TITLE OF INVENTION
[0001] Rotary Fluid Pressure Device With Modular Multi-Speed Control
Mechanism.
BACKGROUND OF THE DISCLOSURE
[0002] The present invention relates to rotary fluid pressure devices, and
more particularly, to such devices that are provided with a single-speed option
and a multi-speed option.
[0003] Although the present invention can be used in connection with various
pump and motor configurations that include various types of fluid displacement
mechanism, such as a cam lobe type, it is especially advantageous when used
with fluid motors having fluid displacement mechanisms of the gerotor type and
will be discussed in connection therewith. While the present invention may also
be used in connection with fluid motors having various types of valve
arrangements, it is especially advantageous when used in connection with fluid
motors of the disc valve type. Therefore, the present invention will be discussed
in connection with disc valve gerotor motors without intending to limit the scope
of the invention.
[0004] Fluid motors of the type utilizing a gerotor displacement mechanism to
convert fluid pressure into a rotary output are widely used in a variety of low-
speed, high-torque commercial applications, such as skid-steer loaders. One
common use for fluid motors in low-speed, high torque commercial applications
is vehicle propulsion, wherein the vehicle includes an engine driven pump which
provides pressurized fluid to a pair of fluid motors, with each motor being
associated with one of the drive wheels.
[0005] For many years, vehicle manufacturers have provided vehicles with
the option of fluid motors capable of operation in a low-speed, high-torque mode
only (single-speed motors) or with fluid motors capable of operation in both low-
speed, high-torque mode and high-speed, low-torque mode (two-speed motors).

While choosing between a vehicle with either single-speed propulsion motors or
two-speed propulsion motors for vehicle applications enables the vehicle
manufacturer's customers to choose the best vehicle for their particular needs,
this propulsion motor option creates some difficulties for the vehicle
manufacturers. One such difficulty is that the manufacturer is required to
maintain two part numbers for motors used on the same vehicle model. In other
words, the manufacturer must maintain part numbers for a single-speed version
of a propulsion motor, as well as a two-speed version of the propulsion motor in
order to accommodate the option choice of the customer. While the single-
speed motor and the two-speed motor are not identical given that one is capable
of only single-speed functionality and the other is capable of two-speed
functionality, the motor mounting, displacement, valve type, output shaft, and
porting type are typically the same.
[0006] Another difficulty that vehicle manufacturers have in providing this
option to customers is that this option requires manufacturers to have accurate
build orders early in the assembly process. Typically, fluid motors are
assembled onto the vehicle frame very early in the assembly process. Many
times, the fluid motors are installed on the vehicle frame before the build orders
have been placed. Therefore, if the assemblers are building single-speed
versions of a vehicle and incoming build orders, which were submitted after
assembly had started, require two-speed versions of the vehicle, the single-
speed fluid motors must be removed from the partially assembled vehicle and
replaced with two-speed fluid motors. This becomes difficult because after the
fluid motors and other vehicle components have been assembled to the frame,
access to the mounting surfaces of the fluid motors is limited.
[0007] In addition to these difficulties, some vehicle manufacturers receive
requests from customers to "upgrade" their current vehicle, which is configured
for single-speed functionality, to a vehicle with two-speed functionality. While
vehicle manufacturers have done this successfully in the past, the removal and

replacement of the single-speed fluid motors with two-speed fluid motors is a
labor intensive task.
BRIEF SUMMARY OF THE INVENTION
[0008] Accordingly, it is an object of the present invention to provide a rotary
fluid pressure device that overcomes the above discussed disadvantages of the
prior art.
[0009] It is another object of the present invention to provide a method for
conversion of a rotary fluid pressure device that overcomes the above discussed
disadvantages of the prior art.
[0010] In order to accomplish the above mentioned objects, the present
invention provides a rotary fluid pressure device comprising a housing means
defining a fluid inlet and a fluid outlet, a fluid energy-translating displacement
means including a first member and a second member, which is operably
associated with the first member. The first member and the second member of
the fluid energy-translating displacement means have relative movement and
interengage to define a plurality N of expanding and contracting fluid volume
chambers in response to that relative movement. The rotary fluid pressure
device also includes a valve means that cooperates with the housing means to
provide fluid communication between the fluid inlet and the expanding volume
chambers, and between the fluid outlet and the contracting volume chambers.
The valve means comprises a stationary valve member fixed to be non-rotatable
relative to the housing means, and a moveable valve member, operable to move
relative to the stationary valve member. A selector plate member defines a
plurality N of upstream fluid passages in commutating fluid communication with
the valve means and a plurality N of downstream fluid passages, with each of the
downstream fluid passages being in open fluid communication with one of the
plurality of volume chambers. A plurality of upstream fluid passages being in
direct, relatively unrestricted, continuous fluid communication with a plurality of
downstream fluid passages.

[0011] The rotary fluid pressure device is characterized by a selector plate
assembly including the selector plate member and an assembly selected from
the group consisting of a cover plate assembly and a control valve assembly.
The selector plate member includes a plurality M of upstream passages, which
are in open fluid communication with a plurality M of upstream fluid passages,
and have an opening in an exterior surface of the selector plate member. The
selector plate member also includes a plurality M of downstream passages which
are in fluid communication with a plurality M of downstream fluid passages, and
have an opening in the exterior surface of the selector plate member. The cover
plate assembly defines a surface that is in sealing engagement with the exterior
surface of the selector plate member with the cover plate assembly providing
unrestricted fluid communication between the upstream passages and the
downstream passages in the selector plate member. The control valve assembly
defines a surface that is in sealing engagement with the exterior surface of the
selector plate member with the control valve assembly being operable in a first
position to provide relatively unrestricted flow between the upstream passages
and the downstream passages in the selector plate member, and operable in a
second position to block fluid communication between the upstream passages
and the downstream passages in the selector plate member.
[0012] In order to further accomplish the objects mentioned above, the
present invention also provides a method for converting a single-speed rotary
fluid pressure device to a multi-speed fluid pressure device wherein the rotary
fluid pressure device is of the type comprising a housing means, which defines a
fluid inlet and a fluid outlet, and a fluid displacement means, which includes a
first member and a second member, with the second member being operably
associated with the first member. The first member and second member have
relative movement and interengage to define a plurality of expanding and
contracting fluid volume chambers in response to said relative movement. The
rotary fluid pressure device also includes a valve means, which cooperates with
the housing means to provide fluid communication between the fluid inlet and the

