U.S. patent application number 14/223006 was filed with the patent office on 2014-07-24 for compact radial piston hydraulic machine having a cylinder block with deforming regions.
This patent application is currently assigned to HUSCO International, Inc.. The applicant listed for this patent is HUSCO International, Inc.. Invention is credited to Bradley J. Kramer, Dwight B. Stephenson.
Application Number | 20140202325 14/223006 |
Document ID | / |
Family ID | 51206701 |
Filed Date | 2014-07-24 |
United States Patent
Application |
20140202325 |
Kind Code |
A1 |
Kramer; Bradley J. ; et
al. |
July 24, 2014 |
Compact Radial Piston Hydraulic Machine Having a Cylinder Block
with Deforming Regions
Abstract
A hydraulic machine has a cylinder body with first and second
ports and a plurality of cylinder bores disposed radially with
openings through a side surface. Deformation regions, formed around
each cylinder bore opening, expand and contract in response to
pressure changes in the cylinder bores. A continuous band extends
around the cylinder body closing the cylinder bore openings and
applying a pre-stress compressive force to each deformation region.
A plurality of pistons are slideably received in the plurality of
cylinder bores and a plurality of valve arrangement couple the
cylinder bores to the first and second ports. A shaft with an
eccentric cam drives the pistons to slide within the cylinder
bores. Each deformation region distorts in response to pressure in
the associated cylinder bore wherein the circumference of that
cylinder bore becomes more circular as the cylinder pressure
increases.
Inventors: |
Kramer; Bradley J.;
(Oconomowoc, WI) ; Stephenson; Dwight B.;
(Oconomowoc, WI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
HUSCO International, Inc. |
Waukesha |
WI |
US |
|
|
Assignee: |
HUSCO International, Inc.
Waukesha
WI
|
Family ID: |
51206701 |
Appl. No.: |
14/223006 |
Filed: |
March 24, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13266378 |
Oct 26, 2011 |
|
|
|
PCT/US2010/036072 |
May 25, 2010 |
|
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14223006 |
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Current U.S.
Class: |
91/491 |
Current CPC
Class: |
F01B 31/06 20130101;
F04B 1/0448 20130101; F04B 1/0413 20130101; F04B 1/053 20130101;
F04B 53/162 20130101; F04B 1/0421 20130101 |
Class at
Publication: |
91/491 |
International
Class: |
F04B 1/04 20060101
F04B001/04 |
Claims
1. A hydraulic machine comprising: a cylinder body with a first
port, a second port and a side surface, and having a plurality of
cylinder bores disposed radially about an axis with each cylinder
bore having an opening through the side surface, the cylinder body
further having deformation regions formed around each opening,
wherein the deformation regions expand and contract radially with
respect to the axis in response to pressure changes in the cylinder
bores; a closing band extending around the cylinder body and
closing the openings of the plurality of cylinder bores, wherein
the closing band applies force to each deformation region that
compresses the cylinder body; a plurality of piston assemblies each
slideably received in a different one of the plurality of cylinder
bores; a plurality of valve arrangements the plurality of cylinder
bores to the first and second ports; and a drive shaft rotatably
received in the cylinder block for driving the plurality of piston
assemblies within the plurality of cylinder bores.
2. The hydraulic machine as recited in claim 1 wherein the cylinder
body further comprises: a cylinder block that has the plurality of
cylinder bores and the side surface; an inlet manifold having the
first port; and an exhaust manifold having the second port.
3. The hydraulic machine as recited in claim 1 wherein the side
surface of the cylinder block is cylindrical and the closing band
is circular.
4. The hydraulic machine as recited in claim 1 wherein the closing
band extends in a continuous circle.
5. The hydraulic machine as recited in claim 1 wherein each
deformation region comprises a rim extending around each cylinder
bore opening and proud of the side surface.
6. The hydraulic machine as recited in claim 1 wherein each
deformation region comprises a cantilevered portion of the cylinder
body extending as least partially around the associated cylinder
bore.
