Note: Descriptions are shown in the official language in which they were submitted.
12999~7
The invention relates to an improved radial
piston hydraulic motor, more especially the invention
is concerned with a radial piston hydraulic motor of
high versatility and performance especially suitable
for applications requiring uniform torque, constant
or variable speed, and high starting torque, which
includes an in-board computer.
Radial piston hydraulic motors include a
plurality of piston-cylinder assemblies mounted
radially about a rotatable shaft. The pistons engage
a cam keyed to a shaft, and sequentially act on the
cam to drive the shaft. A mechanical valve system for
control of the flow of hydraulic fluid to the piston-
cylinder assemblies is mounted in a stationary manifold
about the shaft. Free wheeling of the shaft is pos-
sible by means of a clutch assembly in the shaft.
The piston-cylinder assemblies are control-
led collectively by the mechanical valve system so
that all of the piston-cylinder assemblies are used to
drive the shaft and it is not possible to disengage
individual piston-cylinder assemblies to reduce power
input.
, .
.,
" ~
~z9~9~7
- 2
Existing radial piston hydraulic motors have
limited possibilities for variation of parameters
controlling operation of the motor or recognizing
mechanical faults at an early stage.
This invention seeks to provide a radial
~` piston hydraulic motor which can adapt a free-wheeling
configuration without the use of a clutch assembly.
The invention also seeks to provide a
radial piston hydraulic motor in which individual
piston-cylinder assemblies can be readily brought
into and out of operation.
Still further the invention seeks
to provide a radial piston hydraulic motor
which has an in-board computer and is susceptible to
increased control, and in which various parameters can
be monitored continuously to optimize the control.
In accordance with the invention a radial
piston hydraulic motor has position code means on the
output shaft for rotation therewith. A cam on the
~, 20 shaft is drivingly rotated by a plurality of fluid
actuated piston-cylinder assemblies disposed radially
;; about the shaft. An electronic sensing device senses
the position code means during rotation of the shaft
and provides a signal responsive thereto. A control
~`
" ' , ' ` `
,
.
129991~
- 3 -
device receives the signal and provides a control
signal to control valves associated with the piston-
cylinder assemblies.
The position code means extends circum-
ferentially about the shaft and comprises a code in
the form of a plurality of markings. The markings
are in predetermined locations about the shaft and
- provide information as to the location of the lobe of
the cam relative to the individual piston-cylinder
assemblies.
The position code means may be in the form
of an annular disc-shaped member extending radially
outwardly of the shaft, the code being formed on the
disc face. The code will typically be in the form
of a plurality of markings on the disc face spaced,
radially of and circumferentially about the shaft.
Markings associated with the position of the cam lobe
relative to different piston-cylinder assemblies are
located at different radial distances from the shaft.
In this way the disc face is divided into a plurality
~ of ring-like or annular zones extending circum-
; ferentially about the shaft and spaced at different
radial distances from the shaft. Each zone is
associated with a particular piston-cylinder assembly
and markings are located in predetermined positions
' ''''
:
. .
lZ9~917
,~
J 4 -
along the zone which provide information as to the
position of the cam relative to the particular
piston-cylinder assembly.
The position code means may also be in the
form of an annular band mounted circumferentially
about the shaft, the code or markings being in pre-
determined positions on a cylindrical surface of said
band and thus extending axially, or parallel to the
shaft axis, rather than radially of the shaft.
The position code means may also be in the
form of a code or markings applied directly, for
example, by printing, to the surface of the shaft,
and extending circumferentially about the shaft
surface.
The hydraulic motor may also include pres-
sure and temperature sensors which are sensed by the
electronic sensing device. The information sensed
in this way may also be used to control the motor,
by means of the control device which can be arranged
to control different components of the motor. For
example, the control device may be used to control
a hydraulic pump which pumps hydraulic fluid to the
motor to drive the pistons.
The information sensed by the electronic
` sensing device may be fed to a computer and different
parameters, for example, shaft horse power, tcrque
, ' , ' .
: , .
129g917
and speed Or rotation can be calculated and compared
with pre-programmed data, and an output signal to
the control device may then be established to alter
the parameters as desired or based on the pre-pro-
grammed data.
The invention is illustrated in particular
and preferred embodiments by reference to the
accompanying drawings in which:
FIG. 1 is a partial front elevation in
10cross-section showing a radial piston
hydraulic motor of the invention,
FIG. 2 shows a detail in side elevation of a
piston-cylinder assembly of the motor
of FIG. 1,
- FIG. 3 is a side elevation in partial cross-
: section of the motor of FIG. 1, and
-. FIG. 4 is a circuit diagram of the
hydraulic fluid and electronic
circuits of a motor of the invention.
;~ 20With further reference to FIGS. 1, 2 and 3,
a hydraulic motor 10 includes a main body 12 and a
;. shaft 14 journalled for rotation therein.
1299917
.