expanding volume chambers, and a selector plate assembly which includes a
selector plate member.
[0013] The method for converting a single-speed rotary fluid pressure device
to a multi-speed fluid pressure device is characterized by removing at least one
cover plate assembly from at least one exterior surface of the selector plate
member, with the exterior surface defining a plurality of openings in fluid
communication with a plurality of upstream passages in the selector plate
member and a plurality of openings in fluid communication with a plurality of
downstream passages in the selector plate member, providing at least one
control valve assembly comprising a surface, and mounting the surface of the
control valve assembly to the exterior surface of the selector plate member, with
the control valve being operable in a first position to provide relatively
unrestricted fluid communication between the upstream passages and the
downstream passages in the selector plate member, and operable in a second
position to block fluid communication between the upstream passages and the
downstream passages in the selector plate member.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is an axial cross-sectional view of a single-speed rotary fluid
pressure device.
[0015] FIG. 2 is a transverse, plain view of the fluid displacement mechanism,
taken on line 2-2 of FIG. 1.
[0016] FIG. 3 is a transverse, plain view of the selector plate taken on line 3-3
of FIG. 1.
[0017] FIG. 4 is a transverse, plain view of the selector plate taken on line 4-4
of FIG. 1.
[0018] FIG. 5 is a transverse, cross-sectional view of the selector plate taken
on line 5-5 of FIG. 1 with the manifold passages from FIG. 3 superimposed onto
the view and shown as dashed lines.

[0019] FIG. 6 is a transverse, cross-sectional view of the selector plate taken
on line 6-6 of FIG. 1.
[0020] FIG. 7 is transverse, plain view of the manifold surface of the selector
plate taken on line 7-7 of FIG. 1.
[0021] FIG. 8 is an orthogonal view of the cover plate showing primarily the
mounting surface of the cover plate.
[0022] FIG. 9 is an axial cross-sectional view of a two-speed rotary fluid
pressure device.
[0023] FIG. 10 is an axial cross-sectional view of the control valve assembly
taken on line 10-10 of FIG. 9 showing the control valve spool in the lo-speed
mode position.
[0024] FIG. 11 is an axial cross-sectional view of the control valve assembly
similar to FIG. 10, except that the control valve spool is shown in the hi-speed
mode position.
[0025] FIG. 12 is a transverse, cross-sectional view of an alternative
embodiment of the selector plate, similar to FIG. 5, taken on line 12-12 of FIG. 1.
[0026] FIG. 13 is a transverse, plain view of the manifold surface of the
alternative embodiment of the selector plate, similar to FIG. 7, taken on line 13-
13 of FIG. 1.
[0027] FIG. 14 is an orthogonal view of an alternative embodiment of the
cover plate showing primarily the mounting surface of the cover plate.
[0028] FIG. 15 is an axial cross-sectional view of an alternative embodiment
of the control spool assembly similar to FIG. 10, showing the control valve spool
in the lo-speed mode position.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0029] Referring now to the drawings, which are not intended to limit the
invention, FIG. 1 is an axial cross-section of a bi-directional disc-valve motor
made in accordance with the present invention. The disc-valve motor, generally
designated 11, includes a mounting plate 13, a gerotor displacement

mechanism, generally designated 15, a selector plate assembly, generally
designated 17, and a valve housing 19. The sections are held together in tight
sealing engagement by means of a plurality of bolts 21, which are in threaded
engagement with the mounting plate 13.
[0030] Referring now to FIGS. 1 and 2, the gerotor displacement mechanism
15 is well known in the art and will therefore be described only briefly herein.
More specifically, in the subject embodiment, the gerotor displacement
mechanism 15 is a Geroler ® displacement mechanism comprising an internally
toothed ring assembly 23. The internally toothed ring assembly 23 comprises a
stationary ring member 25 which defines a plurality of generally semi-cylindrical
openings 27. Rotatably disposed within each of the semi-cylindrical openings 27
is a cylindrical member 29, as is now well known in the art. Eccentrically
disposed within the internally toothed ring assembly 23 is an externally toothed
rotor member 31, hereinafter referred to as the "star" member, typically having
one less external tooth than the number of cylindrical members 29, thus
permitting the star member 31 to orbit and rotate relative to the internally toothed
ring assembly 23. The relative orbital and rotational movement between the
internally toothed ring assembly 23 and the star member 31 defines a plurality of
expanding and contracting volume chambers 33. The star member 31 defines a
set of internal splines 35 formed at the inside diameter of the star member 31.
The internal splines 35 of the star member 31 are in engagement with a set of
external, crowned splines 37 on a main drive shaft 39. Disposed at the opposite
end of the main drive shaft 39 is another set of external, crowned splines 41, for
engagement with a set of internal splines (not shown) in a customer-supplied
output device, such as a shaft (not shown).
[0031] Also in engagement with the internal splines 35 of the star member 31
is a set of external splines 43 formed about one end of a valve drive shaft 45
which has, at its opposite end, another set of external splines 47 in engagement
with a set of internal splines 49 formed about the inner periphery of a rotatable