7. The hydraulic machine as recited in claim 1 wherein each
deformation region expands as pressure in the adjacent cylinder
bore increases and contracts as pressure in the adjacent cylinder
bore decreases.
8. The hydraulic machine as recited in claim 1 wherein pressure
within a given cylinder bore during a compression stage of an
operating cycle reduces compressive forces that the closing band
exerts on the deformation region associated with that cylinder
bore.
9. The hydraulic machine as recited in claim 1 wherein as pressure
within each cylinder bore increases, the adjacent deformation
region flexes thereby changing a circumference of the cylinder bore
from non-circular towards becoming circular.
10. The hydraulic machine as recited in claim 1 wherein each of the
plurality of piston assemblies comprises a piston and a piston rod,
wherein the piston rod comprises a stem with a curved shoe through
which force is transferred to the drive shaft.
11. The hydraulic machine as recited in claim 10 wherein: the drive
shaft has an eccentric cam; and further comprising a cam bearing
extending around the eccentric cam and having an outer race and a
plurality of rollers between the outer race and the eccentric cam,
wherein the shoe of each piston rod abuts the outer race.
12. The hydraulic machine as recited in claim 11 further comprising
a retaining ring extending around the drive shaft and engaging the
curved shoe of every piston rod, thereby constraining the curved
shoe from moving away from the eccentric cam.
13. The hydraulic machine as recited in claim 1 wherein each of the
plurality of piston assemblies comprises a piston and a piston rod,
wherein the piston rod has an end with a partially spherical head
that engages a partially spherical depression in the piston.
14. The hydraulic machine as recited in claim 1 wherein: the
cylinder block comprises a plurality of first bores, each extending
between the first port and one of the plurality of cylinder bores,
and a plurality of second bores, each extending between the second
port and one of the plurality of cylinder bores; and the valve
arrangement comprises a plurality of first valves, each located in
one of the first bores, and a plurality of second valves, each
located in one of the second bores.
15. The hydraulic machine as recited in claim 14 wherein each of
the plurality of first valves and the plurality of second valves is
a check valve.
16. A hydraulic machine comprising: a cylinder body with a first
port, a second port and a curved side surface, and including a
plurality of cylinder bores disposed radially in the cylinder block
with openings through the side surface and passages connecting the
plurality of cylinder bores to the first and second ports, the
cylinder body having a plurality of deformation regions each
comprising a rim projecting outwardly from the side surface and
around one of the openings, wherein the deformation regions
repeatedly deform in response to pressure changes in the cylinder
bores; a closing band extending around the cylinder body and
closing the openings of the plurality of cylinder bores, wherein
the closing band applies compressive force to the cylinder body
through the rim of each deformation region; a plurality of piston
assemblies each slideably received in a different one of the
plurality of cylinder bores; and a drive shaft rotatably received
in the cylinder block and having an eccentric cam for driving the
plurality of piston assemblies within the plurality of cylinder
bores.
17. The hydraulic machine as recited in claim 16 further comprising
a plurality of valves located in the passages of the cylinder
body.
18. The hydraulic machine as recited in claim 16 wherein the
cylinder body further comprises: a cylinder block that has the
plurality of cylinder bores and the side surface; an inlet manifold
having the first port; and an exhaust manifold having the second
port.
19. The hydraulic machine as recited in claim 16 wherein each
deformation region comprises a cantilevered portion of the cylinder
body extending as least partially around the associated cylinder
bore.
20. The hydraulic machine as recited in claim 19 wherein the
cantilevered portion is defined by a curved cavity within the
cylinder body and opening into the cylinder bore.
21. The hydraulic machine as recited in claim 16 wherein each
deformation region expands as pressure in the adjacent cylinder
bore increases and contracts as pressure in the adjacent cylinder
bore decreases.
22. The hydraulic machine as recited in claim 16 wherein pressure
within a given cylinder bore during a compression stage of an
operating cycle reduces compressive forces that the closing band
exerts on the deformation region associated with that cylinder
bore.
