Note: Descriptions are shown in the official language in which they were submitted.
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CLOSED CENTER HYDRAULIC DEVICE
Field of the Inventlon
This invention relates to hydraulic gerotor motor
devices.
Background of the Invention
Gerotor motor devices are a relatively low-cost way of
transferring large amounts of torque into remote locations.
Typical applications range from industrial robots, through
agricultural mowers, to airplane controls. However, major
limltations to increased applications of the motor devices
include their wear characteristics (i.e. service life span
including seal failure), longitudinal length (i.e. due to the
orbital to rotary transition), their physical complexity (i.e.
due to the numerous seals) and the difficulty of their repair.
Attempts to reduce the effects o these limitations have
produced such ideas as disposable motors, complex planetary
gearing arrangements or offset drives, encapsulated motors and
an "oversize the motor" design technique. These attempts have
not markedly increased the utilization of gerotor motors - the
increased cost/complexity of the devices do not meet with
significant acceptance in the industries involved.
This present invention is directed towards providing a
simple long lasting, short length, quickly exchanged gerotor
motor.
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Summary of the Invention
The present invention is dlrected to providing an
improved gerotor motor device.
It is an object of this inventlon to lncrease the
servlce life of gerotor devices.
It is an object of this invention to reduce the
longltudinal length of gerotor devlces.
It is an object of this invention to facilitate the
repair of gerotor devlces.
It ls an object of thls invention to simplify gerotor
devices.
Other ob~ects and a more complete understanding of the
invention may be had by referring to the following specification
and drawings in which:
Descr;.ption of_~he Drawings
FIGURE 1 is a cent.ral longitudlnal cross-sectional
view of a gerotor structure incorporating the invention,
FIGURES 2-5 are selected lateral cross-sectional vlews
of the manifold plate of the gerotor devlce of FIGURE 1,
FIGURES 6-7 are selected lateral cross-sectlonal views
of the valving section of the gerotor devlce of FIGURE 1, and
FIGURE 8 ls a central longitudlnal cross-sectional
view of a gerotor device incorporating the gerotor structure of
FIGURE 1.
Descriptlon of the Preferred Embodiment
Thls lnventlon relates to an improved gerotor devlce.
The lnventlon wlll be descrlbed ln the preferred envlronment of
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a gerotor motor/pump 10 a having a housing 11 containing a drive
shaft 12 connected to a gerotor structure 13 and rotary valve 14
via a wobblestick 15 (FIGURE 8)-. (The gerotor device 10 can
produce power when fluidically connected as a motor to a source
of high pressure or it can produce high pressure fluid when
physically connected as a pump to a motor (a source of rotary
power). The device is described as a motor.)
The drive shaft 12 is located in the housing 11 for
rotation in respect thereto. In a gerotor motor, such as that
disclosed in Mr. White's prior patent U.S. 3,606,601, the speed
and direction of rotation of this shaft 12 is governed by the
volume, pressure and direction of flow of the fluid through the
gerotor structure 13. In the emhodiment shown the fluid flow
through -the device is controlled by four valves 80, 81, 82 and
83. These valves 80-83 are selectively operated to connect a
port 30, 31 to a fluid pump 85 (source of pressurized fluid) and
to connect the other port 30, 31 to the sump 86 (discharge of
fluid) from which the pump 85 draws fluid. In the embodiment
shown an auxiliary port A can be also selectively connected via
valve 88 to the fluid pump 85 to lubricate and cool the bearings
of the device if needed. A filter 89 filters this lubrication `
loop fluid before discharge to the sump 86, thus effectively
isolating the lubrication function from the power function of
the device. A totally separate fluid loop could also be
utilized.
The shape of the housing 11 of this current motor/pump
10 is designed to match the intended application, even to the
extent of being integral thereto (a feature allowed by the
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isolation of fluid within the gerotor structure 13 as will be
later described).
The gerotor structure 13 is removably attached to the
housing 11, prefera~ly by ~lts (not shown). The gerotor
structure 13 itself includes an end plate 20, a manifold plate
21, a gerotor device 22 and a balancing plate 23 fixedly
attached together so as to produce a single integral unit (by
bolts 25). The gerotor device shown is a rotor 16 within a
stator 17 (FIGIJRE 1). Other pressure mechanisms could also be
used.
