Note: Descriptions are shown in the official language in which they were submitted.
CA 02796539 2012-11-26
MULTI-CLUSTER GEAR DEVICE
FIELD OF THE INVENTION
[0001] The invention relates to a multi-cluster gear device and more
particularly to
a multi-cluster gear hydraulic device that can operate as a pump or motor.
BACKGROUND OF THE INVENTION
[0002] In general, gear pumps and motors use a combination of two gears as
a
mechanical device to cooperate with the transfer of fluid between one fluid
inlet to
one fluid outlet of the device. In order to do mechanical work, gear motors
receive
pressurized oil which flows around the gears. The pressurized oil cannot flow
through the gears at the point where they are meshed and therefore the oil
flows
around the outside of each of the gears causing the gears to rotate and
therefore
work. Accordingly, power obtained from the flow of hydraulic fluid through the
hydraulic gear device is transferred to rotational power of the shaft
connected to one
of the gears, thus providing for a gear motor that transforms hydraulic fluid
power
into rotational power. Alternatively, hydraulic gear devices are often used in
hydraulic fluid power applications such as in transmissions, power steering
and
engines, such that power obtained from rotation of a shaft connected to one of
the
gears is transferred to fluid power causing the flow of hydraulic fluid
through the
pump from the fluid inlet to the fluid outlet, thus providing for a gear pump
that
transforms rotational shaft power into hydraulic fluid power. It is recognized
that
hydraulic gear devices can be external gear devices, in which the gears are
both
external, or internal gear devices, in which one gear is external and one is
internal.
[0003] Gear pumps work on the principal of positive displacement. This
means
that a constant amount of fluid is pumped during each gear revolution. In
general, as
the meshed gears in a gear pump rotate they create a low and a high pressure
side.
Which side is which is determined by the gear rotational direction. Fluid is
drawn into
the low pressure side, or intake side, of the pump. The fluid is carried by
the gears,
to the discharge side of the pump. As the gears connect, or mesh, at the
discharge
side, the fluid is displaced and leaves the pump.
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[0004] Traditional gear pumps use a pair of gears to draw and deliver
fluid
between one fluid inlet and one fluid outlet, such that the fluid output is
dependent on
the size and rotational speed of the gears. In order to deliver a higher
output flow of
fluid, higher shaft RPM, larger gears or more pumps (e.g. in parallel) are
required.
However, increasing the number of pumps can increase the number of independent
components being used which can result in having more parts that may require
maintenance and/or replacement, as well as increased space and weight
requirements. Alternatively, the size of the working gears may be increased to
increase the output flow, however, this can present a challenge if space is
limited, as
well as present inertia issues for changing pump speeds. As well, higher
rotational
speeds can result in higher operational temperatures and overall increased
friction
and associated costs.
[0005] Further, shifting of gear alignments (e.g. axially, laterally)
within the
housing of the gear pump, during higher hydraulic loadings, can cause
undesirable
damage (e.g. abrasive wearing of surface material) to the inside surface of
the gear
housing and/or the gear teeth themselves, as gap tolerances between the gear
teeth
and the housing inside surface are minimized (e.g. to within one thousandth of
an
inch) to inhibit hydraulic fluid blow-by from the high pressure side to the
low pressure
side of the pump. In particular, removal of the surface material due to wear
can also
increase the gap distance between the gear teeth and the housing inside
surface,
which can result in decreased pumping efficiency due to increased blow-by of
hydraulic fluid from the high pressure side of the pump to the low pressure
side of
the pump. Further, excessive tension forces can be experienced by fasteners
used
to assemble multi-piece housings, due to high fluid pressures, which can
result in
fastener failure and/or undesirable increases in predefined tolerance gaps
within a
gear cavity of the device.
SUMMARY OF THE INVENTION
[0006] It is therefore desired to provide a gear pump and/or motor that is
capable
of providing variable output flow while using a number of gears that is not
equal to
the number of hydraulic fluid ports.
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[0007] It is an object of the present invention to provide for a hydraulic
gear
device that has greater number of fluid ports communicating with a gear cavity
than
the number of gears positioned within the gear cavity.
[0008] It is an object of the present invention to provide for a hydraulic
gear
device that obviates or mitigates at least one of the above-presented
disadvantages.
[0009] The present invention provides a multi-cluster gear device.
[0010] In one embodiment, the multi-cluster gear device comprises a shaft
rotatable about a longitudinal axis, a primary gear mounted on the shaft, at
least two
secondary gears spaced about and positioned to engage with the primary gear,
each
of the at least two secondary gears configured to independently receive fluid
from a
fluid reservoir and to allow flow of a portion of the fluid about the
secondary gear and
to allow the remaining portion of the fluid to be carried by the primary gear
to the
adjacent secondary gear.
[0011] In a further embodiment, the multi-cluster gear device includes at
least two
secondary gears, the secondary gears being smaller than the primary gear. In a
further embodiment the at least two secondary gears are spaced evenly about
the
periphery of the primary gear.
[0012] In a further embodiment, 50% of the fluid received by each of the at
least
two secondary gears flows around respective secondary gears and the remaining
50% is carried to the adjacent secondary gear by the primary gear.
[0013] In a further embodiment, each of the secondary gears is
independently
fluidly connected to a fluid inlet and a fluid outlet. In one embodiment, each
of the
secondary gears is configured to receive fluid at low pressure through the
fluid inlet.
In one embodiment, each of the secondary gears is configured to release fluid
at
high pressure through the fluid outlet.
[0014] In an alternative embodiment, the multi-cluster gear device includes
three
secondary gears. In another embodiment, the multi-cluster gear devices
includes
four secondary gears.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The present invention will now be described in further detail with
reference
to the following figures:
[0016] Figures 1A and 1B are examples of a prior art conventional two-gear
pump;
[0017] Figure 2 is a schematic of one embodiment of the multi-cluster gear
device
of the present invention, showing a three gear cluster configuration;
[0018] Figure 3 is one embodiment of a portion of the multi-cluster gear
device of
the present invention, showing a five gear cluster configuration, in
isolation;
[0019] Figure 4 is a partial cut away of an alternative embodiment of the
multi-
cluster gear device of the present invention, having a three pump via a four
gear
cluster configuration;
[0020] Figure 5 is a sectional view of the embodiment of Figure 4, showing
the
three pump configuration in isolation;
[0021] Figure 6 is a perspective view of the multi-cluster gear device of
Figures 4
and 5 within a housing;
[0022] Figure 7 is an alternative embodiment of the multi-cluster gear
device of
Figure 6 shown in a hoisting operation application;
[0023] Figure 8 is a partial cut away view of one embodiment of the four
pump
configuration of the multi-cluster five gear device of the present invention,
showing
an internal gear configuration;
[0024] Figure 9 is an example of the hydraulic circuitry of a four pump,
external
cluster gear device;
[0025] Figure 10 is a schematic of a bypass loop, of an external gear pump
arrangement, that may be used in the multi-cluster gear device described
herein;
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[0026] Figure 11 shows one embodiment of the use of the multi-cluster gear
device wherein two devices are mechanically connected to one common shaft;
[0027] Figure 12 shows an alternative configuration of the gear device of
Figure
1;
[0028] Figure 13 shows an alternative configuration of the gear device of
Figure
12;
[0029] Figure 14a shows a configuration of the gear device of Figure 12 with a
predefined tolerance;
[0030] Figure 14b shows a configuration of the gear device of Figure 12 with a
predefined tolerance reduced due to movement of the gear;
[0031] Figure 15 shows an exploded view of the gear device of Figure 12;
[0032] Figure 16 shows a further unassembled view of the gear device of Figure
12;
[0033] Figure 17 shows a further unassembled view of the gear device of Figure
12;
[0034] Figure 18 shows an alternative configuration of the gear device of
Figure
12;
[0035] Figure 19 shows a expanded view of a mounting mechanism of the gear
device of Figure 18;
[0036] Figure 20 shows an alternative configuration of the gear device of
Figure
12;
[0037] Figure 21 shows an alternative configuration of the gear device of
Figure
12;
[0038] Figure 22 shows a side view of the gear device of Figure 20;
[0039] Figure 23 shows a half exploded view of the gear device of Figure 20;
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CA 02796539 2012-11-26
[0040] Figure 24 shows an alternative configuration of the gear device
of Figure
12;
[0041] Figure 25 shows a half exploded view of the gear device of Figure
24;
[0042] Figure 26 shows a half assembled view of the gear device of
Figure 24;
and
[0043] Figure 27 shows a a further embodiment of the gear device of
Figure 22.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0044] The present invention provides a multi-cluster hydraulic gear
device that
includes a main gear (e.g. a large gear) fluidly connected to at least two
secondary
gears (e.g. a first small gear and a second small gear). Each gear cluster,
i.e. the
mechanical meshed connection between adjacent gears (e.g. of the main gear
with
the secondary gear), is fluidly connected to an adjacent gear cluster (e.g.
connection
of the main gear with the other secondary gear) and is able to, in one working
mode,
defer 50% of the drawn fluid to the downstream secondary gear (e.g. second
small
gear) while also receiving 50% from the upstream secondary gear (e.g. first
small
gear).