23. The hydraulic machine as recited in claim 16 wherein as
pressure within each cylinder bore increases, the adjacent
deformation region flexes thereby changing a circumference of the
cylinder bore from non-circular towards becoming circular.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 13/266,378, that is the national stage of
International Application No. PCT/US2010/036072 filed on May 25,
2010.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
[0002] Not Applicable
BACKGROUND OF THE INVENTION
[0003] 1. Field of the Invention
[0004] The present invention relates to hydraulic machines, such as
pumps and hydraulic motors, and more specifically to such machines
that have pistons which move in cylinder bores that are arranged
radially around an eccentric drive shaft.
[0005] 2. Description of the Related Art
[0006] A common type of radial piston pump comprises a body with a
plurality of cylinder bores radially disposed around a drive shaft.
A piston is slideably received within each cylinder bore and a plug
closes the exterior end of the cylinder bore, thereby defining a
chamber between the piston and the plug. The drive shaft has an
eccentric cam against which the pistons ride due to bias forces
provided by springs. An inlet port supplies fluid to an inlet
passage that is coupled through a separate inlet check valve to
each cylinder chamber. A set of outlet check valves couples the
cylinder chambers to an outlet passage that leads to an outlet port
of the pump.
[0007] As the drive shaft rotates, the eccentric cam causes each
piston to slide cyclically in and out of the respective cylinder
bore, thereby reducing and expanding the volume of the associated
cylinder chamber. During an intake phase of the piston cycle, when
a given cylinder chamber volume is expanding, the inlet check valve
opens allowing fluid to be drawn from the inlet passage into the
cylinder chamber. During the subsequent exhaust phase of each
piston cycle, when the volume of the cylinder chamber is reducing,
fluid is expelled under pressure through the outlet check valve to
the outlet port. The fluid intake and exhaust phases occur
repeatedly during every rotation of the eccentric cam. At any point
in time, some of the radially disposed cylinder bores are in the
intake phase and other cylinder bores are in the exhaust phase.
[0008] Conventional radial piston pumps typically are relatively
large in diameter in order to accommodate the biasing springs and
plugs that close the outer ends of the cylinder bores. In many
installations, the amount of space for the pump is restricted, thus
it is desirable to reduce the size of the pump. Often the pump is
mounted along side an engine or transmission and the radial space
is limited restricting installation of conventional radial piston
pumps.
SUMMARY OF THE INVENTION
[0009] A novel hydraulic machine includes a cylinder body that has
two end surfaces with a curved side surface there between. A first
port and a second port provided for making hydraulic connections to
the cylinder body. A plurality of cylinder bores is disposed
radially in the cylinder body and each cylinder bore has an opening
through the side surface. A deformation regions is formed around
each opening and deforms in response to pressure changes in the
adjacent cylinder bore. A separate piston assembly is slideably
received in each cylinder bore. A drive shaft is rotatably located
in the cylinder block and has an eccentric cam for driving the
plurality of pistons reciprocally within the plurality of cylinder
bores. A valve arrangement couples the cylinder bores to the first
and second ports and allow fluid to enter and exit the bores at
appropriate times during each piston cycle.
[0010] A closing band engages the curved side surface and extends
over the openings of the plurality of cylinder bores. The closing
band applies force to each deformation region thereby applying a
compressive force to the cylinder body
[0011] In one aspect of the present hydraulic machine, each
deformation region comprises a rim extending around each cylinder
bore opening and proud of the side surface.
[0012] In another aspect of the present hydraulic machine, pressure
within each cylinder bore during a compression stage of a piston
cycle reduces the compressive force that the closing band exerts on
the deformation region associated with that cylinder bore. For
example, as pressure within each cylinder bore increases, the cross
sectional shape of the cylinder bore becomes more circular, i.e.,
the circumference changes from a pronounced oval toward a
circle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0013] FIG. 1 is a schematic diagram of a hydraulic system that
incorporates a radial piston, hydraulic machine according to the
present invention;
[0014] FIG. 2 is a radial cross section showing the arrangement of
cylinder bores and pistons in the hydraulic machine;
[0015] FIG. 3 is an axial cross section through the hydraulic
machine along line 3-3 in FIG. 2;
[0016] FIG. 4 is a perspective view of the cylinder block hydraulic
machine;
[0017] FIG. 5 is a cut-away enlargement a section of FIG. 3 at the
top of one cylinder bore; and
[0018] FIG. 6 is a graph depicting the inner circumference of a
cylinder bore at different pressure levels.