The end plate 20 is the termination cap and porting
plate for the device 10. Two ports 30, 31 are machined into the
plate 20 so as to form the fluid connections for the device.
One port 30 connects to a commutation rinq 32 in the opposing
face of the plate 20. This commutation ring 32 in turn
communicates with the central section 34 of the orbiting valve
14 to provide a fluid connection therefor. The other port 31
connects to a ring-shaped cavity 33 on the opposing side of the
plate 20. This cavity 33 surrounds the outside circumferential
edge 35 of the orbiting valve 14 to provide a second fluid
connection to the valve 14.
The orbiting valve 14 is the main valve for the device
10. The center opening 34 of the valve 14 communicates with one
port 30 via the ring 32. The external side about outer edge 35
of the valve 14 communicates with the other port 31. (Due to
the fact that there is a space 36 between the outermost position
37 of the orbiting valve 14, fluid is able to freely move about
the outside of the valve 14).
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The manifold plate 21 is on the opposing side of the
orbiting valve 14 from the end plate 20 between the valve 14 and
rotor 16. The manifold plate 21 serves to connect the center 34
and outer 35 sections of the orbiting valve 14 to the gerotor
cells between the rotor 16 and stator 17 selectively as the
device is operated. The manifold plate 21 itself is formed as a
brazed assembly of four thin stamped plates 40-43. The first
plate 40 (FIGURES 2 and 6) provides the valve openings 45 for
the device 10. The fourth plate 43 (FIGURE 5) provides the
outer gerotor cell openings 46 for the device 10. The second
and third plates 41, 42 (FIGURES 3, 4) contain anqularly shift
passages 48 to connect the valvin~ openings 45 and their
respective gerotor cell openings 46 while compensating for the
substantially 90 degree offset therebetween. To avoid having
the orbiting valve restrict or otherwise impede the commutation
of fluid from the port 30, a series of auxiliary flow paths 53,
54 in the plates 40, 41 are provided. The auxiliary flow
openings 53 in plate 40 are staggered from the recesses 54 in
plate 41 such that neighboring openings 53 communicate with each
other through the recesses 54. In the embodiment shown these
combine to form a supplementary flow path to the center opening~
34 of the valve 14. The openings 53 in plate 40 bridge the
radial arms of the valve 14 (as shown in FIGURE 6). This
effectively eliminates concern for the arms impeding fluid flow,
technically to the extent of allowing one to make the valve 14
of a uniform depth in the center portion 52, radial arms and
outermost portion 37 (i.e. eliminate the recessed portion of the
radial arms of the valve 14). This uniform depth construction
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would increase the surface area of the valve 14 against the
plate 40, strengthening the device against wear and pressure
imbalance effects.
In the prior art gerotor motors the woh~lestick
extends from the rotor to the valve through a plate having a
single uniform diameter. This allows the fluid to easily pass
through the plate and rotor to pressurize the central
wobblestick drive opening of the device, indeed the central
wobblestick drive opening is even actively used as an internal
conduit of pressurized fluid between a housing mounted port and
th orbiting valve in most devices. Due to the containment of
pressurized fluid within the central wobblestick drive opening
in these prior art designs, the entire device is integral from
the shaft 12 end plate 20 with numerous high pressure seals
throughout the device.
The integralness of the device requires that all the
rotary shaft, orbiting rotor and rotary to orbiting mechanical
connection be contained within the device. This adds to the
length of the device (the named parts all being of a certain
length and size) and the weigh~ of the device (the parts
individually having weight). The integralness of the device
also complicates the mount}ng of the device to associated
components (the device needing a certain volume of space) and
the repair of the device (the device needing to be totally
removed mechanically and fluidly from associated components
before repair). Other restrictions also follow the size of the
device.
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The seals are high pressure seals. These seals
include a rotating seal between the main drive shaft and housing
as well as a seal between the housing and gerotor structure.