valve member 51. The valve member 51 is rotatably disposed within the valve
housing 19, and the valve drive shaft 45 is splined to both the star member 31
and the rotatable valve member 51 in order to maintain proper valve timing, as is
generally well known in the art.
[0032] Referring again to FIG. 1, the valve housing 19 defines a first fluid port
53 which is in open fluid communication with a first fluid passage 55. The first
fluid passage 55 is in open fluid communications with an annular fluid chamber
57. The valve housing 19 further defines a second fluid port (not shown) which
is in open fluid communication with a second fluid passage (not shown). The
second fluid passage is in open fluid communication with an annular cavity 59,
which is cooperatively defined by an inner annular surface of the valve housing
19 and the rotatable valve member 51.
[0033] The rotatable valve member 51 defines a plurality of alternating valve
passages 61 and 63. The valve passages 61 are in continuous fluid
communication with the annular fluid chamber 57 in the valve housing 19, while
the valve passages 63 are in continuous fluid communication with the annular
cavity 59. In the subject embodiment, and by way of example only, there are
eight of the valve passages 61, and eight of the valve passages 63,
corresponding to the eight external teeth or lobes on the star member 31.
[0034] Referring still to FIG. 1, a valve-seating mechanism, generally
designated 65, is in sliding and sealing engagement with the rotatable valve
member 51. The purpose of the valve-seating mechanism 65 is to maintain
sealing engagement between a valve confronting surface 67 defined by the
rotatable valve member 51 and a transverse valve surface 69 defined by the
selector plate assembly 17. The valve-seating mechanism 65 illustrated in FIG.
1 has been described in detail in U.S. Pat. App. No. 11/453,490 entitled "Bi-
Directional Disc-Valve Motor and Improved Valve-Seating Mechanism Therefor,"
filed on Jun. 15, 2006, assigned to the assignee of the present invention and
incorporated herein by reference. Therefore, further description of the valve-
seating mechanism 65 will not be provided herein. It should be understood by

those skilled in the art, however, that although the subject embodiment is
described and shown with the improved valve-seating mechanism 65 disclosed
in U.S. Pat. App. No. 11/453,490, the present invention is not limited to rotary
fluid pressure devices utilizing such valve-seating mechanisms.
[0035] Referring now to FIGS. 1 and 3, the selector plate assembly 17
includes a selector plate 71 that defines a central opening 73, which extends
axially through the selector plate 71. The selector plate 71 further defines
several surfaces including the transverse valve surface 69, a transverse gerotor
surface 75 (shown in FIGS. 1 and 4), and a manifold surface 77. The transverse
valve surface 69 of the selector plate 71 defines a plurality of fluid passages,
generally designated 79 (referred to in the appended claims as "upstream fluid
passages"), which are in commutating fluid communication with the valve
passages 61 and 63 in the rotatable valve member 51. The fluid passages 79
include a plurality of manifold passages 79m and a plurality of thru passages
79t. In the subject embodiment, and by way of example only, there are nine fluid
passages 79, three of which are manifold passages 79m and six of which are
thru passages 79t. The manifold passages 79m and the thru passages 79t will
be described in greater detail subsequently. The transverse valve surface 69
further defines a plurality of fluid slots 81 which are alternately positioned on the
transverse valve surface 69 with the fluid passages 79. As is well known to
those skilled in the art, the fluid slots 81 are blind slots and function to maintain
even contact between the transverse valve surface 69 and the valve confronting
surface 67 of the rotatable valve member 51. While the fluid passages 79 and
the fluid slots 81 have been shown in the subject embodiment as an integral
feature of the selector plate 71, it will be understood by those skilled in the art
that the present invention is not limited to such integration of the fluid passages
79 and the fluid slots 81 with the selector plate 71. The present invention would
also include an embodiment in which a separate plate, which is in fluid
communication with the selector plate 71, defines the fluid passages 79 and the
fluid slots 81.

[0036] The transverse valve surface 69 further defines a case drain passage
83 and a pressurized fluid passage 85. The case drain passage 83 extends
axially through the selector plate 71 and is in fluid communication with a case
drain port 87 (shown only in FIG. 1) in the valve housing 19. The pressurized
fluid passage 85 in the selector plate 71 is in open fluid communication with a
fluid passage (not shown) in the valve housing 19. The fluid passage (not
shown) in the valve housing 19 is in fluid communication with a shuttle valve
arrangement (not shown) that allows fluid communication between the fluid
passage (not shown) and either the first fluid port 53 or second fluid port (not
shown), depending on which of those fluid ports in the valve housing 19 is
supplied with high pressure fluid. Therefore, during operation, pressurized fluid
from either the first fluid port 53 or the second fluid port (not shown) in the valve
housing 19 is supplied to the pressurized fluid passage 85 in the selector plate
71. Since shuttle valve assemblies that function as previously described are well
known to those skilled in the art, such an assembly will not been described
herein.
[0037] Referring now to FIG. 4, the transverse gerotor surface 75 of the
selector plate 71 includes a plurality of fluid ports, generally designated 89
(referred to in the appended claims as "downstream fluid passages"). Each fluid
port 89 is in open fluid communication with an adjacent volume chamber 33 in
the gerotor displacement mechanism 15. The fluid ports 89 include a plurality of
fluid manifold ports 89m and a plurality of fluid thru ports 89t. In the subject
embodiment, and by way of example only, there are nine fluid ports 89, three of
which are fluid manifold ports 89m and six of which are fluid thru ports 89t. The
fluid thru ports 89t are in open and relatively unrestricted fluid communication
with the thru passages 79t.
[0038] Referring now to FIG. 5, a cross sectional view of the selector plate 71
is illustrated. For ease of description, the manifold passages 79m have been
superimposed on to the cross-sectional view of the selector plate 71 and
represented as dashed lines. Each manifold passage 79m is in open fluid