A drive cam 16 is fixedly mounted on shaft
14 and a plurality of piston-cylinder assemblies 18
is disposed radially about shaft 14, to engage drive
cam 16.
A coded or marked disc 20 is mounted for
rotation with shaft 14 and an electronic sensor 22
surrounds shaft 14 in spaced apart relationship with
disc 20.
The piston-cylinder assemblies 18 each
include a piston 24 mounted for reciprocating move-
ment in a cylinder 26.
A valve manifold 28 housing a solenoid valve
30 is mounted on the outer casing of each piston-
cylinder assembly 18.
An inner end of each piston 24 has a shoe
32 and a ball 34.
A central fluid passage 36 passes longitudi-
nally of each piston 24 and includes a check valve 38.
Shoe 32 includes a socket 40 which receives
_ .
the ball 34, and a cavity 44 which is in opposed
~: relationship with cam 16. A passage 42 through shoe
32 communicates passage 36 with cavity 44.
An annular fluid line 46 provides passage
for flow of hydraulic fluid to the piston-cylinder
assemblies 18 through their respective valve manifolds
28, and a fluid line 48 provides for flow of hydraulic
.~ .
lZgg917
_ 7
fluid out of the piston-cylinder assemblies 18
through their respective valve manifolds 28.
A chamber 43 is disposed below cylinder 26
about shoe 32 and communicates with an outlet passage
45 having a check valve 47.
A chamber 49 is disposed in an upper end of
cylinder 26 above piston 24 when piston 24 is in the
upstroke position shown in Fig. 2, and in this position
a spacing 51 is defined between shoe 32 and the lower
end of cylinder 26.
~ '
`
~299917
Electronic sensor 22 includes a reader panel
50 mounted in spaced apart relationship with disc 20
and a controller 52.
A pressure sensor 54 is disposed in fluid
line 46 and is electronically connected to controller
52.
Disc 20 includes a disc face 19 having a
plurality of discrete annular zones 21. Each zone 21
is associated with one of the piston-cylinder
assemblies 18 and has markings 23 in predetermined
; locations within the zones 21. The positions of the
markings 23 in a particular zone 21 are characteristic
of the location of cam 16 relative to the piston-
cylinder assembly 18 associated with such zone 21.
: With further reference to FIG. 4, there is
shown a systems circuit including an electronic
circuit 56 and a hydraulic fluid circuit 58.
Electronic circuit 56 includes controller
52 which includes an internal dynamometer 60 and an
internal tachometer 62. An in-board computer 64 is
connected to controller 52.
-'
' .
. , .
~'; , .
~ ;zg99~7
, g
Shaft 14 is shown symbolically as is the
motor 10.
The hydraulic circuit 58 includes fluid
lines 46 and 48 shown communicating with the valve
manifolds 28 and control valves 30. Circuit 58
further includes a hydraulic pump 66, a motor 68 to
drive pump 66 and a hydraulic fluid reservoir 70.
Electronic circuit 56 includes a connection
: 72 between internal tachometer 62 and the valve mani-
folds 28, housing the control valves 30, and a con-
nection 74 between internal dynamometer 60 and
hydraulic pump 66.
In operation of the hydraulic motor 10, high
pressure hydraulic fluid, for example, oil at a pres-
sure up to 6000 p.s.i. enters fluid line 46 and
branches off to each piston-cylinder assembly 18.
Passage of the hydraulic fluid from line 46
into the respective cylinders 26 to drive the pistons
24 is precisely timed and controlled by solenoid
valve 30 of each assembly 18. The hydraulic fluid
exerts a force on each piston 24 at a particular
instant in time.
At a particular point in time a piston 24
drives shoe 32 in engagement with the lobe of cam 16,
to rotatingly drive shaft 14.
` .
. ~ .
''~
-`` 1;~999~7
-- 10 --
The shoe 32 is hydrostatically balanced
against the cam 16, the hydraulic force transmitted
through the shoe 32 resulting in a normal force, i.e.,
vectored piston force, on the periphery of cam 16.
The remaining piston-cylinder assemblies 18
at this point experience varying volume displacements
depending on the position of each piston 24 relative
to the shaft 14 at that point in time.
As the pistons 24 are pushed up or retracted,
the volume of hydraulic fluid displaced flows into
low pressure fluid line 48 and back to the oil
reservoir 70 in circuit 58 (FIG. 4).
In operation hydraulic fluid is pumped down-
wardly through central fluid passage 36 via check
valve 38 and thence through passage 42 and into
cavity 44, where the pressure is reduced along a
pressure gradient. The hydraulic fluid bleeds from
cavity 44 to the interface of shoe 32 and cam 16 to
provide a film of fluid which creates an upward
, .
20 hydraulic force which is about 90% of the main down-
ward force, so that a small part of the load is
carried by the shoe 32. The result is the creation
of a hydrostatic floating of the shoe 32 on the cam
16.