These high pressure seals add to the complexity and cost of the
device in construction (high pressure seals are tight tolerance
seals with intricate seat requirements) and repair (high
pressure seals require care in handling). The seals also place
operational restrictions on the device (the seals requiring a
restricted range of operation). In addition to high pressure
seal requirements, the fluid in the central drive opening also
serves to contaminate the gerotor fluid with debris and heat
from the central wobblestick drive, further reducing the service
life of the device. The presence of this fluid also complicates
repair by necessitating the removal of pressure and drainage of
the fluid at the time of any work on the device. These
disadvantages and others limit the market for the prior art
devices.
In marked contrast to these prior art designs in the
current invention pressurized fluid is not introduced into the
central wobblestick drive opening unless desired (for example, a
separate bearing lubrication loop in FIGURE 8~. The pressurized
fluid is instead segregat~d ~o the area of the device near the
orbiting valve 14 ~y the sealing of the wobblestick drive
connection to the valve 14. In the preferred embodiment shown
this sealing is accomplished by restricting the effective size
of the drive opening 50 through the valving plate 40 of the
manifold plate 21 to an area less than that capable of being
sealed by the inside drive surface 52 of the valve 14. To
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accomplish this the radius of the drive surface 52 of the valJe
is slightly greater than the radius of the opening 50 plus the
offset of the center of the valve 14 from the center of the
valve manifold 21. With this relationship the inside drive
surface 52 of the valve 14 will seal the opening 50 throughout
the operational valving orbit of the valve 14. Central seals 38
improve the seal against fluid from passing into the wobblestick
drive connection at the center of the valve 14. Note that the
central seal 38A on the inside of the valve 14 against the
valving plate 40 is larger than the central seal 38B of the
valve 14 against the porting end plate 20. The reason for this
is that the seal 38A seals fluid from the wobblestick drive
connection access hole 50 in plate 40. The seal 38A must be of
a sufficient diameter to continually seal this hole 50 during
the entire orbiting motion of the valve 14. The seal 38A must
therefor have a radius greater than the radius of the hole 50
plus the amount of orbit offset. Since the hole 50 is of
significant diameter, the seal 38A must also have a significant
diameter. In contrast, the seal 38B seals the wobblestick drive
connection 51 to the valve 14. The seal 38B must be of a
diameter to continually seal this connection 51 while at the
same time fitting within the diameter of the commutation grove
32 in the end plate 20 (so as to not subject the seal to
inordinate wear). The seal 38B must therefor have a diameter
larger than the connecticn 51 and also a diameter smalier than
the radius of the groove 32. The size of the seal 38B is thus
normally different from the size of the seal 38A. Outer seals
39 prevent fluid from passing between the central section 34 and
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the space 36 about the outer edge 35 of the valve 14. (Mote
that any seal 39 on the outer ring of the valve 14 against the
manifold plate 21 would travel over the valve openings 45 for
the device, subjecting such seal to significant wear. Therefor
in the preferred embodiment shown the seal at this point is
limited to the flat steel of the outer ring of the valve 14;
this flat steel having no edges is not subject to the wear a
conventional seal would be).
Any fluid that does leak through the seals 38 into the
central wobblestick cavity is easily drained off: the fluid
would be of very low volume and would be unpressurized. The
device shown in FIGURE 1 has an internal drain connection for
this fluid. In this device a passage 61 connects the central
opening 56 to the housing ring-shaped channel 62 in the valve
spacing plate. The ring-shaped channel 62 is in turn connected
via check valves 63, 64 to the two ports 30, 31 respectively for
the device. These check valves 63, 64 operate to selectively
connect the ring channel 62 (and thus the central opening 56 of
the housing 11) to the port 30, 31 having the lowest relative
pressure. This provides an automatic internal drain for any
fluid in the central opening 56.
Due to the confinement of the high pressure to the
area near the valve 14, the invention of this application allows
one to treat the gerotor structure 13 as a self-contained unit.
The associated mechanical structure (like housing 11) need not
have high pressure seals or other fluid containment means. The
gerotor structure unit can be bolted onto a housing 11 or
otherwise integrated into mechanical structures with little
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regard for the existence of the high pressure fluid within the
gerotor structure 13. This fluid isolation allows the functions
of the drive shaft 12 and housing 11 to be incorporated into the
mechanical structures without the need for incorporating high
pressure seals in such mechanical structures, significantly
shortening the effective longitudinal length of the device. The
fluid isolation also allows one to remove the gerotor structure
13 from its associated mechanical structure without regard for
the fluid in the gerotor structure. Both the gerotor and
mechanical structure can thus be easily interconnected,
separated and repaired without regard for the other. Other
advantages also flow from th~ isolation of fluid within the
gerotor structure 13.