[0045] The present invention will now be described in further detail
with reference
to Figures 1-11 in which the multi-cluster hydraulic gear device is indicated
generally
at numeral 20. The multi-cluster hydraulic gear device 20, described herein,
may be
utilized in any arrangement that requires the use of a gear pump or motor. In
use as
a gear pump the device provides a means for fluid to be drawn from a fluid
source,
e.g. tank, and force it to and or through a flow/pressure control device or
fluid sink.
Examples of the types of applications in which the multi-cluster hydraulic
gear
device, described herein, may be used include, but are not limited too,
primary or
secondary brake systems that may be used on, for example, a vehicle such as a
truck or rail car, or in commercial non-vehicular applications such as in
mining
equipment, elevator equipment, oil drilling equipment and other stationary
applications.
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[0046] The present invention provides a multi-cluster hydraulic gear device
that
includes a main drive gear, also referred to herein as a large or primary
gear, and at
least two additional secondary gears (e.g. each smaller than the main gear).
In one
embodiment, fluid is drawn into a low pressure cavity of the device where it
is split
into two or more parts. One follows the rotation of one of the secondary gears
into
the high pressure cavity of the same cluster while a second part of the flow
follows
the rotation of the main gear into the high pressure side of the next nearest
cluster
(between the next secondary gear and the main gear) as per the main gear's
rotation
direction. The multi-cluster hydraulic gear device is able to operate in a
working (e.g.
full flow) mode and also in a by-pass mode, both modes are discussed further
below.
[0047] The multi-cluster hydraulic gear device can include a ring gear, or
large
gear, having internal or external teeth, that is supported within a housing.
One or
more spur gears, or pinion gears, also referred to herein as small/secondary
gears,
include external teeth, that are sized to mesh with the teeth of the large
gear. For a
main gear having internal teeth, each of the secondary gears is located
internally of
the main gear. For a main gear having external teeth, each of the secondary
gears is
located externally of the main gear. The teeth on each secondary gear are
sized to
mesh with the teeth on the main gear. Rotation of the main gear will initiate
rotation
of each of the secondary gears, and vice versa, i.e. each of the gears can be
driving
or can be driven. It is recognized that the main gear can be of a diameter
greater
than any one or all of the secondary gears. It is recognized that the main
gear can
be of a diameter smaller than any one or all of the secondary gears. It is
recognized
that the main gear can be of the same diameter as any one or all of the
secondary
gears.
[0048] Due the presence of two or more secondary gears, each of these gears
acts as a gear device (e.g. pump or motor), also referred to as a gear
cluster, due to
the individual interaction of each secondary gear with its respective portion
of the
main gear as a respective gear cluster of the multi-gear cluster. Accordingly,
it is
recognized that the multi-cluster hydraulic gear device 20 contains multiple
gear
devices (e.g. pump or motor) within a common housing, such that each of the
gear
devices contributes a respective portion of the total hydraulic fluid output
of the multi-
cluster hydraulic gear device 20. It is also recognized that each gear device
of the
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multi-cluster hydraulic gear device 20 can have a pair of hydraulic ports
(e.g. an inlet
port and an outlet port) associated therewith, such that each port
communicates
hydraulic fluid between an exterior of a gear cavity containing the multiple
gear
devices and the interior of the gear cavity. This configuration of ports can
result in a
greater number of fluid ports communicating fluid to and from the gear cavity
than
the number of actual gears positioned within the gear cavity. In one
embodiment,
there can be a pair of hydraulic ports associated with each of the secondary
gears,
however it is recognized that there can be more than two ports per secondary
gear in
the case of multi-port configurations. For example, each secondary gear can
have
two inlet ports and two outlet ports associated therewith, as desired.
Alternatively,
the number of inlet ports and outlet ports per secondary gear can be unequal
(e.g.
an inlet port with a pair of outlet ports or a pair of inlet ports with an
outlet port).
[0049] Turning to Figures 1A and 1B, an embodiment of a prior art,
conventional,
gear pump 10 is shown having two gears 12. This conventional two gear pump 10
delivers approximately 50% of its output flow via one gear 12 and the other
approximately 50% through its mated gear 12 to create close to total 100%
output.
The gear pump 10 draws in fluid at the low pressure side of the pump 10. The
total
amount of the fluid that is drawn into the gear pump 10, i.e. 100%, is then
divided in
two by rotation of the gears 12. 50% will flow around one of the gears 12 and
50%
about the other gear 12, as shown by the arrows. As stated above, the fluid is
inhibited from passing between the gears 12 at the point where they are
meshed.
Each of the separate 50% fluid flows will then rejoin at the outlet of the
pump 10, i.e.
the high pressure side, shown at arrow A in Figure 1B. It will be understood
that, in
general, while a theoretical pump 10 will deliver a portion (e.g. 50%) via one
gear 12
and the remaining portion(s) (e.g. 50%) through its mated gear(s) 12 to create
100%,
with zero leakage, the actual real application may not achieve 100% output, as
stated above.
[0050] The configuration of the individual gears used within the multi-
cluster
hydraulic gear device 20 will now be described. Turning now to Figure 2, a
schematic is provided showing one example of the multi-cluster hydraulic gear
device 20 of the present invention. It should be noted that the multi-cluster
hydraulic
gear device 20, described herein, may also be referred to as a multi-cluster
hydraulic
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gear pump or motor. As seen in Figure 2, the multi-cluster gear device 20
includes a
main (e.g. internal large) gear 22 coupled to two secondary (e.g. small) gears
24.
The main gear 22 includes internal teeth, not shown, that mesh with the
external
teeth, not shown, on the secondary gears 24. The meshing of the teeth is shown
clearly in the embodiment illustrated in Figure 3, for example.
[0051] The rotational direction of the main gear 22 and the secondary gears
24A,
24B, is shown by the arrows in Figure 2. In this embodiment, all the gears
turn in the
same direction and at the same rotational rate (e.g. angular gear or tooth
velocity). It
will be understood that in one mode of operation, the main gear 22 drives the
secondary gears 24A and 24B, as the main gear 22 can be connected to an
external
drive shaft ¨ not shown ¨ that is mechanized to force rotation of the main
gear 22. In
an alternate mode, the secondary gears 24A and 24B can drive the main gear, as
the secondary gears 24A,B can be connected to respective external drive shafts
¨
not shown ¨ that are mechanized to force/drive rotation of the secondary gears
24.
Alternatively, one of the secondary gears 24A or 24B can drive the main gear,
as the
one secondary gear 24A or 24B can be connected to a respective external drive
shaft ¨ not shown ¨ that is mechanized to force/drive rotation of the one
secondary
gear 24A or 24B. In any event, it is recognized that there are two or more
gear
devices 23 within a gear cavity 25 of a housing 42 of the multi-cluster
hydraulic gear
device 20. Again it is recognized that each of the gear devices 23 is
considered one
gear cluster of the multi-cluster hydraulic gear device 20, whereby one gear
cluster
provides for the meshing of teeth between a respective portion of the teeth of
the
main gear 22 with teeth of the respective secondary gear 22.