DETAILED DESCRIPTION OF THE INVENTION
[0019] With initial reference to FIG. 1, a hydraulic system 10 has
a prime mover 12, such as an internal combustion engine or an
electric motor, that is coupled by a shaft to drive a hydraulic
machine 14 to function as a pump. The hydraulic machine 14 can be
configured as a fixed or variable displacement pump to draw fluid
in from the first conduit 15 and force the fluid under pressure
into the second conduit 16, thereby driving a hydraulic motor 18 in
one direction. The hydraulic motor 18 rotates a component, such as
one or more wheels 19 of a vehicle, for example.
[0020] The same design of the hydraulic machine also can be used as
a hydraulic motor, such as hydraulic motor 18. Here the hydraulic
machine receives pressurized fluid at one port and converts that
fluid power into mechanical energy that is applied to a shaft
connected to the wheel 19.
[0021] Therefore, the apparatus described herein is generically
referred to as a "hydraulic machine" because it can be configured
to function as either a pump or a hydraulic motor depending upon
how and where it is used in a hydraulic system. In some situations,
the same hydraulic machine may operate as both a pump and a motor
at different times depending upon whether the machine is driving
the load, such as wheels 19, or is being driven by fluid received
from the load, such as when the vehicle coasts to a stop.
[0022] With reference to FIGS. 2, 3 and 4, the hydraulic machine 14
has a cylinder block 20 with first and second flat, circular end
surfaces 21 and 22 between which a cylindrically curved side
surface 38 extends. The cylinder block 20 has a plurality of
cylinder bores 36 extending radially inward from side surface 38 to
a central shaft bore 41. The exemplary hydraulic machine 14 has
nine cylinder bores 36 spaced at 40 degree increments around the
central shaft bore 41, however other hydraulic machines may have a
greater or lesser number of cylinder bores.
[0023] A plurality of first bores 24 extends into the first end
surface 21 of the cylinder block 20 with each of those bores
communicating with a different one of the cylinder bores 36 through
an curved cavity 43 that extends in an annular manner around and
opens into that one cylinder bore. An end plate 23 is bolted
against the first end surface 21 and a plurality of apertures 27
extend through that plate aligned with the plurality of first bores
24. Each pair of a first bore 24 and an aperture 27 form an intake
passage for one of the cylinder bores 36. An inlet manifold 26
abuts an exposed surface of the end plate 23 and has an annular
inlet passage 31 connecting all of the end plate apertures 27 to an
inlet port 32 of the hydraulic machine 14. Fluid entering the
hydraulic machine though the inlet port 32 flows via the inlet
passage 31, apertures 27, and first bores 24 to each of the
cylinder bores 36, as will be described.
[0024] A plurality of second bores 25 extends into the second end
surface 22 of the cylinder block with each of the second bores
communicating with a different one of the cylinder bores 36 through
the respective curved cavity 43. An exhaust manifold 28 abuts the
second end surface 22 and has an annular outlet passage 29
connecting all the second bores 25 to an outlet port 35 of the
hydraulic machine 14. The annular inlet passage 31 and the annular
outlet passage 29 encircle the shaft bore 41 that extends through
center of the cylinder block 20. The cylinder block 20, the end
plate 23, the inlet manifold 26 and the exhaust manifold 28 combine
to form a body 30 of the hydraulic machine 14.