Hydraulic fluid also bleeds into the inter-
face between socket 40 and ball 34.
;'````~
. . .
1299917
-
-- 11
The presence of the hydraulic fluid at the
interface of the shoe 32 and the cam 16, and the
interface of socket 40 and ball 34, results in hydro-
dynamic lubrication, greatly reducing rotational
friction, oil viscosity dilution due to temperature
rise and unnecessary shoe wear. Thus the motor 10
experiences practically no metal to metal contact
between pistons 24, and shoes 32 and the cam 16.
The drive cam 16 and hence the shaft 14 is
thus rotated by the successive action of the piston-
cylinder assemblies 18.
Hydraulic fluid is maintained under pressure
in chamber 43. Check valves 38 and 47 serve to
maintain the pressurized fluid in chamber 43 during
operation. The pressure in chamber 43 is typically
of the order of 200 p.s.i.
With the rotation of shaft 14, disc 20 also
rotates and its relative position can be monitored by
the reader panel 50 and controller 52. In particular
the top dead centre of cam 16 relative to any piston-
cylinder assembly 18 is readily obtained by monitor-
ing disc 20. In response to this information the
controller 52 can control the valves 30 to disengage
particular piston-cylinder assemblies 18, or all of
~; the piston-cylinder assemblies 18 from cam 16.
12999~7
- 12 -
~ hus with all of the valves 30 open, the
piston-cylinder assemblies 18 can be lifted off cam
16 so that the motor 10 is in a "free-wheel" mode.
When the valves 30 are opened the piston-
cylinder assemblies 18 are lifted from cam 16 by the
pressurized fluid in chamber 43. The piston 24 being
lifted or raised so that its upper end is accommod~ted
in chamber 49 and shoe 32 extends into spacing 51 and
is thereby spaced from cam 16.
By means of the in-board computer 64, the
position of the lobe of the cam 16, specifically the
top dead centre can be determined at any point in time
relative to the piston-cylinder assemblies 18, so
that the point in time at which control valves 30
can be opened for a smooth lifting of the piston-
cylinder assemblies 18, from cam 16 can be readily
determined.
Additionally a "variable displacement" mode
can be effected by appropriate control of valves 30
by controller 52 in response to the information in
the in-board computer 64 received from disc 20, to
meet reduced torque requirements.
The motor 10 thus has increased flexibility
and can be stalled, reversed and even locked up to
maintain a static.load without any external braking
:.
ll system.
"`)
~''
. .
: .
~ Z999~7
- 13 -
In adopting the "free wheel" mode, the load
on cam 16 and thus shaft 14 is thus effectively dis-
; engaged without the use of a clutch mechanism.
Motor 10 exhibits torque values of consistencyand smoothness with a variable speed range, even at
low r.p.m., thereby eliminating the need for costly
gear reduction. It provides a wide range Or motor
capacities, so that higher speeds can be obtained
without necessarily increasing the flow rate of
hydraulic fluid.
By means of the electronic sensor 22 and
in-board computer 64 it is possible to disable or
remove or introduce selected piston-cylinder
assemblies 18 to suit particular speed requirements.
By means of the electronic sensor 22 various
computer-related instructions can be implemented from
a remote station fed solely by electronic control
lines, and without hydraulic control lines.
Additional sensors can be introduced to
sense different parameters of the motor 10. The
: pressure sensor 54 senses the pressure in the fluid
line 46 through which the hydraulic fluid is intro-
duced into the piston-cylinder assemblies 18. This
pressure is monitored by the electronic sensor 22 and
the information is maintained in computer 64 and used
~; in conjunction with sensed information to calculate
: '
.
-- lZ999~7
- 14 _
and provide a continuous reading of other operating
parameters. Appropriate signals can be directed to
alter the pressure as required to change the operating
parameters.
A pressure sensor can also be disposed in
the fluid line 48 and temperature sensors can be
introduced whereby any significant fluctuations in
temperature indicative of problems such as metal to
metal contact, can be recognized in advance and
appropriate precautions taken.
The coded disc 20 and in-board computer 64
can be employed to provide information based on
which various operating parameters of motor 10 can
be modified including speed, torque and power.
The motor 10 will typically include an odd
number of piston-cylinder assemblies 18, for example,
7 or 9, so as to avoid hydraulic locking.
The hydraulic motor 10 can be employed in
a variety of applications including excavators,
concrete mixers, winch drives, dredge cutters,
plastic extrusion machinery, mining, timberland tree
; farming machinery, material handling, offshore
drilling rigs, amusement rides, conveyor drives,
carbage compactors, sugar cane harvesters, log
debarkers, asphalt pavers, snowblowers, lathe drives,
lZ999~7
,,-
steel forming, core drilling/tunnel boring, trans-
mission line tensioners, robotlcs and other appli-
cations where uniform torque, constant or variable
- speed and high starting torque are required.
.