[0052] In operation of the multi-cluster hydraulic gear device 20 of Figure
2,
hydraulic fluid is drawn into the multi-cluster gear device 20 at a low
pressure side of
the main gear 22 and secondary gear 24A, indicated at fluid inlet port A, such
that a
portion (e.g. 50%) of the drawn fluid from the reservoir 27 flows around the
secondary gear 24A while the remaining portion (e.g. 50%) of the drawn fluid
is
carried by the main gear to the next nearest secondary gear 24B, as shown by
the
directional arrows. Fluid is also drawn from the reservoir 27 into the gear
pump 20 at
a low pressure side of secondary gear 24B and main gear 22, indicated at fluid
inlet
port B, and a portion (e.g. 50%) flows around secondary gear 24B while the
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remaining portion (e.g. 50%) is carried to secondary gear 24A. The portion
(e.g. 50
%) that is carried from secondary gear 24B to 24A combines with the portion
(e.g.
50%) volume that has come around with the secondary gear 24A to output at 100%
at a high pressure side of the secondary gear 24A and the main gear 22, as
indicated at fluid outlet port C. Likewise the portion (e.g. 50%) that is
carried from
the secondary gear 24A to 24B combines with the portion (e.g. 50%) volume that
has come around with the secondary gear 24B to output at 100% at a high
pressure
side of secondary gear 24B and main gear 22, as indicated at fluid outlet port
D. It
should be noted that each gear device 23 has both a low pressure port and a
high
pressure port that communicates fluid into/ out of the gear cavity 25 common
to all
gear devices 23. Each pump 20 has therefore deferred a portion (e.g. 50% flow)
to
the downstream secondary gear while receiving a portion (e.g. 50% flow) from
the
upstream secondary gear. The combined total output flow (as the combined
portions) of the two secondary gears 24A,B is equivalent to the output of two
pump
pairs (e.g. gear devices 23), but the multi-cluster hydraulic gear pump 20
configuration only uses three gears for the output, whereas two separate pumps
requires four individual gears (i.e. two for each pump). It is recognized that
the multi-
cluster hydraulic gear pump 20 has less number of clustered gears than double
that
of the number of gear devices 23 (e.g. three gears for two gear devices, four
gears
for three gear devices, etc.). This provides that the multi-cluster hydraulic
gear pump
20 that has fewer numbers of gears than more traditional two gear pumps (see
Figure 1A), which can result in overall reduced gear noise, gear friction and
wear, as
well as reduced gear parts (e.g. shafts, bearings, etc.) and cost.
[0053] Turning to Figure 3, an alternate configuration of the multi-cluster
gear
device 20 is shown. In this embodiment, the multi-cluster hydraulic gear
device 20
includes a main (e.g. internal large) gear 22 and a four secondary (e.g.
small) gears
24. The secondary gears 24 are spaced around the (e.g. internal) surface of
the
main gear 22 at equal spacings in the Figure, however the relative spacing of
the
secondary gears to one another can differ in length and the secondary gears
can be
placed at preferred unequally spaced locations about the periphery of the main
gear
22 depending on the use and/or application. The teeth 26 (e.g. external) on
each of
the secondary gears 24 are configured to mesh with the teeth 28 (e.g.
internal) of the
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main gear 22 as the main gear 22 and secondary gear 24 rotate, thus defining
each
of the respective gear devices 23 as the respective gear clusters of the multi-
gear
cluster environment in the common gear cavity 23 of the multi-cluster
hydraulic gear
device 20. The main gear 22 and the secondary gears 24 are held in a meshed
configuration and are positioned inside the common gear cavity 23 of the
device
case, or housing. It will be understood that each of the secondary gears 24
can be
held at a predefined distance (e.g. gear center to center distance) from the
main
gear 22 that allows for meshing of the teeth 26 with the teeth 28 (direct
contact
there-between) whilst also allowing for rotation of the secondary gears 24,
being
driven by the rotation of the main gear 22, or vice versa. Further, the
positioning of
the main .gear 22 and the secondary gears 24 can provide for fluid flow
between
adjacent secondary gears 24 via the main gear 22. It will be understood that
the
positioning of the main gear 22 and secondary gears 24 are not held so as to
prevent rotation thereof.
[0054] In an alternative embodiment, shown in Figure 4, the main gear 22
includes external teeth 32 that mesh with external teeth 34 located on each of
the
secondary gears 24. It will be understood that the difference between these
two
embodiments (Figure 3 and 4) includes the fact that in the embodiment shown in
Figure 3 the main gear 22 and secondary gears 24 all rotate in the same
direction.
However, in the embodiment shown in Figure 4, the secondary gears 24 rotate in
the
opposite direction to the main gear 22. However, the overall function of the
multi-
cluster hydraulic gear device 20 is the same, irrespective of the direction of
fluid flow
or main gear or secondary gear rotation.
[0055] Figure 4 illustrates an alternate embodiment of the multi-cluster
hydraulic
gear device 20 described herein. In this embodiment, the device 20 includes a
main
larger central gear 22 with three smaller secondary gears 24, located about
the
periphery of the main gear 22, such that each of the secondary gears 24 meshes
with a portion of the teeth of the main gear 22. While only two small gears 24
can be
seen in Figure 4, it will be clear from Figure 5 that the embodiment
illustrated in
Figure 4 includes three secondary gears 24. Each of the secondary gears 24
include (e.g. external) teeth that mesh with the (e.g. external) teeth located
on the
main gear 22. At least a pair of hydraulic fluid ports 40 (e.g. an inlet and
an outlet
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port) are positioned at each meshing point of the two meshing gears, in other
words
for each gear device 23. Each of the ports 40 is operable to act as either an
inlet or
outlet for hydraulic fluid flow either into or our of the common gear cavity
25. It will be
understood that when the multi-cluster hydraulic gear device 20 acts as a
pump, fluid
is drawn by each of the inlet ports 40, when the device is active. Conversely,
when
the multi-cluster hydraulic gear device 20 is used as a motor, external fluid
pressure
is applied to one side of one of the port pairs, or multiple pairs, to
increase HP and
torque, depending on the preferred vehicle travel direction. For example,
referring to
Figure 2, fluid pressure may be applied at the port identified at arrow A or
at arrow C.
In any event, it is recognized that each of the gear devices 23 has a pair of
ports 40
associated therewith, consisting of at least one inlet port and one outlet
port for the
pair.
[0056] The multi-cluster hydraulic gear device 20 is housed in a housing,
identified at numeral 42 in Figure 4, which encloses the gears 22, 24,
bearings 41
upon which shafts 44,39 of the gears 22, 24 are mounted, wear plates 43, ports
40
and other mechanical components. It will be understood that the housing 42 may
be
any size and/or shape provided that it encases all the components of the multi-
cluster hydraulic gear device 20 in the common gear cavity 25. The size and/or
shape of the housing 42 may be governed by the internal components and also
the
application within which the multi-cluster hydraulic gear device 20 is to be
used.
Figure 4 is an example of a split housing having one or more housing portions.
[0057] Also shown is a input shaft 44 of the multi-cluster hydraulic gear
device 20
which accepts or delivers rotational torque to the main gear 22. The device 20
may
also include a shaft seal 47, as well as other seals (not shown) as part of
the housing
42, to withstand low pressure and retain hydraulic fluid within the device
housing 42.
It will be understood that the multi-cluster hydraulic gear device 20, when
used as a
gear pump, may also include additional components such as an input shaft 46,
for
connection to a rotational energy source via the device input shaft 44, i.e.
torque, a
clutch 48 (see Figure 8), which is used to mechanically couple a rotational
source/load from the device, or a gearbox, which is used to match the device
RPM to
the source or load requirements. The housing 42 may include a series of
apertures
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50, through which bolts, or other fastening means (not shown), are placed to
assemble and secure components together.
[0058] Figure 5 is a cross sectional view of a portion of the multi-cluster
hydraulic
gear device 20. The three gear device 23 multi-cluster arrangement includes
three
secondary gears 24 located about, and engaging with, the periphery of a
central
main gear 22. Ports 40 are located about each secondary gear 24 and are
operable
to allow for fluid flow there through. Figure 6 is an external perspective
view of the
multi-cluster hydraulic gear device 20 enclosed within the housing 42, with
port 40
apertures shown in the housing 42.
[0059] Figure 7 illustrates one embodiment of the multi-cluster hydraulic
gear
device 20, in use as a motor that may be used in an application such as a
crane, for
hoisting a load. Figure 7 shows the multi-cluster hydraulic gear device 20 in
housing
42 connected to a winch drum 52. The multi-cluster gear device 20 can be used
in
motor mode to hoist the load and, when required, can be used as a brake, i.e.
in
pump mode, when the load is lowered. This example serves as one application
for
the use of the multi-cluster hydraulic gear device 20 described herein.