communication with one of a plurality of fluid passages 91a, 91b, and 91c
(referred to in the appended claims as "upstream manifold passages"). Each
fluid passage 91a, 91b, and 91c extends from each manifold passage 79m to
the manifold surface 77 of the selector plate 71.
[0039] Referring now to FIG. 6, each fluid manifold port 89m is in open fluid
communication with one of a plurality of fluid passages 93a, 93b, and 93c
(referred to in the appended claims as "downstream manifold passages"). Each
fluid passage 93a, 93b, and 93c extends from the corresponding fluid manifold
port 89m to the manifold surface 77 of the selector plate 71.
[0040] Referring now to FIG. 7, the manifold surface 77 of the selector plate
71 is shown. The manifold surface 77 defines a plurality of fluid passage
openings 95a, 95b, and 95c, with each fluid passage opening 95a, 95b, and 95c
being in open fluid communication with one of the plurality of fluid passages 91a,
91b, and 91c (shown in FIG. 5), respectively. The manifold surface 77 further
defines a plurality of fluid passage openings 97a, 97b, and 97c, with each fluid
passage opening 97a, 97b, and 97c being in open fluid communication with one
of the plurality of fluid passages 93a, 93b, and 93c (shown in FIG. 6). Also
defined by the manifold surface 77 are a plurality of threaded mounting holes 99.
The manifold surface 77 also defines a drain passage 101 and a fluid passage
103. The drain passage 101 and the fluid passage 103 in the manifold surface
77 are in open fluid communication with the case drain passage 83 and the
pressurized fluid passage 85, respectively.
[0041] Referring now to FIGS. 1, 7 and 8, a cover plate 105 is used when only
single-speed functionality of the disc valve motor 11 is required. The cover plate
105 defines a mounting surface 107, disposed in which are a plurality of fluid
grooves 109a, 109b, and 109c. The cover plate 105 is held in tight sealing
engagement with the selector plate 71 by a plurality of bolts 111 (shown only in
FIG. 1) that pass through a plurality of holes 113 in the cover plate 105 and
thread into the mounting holes 99 in the mounting surface 77 in the selector

plate 71. With the mounting surface 107 of the cover plate 105 in tight sealing
engagement with the manifold surface 77 of the selector plate 71, the fluid
grooves 109a, 109b, and 109c provide open fluid communication between the
fluid passage openings 95a, 95b, and 95c and the fluid passage openings 97a,
97b, and 97c, respectively. It should be understood by those skilled in the art
that although the cover plate 105 has been described and illustrated as a single
plate, the present invention is not limited to such a configuration. It should be
understood by those skilled in the art that the cover plate 105 could include a
plurality of separate plates which provide fluid communication between the fluid
passage openings 95a, 95b, and 95c and the fluid passage openings 97a, 97b,
and 97c, in the manifold surface 77 of the selector plate 71.
[0042] Referring now to FIGS. 1 through 8, in operation, pressurized fluid
entering the first fluid port 53 will flow through the fluid passage 55 and into the
annular fluid chamber 57. The pressurized fluid will then flow into the valve
passages 61 in the rotatable valve member 51, which are in commutating fluid
communication with the fluid passages 79 in the selector plate 71. Pressurized
fluid that enters the fluid passages 79t in the selector plate 71 is openly
communicated to the fluid thru ports 89t in the selector plate 71 and to the
adjacent expanding volume chambers 33 in the gerotor displacement
mechanism 15. Pressurized fluid that enters the fluid passages 79m in the
selector plate 71 flows through the corresponding fluid passages 91a, 91b, and
91c and into the fluid passage openings 95a, 95b, and 95c, respectively, in the
manifold surface 77 of the selector plate 71. The pressurized fluid then flows
from the fluid passage openings 95a, 95b, and 95c through the fluid grooves
109a, 109b, and 109c in the mounting surface 107 of the cover plate 105 and
into the fluid passage openings 97a, 97b, and 97c, respectively, in the manifold
surface 77 of the selector plate 71. The pressurized fluid is then communicated
to the fluid passages 93a, 93b, and 93c and to the corresponding fluid manifold
ports 89m, from where the pressurized fluid enters the adjacent expanding

volume chamber 33 in the gerotor displacement mechanism 15. Exhaust fluid
from the contracting volume chambers 33 in the gerotor displacement
mechanism 15 follows the reverse of the path previously described through the
selector plate 71 to the valve passages 63 in the rotatable valve member 51 and
to the second fluid port (not shown) in the valve housing 19.
[0043] As previously mentioned, the cover plate 105 is used when only single
speed functionality of the disc valve motor 11 is required. However, in the event
that a manufacturer of commercial applications requires multi-speed functionality
instead of single-speed functionality from the disc valve motor 11, the conversion
can be accomplished by replacing the cover plate 105 with a control valve
assembly, generally designated 115 (shown in FIG. 9), which will be described in
greater detail subsequently. Referring now to FIGS. 1, 8 and 9, conversion from
a single-speed disc valve motor 11 to a multi-speed disc valve motor 11 requires
removal of the plurality of bolts 111, which maintain the tight sealing engagement
between the mounting surface 107 of the cover plate 105 and the manifold
surface 77 of the selector plate 71, and removal of the cover plate 105 from the
manifold surface 77 of the selector plate 71. With the cover plate 105 removed,
the control valve assembly 115 is mounted to the manifold surface 77 of the
selector plate 71. A plurality of bolts 116 (shown only in FIG. 9) maintain tight
sealing engagement between the manifold surface 77 of the selector plate 71
and a mounting surface 117 of the control valve assembly 115.
[0044] Referring now to FIGS. 9 and 10, the control spool assembly 115 will
now be described. In the present embodiment, and by way of example only, the
control spool assembly 115 provides two modes of operation, lo-speed mode
and hi-speed mode. FIG. 10 illustrates the control spool assembly 115 in the lo-
speed mode.
[0045] Referring now primarily to FIG. 10, the control spool assembly 115
includes a spool block 119, a control valve spool 121, and a spring member 123.
The spool block 119 defines a spool bore 125, disposed in which is the control