[0025] A separate inlet check valve 33 is located in each of the
first bores 24. The inlet check valve 33 opens when the pressure
within the inlet passage 31 is greater than the pressure within the
associated cylinder chamber 37, as occurs during the intake phase
of the piston cycle. A separate outlet check valve 34 is located
each of the second bores 25. The outlet check valve 34 opens when
pressure within the associated cylinder chamber 37 is greater than
the pressure within the outlet passage 29, as typically occurs
during the exhaust phase of the piston cycle. Each of the inlet and
outlet check valves 33 and 34 is passive meaning that it operates
in response to pressure exerted thereon and is not electrically
operated.
[0026] Referring specifically to FIGS. 2 and 3, a drive shaft 40
extends through the shaft bore 41 and is rotatable therein being
supported by separate bearings 42 at each end of the cylinder block
20. The central section of the drive shaft 40, that is within the
cylinder block 20, has an eccentric cam 44. The cam 44 has a
circular outer surface, the center line of which is offset from the
axis 45 of the remainder of the drive shaft 40. As a consequence,
as the drive shaft 40 rotates within the cylinder block 20, the cam
44 rotates in an eccentric manner about the axis 45. A cam bearing
46 extends around the drive shaft cam 44. The cam bearing 46 may
have an optional inner race that is pressed onto the outer
circumferential surface of the drive shaft cam. A plurality of
rollers 49 are located between the inner race and an outer race 48.
The inner race may be eliminated by heat treating and machining the
surface of the eccentric cam 44 to function as that race. Although
a cam bearing 46 with cylindrical rollers is depicted, a bearing
with other types rolling elements or a journal type bearing with or
without lubrication may be used.
[0027] A piston assembly 50 is slideably received within each of
the cylinder bores 36, thereby defining a chamber 37 within the
cylinder bore. Each piston assembly 50 comprises a piston 54 and a
piston rod 52. The piston rod 52 extends between the piston 54 and
the cam bearing 46. The piston rod 52 has a curved shoe 56 that
abuts the outer race 48 of the cam bearing 46 and which is wider
than the shaft of the piston rod creating a flange portion. A pair
of annular retaining rings 58 extend around the cam 44 engaging the
flange portion of each piston rod shoe 56, thereby holding the
piston rods 52 against the cam bearing 46, which is particularly
beneficial during the intake phase of a piston cycle. The curved
piston rod shoe 56 evenly distributes the piston load onto the
outer race 48 of the cam bearing 46 and also distributes local load
forces onto the rollers 49 of that bearing. As the drive shaft 40
and cam 44 rotate within the cylinder block 20, the outer race 48
of the cam bearing 46 rotates at a very slow rate as compared to
the rotational speed of the drive shaft. Therefore, there is little
relative motion between each piston rod shoe 56 and the cam
bearing's outer race 48.
[0028] The piston 54 is cup-shaped having an interior cavity that
opens toward the drive shaft 40. An end of the piston rod 52 is
received within that interior cavity and has a spherical head that
engages a mating partially spherical depression in the piston 54.
The piston rod 52 is held against the piston 54 by a bushing 57 and
a snap ring 59 that rests in an interior groove in the piston's
interior cavity (see FIG. 5). As the piston rod 52 follows the
eccentric motion of the cam 44 and the piston 54 in turn follows by
sliding within the cylinder bore 36, the bushing and snap ring
arrangement allows the spherical head of the piston rod to pivot
with respect to the piston 54 when a rotational moment is imposed
onto the piston rod 52 by rotation of the cam 44. Because of that
pivoting, the rotational moment is not transferred into the piston
54, thereby minimizing lateral forces between the piston and the
wall of the cylinder bore 36.
[0029] With particular reference to FIG. 3, the drive shaft 40
includes an internal lubrication passage 60 extending from one end
to the outer surface at the center of the eccentric apex of the cam
44 to feed lubricating fluid into the cam bearing 46. The
lubrication passage 60 at the end of the drive shaft opens into a
supply chamber 62 that receives lubricating fluid that is fed into
a lubrication port 64. As the drive shaft 40 rotates, centrifugal
force expels fluid from the lubrication passage 60 into the cam
bearing 46. This action draws additional fluid into the lubrication
passage 60 from the supply chamber 62, thereby providing a pumping
action for fluid that lubricates the cam bearing 46. The outer race
48 has apertures through which the fluid flows to lubricate the
piston rod shoes 56. If the cam bearing 46 has an inner race, that
inner race has apertures to convey the lubricating fluid to the
rollers 49.