[0060] Figure 8 shows a further embodiment of the multi-cluster hydraulic
gear
device 20, and in particular the use of the device 20, described herein. In
this
embodiment the device 20 includes several gear cluster devices 23 with the
secondary gears 94 located on the inside of the main gear 92. The illustrated
embodiment includes four secondary gears 94, of which two can be seen in
Figure 8.
The embodiment shown illustrates the use of the multi-cluster gear device 20
in a
towed vehicle. The use will be described further below.
[0061] Figure 9 illustrates one example of the hydraulic circuitry of the
four
external gear cluster system similar to Figure 8 but with the secondary gears
located
externally relative to the main gear. As can be seen in Figure 9, fluid is
operable to
flow from one external secondary gear, 24, to the adjacent external small
gear.
Figure 9 includes a series of arrows showing direction of fluid flow. Each
arrow
includes the portion (e.g. %) of fluid that flows along the path taken from
the original
total (e.g. 100%) fluid input. As described above, a portion (e.g. 50%) of the
total
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fluid flow for each secondary gear is carried around each secondary gear and
the
remaining portion (e.g. 50%) is carried by the main gear and carried to the
adjacent
secondary gear where it combines with the portion (e.g. 50%) that has been
carried
around the adjacent secondary gear to output at as the total (e.g. 100%)
output for
that gear cluster 23 (see Figure 8). Each secondary gear 24, is able to draw
its own
source of fluid, from a fluid reservoir indicated by arrows showing input of
total (e.g.
100%), of which the portion (e.g. 50%) rotates around the small gear and
remaining
portion (e.g. 50%) of which is carried to the adjacent secondary gear 24 via
the main
gear.
[0062] For example, as seen in the figure, the portion (e.g. 50%) of the
fluid that
is drawn into the low pressure side, shown at 1A, of the top secondary gear 24-
1, is
carried around the secondary gear 24-1 and is carried over to 1B. The
remaining
portion (e.g. 50%) is carried over to 2B by the main gear 22 where it joins
with
portion (e.g. 50%) that has passed around the small secondary 24-2 to result
in port
output total (e.g. 100%) at the high pressure side 2B. The inlet fluid drawn
by 2A,
see arrows at 2A, is divided into two parts by the related gear cluster device
23, i.e.
the secondary gear 24-2 and the main gear 22. Portion (e.g. 50%) of the drawn
fluid
follows the secondary gear 24-2 around to the high pressure side 2B, as
indicated by
the direction of the arrow around the secondary gear, where it combines with
the
portion (e.g. 50%) from secondary gear 24-1, as discussed above. The other
portion
(e.g. 50%) is carried by the main gear 22 over to the high pressure side of
the
adjacent secondary gear 24-3, indicated at 3B. Likewise, inlet fluid is drawn
by 3A,
see arrows at 3A, and is divided into two parts by the related gear cluster
device 23,
i.e. the secondary gear 24-3 and the main gear 22. Portion (e.g. 50%) of the
drawn
fluid follows the secondary gear 24-3 around to the high pressure side 3B, as
indicated by the direction of the arrow around the secondary gear 24-3, where
it
combines with the portion (e.g. 50%) received via the main gear 22 from
secondary
gear 24-2. The other portion (e.g. 50%) is carried by the main gear 22 over to
the
high pressure side of the adjacent secondary gear 24-4, indicated at 4B. The
fluid
flow at secondary gear 24-4 is as per the above. Fluid is drawn in at low
pressure
side 4A. Of this inlet fluid, portion (e.g. 50%) is carried by secondary gear
24-4
around to the high pressure side 4B, where it merges with the portion (e.g.
50%)
- 14-
CA 02796539 2012-11-26
received from secondary gear 24-3. The remaining portion (e.g. 50%) is carried
by
main gear 22 to the high pressure side 1B of secondary gear 24-1 to combine
with
the portion (e.g. 50%) that has been carried around secondary gear 24-1. Each
high
pressure side, 1B, 2B, 3B and 4B is therefore releasing respective port output
total
fluid (e.g. 100%) at fluid pressures higher than the inlet fluid pressures.
[0063] The total output of the system illustrated in 9 is therefore able
to deliver the
output flow equivalent of four pump pairs (i.e. 8 gears) using only 5 gears
associated
with 4 gear devices 23 in a common gear cavity 25, within the multi-cluster
hydraulic
gear device 20.
[0064] As can be seen, check valves, indicated generally at 30, and
solenoids,
indicated generally at 32, may be located within the fluid lines. Check valves
may be
located on the high pressure line, as seen in Figure 9. The inclusion of a
solenoid
valve 32, at each gear 24 allows for flow of hydraulic fluid cycling back
through the
rotating gear 24, as opposed to out of the multi-duster hydraulic gear device
20.
[0065] Reference will now be made to Figure 8 in which one embodiment of
the
use of the multi-cluster hydraulic gear device 20 in a vehicle brake system is
shown.
[0066] The following description of one use of the multi-cluster
hydraulic gear
device 20, described above, is provided as an example only and is not meant to
be
limiting to the application of the multi-cluster hydraulic gear device 20
described
herein. For the purposes of this description, the use of the multi-cluster
hydraulic
gear device 20 will be described herein in reference to its use as a gear pump
in a
vehicle braking system. Examples of the types of vehicles that it may also be
used in
include, but are not limited to, rail applications over the road tractors,
trailers, city
buses, heavy duty commercial vehicles, light duty commercial and passenger
vehicles.
[0067] The multi-cluster hydraulic gear device 20 includes an outer case
80 that
is connected to a rotating towing or towed vehicle wheel. The device 20, used
in a
pump mode in this example, includes spur gears, or small gears, 94, which are
fixed
within a stationary housing 83 located inside the outer case 80. When braking
is
invoked, pilot fluid is injected into the clutch cylinder 82, which moves the
clutch
- 15 -
CA 02796539 2012-11-26
block 84 radially outward to engage with the rotating outer case. This action
results
in engagement of clutch plate 87 to the rotating outer case 80. Following
this, clutch
plate 87 starts to rotate mechanical drive gear 88, which is mechanically
connected
to clutch plate 87. This in turn spins all four mechanical spur gears 90,
which are
each connected to one of four small hydraulic spur gears, or secondary gears
94.
The secondary gears 94 are as per the secondary gears 24 described above. Each
of the secondary gears 94 in turn is connected to, and passively rotate, the
ring gear,
or main gear, 92. The main gear 92, is as per the main gear 22 described
above.
This initiates pumping action and fluid is drawn from a reservoir to the pump
ports,
not shown, at the meshing point. A partition wall 96 is positioned between the
mechanical and hydraulic zones and is fitted with seals isolating the two
compartments and the fluid.
[0068] Braking effort may be modulated by controlling (i) the displaced
volume,
i.e. how many pumps are activated; and (ii) the pressure head. When the fluid
leaves
the control valve, it may be sent to a filter for cleaning and a heat
exchanger to
dissipate kinetic brake energy before it is recirculated back to the pump.
When the
clutch is engaged to initiate fluid flow, all the secondary gears 94 begin to
rotate,
transferring fluid in direct proportion to their rotational speed and size.
Total braking
effort can then be modulated by a combination of two modes (i) step modulation
and/or (ii) analog modulation.
[0069] In step modulation, opening of bypass solenoid(s) enables the
individual
pumps output by "shorting" fluid flow. In the case of the illustrated four
pump cluster,
seen in Figure 9, flow volume at levels of more than 0 to 100% of total can be
invoked. This technique is sometimes referred to as "staircase modulation"
owing to
its stepped nature. In analog modulation, by electronically modulating head
pressure
generated by the control valve, brake effort can be continuously varied,
creating
infinite intermediate control levels between the stepped values. By
synchronizing
commands between the two modes, "bumpless" transition between steps can be
achieved.
[0070] Figure 10 is a schematic of a by-pass loop. As described earlier
each
pump "hands off' portion (e.g. 50%) of its total intake to the nearest cluster
device
- 16-
CA 02796539 2012-11-26
23, the handoff direction dictated by pump rotational direction. When a valve
is
opened to "short" hydraulic flow, the fluid does not simply loop locally.