valve spool 121. The spool block 119 further defines a plurality of valve control
passages 127a, 127b, and 127c, a plurality of gerotor control passages 129a,
129b, and 129c, and a plurality of high-pressure passages 131a, 131b, and
131c that are in fluid communication with the spool bore 125. For ease of
illustration, the valve control passages 127, the gerotor control passages 129,
and the high-pressure passages 131 have been shown in FIGS. 10 and 11 to be
planar. However, it should be understood by those skilled in the art that the
valve control passages 127, the gerotor control passages 129, and the high-
pressure passages 131 are disposed on different planes in the spool block 119.
The planes corresponding the valve control passages 127 and the gerotor
control passages 129 are defined by the location of the fluid passage openings
95 and the fluid passage openings 97, respectively, in the manifold surface 77 of
the selector plate 71 and the spool bore 125 in the spool block 119. The
orientation of the gerotor control passages 129 is illustrated in FIG. 9. However,
it should be understood by those skilled in the art that the present invention is not
limited to the valve control passages 127, the gerotor control passages 129, and
the high-pressure passages 131 being nonplanar.
[0046] Also defined by the spool block 119 is a pressure passage 133 which
is in fluid communication with each of the high-pressure passages 131a, 131b,
and 131c. While it has been shown in FIG. 10 that the high-pressure passages
131a, 131b, and 131c are interconnected by the pressure passage 133, it will be
understood by those skilled in the art that the subject embodiment is not limited
to the presence of such a passage in the spool block 119 since pressurized fluid
could be provided to each high-pressure passage 131a, 131b, and 131c
individually. The spool bore 125 includes a first axial end 135 and a second axial
end 137. The first axial end 135 is in fluid communication with a pilot pressure
port 139, and the second axial end 137 is in fluid communication with the drain
passage 101 in the manifold surface 77 through a fluid passage 141.

[0047] Referring still primarily to FIG. 10, the control valve spool 121 defines a
plurality of lands 143, 145, 147, and 149 and a protrusion 151 that extends from
an axial end 153 of the control valve spool 121. The axial end 153 of the control
valve spool 121 and a plug member 155, which is in threaded engagement with
the second axial end 137 of the spool bore 125, serve as seats for the spring
member 123, which biases the control valve spool 121 toward the left in FIG. 10,
i.e. toward the lo-speed mode of operation.
[0048] Since the operation of a control valve spool that is similar to the control
valve spool 121 of the present embodiment has been described in great detail in
U.S. Pat. No. 6,099,280, assigned to the assignee of the present invention and
incorporated herein by reference, the operation of the control valve spool 121 will
be only briefly described herein. Those skilled in the art, however, will
understand that the details of the operation of the control valve spool 121 are not
essential features of the present invention, except to the extent so indicated
hereinafter, and in the appended claims.
[0049] In the lo-speed mode of operation, the spring member 123 biases the
control valve spool 121 toward the left in FIG. 10. In this position, the control
valve spool 121 allows open fluid communication between the plurality of valve
control passages 127a, 127b, and 127c, and the gerotor control passages 129a,
129b, and 129c, respectively, while the lands 145, 147 and 149 of the control
valve spool 121 block the high-pressure passages 131a, 131b, and 131c,
respectively.
[0050] Referring now to FIGS. 2 through 7, 9 and 10, in operation,
pressurized fluid entering the first fluid port 53 will flow through the fluid passage
55 and into the annular fluid chamber 57. The pressurized fluid will then flow
into the valve passages 61 in the rotatable valve member 51, which are in
commutating fluid communication with the fluid passages 79 in the selector plate
71. Pressurized fluid that enters the fluid passages 79t in the selector plate 71 is
openly communicated to the corresponding fluid thru ports 89t in the selector
plate 71 and to the adjacent expanding volume chambers 33 in the gerotor

displacement mechanism 15. Pressurized fluid that enters the fluid passages
79m in the selector plate 71 flows through the respective fluid passages 91a,
91b, and 91c in the selector plate 71, through the respective fluid passage
openings 95a, 95b, and 95c in the manifold surface 77 of the selector plate 71,
and into the respective valve control passages 127a, 127b, and 127c. As stated
previously, with the control valve spool 121 biased toward the lo-speed mode of
operation, the valve control passages 127a, 127b, and 127c and the gerotor
control passages 129a, 129b, and 129c are in open fluid communication.
Therefore, pressurized fluid in the valve control passages 127a, 127b, and 127c
is communicated to the respective gerotor control passages 129a, 129b, and
129c and through the respective fluid passage openings 97a, 97b, and 97c in
the manifold surface 77 of the selector plate 71. The pressurized fluid is then
communicated to the respective fluid passages 93a, 93b, and 93c and to the
respective fluid manifold ports 89m, from where it enters the corresponding
adjacent expanding volume chamber 33 in the gerotor displacement mechanism
15. Fluid from the contracting volume chambers 33 in the gerotor displacement
mechanism 15 follows a reverse path similar to the one previously described
through the selector plate 71 to the valve passage 63 in the rotatable valve
member 51 and to the second fluid port (not shown) in the valve housing 19.
[0051] Referring now to FIG. 11, the control spool assembly 115 is shown in
the hi-speed mode of operation. In this mode of operation, the control valve
spool 121 is biased toward the right in FIG. 11 by pilot pressure supplied to the
pilot pressure port 139, thereby resulting in the compression of the spring
member 123. By way of example only, in a closed loop propel system, the
pressure from a charge pump (typically 200 to 400 psi) could serve as the pilot
pressure. The protrusion 151, which extends from the axial end 153 of the
control valve spool 121, is operably associated with the plug member 155 such
that the plug member 155 provides a positive stop for the protrusion 151 of the
control valve spool 121 after the control valve spool 121 has translated a given