[0030] Each cylinder bore 36 has an opening 39 through the curved
side surface 38 of the cylinder block 20. With specific reference
to FIG. 4, a separate raised annular rim 66 projects proud of the
side surface 38 around each cylinder bore opening As seen in FIGS.
2 and 3, a continuous closing band 68 is shrunk fitted to extend
circumferentially around the cylinder block 20 tightly abutting
each of the cylinder rims 66, thereby sealing every cylinder bore
opening To achieve that sealing, the annular surface of each rim 66
that contacts the closing band 68 is curved to conform to the inner
circumferential surface of the closing band. The continuous closing
band 68 eliminates the plugs previously inserted into the outer end
of each cylinder bore, which required longer bores in which to
receive those plugs. Thus using the closing band 68 reduces the
overall diameter of the cylinder block 20 and the size of the
hydraulic machine 14.
[0031] The closing band 68 compressively pre-stresses the cylinder
block 20, which has a greater material strength in compression than
in tension. The compressive force from the closing band 68 is
concentrated through each annular rim 66. Although bands had been
used previously around a cylindrical cylinder block, the curved
side surface of such cylinder blocks was smooth and did not have
the annular rims 66 extending proud of that side surface. As a
consequence, the compressive force from the prior band was evenly
distributed over a relatively large surface area of the cylinder
block. In contrast, the compressive force from the present closing
band 68 is concentrated at each annular rim 66. As a result, the
present closing band may apply a force of 76,000 psi (5,343
kgf/cm.sup.2) to the cylinder block, for example, which force is
more than ten times the force applied by previous bands. As a
result, previous bands tended to move away from the cylinder bore
opening as the cylinder chamber pressure increased during normal
operation. That movement allowed fluid from the cylinder chamber to
leak between the band and the cylinder block. In fact, it was
common practice to provide channels in the side surface of the
cylinder block to direct such leakage toward the drain port or the
low pressure outlet port of the previous hydraulic machine
[0032] As indicated in FIG. 5, the annular rim 66 and a portion of
the cylinder block 20 between the rim and the annularly curved
cavity 43 form a deformation region 70, that flexes or distorts
resiliently as pressure within the associated cylinder chamber 37
changes. The deformation region 70 is portion of the cylinder block
that extends in a cantilevered manner over the curved cavity 43
beneath the rim 66. With reference to FIG. 6, before the closing
band 68 is placed around the cylinder block 20, the circumference
of the cylinder bore 36 is circular, being equidistant along a
longitudinal axis L that is parallel to the axis 45 of the drive
shaft 40 and along a radial axis R in a radial plane through the
cylinder block. Upon being shrunk fitted around the cylinder block
20, the closing band applies a radially compressive force onto each
of the cylinder rims 66 which distorts the associated deformation
region 70 and the cross sectional shape of the respective cylinder
bore 36. Specifically, the deformation region 70 is pressed inward,
wherein the dimension of the cylinder bore circumference along the
radial axis R decreases, while the dimension along the longitudinal
axis L increases as denoted by the dotted line in FIG. 6. That
deformation results in the cylinder bore circumference having a
pronounced non-circular shape, such as a oval. It is engagement of
the closing band with the annular rim 66 around the opening of each
cylinder bore 36 which concentrates exertion of the compressive
forces into the deformation region 70 of the cylinder block 20. The
contracted first position of the deformation region 70 in this
unpressurized or low pressurized state of the associated cylinder
chamber 37 is depicted by solid lines in FIG. 5. The curved cavity
43 beneath the rim 66 limits the degree to which forces from the
closing band 68 deform the section of the cylinder bore 36 within
which the piston 54 slides.