Fluid is drawn
from a fluid reservoir, at the interface of pump A and the drive gear 22,
shown at
arrow A. Portion (e.g. 50%) of the fluid follows pump A, as it rotates, to the
high
pressure side, shown at arrow B.
[0071] The working pump A continuously pushes a portion (e.g. 50%) flow
volume, of the fluid drawn in, to the bypassed pump B via drive gear 22, i.e.
portion
(e.g. 50%) is carried by drive gear 22 to pump B. An initial fluid is drawn
into the low
pressure side of Pump B, at position C, of this portion (e.g. 50%) is carried
by the
drive gear 22 to join with the portion (e.g. 50%) carried around pump A to
result in
total fluid output. Of the fluid drawn in at position C, portion (e.g. 50%)
follows pump
B around to meet with the portion (e.g. 50%) that has been passed from working
pump A. The combined portions are then recirculated through the cluster. The
net
effect: the bypass solenoid has shorted out pump B and the circuit behaves as
if that
pump simply does not exist. Instead of outputting portion (e.g. 50%) of the
fluid, the
fluid is simply recirculated within pump B via the solenoid. In other words,
the portion
(e.g. 50%) volume has simply passed through as though pump B were not there.
It
will therefore be clear that every cluster that is in the bypass mode will
always a
fresh injection of portion (e.g. 50%) of cooled oil with every revolution. One
advantage of the injection of fresh oil in the bypass mode is for cooling
purposes of
the overall device 20 and/or for respective gear devices 23 adjacent to the
bypassed
gear device 23.
[0072] Referring to Figure 10, shown is that inlet fluid A is split into
fluid portions
Al and A2 and inlet fluid C is split into fluid portions Cl and C2. As pump A
is not in
bypass mode, the secondary gear of pump A carries fluid portion Al over to
output
port B and main gear 22 carries fluid portion C2 over to output port B, thus
providing
for total output at port B of combined fluid portions C2 and Al. In terms of
bypassed
secondary gear/pump B, inlet fluid portion Cl is carried around by the
secondary
gear to meet incoming fluid portion A2 carried by main gear 22. These two
portions
then meet and combine as portions Cl +A2 and flow via the bypass valve 9 over
to
inlet port C. Next, a portion of the combined C1+A2 is directed as new portion
C2
and the remainer is drawn from the reservoir as new portion Cl. When bypass
valve
- 17-
CA 02796539 2012-11-26
9 is opened, as described, the fluid will take the path of least amount of
resistance.
In other words, given that pump A is working it is understood that a control
valve 8
can be partially closed, thus offering a flow restriction for the output of
gear device A
in Figure 10. The fluid will therefore have an easier time flowing via the
bypass valve
9 than via the flow restriction offered by control valve 8. Fluid will
therefore flow or
otherwise partially recirculate (e.g. portion Cl carried by secondary gear
first to meet
portion A2 and then back through valve 9 to inlet port C) in the bypassed gear
device
23 and not to the output port (not shown where A2 and Cl meet) of the bypassed
pump B. It is noted that every gear device 23 can have a respective bypass
valve 9
associated therewith, thereby providing for the passage of fluid directly from
the
outlet port 40 of the gear device 23 directly to the input port 40 of the gear
device 23,
for use as part of the next draw of fluid into and processed by the bypassed
gear
device 23.
[0073] Therefore, in situations where higher hydraulic pressure with
reduced fluid
flow rates (e.g. fluid volume) is desired as total fluid output from the
device 20,
bypass valve(s) 9 are opened for one or more respective gear devices 23 so
that the
remaining working (e.g. pumping) gear device(s) 23 (those gear devices 23 not
in
bypass mode) can be used to provide the hydraulic higher pressure total fluid
output.
It is recognized that the terms higher and lower are relative to the gear
device 20
working in non-bypass mode or otherwise having a greater number of gear
devices
23 in non-bypass mode, as compared to the higher pressure and reduced volume
provided by the remaining gear devices 23 that are hydraulically coupled to
the total
output of fluid from the gear device 20.
[0074] As noted, the gear device 20 can contain multiple gear devices 23
with
respective by pass vales 9, such that selective bypass (via bypass valve 9
operation)
of each gear device 23 within the gear device 20 can be implemented via
operational
control of the respective bypass valve 9 of the respective (i.e. associated
with) gear
device 23. It is also recognized that <zae bypass valve 9 can be associated
with and
therefore control the bypass mode with two of more gear devices 23, as
desired.
Another way to define bypass valve 9 operation is that bypass valve(s) 9 can
be
used to either engage hydraulically (via valve 9 close to block fluid flow
there-
through) or disengage hydraulically (via valve 9 open to allow fluid flow
there-
- 18 -
CA 02796539 2012-11-26
through) the respective associated gear device(s) 23 from the other gear
device(s)
23 of the gear device 20.
[0075] Therefore, in effect the use of the bypass valve(s) 9 provides for
hydraulic
decoupling of the associated gear device(s) 23 from the total output flow of
the
device 20 while at the same time providing for the associated gear device(s)
23 to
remain mechanically coupled in the gear cavity 25 with all of the other gear
devices
23 contained therein. This is advantageous for gear cooling and lubrication
purposes.
[0076] This can be repeated for more than one pump provided each includes a
solenoid valve (e.g. bypass valve 9), or any other means that allows a pump
gear
cluster to be by-passed from the total number of gear devices/clusters 23 of
the gear
device 20, and allows for repeated flow of the fluid within pump B. Since
pumps 23
are mechanically geared together, displacement can be identical and portion
(e.g.
50%) of each input is passed to the nearest pump 23 output, limited pressure
head
can be generated and the serial handoff can occur at minimal pressure. Upon
finally
arriving at a "working pump" 23, the carried portion (e.g. 50%) joins the
awaiting
portion (e.g. 50%), and total combined portions exit (positive displacement
device).
Pressure output of the gear device 23 can be dictated by the control valve 8
setting.
It will be understood that when the multi-cluster gear device 20 is engaged,
if only
one gear cluster device 23 is working, the by-pass loop allows for the rest of
the
gears to be kept lubricated and therefore cooled, i.e. whenever a situation
arises
where one or more pump gear cluster devices 23 is not working the gears do not
run
dry. In addition the gears are kept cool by continuous fluid flow.
[0077] In one embodiment, shown in Figure 11, more than one multi-gear cluster
device 20 may be used at one time. Figure 11 shows a first housing 99,
containing a
multi-gear cluster showing the secondary gears 24, and a second housing 101,
showing another multi-gear cluster including a main gear 22 connected to a
common
main shaft 104 and secondary gears 24 connected to common shafts 100. In such
an embodiment, the multi-gear cluster devices would be mechanically connected
together, e.g. along the one drive shaft or other shaft. Each device 20 may be
connected to a source of hydraulic fluid independently of the adjacent device
20. The
-19-
CA 02796539 2012-11-26
total volume output of the aggregated devices would be cumulative, i.e. the
sum of
the output of the individual devices 20. The advantage of using the device 20
in this
configuration is that it allows for a greater overall output based on the use
of a series
of multi-cluster devices versus using a series of two gear pumps. In other
words, if
two multi-cluster gear devices are used, each having a four cluster
configuration, the
total output is equivalent to 8 two gear traditional pumps. The output is
reached
using only 10 gears compared with 16 that would be used in the traditional
pump
arrangement. This means that the space requirement of the multi-cluster gear
device
is smaller compared to the traditional two gear pumps. In addition, less
components
generally means reduced RPM and less overall maintenance required.
Alternative Embodiments of Multi-cluster hydraulic gear device 20
[0078] Referring to Figure 12, shown is a multi-cluster hydraulic gear
device 20
showing an open gear cavity 25 of the housing 42. Ports 40 on either side of
their
respective gear devices 23 provide for ingress and egress of fluid through the
housing with respect to gear cavity 25. The present embodiment shows a three
gear
hydraulic gear device 20, however other gear numbers are contemplated, such
that
the number of gears is less than double the number of gear devices 23
contained
within the multi-cluster hydraulic gear device 20 (e.g. in the three gear case
shown,
three gears is less than 2 times 2 gear devices 23). Further, it is recognised
that in
order to inhibit blow-by effects, tolerances (e.g. clearance TOL) between a
radial
distal end surface 107 of teeth 108 and the adjacent inner surface 110 of the
gear
cavity 25 is minimized. Example clearance TOL are 1/2 to 1 thousandth of an
inch.