The plate 23 is a thin plate trapped between the
housing 11 and gerotor 22. The plate 23 generally seals the
gerotor structure 13 against fluid leakage. If desired a small
pocket can be incorporated behind it in the housing 11 which
pocket is connected to a high pressure feed. This could be
accomplished for example by including holes running axially
through the rotor terminating at each face of the rotor. Other
holes in the manifold plate 21 and plate 23 would be located
within the confines of the area continually swept by the holes
in the rotor. The holes in the rotor would sweep the holes in
the manifold plate that are pressurized by high pressure, with
the hole in the rotor in turn sweeping the holes in the plate 22
to pressurize the pocket in the housing 11. The pressure of
fluid in the pocket in the housing would in turn force the plate
22 back towards the rotor pressure balancing same. If the
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device is designed for bi-directional rotation, small chec~
valves could be utilized to insure the appropriate high pressure
only connection. The size of the pocket in the housing 11 would
be designed to match the rotor's axial imbalance for the
incoming high pressure. The balancing plate is described in
detail in the U. S. Patent Application 798,301 filed Novemher
15, 1985 by Mr. ~hite.
The wobblestick 15 connects the drive shaft 12 to both
the rotor 16 and valve 14, translating rotary and orbital
forces. Normally the wobblestick is merely contained within the
central cavity of the device with any specific location due more
to chance than design. This produces wear in the device, both
at the ends of the wobblestick 15 and in the drive connections.
In contrast in the preferred embodiment of the present invention
a small flange 70 extending radially of the valve end of the
wobblestick 15 cooperates with two reduced diameter plates 40,
43 of the manifold plate 21 to exactly locate the wobblestick
15. In the embodiment shown the flange 70 is designed with a
slight taper equal to the angle ~f the wobblestick 15 to the
central axis of the device with the thickness of the flange 70
such that both plates 40, 43 are contacted when the wobblestick`
15 is located in its operational position. With this
orientation the wobblestick 15 is confined against any axial
movement, precisely located in its proper axial position when
the device at rest and when operational. This reduces the wear
on the device. Note that in the embodiment shown the diameter
of the flange 70 is greater than the diameter of the wobblestick
access hole 71 in plate 43. This relationship insures that the
127S~3S~
wobblestick will not separate from the gerotor structure 13.
The relationship, however, is not strictly needed; the
wobblestick 15 would be located adequatel~ if the flange 70
contacted even a single arc of the plates 40, 43 - and given the
angular offset of the wobblestick this could occur with a hole
even larger than the flange 70 (as long as the difference in
radii was less than the distance of offset of the wobblestick at
the contact plane between flange 70 and plate).
In its orbiting motion the valve 14 connects the port
30 through the central opening 34 to some gerotor cells of the
gerotor device 22 while connecting the port 31 through the
surrounding edge 35 to others of gerotor cells of the gerotor
device 22 through the manifold plate 21 as is customary for
separate orbiting valve devices. In a major point of departure,
however, fluid is generally isolated totally within the gerotor
structure 13; neither the central opening 55 of the rotor 16 nor
the central opening 56 of the housing 11 are connected to any
source of fluid; the fluid of one port 30 is sealed from these
openings by means of the seal 38 and the fluid of the other port
31 is sealed from these openings by means of the seals 38 and
39. Any residue fluid that does manage to get into the opening`s
or otherwise into this section of the device is easily drained
off via a small passage 60 leading off of the openings to an
external sump (as 86).
Due to the fluid isolation, the gerotor structure 13
forms a separate, totally integral device. This device can be
attached and separated at any time without any concern for the
condition of the fluid pressure fed to the ports 30, 31. The
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device can also be utilized with housings 11 not designed or
otherwise supplied with high pressure seals. This isolation
allows one to utilize gerotor structures in a greater variet~ of
devices. Therefor, although the invention has been described in
its preferred form with a certain degree of particularity, it is
to be understood that numerous changes and deviations may be
made without departing from the invention as hereinafter
claimed.