axial distance. In order to prevent the trapping of fluid in the second axial end
137 of the spool bore 125, any fluid that leaks into the second axial end 137 of
the spool bore 125 flows into the drain passage 141 in the spool block, through
the drain passage 101 in the manifold surface 77, and into the case drain
passage 83 in the selector plate 71 where the fluid is communicated to the case
drain fluid port 87 in the valve housing 19.
[0052] With the control valve spool 121 in the hi-speed mode position, the
lands 143, 145, and 147 of the control valve spool 121 block the valve control
passages 127a, 127b, and 127c. Pressurized fluid from the pressurized fluid
passage 85 in the selector plate 71 flows through the fluid passage 103 in the
manifold surface 77 and into the high-pressure passage 131b where the
pressurized fluid is communicated to the other high-pressure passages 131a and
131c through the pressure passage 133 in the spool block 119. With the control
valve spool 121 blocking the valve control passages 127a, 127b, and 127c, the
high-pressure passages 131a, 131b, and 131c are now in open fluid
communication with the respective gerotor control passages 129a, 129b, and
129c.
[0053] Referring now to FIGS. 2 through 7, 9, and 11, in operation,
pressurized fluid entering the first fluid port 53 will flow through the fluid passage
55 and into the annular fluid chamber 57. The pressurized fluid will then flow
into the valve passages 61 in the rotatable valve member 51, which are in
commutating fluid communication with the fluid passages 79 in the selector plate
71. Pressurized fluid that enters the fluid passages 79t in the selector plate 71 is
openly communicated to the fluid thru ports 89t in the selector plate 71 and to
the expanding volume chambers 33 in the gerotor displacement mechanism 15.
Pressurized fluid that enters the fluid passages 79m in the selector plate 71
flows through the respective fluid passages 91a, 91b, and 91c in the selector
plate 71 and through the respective fluid passage openings 95a, 95b, and 95c in
the manifold surface 77 of the selector plate 71 and into the respective valve

control passages 127a, 127b, and 127c. As stated previously, with the control
valve spool 121 biased toward the hi-speed mode of operation, the valve control
passages 127a, 127b, and 127c are blocked. Pressurized fluid from the
pressurized fluid passage 85 in the selector plate 71 flows through the fluid
passage 103 in the manifold surface 77 and into the high-pressure passage
131b where the pressurized fluid is communicated to the other high-pressure
passages 131a and 131c through the pressure passage 133 in the spool block
119. The high-pressure passages 131a, 131b, and 131c are in open fluid
communication with the j-ej§pective gerotor control passages 129a, 129b, and
129c. This pressurized fluid from the pressurized fluid passage 85 then flows
through the respective fluid..p3ssage openings 97a, 97b, and 97c in the manifold
surface 77 of the selector plate 71 to the respective fluid passages 93a, 93b, and
93c. The pressurized fluid from the pressurized fluid passage 85 in the selector
plate 71 then flows to the respective fluid manifold ports 89m, from where it
enters the adjacent volume chambers 33 in the gerotor displacement mechanism
15, regardless of whether the volume chamber 33 is expanding or contracting.
As is well known to those skilled in the art, by supplying pressurized fluid to a
contracting volume chamber 33, the effective displacement of the gerotor
displacement mechanism 15 is reduced which results in a higher speed for a
given flow rate of fluid.
[0054] Fluid from contracting volume chambers which are adjacent to the fluid
thru ports 89t flows through the selector plate 71 to the thru passages 79t. The
fluid then flows through the valve passages 63 in the rotatable valve member 51
and to the second fluid port (not shown) in the valve housing.
[0055] Referring now primarily to FIG. 12, which is similar to FIG. 4, there is
illustrated an alternative embodiment of a selector plate 271 in which the same
or similar elements bear the same reference numerals, plus "200". The primary
distinction between this embodiment of the selector plate 271 and the previously
described embodiment of the selector plate 71 is that this alternative

embodiment of the selector plate 271 defines a plurality of manifold surfaces
277a, 277b, 277c. As a result of the plurality of manifold surfaces 277a, 277b,
277c, the selector plate 271 further defines a plurality of case drain passages
283a, 283b, 283c, which are in fluid communication with the case drain port 87
(shown only in FIG. 1) in the valve housing 19, and a plurality of pressurized fluid
passages 285a, 285b, 285c, which are in fluid communication with the first fluid
port 53 and the second fluid port (not shown) via the shuttle valve arrangement
(not shown). Each of a plurality of manifold passages 279m, which have been
superimposed onto FIG. 12 and represented as dashed lines for ease of
description, is in fluid communication with one of a plurality of fluid passages
291a, 291b, 291c. Each fluid passage 291a, 291b, 291c extends from one of
the manifold passages 279m to one of the manifold surfaces 277a, 277b, 277c,
respectively.
[0056] Referring now to FIG. 13, the manifold surfaces 277a, 277b, 277c of
the selector plate 271 are shown. Each manifold surface 277a, 277b, 277c
defines one of a plurality of fluid passage openings 295a, 295b, 295c, each of
which is in fluid communication with one of the fluid passages 291a, 291b, 291c,
respectively, and one of a plurality of fluid passage openings 297a, 297b, 297c,
each of which is in fluid communication with one of the fluid passages 293a,
293b, 293c, respectively. Also defined by the manifold surfaces 277a, 277b,
277c are a plurality of treaded mounting holes 299. Each manifold surface 277a,
277b, 277c further defines one of a plurality of drain passages 301a, 301b,
301c, and one of a plurality of fluid passages 303a, 303b, 303c which are in
open fluid communication with the case drain passages 283a, 283b, 283c and
the pressurized fluid passages 285a, 285b, 285c, respectively.
[0057] Referring now to FIG. 14, there is illustrated an alternative
embodiment of a cover plate 305. The cover plate 305 defines a mounting
surface 307, disposed in which is a fluid groove 309. The cover plate 305 further
defines a plurality of holes 313 through which a plurality of bolts (not shown but