Further, as is shown in Figure 14a, the distance TOL is used to provide for a
minimized spaced apart configuration of the radial distal end surface 107 of
teeth
108 with the adjacent inner surface 110 of the gear cavity 25, so as to
inhibit contact
between the radial distal end surface 107 of teeth 108 with the adjacent inner
surface 110 to minimize the blow-by effect within a clearance zone 120. It is
recognised that practically, portions of the circumference of the gear are
spaced
apart from the inner surface 110 by a distance greater than the clearance TOL,
particularly in those regions outside of the clearance zone 120, for example
where
meshing of gear teeth between adjacent gears 102,106 occurs as well as in port
regions when the ingress and egress of hydraulic fluid occurs. It is
recognised that
- 20 -
CA 02796539 2012-11-26
the gear cavity 25 contains respective gear chambers, two for each of the gear
devices 23, e.g. one low pressure and one high pressure chamber associated
with
the respective port 40.
[0079] Due to separation distances between shafts 100 for the secondary
gears
102, in order to accommodate the main gear 106 positioned on shaft 104 between
the two secondary gears 102, and potential unequal hydraulic pressures at the
respective fluid ports 40, the gears 102 and/or the gear 106 can be forced
away from
one of their respective ports 40 and towards the other of their respective
ports 40
due to a differential in port pressures, i.e. the respective gear(s) would be
forced in a
direction lateral to the longitudinal axis of their shaft 100,104 For example,
where
the multi-cluster hydraulic gear device 20 is used as a pump, then inlet port
A would
be at a lower pressure than outlet port B and thus secondary gear 102 there-
between would be forced or otherwise biased by the fluid pressure differential
of the
ports A,B laterally away from port B and towards port A. In the present three
gear
example, the rotations of the gears is such that inlet port D would be at a
lower
pressure than outlet port C and thus secondary gear 102 there-between would
also
be forced or otherwise biased by the fluid pressure differential of the ports
C,D
laterally away from port C and towards port D. Thus it can be seen for some
configurations of the multi-cluster hydraulic gear device 20, each port side
of the
gear cavity 25 includes both a high pressure port and a low pressure port. In
other
words, each port side of the gear cavity 25 includes both an inlet port and an
outlet
port.
[0080] A consequence of the lateral movement of the secondary gears 102 with
respect to their longitudinal axis is that the separation clearance TOL is
reduced (see
Figure 14b), as the distal ends 107 of the teeth 108 are shifted (or otherwise
pushed
or drawn) closer towards the adjacent inner surface 110 of the gear cavity 25
during
operation of the multi-cluster hydraulic gear device 20. Accordingly, when the
separation clearance TOL is reduced to zero, any further shift will result in
undesirable contact between the distal ends 107 of the teeth 108 and the
adjacent
inner surface 110, as the gears 102, 106 rotate, thus causing abrasive wear of
the
teeth 108 material and/or the adjacent inner surface 110 material. It is
recognised
that during operation of the multi-cluster hydraulic gear device 20, the
actual
- 21 -
CA 02796539 2012-11-26
separation clearance TOL can vary due to variability in pressure input (and/or
output)
of the fluid ports, thus causing variability in the pressure differential
between
opposing ports A,B or C,D. For example, the variability in pressure
differential can
be caused due to variations in rotational speed of the gears 102,106 or can be
caused due to variations in inlet and/or outlet hydraulic fluid pressures due
to
variable operation of other hydraulic devices (e.g. line valves
opening/closing and/or
changing hydraulic load device or supply device conditions) connected via
hydraulic
lines with the ports 40. Thus a spike in normal operating fluid pressure (e.g.
during a
braking condition when the device 20 is used in a hydraulic braking system)
can
cause temporary contact between the teeth 108 material and/or the adjacent
inner
surface 110 material due to a sudden and transient increase in differential
fluid
pressures.
[0081] One mechanism to provide for acceptable material wear inside of the
gear
cavity 25 is to use a disposable (e.g. replaceable) sleeve 112, which is
inserted via
cavity face 115 of the gear cavity 25, between an inner surface 118 of the
housing
42 body forming the gear cavity 25 and the distal ends 107 of the teeth 108 of
the
gears 102, 106. In this case the inner wall 118 located in the clearance zone
120 is
positioned a combined distance of a thickness T of the sleeve 112 and the
clearance
TOL away from the nearest portion of the radial distal end surfaces 107 of the
teeth
108, of the respective gear 102, 106. The inner surface 110 material of the
sleeve
112 is selected so that if, and when, the distal ends 107 of the teeth 108
contact the
inner surface 110, the material of the sleeve 112 is preferentially abraded
over the
material of the teeth 108. One advantage to using the sleeve 112 is that it
can be
replaced with excessive wear and can be a relatively low cost part compared to
replacing damage or wear to the precision machined housing 42 itself (e.g. in
the
extreme case damage directly to the housing inner surface of the gear cavity
25 can
require replacement of the entire machined housing 42). For example, the
material
of the sleeve 112 can be made of a material that is metallurgically softer
than the
material of the gear teeth themselves. Otherwise, the material of the gear
teeth is of
a different hardness (e.g. harder) than that of the material of the sleeve
112.
[0082] Sleeve 112 can be comprised of ductile material (e.g. iron) that
will wear
away preferably as a particulate (e.g. powder) rather than as shavings. In
general,
- 22 -
CA 02796539 2012-11-26
sleeve 112 preferably wears away as a powder rather than shavings, which can
be
destructive to the internal components (e.g. gears 102,106) of device 20. In
some
embodiments, sleeve 112 can be comprised of an oil-impregnated alloy,
including
copper or iron alloys, for example, that help reduce friction and wear between
gears
102,106 and sleeve 112. Other examples of the sleeve 112 material can be
sintered
materials. These sintered materials are initially powder material held in a
mold and
then heated to a temperature below the melting point so that the atoms in
powder
particles diffuse across the boundaries of the particles, thus fusing the
particles
together and creating one solid piece as the sleeve 112. As noted, sleeve 112
has
tight tolerances with gears 102 and gear 106 with respect to the inner surface
110.
Tight tolerances using clearance TOL with sleeve 112 increases the efficiency
of the
gear device action of gear 102 and gear 106 to inhibit blow-by fluid loss
between the
gears 102,106 and interior surface 110 of housing 42, which would decrease the
operational efficiency (e.g. pump efficiency) of the device 20. Sleeve 112 can
include
fluid apertures 41 that align with fluid ports 40 of the housing 42.
[0083] In terms of coupling of the sleeve 112 with the gear cavity 25,
the sleeve
112 can be press fit (e.g. friction fit) into the gear cavity 25.
Alternatively, or in
addition to, the sleeve 112 can be fastened by a plurality of releasably
secure
fasteners 116 (see Figure 13), including examples such as but not limited to
pins,
threaded fasteners, etc., thus securing the sleeve 112 to the body of the
housing 42.
It is recognised that movement of the sleeve 112 within the gear cavity 25,
relative to
the body of the housing 42, can be undesirable due to the close tolerances of
the
tolerance clearance TOL.
[0084] In some embodiments, sleeve 112 can have a non-uniform thickness.
For
example, a portion (or portions) of sleeve 112 that is/are subject to
increased wear
may have increased thickness over that of adjacent portions, so that sleeve
112 can
have a longer service time before requiring replacement due to wear.
[0085] A hydraulic system can also be used to measure wear of sacrificial
sleeve
112. As sleeve 112 becomes more worn the efficiency of the device 20 action of
gears 102,106 decreases of the gear devices 23. By measuring fluid flow
relative to
RPM of the drive shaft that is coupled to gears 102,106, the hydraulic system
can
- 23 -
CA 02796539 2012-11-26
measure the efficiency of device 20 and thus wear of sleeve 112. Hydraulic
system
can be coupled to a vehicle data bus to indicate a service requirement for the
sleeve
112.
