Note: Descriptions are shown in the official language in which they were submitted.
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AGI0072-02
Michael J. Eifert
SPRING LOADED SHAFT ASSEMBLY
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit under Title 35, U.S.C. 119(e)
of U.S. Provisional
Patent Application Serial No. 61/708,401, filed October 1, 2012 and entitled
SPRING LOADED
SHAFT ASSEMBLY, the entire disclosure of which is hereby expressly
incorporated by
reference herein.
BACKGROUND
1. Field of the Disclosure.
[0002] The present disclosure relates to a spring biased shaft
arrangement, and in
particular, to a spring biased shaft used to selectively engage internal
gearing of a transmission.
2. Description of the Related Art.
[0003] Large industrial machinery, such as earth moving equipment and
other
construction vehicles, may use individual power transmission units mounted at
the hub of each
driven wheel. These individual power transmission units are sometimes referred
to as "wheel
drives" and may house a transmission device which provides large gear
reduction for the heavy
loads, large wheels and low speeds frequently employed by such vehicles. Wheel
drives may
receive power from a drive shaft drivingly connected to the vehicle power
source and output a
lower-speed, higher-torque rotation.
[0004] In some configurations, gearing mechanisms of wheel drives are
selectively
engageable with the driven input shaft, such that the wheel drive is
configurable into driving and
free-wheeling configurations. In the driving configuration, the input shaft is
operably coupled to
the output hub via the gearing mechanism, while the free-wheeling
configuration renders the
input shaft operably decoupled from the output hub such that the wheel is free
to spin
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independent of influence by the vehicle power source. To achieve this
selective engagement,
some wheel drive units include a coupling shaft or sleeve which is axially
displaceable to
selectively engage the powered input to the gearing mechanism, and ultimately
to the output hub.
Generally speaking, such axially displaceable coupling shafts or sleeves are
manipulated by the
drive unit operator, either manually or automatically, to toggle the drive
unit between engaged
and disengaged configurations.
[0005] One known wheel drive unit with an axially translatable shaft which
operates as a
disconnect mechanism is disclosed in U.S. Patent No. 6,607,049 to Cigal. A
portion of this
known mechanism is illustrated as disconnect mechanism 112 in Figs. lA and 1B.
Mechanism
112 includes disconnect shaft 114, which is axially displaceable between
engaged and
disengaged positions. More particularly, shaft 114 is shown in the engaged
position in Fig. IA,
in that shaft 114 is rotatably fixed to both input coupler 118 and output gear
122, thereby
transferring motive force and torque therebetween. Spring 168 is compressed by
application of
force F (Fig. 1B) when disconnect shaft 114 is moved from the engaged position
to the
disengaged position, and operates to bias shaft 114 back toward the engaged
position. Spring
168 is interposed between thrust washers 178 positioned at respective axial
terminal ends of
spring 168. At the input-side axial end of spring 168, thrust washer 178 abuts
a shoulder formed
in the spindle of the wheel drive, while the output-side axial end of spring
168 utilizes retaining
ring 124. Retaining ring 124 is connected to a corresponding groove formed in
disconnect shaft
114. The retaining ring groove formed in shaft 114 reduces the overall
diameter of shaft 114 in
the vicinity of retaining ring 124, by a sufficient amount that the minor
diameter of shaft 114
(i.e., the smallest diameter) is the diameter of the retaining ring groove.
[0006] In the context of wheel drive mechanisms, substantial force and
torque may be
transmitted via the above described axially translatable disconnect shafts.
Accordingly, it is
desirable to produce disconnect shaft arrangements and assemblies which
maximize power
transmission capability while avoiding unnecessary cost, weight and/or size.
Therefore, what is
needed is a disconnect shaft arrangement that is robust, cost effective and
capable of handling a
large amount of torque and force for a given shaft size.
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SUMMARY
[0007] The present disclosure provides a disconnect shaft arrangement
which interposes
a biasing element between a shoulder formed on the disconnect shaft and a cup-
shaped washer,
in which the cup-shaped washer is sized and configured to be axially
displaceable with respect to
the disconnect shaft. The cup-shaped washer selectively engages an axially
fixed adjacent
structure, such as a thrust washer, during disengagement of the disconnect
shaft and attendant
spring compression. The present disconnect shaft arrangement obviates the need
for a retaining
ring against which the spring compresses, such that the relatively deep
retaining ring groove
needed for such a retaining ring need not be cut into the outer surface of the
disconnect shaft.
Removal of material in the outer surface of the shaft is therefore minimized,
such that the torque
transmission capability of the shaft is maximized.
100081 In one form thereof, the present disclosure provides a transmission
disconnect
system including: a disconnect shaft axially moveable between an engaged
position and a
disengaged position along a longitudinal shaft axis, the disconnect shaft
having a first end
defining a first minor diameter and a second end opposite the first end; a
first torque transmitter
rotatably fixed to the first end of the disconnect shaft such that a torque is
transmissible between
the first torque transmitter and the disconnect shaft; a second torque
transmitter rotatably fixed to
the second end of the disconnect shaft when the disconnect shaft is in the
engaged position and
rotatably decoupled from the second end of the disconnect shaft when the
disconnect shaft is in
the disengaged position, such that the torque is transmissible from the first
torque transmitter to
the second torque transmitter via the disconnect shaft when the disconnect
shaft is in the engaged
position; a cup-shaped washer having a longitudinal washer axis, the cup-
shaped washer
including: a sidewall having an length measured along the longitudinal washer
axis; and a
mounting flange extending radially inwardly from a first terminal axial end of
the sidewall to
define a mounting bore having a diameter larger than the first minor diameter
of the disconnect
shaft, the first end of the disconnect shaft axially translatable within the
mounting bore; a second
axial end of the sidewall opposite the first axial end and defining a seating
surface transverse to
the longitudinal washer axis, the second axial end disposed nearer to the
first end of the
disconnect shaft than the first axial end when the cup-shaped washer is
mounted to the
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,
disconnect shaft; and a biasing element constrained against axial displacement
by the mounting
flange of the cup-shaped washer and biasing the disconnect shaft into the
engaged position.
