111, respectively. Connector
apertures 112, 113 are formed in the reduced diameter portions,
which connector apertures, in the straddling position of the links
98, are aligned with the cross apertures 109 in the legs 107, 108,
the parts being maintained in the assembled position by the locking
pins 114, which are inserted through the registering apertures.
As best seen in FIGS. 2 and 3, the body portion 115 of the cross
link 99 defines a hollow cylindrical portion, 116 representing the
axis of the cylinder 115. Connection between the long link and an
opposed pair of slide blocks 83 is effected by the tubular
connector sleeve 100. The outer surface of the sleeve 100 fits
intimately and rotatably within the cylindrical portions 115 of the
cross link 99. The ends 117, 118 of the connector sleeve 100 are
recessed at 119 and 120, to provide clearance for pivotal movement
of the short links 92. The ends 117, 118 of the connector sleeves
100 are received within the semi-cylindrical recessed portions 121,
121 in the tandem slide blocks 83. For this purpose, apertures 122
are formed through the sleeves adjacent the ends 117, 118, machine
screws 123 being passed through the apertures 122 and threadedly
connected into complemental tapped bores 124 formed in the slide
blocks 83.
From the foregoing it will be apparent that the long link assembly
is connected to the piston for pivoting movement about parallel
pivot axes 125, 126; that the short links are free to pivot
relative to the connector link portion 99 of the long link about
the pivot axis 103; and that the long links are free to pivot
relative to the blocks 83 about the pivot axis 116.
For convenience, and for purposes of improved understanding, the
axes 116, 103 and 125, corresponding respectively with the pivot
points A, C and E, have been applied to FIG. 4.
From the foregoing, the operation of the apparatus of FIGS. 1 to 3
will be evident.
Where the device is used as a pump, the shaft 20 is driven, thus to
rotate the reaction assembly 68. It will be appreciated, as best
seen from FIG. 2, that the axis of rotation 135 of the block will
have been offset from the axis of rotation 82 of the reaction
assembly. As is known, the distance between the axes 82 and 135
will determine the displacement of the pump, the greater the
distance, the greater the displacement. The rotation of the
reaction assembly causes concomitant rotation of the block by
reason of the interconnection of the linkages, pistons and reaction
assembly previously described.
It is important to note that since torque is transmitted to the
reaction ring rather than to the block where the device is used as
a pump (and extracted from the reaction ring rather than the block
when the device is used as a motor), substantial operating torques
are not transferred through the pistons and linkages. It should be
noted that the sole transmitted torques through such pistons and
linkages are the torques required to overcome friction and rotate
the block. This is so because the positions of the pistons within
the block are stabilized by reason of the novel linkage.
It will be further appreciated that with continued rotation, the
pistons are reciprocated inwardly and outwardly relative to the
cylinders, the short links being disposed in parallelism with the
long links at two positions during each rotation of the block and
the reaction ring, notably at the point of maximum outwardmost
movement of the pistons, as represented by the lefthandmost set of
links shown in FIG. 2, and at a position 180.degree. displaced
therefrom, representing the radial innermost position of the
pistons.
It will be understood that the oscillation of the pistons relative
to the cylinders will cause fluid to be sucked into the cylinder
chambers during one half of the rotative cycle from one of the
chambers 59 or 60, depending upon the direction of rotation, the
fluid being discharged under pressure into the other of the
chambers during the radial inward movement of the pistons. In
common with other radial piston pumps and motors, it will be
appreciated that higher pressures and lower volumes may be
developed with a given torque input where the eccentricity is
reduced, and vice versa.
The radial pump or motor employing the novel linkage hereinabove
described has the unique advantage, as contrasted with any pump or
motor heretofore known, of providing a fully stabilized piston
(i.e. stabilized against both cocking forces of the piston relative
to the cylinder and lateral forces against the cylinder walls),
without concomitant drawbacks. Most particularly, the pump-motor of
the present invention provides full stabilization without requiring
a linear or arcuate sliding movement between the outermost end of a
piston and an arcuate or planar track portion.
For instance, in one known type of radial piston pump or motor, the
outermost end of the piston is stabilized by being pressed against
a flat reaction track forming a portion of a polygonal reaction
assembly. It will be appreciated that in such construction the
piston is stabilized relative to the cylinder by its engagement
against a flat track portion. However, such stabilization is
achieved only at the cost of great mechanical losses, since the
outermost end of the piston is scanned back and forth across the
flat track portion during each rotation a distance approximating
the radial displacement of the piston. Since the outward forces of
the piston against the track may amount to many tons, it will be
evident that great mechanical losses and wear will result from the
noted movement and, by reason of the quantum of forces, unusual and
expensive bearings must be interposed between the relatively moving
parts. Use of simple but effective hydrostatic bearing principles
alone is not feasible or effective.
The advantages of the herein described linkage will be immediately
appreciated when contrasted with radial pumps or motors employing
conventional annular reaction ring assemblies. In such assemblies,
the outermost end of the piston engages against an annular reaction
track or ring, resulting in the application of forces between the
ring and the piston which are, during the majority of the rotating
cycle, directed non-axially of the piston. As will be readily
understood, such non-axial forces tend to cock the piston relative
to the cylinder bore, resulting in premature wear. Attempts to
overcome wear problems by elongating the pistons, thus elongating
the contacting cylinder-piston overlap, creates still other
problems, such as increase in overall diameter and weight of the
pump-motor without concomitant displacement increase, and
difficulties in maintaining adequate lubrication in the overlapping
areas of the piston and cylinder.