[0086] In some embodiments, sleeve 112 can be a partial sleeve 114 (or
sleeves)
that does/do not completely surround all of the distal radial surface ends107
of the
teeth 108 of gears 102,106, rather covers all or a portion of the interior
surface 118
of the gear cavity 25 extending about the distal ends 107 of the teeth 108 in
the
clearance TOL zone 120 (see Figure 14a). For example, referring to Figure 13,
the
sacrificial sleeve 112 has a plurality of sleeve portions 114-1, 114-2, 114-3,
114-4,
such that four sleeve portions 114 are shown, however it is recognised that
one or
more portions 114 can be used as desired. The partial sleeves 114 can be
positioned in the gear cavity 25 between the interior surface 118 of the
housing 42
and the radial distal end surfaces 107 of the teeth 108 of one or more of the
gears
102, 106. It is recognised that the individual sleeve portions 114 can extend
about
all or a portion of the circumference of the gears 102, 106 in the tolerance
zone 120.
Example portions of this extension can be such as but not limited to: over one
half
circumference but less than full circumference of the respective gear; up to
one half
circumference of the respective gear; up to one third circumference of the
respective
gear; up to one quarter circumference of the respective gear; etc. Further, it
is
recognised that the partial sleeve 114 may not include the portion of gear
cavity
surface 118 containing fluid ports 40 because these surface 118 portions are
adjacent to the meshing location of the gear teeth 108 and as such would not
come
into contact with gears 102,106, as greater clearance is provided in these
locations
for ingress and egress of hydraulic fluid with respect to the gear cavity 25.
[0087] In particular, the partial sleeve portion 114 can be positioned on
the inner
wall 118 of the gear cavity 25 and adjacent to the portion of the radial
distal end
surfaces 107 of the teeth 108 of the respective gear that are configured to
have the
predefined clearance TOL between the radial distal end surfaces 107 and the
adjacent gear cavity 25 surface ¨ e.g. surface 110 when sleeve 114 is used. In
this
case the inner wall 118 is positioned a combined distance of a thickness T of
the
inner sleeve portion 114 and the clearance TOL away from the nearest portion
of the
radial distal end surfaces 107 of the teeth 108, of the respective gear 102,
106.
- 24 -
CA 02796539 2012-11-26
Alternatively, the partial sleeve portion 114 can be used only for a portion
of a
clearance TOL zone 120 to provide for sacrificial (e.g. predetermined,
predefined,
preferred) wear surface 110 while the remaining portion of the clearance TOL
zone
120 can be provided by a non-sacrificial (e.g. non-predetermined, non-
predefined,
non-preferred) wear surface 118 of the housing 42 exposed in the gear cavity
25.
An example of this configuration is shown in Figure 14a, such that an area 120
having the predefined clearance TOL between the radial distal end surfaces 107
of
the teeth 108 (not shown for convenience) and the adjacent exposed gear cavity
25
surface (e.g. surface 110, surface 118, combined as surface 118 and surface
110),
such that it is recognised that surface 110 is provided in the gear cavity 25
by the
sleeve 114 and surface 118 is provided by the housing 42. In this example, it
is
contemplated that the lateral movement of the gear 102, 106 during hydraulic
loading is designed to move (and potentially contact) only the surface 110
rather
than the surface 118, as shown in Figure 14b.
[0088] Referring to Figure 15, shown is the housing 42 having a series of
one or
more cavities 122 in the inner wall 118 of the gear cavity 25. One or more of
the
sleeve portions 114-1,-2,-3,-4 of the segmented sleeve 114 is coupled to a
mounting
block 120, sized to be received in the respective cavity 122, thus positioning
the
sleeve 114 portion adjacent to the respective gear 102,106 when the gear
102,106 is
installed in the gear cavity 25. The mounting block 120 and sleeve 114 portion
114
can be referred to as a sleeve assembly 123. The mounting block 120 is
fastened to
housing via a press fit within the cavity 122 and/or by one or more fasteners
116
(e.g. threaded fasteners). The mounting blocks 120 can be integrally attached
to the
sleeve 114 portions, thus forming an integral sleeve assembly 123. The
mounting
blocks 120 can also be releasably coupled to the sleeve 114 portions (not
shown)
using appropriate fasteners, thus forming a multiple component sleeve assembly
123. Further, it is recognised that the material used to manufacture the
mounting
blocks 120 can be different from the material used to manufacture the sleeve
114
portions of the sleeve assembly 123 and/or gears 102,103. For example, only
the
sleeve 114 portion of the sleeve assembly 123 can be made of the preferential
wear
material (e.g. powder forming material) as discussed above. Referring to
Figure 16,
- 25 -
CA 02796539 2012-11-26
shown is an assembly of the segmented sleeve 114 prior to installation of the
plurality of gear devices 23 including the plurality of gears 102,106.
[0089] Referring to Figure 17, shown is the sleeve assembly 123 connected
to
the body of the housing 42 via connecting pin 124, once the mounting block 120
is
received in the cavity 122. The pin 124 is inserted via aligned hole 126 in
housing
42 with hole 128 in mounting block 120. Also shown is a seal 128 for
positioning
between the cavity 122 and the mounting block 120, used to inhibit leakage of
hydraulic fluid out of the gear cavity 25 via the cavity 122. The pin 124
connection
can also be used to provide for pivot of assembly 123 about the pivot point to
provide
for the sleeve 114 to move out of the way of the advancing gear 102,106 to
reduce
severity of sleeve 114 wear, due to potential contact between the gears
102,106 and
the sleeve 114.
[0090] Referring to Figure 18, shown is an alternative embodiment of the
sleeve
assembly 123, including a slider block 130 configured to move within the
cavity 122
relative to the mounting block 120. Within the sleeve assembly 123, the slider
block
130 is connected to the sleeve 114 and the slider block 130 is also movably
coupled
to the mounting block 120. In this embodiment, the mounting block 120 is
fixedly
connected to the housing in the cavity 122, such that the slider block 130 is
free to
move relative (referrer to by arrow RM) to the mounting block 120, thus
providing for
displacement of the sleeve 114 laterally to the axis of shaft 100,104 of the
gear
102,106, as the respective gear 102,106 also is displaced laterally (referred
to as
LD) due to fluid port pressure differentials as discussed above (see Figure
12). It is
recognised as the gear 102,106 moves towards the sleeve surface 110 (see
Figure
12) clearance TOL is reduced towards contact and therefore biases the sleeve
114
of the sleeve assembly 123 for movement within the cavity 122 in the same
direction
as the movement (e.g. shifting) of the gear 102,106. This relative movement of
the
sleeve 114 is advantageous, as the sleeve 114 can move out of the way of the
gear
102,106 as the gear 102,106 is laterally displaced due to the pressure
differential,
thus providing for reduced wear of the sleeve 114. It is recognised that a
coupling
mechanism 132 (see Figure 19) between the mounting block 120 and the sliding
block 130 provides for relative movement there-between. The cavity 122 (in
ghosted
view) in the Figure is shown enlarged, in order to illustrate the movement of
the
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CA 02796539 2012-11-26
slider block 130 therein. Is also recognised that the slider block 130 could
be
positioned outside of the cavity 122, and thus relative movement of the slider
block
130 would not be unduly restrained by the interior walls of the cavity 122.
[0091] One example of the coupling mechanism 132 is a tongue 134 and
groove
136 connection, such that the tongue 134 is slidably engaged with the groove
or
channel 136. It is recognised that the tongue 134 can be mounted on the slider
block 130 and the groove is positioned in the mounting block 120.
Alternatively, the
tongue 134 can be mounted on the mounting block 120 and the groove is
positioned
in the slider block 120. The coupling mechanism 132 can be of a dovetail cross
sectional shape, for example.
[0092] Referring to Figure 20, shown is a thrust plate 134 that is
positioned
between an end face 136 of the housing 42. As an example, the housing is made
up
out of a number of components 42-1, 42-2, 42-3, coupled together via a number
of
threaded fasteners 138. The housing components 42-1, 42-3 provide the end
faces
136 providing end walls for the gear cavity 25 in the housing portion 42-2. As
shown in Figure 22, the thrust plate is positioned in the gear cavity 25
between the
end face 136 and sidewalls 140 (or side face 140) of the gears 102,106, thus
providing for a separation clearance TOL2 of clearance approximately similar
in
magnitude to that of clearance TOL (e.g. 1/2 to 1 one thousandth of an inch).