similar to those referred to in FIG. 1 by reference numeral 111), which are in
threaded engagement with the mounting holes 299 in the manifold surfaces
277a, 277b, 277c, pass. With the cover plate 305 in tight sealing engagement
with the mounting surface 277b of the selector plate 271, the fluid groove 309
provides open fluid communication between the fluid passage opening 295b and
the fluid passage opening 297b. Similarly, with cover plates 305 in tight sealing
engagement with the mounting surface 277a and 277c, the fluid grooves 309 will
provide open fluid communication between fluid passage openings 295a and
295c and fluid passage openings 297a and 297c, respectively.
[0058] Referring now to FIG. 15, an alternative embodiment is illustrated of a
control spool assembly 315 in lo-speed mode. The control spool assembly 315
includes a spool block 319, a control valve spool 321, and a spring member 323.
The spool block 319 defines a spool bore 325, disposed in which is the control
valve spool 321. The spool block 319 further defines a valve control passage
327, a gerotor control passage 329, and a high-pressure passage 331 that are in
fluid communication with the spool bore 325. Similar to FIG. 10, the valve
control passage 327, the gerotor control passage 329, and the high-pressure
passage 331 have been shown to be planar for ease of illustration. As the
operation of the control spool assembly 315 is similar to the operation of the
control spool assembly 115 previously described, no description of the operation
of the control spool assembly 315 will be provided herein.
[0059] In the alternative embodiment, when only single speed functionality of
the disc valve motor 11 is required, the plurality of cover plates 305 are mounted
in tight sealing engagement with the plurality of mounting surfaces 277a, 277b,
277c. However, in the event that a manufacturer of commercial applications
requires multi-speed functionality instead of single-speed functionality from the
disc valve motor 11, the conversion can be accomplished by replacing at least
one of the plurality of cover plates 305 with a control valve assembly 315. The
number of cover plates 305 replaced with control valve assemblies 315 only

affects the speed ratio between lo-speed mode and hi-speed mode of the disc
valve motor 11. Conversion from a single-speed disc valve motor 11 to a multi-
speed disc valve motor 11 requires removal of the plurality of bolts (not shown),
which maintain the tight sealing engagement between the mounting surface 307
of at least one of the plurality of cover plates 305 and at least one of the manifold
surfaces 277a, 277b, 277c of the selector plate 271, and removal of at least one
of the cover plates 305 from at least one of the manifold surfaces 277a, 277b,
277c of the selector plate 271. A control valve assembly 315 is mounted to the
manifold surface 277a, 277b, 277c of the selector plate 271 from which the
cover plate 305 was removed. A plurality of bolts (not shown but similar to those
referred to in FIG. 9 by reference numeral 116) maintain tight sealing
engagement between the manifold surface 277a, 277b, 277c of the selector
plate 271 and a mounting surface 317 of the control valve assembly 315.
[0060] The invention has been described in great detail in the foregoing
specification, and it is believed that various alterations and modifications of the
invention will become apparent to those skilled in the art from a reading and
understanding of the specification. It is intended that all such alterations and
modifications are included in the invention, insofar as they come within the scope
of the appended claims.

What is claimed is:
1. A rotary fluid pressure device of the type having a housing means defining
a fluid inlet and a fluid outlet, a fluid energy-translating displacement
means including a first member and a second member, operably
associated with said first member; said first member and said second
member having relative movement, and interengaging to define a plurality
N of expanding and contracting fluid volume chambers in response to said
relative movement; a valve means cooperating with said housing means to
provide fluid communication between said fluid inlet and said expanding
volume chambers, and between said fluid outlet and said contracting
volume chambers; said valve means comprising a stationary valve
member fixed to be non-rotatable relative to said housing means, and a
moveable valve member, operable to move relative to said stationary
valve member; said stationary valve member being in commutating fluid
communication with said moveable valve member; a plate member
defining a plurality N of upstream fluid passages in commutating fluid
communication with said valve means and a plurality N of downstream
fluid passages, with each said downstream fluid passage being in open
fluid communication with one of said plurality of volume chambers; a
plurality M of upstream fluid passages being in direct, relatively
unrestricted, continuous fluid communication with a plurality M of
downstream fluid passages; characterized by:
(a) a plate assembly including said plate member and at least one
assembly selected from the group consisting of a cover plate
assembly and a control valve assembly;
(b) said plate member including a plurality M of upstream manifold
passages, with each of said plurality of upstream manifold
passages being in open fluid communication with one of a plurality

M of upstream fluid passages and having an opening in an exterior
surface of said plate member, and a plurality M of downstream
manifold passages, with each of said plurality of downstream
manifold passages being in fluid communication with one of a
plurality M of downstream fluid passages and having an opening in
said exterior surface of said plate member; wherein:
(i) said cover plate assembly defining a mounting surface being
in sealing engagement with said exterior surface of said
plate member with said cover plate assembly providing
unrestricted fluid communication between at least one of
said plurality of upstream manifold passages and at least
one of said plurality of downstream manifold passages in
said plate member; and
(ii) said control valve assembly defining a mounting surface
being in sealing engagement with said exterior surface of
said plate member with said control valve assembly being
operable in a first position to provide relatively unrestricted
fluid communication between at least one of said plurality of
upstream manifold passages and at least one of said
plurality of downstream manifold passages in said plate
member, and operable in a second position to block fluid
communication between at least one of said plurality of
upstream manifold passages and at least one of said
plurality of downstream manifold passages in said plate
member.
2. A rotary fluid pressure device as claimed in claim 1, characterized by said
fluid displacement means being of the gerotor type.