[0033] Such low pressure conditions exists during the intake phase
of a given piston cycle. The intake phase begins after the piston
54 has passed top dead center, the outlet check valve 34 has closed
and the piston chamber pressure has decompressed as the piston
moves in the respective cylinder bore 36 toward the center axis 45
and the cylinder chamber 37 is expanding. Due to that expansion,
pressure within cylinder chamber 37 is less than pressure in the
inlet passage 31, which causes the inlet check valve 33 for that
cylinder bore to open. Thus fluid flows from the inlet passage 31
through the associated aperture 27 and first bore 24 into the
expanding cylinder chamber. That cylinder chamber pressure is less
than the pressure in the outlet passage 29, thereby holding the
associated outlet check valve 34 closed.
[0034] After the volume of the cylinder chamber 37 is filled, the
compression or exhaust phase of the piston cycle begins. In the
exhaust phase, the piston slides away from the center axis 45
decreasing the volume of the cylinder chamber 37 and causing
pressure within the cylinder chamber to increase. As that pressure
rises, the inlet check valve 33 closes preventing flow from the
cylinder chamber 37 outward through the respective first bore
24.
[0035] The higher pressure acting on the inside surface of the
closing band 68 pushes the band radially outward, thereby reducing
the compressive forces that the band exerts on the curved side
surface 38 of the cylinder block 20. In response, the deformation
region 70 around the respective cylinder bore 36 also expands
outward, i.e., the annular surface of the rim 66 moves radially
outward maintaining contact and a seal with the closing band 68,
ultimately reaching a second position shown by the dashed lines in
FIG. 5. Deflection of the deformation regions 70 follows motion of
the closing band 68 which tends to prevent leakage from the piston
chamber as the pressure increases. The amount of cylinder block
movement has been exaggerated in FIG. 5 for illustration purposes.
Stresses within the cylinder block 20 decrease due to the
distortion of the compression regions as the pressure within the
cylinder chambers 37 increase. By the closing band 68 pre-stressing
the cylinder block 20 in compression, the tensile stresses
resulting from increased pressure in the cylinder chamber 37 are
mitigated which enables higher pressure and power density operation
of the hydraulic machine Movement of the deformation region 70
changes the shape of the circumference of the cylinder bore 36
toward a circular shape, as depicted by the dashed line in FIG. 6.
In other words the difference between the dimensions of the
cylinder bore along the radial and longitudinal axis becomes
smaller. Thus, as a piston moves through the exhaust phase, the
cylinder bore becomes more circular mitigating power loss due to
fluid leakage past the piston and mitigating interference with the
sliding piston, thereby improving machine efficiency.
[0036] The increasing pressure within the cylinder chamber 37
eventually exceeds the pressure within the outlet passage 29 by an
amount that causes the outlet check valve 34 to open. At that time,
fluid flows from the cylinder chamber 37 through the outlet passage
29 to the outlet port 35 of the hydraulic machine 14. The inlet
check valve 33 remains closed until pressure in the cylinder
chamber 37 once again become less than pressure in the inlet
passage 31 during another intake phase of the piston cycle.
[0037] When the pressure within the cylinder chamber 37 decreases
during the subsequent intake phase, the deformation region 70
contracts back to the first position shown in FIG. 5 in response to
the compressive force from the closing band 68. Thus, the
deformation region 70 of the cylinder block 20 resiliently flexes
or distorts back and forth between the first and second positions
depicted in FIGS. 5 and 6 as pressure in the cylinder chamber 37
repeatedly increases and decreases during a series of piston
cycles.
[0038] The foregoing description was primarily directed to a
preferred embodiment of the invention. Although some attention was
given to various alternatives within the scope of the invention, it
is anticipated that one skilled in the art will likely realize
additional alternatives that are now apparent from disclosure of
embodiments of the invention. Accordingly, the scope of the
invention should be determined from the following claims and not
limited by the above disclosure.
* * * * *