During
operation of the hydraulic gear device 20, hydraulic fluid is allowed to flow
between
the thrust plate 134 and the end face 136, thus providing for balanced
pressure
forces to keep the thrust plate 134 from contacting the end surface 136 or the
sidewalls 140. The provision of separation clearance TOL2 as a tight tolerance
with
thrust plate 134 increases the efficiency of the gear device action of gear
102 and
gear 106 to inhibit blow-by fluid loss between the sidewalls 140 of the gears
102,106
and the adjacent face of the thrust plate 134. This fluid loss due to blow-by
would
decrease the operational efficiency (e.g. pump efficiency) of the device 20.
[0093] However, as discussed above, due to potential unequal hydraulic
pressures in the gear cavity 25 at the respective fluid ports 40, different
portions of
the thrust plates 134 can be forced away from or towards the nearest adjacent
port
40 to the thrust plate 134 portion. A consequence of this biasing of different
portions
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CA 02796539 2012-11-26
of the thrust plate 134 in respective different directions (e.g. either away
from or
towards) with respect to their respective adjacent port 40, is that the thrust
plate 134
can become warped due to a differential in port 40 pressures. For example, as
discussed for Figure 12, where the multi-cluster hydraulic gear device 20 is
used as
a pump, then inlet port A would be at a lower pressure than outlet port B and
thus
the portion of thrust plate 134 nearest port A would be drawn towards port A
while
the portion of thrust plate 134 nearest port B would be forced or otherwise
biased by
the fluid pressure away from the port B. In the present three gear example,
the
rotations of the gears 102,106 is such that inlet port D would be at a lower
pressure
than outlet port C and thus the portion of thrust plate 134 nearest port D
would be
drawn towards port D while the portion of thrust plate 134 nearest port C
would be
forced or otherwise biased by the fluid pressure away from the port C.
[0094] Accordingly, one can understand that as this port pressure differences
become more manifest due to increased operating pressures, the degree of warp
and/or twist of thrust plate 134 can become more and more pronounced. The
consequence of warp or twisting of the thrust plate 134 is that due to the
tight
tolerances of clearance TOL2, the degree of warping of the thrust plate 134
can
become such that the clearance TOL2 is breached by the warping and therefore
surface 142 opposing the sidewalls 140 of the gears 102,106 can come into
contact
therewith, thus causing undesirable wearing or abrading of the gear material
and/or
thrust plate material. The damage caused by this undesirable wear can result
in
undesirable increases in the clearance TOL2 (due to gear surface 140 wear
and/or
plate surface 142 wear) as well as damage to the gear teeth themselves due to
wear
material circulating in the gear cavity 25. This damage can be
realaized/expressed
as increase in blow-by of the fluid.
[0095] Referring again to Figure 20 and 21, the tendency of the thrust plate
134
to warp can be inhibited by the use of thrust bearings 144 positioned between
the
thrust plate 134 and the sidewall 140 of the gear (in this case, by example
only
shown as gear 106). The thrust bearings 144 can be positioned (e.g. via
friction or
press fit) in a recess 146 in the face 136 of the thrust plate 134. Thus,
where the
portion of the face 136 having the thrust bearing 144 moves into contact with
the
adjacent sidewall 140 of the gear 106, the rollers 148 of the thrust bearing
can ride
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CA 02796539 2012-11-26
on the surface of the sidewall 140, as the gear 106 rotates, thus inhibiting
wear of
the sidewall 140 as well as inhibiting further warping of the thrust plate
134. A
hardened washer or surface 147 can be optionally provided on the sidewall 140
in
the vicinity of contact with the rollers 148 of the thrust bearing 144, to
help reduce
wear of the sidewall 140 as well as to help reduce drag on the gear 106
operation
(e.g. slow down the gear 106 or otherwise introduce unnecessary additional
friction
forces to rotation of the gear 106). It is recognised that the shafts 100 as
well as
shaft 104 can be positioned on respective bearings 150 (e.g. roller), which
can be
mounted (e.g. press fit) into cavities 152 provided in the thrust plate 134
and/or in the
housing 42. Distance of the projection of the thrust bearing 144 from surface
of the
thrust plate can be similar to clearance TOL2, this providing for non-contact
between
thrust plate surface 134 and the sidewalls 140. It is recognised that the
thrust plates
134 can be floating between the face 136 and the sidewalls 140 of the gears
102,106, and thus the thrust plate 134 is not fixedly connected to the housing
via any
fasteners.
[0096] Referring to Figure 23, shown is a half section of the gear
assembly of
gears 102,106 with thrust plates 134. Show is an installed thrust bearing 144
in
recess 146, and hardened surface or washer 147 configured for coming into
contact
and providing a riding surface for the rollers 148. Noted are the shafts 100,
104 that
fit through apertures 156 of the thrust plates 134, such that sides of the
shaft
100,104 are free to move/rotate within the aperture 156.
[0097] Referring to Figure 24, shown is a thrust plate assembly 160 that
is fixedly
connected to the housing 42 via the fasteners 162, for example as a sandwich
design between housing portions 42-2 and 42-1 (not shown) or 42-3. It is also
recognised that housing portion 42-1 (see Figure 20) could be replaced by a
gearbox
housing (not shown), as desired. In this case, the shafts 100, 104 are mounted
on
an interior portion (e.g. race) 164 of bearings (e.g. roller) 166, and an
exterior portion
168 (e.g. cage) of the bearings 166 is mounted in respective cavity 170 of the
thrust
plate assembly 160. It is recognised that the area of surface 142 of thrust
plate 134
is less than area of surface 172 of the end housing portion 42-3 adjacent to
the
thrust plate assembly 160. This configuration is advantageous, as the force
Fin (due
to hydraulic pressure of the gear device fluid) directed inwards towards and
acting on
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CA 02796539 2012-11-26
the thrust plate assembly 160 is greater than a force Fout (due to hydraulic
pressure
of the gear device fluid) directed outwards towards and acting on the thrust
plate
assembly 160. As such, this configuration of differential surface areas
provides for a
net inward force of the thrust plate assembly 134 towards the gears 102,106
and
thus helps to relieve hydraulic bias of the thrust plate assembly 160 movement
away
from the gears 102,106 which would result in an increase in the clearance
TOL2.
[0098] Referring to Figures 25 and 26, in order to help maintain the axial
position
of the gears 102, 106 on their longitudinal axes, one example mechanism are
bushings 176 having a shoulder 178 thereon, which seats up against a sidewall
180
of the bearings 166. Alternatively, the shoulder 178 could be positioned (e.g.
machined) directly on the shaft 100, 104 upon which the gear 102, 106 is
mounted.
It is recognised that each of the gears 102,106 could be mounted on shafts
100,104
having the shoulders 180. It is recognised that each of the gears 102,106
could be
positioned adjacent to (or otherwise have bushings 176 integrally made with
the
gears 102,106) on shafts 100,104, such that it is the bushings 176 having the
shoulders 180.
[0099] Referring again to Figure 21, it is recognised that housing
portions 42-2
and 42-3 could be integrally machined out of one piece of material as housing
42,
such that integral housing portions 42-2 and 42-3 are not connected to one
another
by threaded fasteners as is the case in the housing 42 configuration of the
device 20
of Figure 24. As such, the thrust plate 134 could be configured as a floating
design
between the gears 102,106 and the end face 136 of the integral housing portion
42-3
(not shown), which is similar to the face 136 of separate housing portion 42-3
of
Figure 20. Further, the thrust plate 134 position in the integral housing 42
of Figure
21 is similar to that shown in Figure 20.
[00100] Alternatively, the housing portions of thrust plate assembly 160 and
housing portion 42-2 (see Figure 24) could be integrally machined out of one
piece
of material as housing 42. This configuration would also result in a
fixed
configuration (i.e. non-floating) for the thrust plate situated in the
integrated thrust
plate assembly 160 and housing portion 42-2.
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CA 02796539 2012-11-26
[00101] While this invention has been described with reference to illustrative
embodiments and examples, the description is not intended to be construed in a
limiting sense. Thus, various modification of the illustrative embodiments, as
well as
other embodiments of the invention, will be apparent to persons skilled in the
art
upon reference to this description. It is therefore contemplated that the
appended
claims will cover any such modifications or embodiments. Further, all of the
claims
are hereby incorporated by reference into the description of the preferred
embodiments.
[00102] Any publications, patents and patent applications referred to herein
are
incorporated by reference in their entirety to the same extent as if each
individual
publication, patent or patent application was specifically and individually
indicated to
be incorporated by reference in its entirety.
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