3. A rotary fluid pressure device as claimed in claim 2, characterized by said
valve means being of the disc valve type.
4. A rotary fluid pressure device as claimed in claim 1, characterized by a
transverse surface of said plate member being in direct commutating fluid
communication with said rotary valve member.
5. A rotary fluid pressure device as claimed in claim 1, characterized by said
control valve assembly being operable in said second position to provide
relatively unrestricted fluid communication between each of said plurality
of downstream manifold passages.
6. A rotary fluid pressure device as claimed in claim 5, characterized by said
control valve assembly defining a passage in fluid communication with a
source of pressurized fluid.
7. A rotary fluid pressure device as claimed in claim 6, characterized by said
passage in the control valve assembly being in fluid communication with a
pressurized fluid passage in said plate member.
8. A method for converting a single-speed rotary fluid pressure device to a
multi-speed rotary fluid pressure device wherein the rotary fluid pressure
device is of the type comprising a housing means defining a fluid inlet and
a fluid outlet, a fluid displacement means including a first member and a
second member operably associated with said first member; said first
member and said second member having relative movement, and
interengaging to define a plurality of expanding and contracting fluid
volume chambers in response to said relative movement, a valve means
cooperating with said housing means to provide fluid communication

between said fluid inlet and said expanding volume chambers; and a plate
assembly including a plate member; said method being characterized by:
(a) removing at least one cover plate assembly from at least one
exterior surface of said plate member, with said exterior surface
defining at least one opening in fluid communication with at least
one upstream manifold passage in said plate member and at least
one opening in fluid communication with at least one downstream
manifold passage in said plate member;
(b) providing at least one control valve assembly having a mounting
surface; and
(c) mounting said mounting surface of said control valve assembly to
said exterior surface of said plate member, with the control valve
being operable in a first position to provide relatively unrestricted
fluid communication between at least one of said upstream
manifold passages and at least one of said downstream manifold
passages in said plate member, and operable in a second position
to block fluid communication between at least one of said upstream
manifold passages and at least one of said downstream manifold
passages in said plate member.
9. A rotary fluid pressure device of the type having a housing means defining
a fluid inlet and a fluid outlet, a fluid energy-translating displacement
means including a first member and a second member, operably
associated with said first member; said first member and said second
member having relative movement, and interengaging to define a plurality
N of expanding and contracting fluid volume chambers in response to said
relative movement; a valve means cooperating with said housing means to

provide fluid communication between said fluid inlet and said expanding
volume chambers, and between said fluid outlet and said contracting
volume chambers; said valve means comprising a stationary valve
member fixed to be non-rotatable relative to said housing means, and a
moveable valve member, operable to move relative to said stationary
valve member; a plate member defining a plurality N of upstream fluid
passages in commutating fluid communication with said valve means and
a plurality N of downstream fluid passages, with each said downstream
fluid passage being in open fluid communication with one of said plurality
of volume chambers; a plurality M of upstream fluid passages being in
direct, relatively unrestricted, continuous fluid communication with a
plurality M of downstream fluid passages; characterized by:
(a) a plate assembly including said plate member, at least one cover
plate assembly, and at least one control valve assembly;
(b) said plate member including a plurality M of upstream manifold
passages being in open fluid communication with a plurality M of
upstream fluid passages and having an opening in an exterior
surface of said plate member and a plurality M of downstream
manifold passages being in fluid communication with a plurality M
of downstream fluid passages and having an opening in said
exterior surface of said plate member; wherein:
(i) said cover plate assembly defining a mounting surface being
in sealing engagement with said exterior surface of said
plate member with said cover plate assembly providing
unrestricted fluid communication between at least one of
said upstream passages and at least one of said
downstream passages in said plate member; and

(ii) said control valve assembly defining a mounting surface
being in sealing engagement with said exterior surface of
said plate member with said control valve assembly being
operable in a first position to provide relatively unrestricted
fluid communication between at least one of said upstream
manifold passages and at least one of said downstream
manifold passages in said plate member, and operable in a
second position to block fluid communication between at
least one of said upstream manifold passages and at least
one of said downstream manifold passages in said plate
member.
10. A rotary fluid pressure device as claimed in claim 9, characterized by said
cover plate assembly having a plurality of separate plates, each defining a
mounting surface being in sealing engagement with said exterior surface
of said plate member.
11. A rotary fluid pressure device as claimed in claim 9, characterized by said
fluid displacement means being of the gerotor type.
12. A rotary fluid pressure device as claimed in claim 11, characterized by
said valve means being of the disc valve type.
13. A rotary fluid pressure device as claimed in claim 9, characterized by a
transverse surface of said plate member being in direct commutating fluid
communication with said rotary valve member.
14. A rotary fluid pressure device as claimed in claim 9, characterized by said
control valve assembly being operable in said second position to provide

relatively unrestricted fluid communication between each of said plurality
of downstream manifold passages.
15. A rotary fluid pressure device as claimed in claim 14, characterized by
said control valve assembly defining a passage in fluid communication
with a source of pressurized fluid.
16. A rotary fluid pressure device as claimed in claim 15, characterized by
said passage in the control valve assembly being in fluid communication
with a pressurized fluid passage in said plate member.

A rotary fluid pressure device (11) includes a plate assembly (17) having a plate member (71) and at least one cover plate (105), which defines a mounting surface (107) adapted for sealing engagement with an exterior
surface (77) of the plate member (71), or at least one control valve assembly (105), which defines a mounting surface (117) adapted for sealing engagement with the exterior surface (77). The cover plate assembly (105),
when mounted to the exterior surface (77), provides fluid communication between openings (95, 97) of upstream and downstream fluid passages (91, 93), thereby providing single- speed functionality. The control valve assembly (115), when mounted to the exterior surface (77), provides selective fluid communication between the openings (95, 97) of upstream
and downstream fluid passages (91, 93), thereby
providing multi-speed functionality.