In addition, structures using the conventional annular reaction
ring embody the same problems of sliding movements between the
piston slipper and the reaction ring discussed in connection with
polygonal reaction track pumps and motors, with consequent wear and
efficiency losses, etc.
A further solution which has been attempted is exemplified by the
patent to Centervall, U.S. Pat. No. 2,001,706 of May 21, 1935. In
that construction, attempts have been made to stabilize the piston
against cocking by the interposition of a parallelogram linkage
between the piston and a reaction ring assembly. While such
apparatus does, to a degree, reduce the forces which tend to cock
the piston axis and displace it from the cylinder axis, it does not
prevent the application of considerable forces, tending to displace
the piston from the center line of the cylinder. Moreover, in a
device of the Centervall type, operating torque is transmitted
through the piston and piston linkages, magnifying the wear
problems inhering in the application of piston displacing
forces.
In similar fashion, Tobias U.S. Pat. No. 3520,233 tends to combat
both cocking and displacing forces but involves manufacturing
difficulties which limit the widespread employment of this
design.
In accordance with the present invention and for the first time in
a radial piston pump or motor assembly, the use of the novel
linkage hereinabove set forth enables the production of a pump or
motor having lower mechanical losses by a significant margin as
contrasted with any such pump or motor heretofore known.
It will be appreciated further that the paired Scott-Russell
linkages may be interposed between the piston and the reaction
assembly in a plurality of different arrangements while still
enjoying the advantages of the present invention.
For purposes of illustration there are shown three modified linkage
connection arrangements, namely, those of FIGS. 6-7, 8-9, and
10-11.
The illustrated arrangements are not considered to exhaust the
possible orientations of linkage arrangements which may be utilized
without departing from the spirit of the present invention which,
in its broadest phases, is considered to reside in the use of
paired Scott-Russell linkages. Thus, by way of example, while all
of the embodiments have illustrated the use of a slide block which
extends generally radially of the reaction assembly or the block
assembly, it will be appreciated that an arrangement wherein the
slide block shifts normal to such radial direction is feasible.
In the device of FIGS. 6 and 7, 200 represents the reaction
assembly having a guideway for controlling each piston, which
guideway is defined by the parallel walls 201, 202. The slide block
is shown at 203, the block being shiftable reciprocably in the
direction of the line 204. 205 represents the piston. 206 and 207
represent the long links of separate paired Scott-Russell
assemblies and 208 and 209 are the short links, respectively, of
such assemblies.
The ends of link 206 are connected at 210 and 211 to the piston 205
and the block 203, respectively. The ends of the long link 207 are
connected at 212 and 213 to the piston 205 and the block 203,
respectively.
The short link 208 has one end connected at 214 to the central
point of long link 206, the opposite end 215 of the link 208 being
connected at 216 to a fixed pivot point on the reaction assembly
200. In similar fashion, short link 209 has one end 217 pivotally
connected to the central point of long link 209, the opposite end
218 of the link 209 being pivotally connected at 219 to a pivot
point on the reaction assembly.
The effective length of the links 208 and 209 is one half the
effective length of the links 206, 207 and, accordingly, points 210
and 212, the points of connection to the piston, will be stabilized
by reason of the use of such linkage.
It will be recognized that the embodiment of FIGS. 6 and 7 is
essentially an inversion of the embodiment of FIGS. 3 to 5.
In the embodiment of FIGS. 8 and 9, the piston 220 is provided with
an extension portion 221 forming a guideway for an axially
shiftable slide block 222, having a bearing portion enabling the
block to be reciprocated in an axial direction only relative to the
piston, as indicated by the line 223.
224 and 225 are paired Scott-Russell linkages having their long
links pivotally connected at their upper ends 226, 227,
respectively, to the slide block 222. The other ends 228, 229 are
fixed to the reaction assembly. The free ends of the short links of
the Scott-Russell assemblies 224, 225 are fixed at 230, 231,
respectively, to the piston 220.
The embodiment of FIGS. 10 and 11 consists essentially of an
inversion of the apparatus of FIGS. 8 and 9, wherein 240 and 241
are the paired Scott-Russell linkages, 242, 243 are the pivotal
points of connection to fixed positions on the reaction
assembly,244 is the slide block, slidably reciprocable on guide
surface 245 of the piston 246. 247 and 248 are the points of
connection of the free ends of the short links to the piston
246.
In each of the diagrammatically illustrated embodiments of FIGS. 6
to 11, it will be observed that the piston is stabilized relative
to the cylinder and is reciprocated by the paired Scott-Russell
linkages to effect the desired oscillating movement.
Numerous modifications may readily suggest themselves to the
skilled worker in the light of the teachings hereof, such
modifications to be considered within the scope of the present
invention. Accordingly, the present invention is to be broadly
construed within the scope of the appended claims.
* * * * *