100091 In another form thereof, the present disclosure provides a
transmission including a
disconnect shaft axially moveable between an engaged position and a disengaged
position along
a longitudinal shaft axis, the disconnect shaft including a first end defining
a first minor
diameter; a second end opposite the first end; and a central portion disposed
between the first end
and the second end, the central portion defining a shoulder extending radially
outward; an input
coupler rotatably fixed to the first end of the disconnect shaft such that a
torque is transmissible
between the input coupler and the disconnect shaft; an output gear rotatably
fixed to the second
end of the disconnect shaft when the disconnect shaft is in the engaged
position and rotatably
decoupled from the second end of the disconnect shaft when the disconnect
shaft is in the
disengaged position, such that the torque is transmissible from the input
coupler to the output
gear via the disconnect shaft when the disconnect shaft is in the engaged
position; a cup-shaped
washer having a longitudinal washer axis, the cup-shaped washer including: a
sidewall having
an length measured along the longitudinal washer axis; and a mounting flange
extending radially
inwardly from a first terminal axial end of the sidewall to define a mounting
bore having a
diameter larger than the first minor diameter of the disconnect shaft, the
first end of the
disconnect shaft axially translatable within the bore; a second axial end of
the sidewall opposite
the first axial end and defining a seating surface transverse to the
longitudinal washer axis; a
seating structure interposed between the input coupler and the output gear,
the seating structure
axially fixed and having a bore large enough to allow passage of the
disconnect shaft
therethrough, the bore small enough to prevent passage of the second axial end
of the cup-shaped
washer therethrough; and a biasing element captured between the cup-shaped
structure and
shoulder of the disconnect shaft, such that the biasing element urges the
seating surface of the
cup-shaped washer toward the seating structure, and urges the disconnect shaft
into the engaged
position.
100101 In yet another form thereof, the present disclosure provides
a cup-shaped washer
including: an annular sidewall having an length measured along a longitudinal
washer axis; and a
mounting flange extending radially inwardly from a first terminal axial end of
the sidewall to
define a mounting bore having a splined inner periphery adapted to be
rotatably fixe to a splined
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outer surface of a shaft; and a seating flange extending radially outwardly
from a second terminal
axial end of the sidewall opposite the first terminal axial end, the seating
flange defining a
seating surface substantially perpendicular to the longitudinal washer axis.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The above-mentioned and other features and advantages of the
present disclosure,
and' the manner of attaining them, will become more apparent and the invention
itself will be
better understood by reference to the following description of an embodiment
of the invention
taken in conjunction with the accompanying drawings, wherein:
[0012] Fig. lA is a an elevation, cross-sectional view of a portion of a
wheel drive
utilizing a known spring loaded shaft assembly arrangement, with the
disconnect shaft shown in
an engaged position;
[0013] Fig. 1B is an elevation, cross-sectional view of the portion of the
wheel drive of
Fig. 1A, with the disconnect shaft shown in a disengaged position;
[0014] Fig. 2A is an elevation, cross-sectional view of a wheel drive
transmission
assembly utilizing a disconnect shaft arrangement made in accordance with the
present
disclosure, in which the disconnect shaft shown in an engaged position;
[0015] Fig. 2B is an elevation, cross-sectional view of a portion of the
transmission
assembly shown in Fig. 2A, illustrating the disconnect shaft in a disengaged
position;
100161 Fig. 3A is an elevation, cross-sectional partial view of the
transmission disconnect
system shown in Fig. 2A, illustrating only the disconnect shaft and adjacent
components in their
respective engaged configurations;
[0017] Fig. 3B is an elevation, cross-sectional view of the transmission
disconnect
system shown in Fig. 3A, with the components shown in their respective
disengaged
configurations;
[0018] Fig. 4 is a perspective view of a cup-shaped washer made in
accordance with the
present disclosure;
[0019] Fig. 5 is an elevation, cross-sectional view of the cup-shaped
washer shown in
Fig. 4;
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100201 Fig. 6A is an elevation, sectional view of a disconnect shaft made
in accordance
with the present disclosure; and
[0021] Fig. 6B is an enlarged elevation view of a portion of the shaft
shown in Fig. 6A,
illustrating a snap ring groove formed therein.
[0022] Corresponding reference characters indicate corresponding parts
throughout the
several views. The exemplification set out herein illustrates an exemplary
embodiment of the
invention, and such exemplification is not to be construed as limiting the
scope of the invention
in any manner.
DETAILED DESCRIPTION
[0023] Figs. 2A and 2B illustrate wheel drive transmission unit 10
including transmission
disconnect system 12 in engaged and disengaged configurations, respectively.
As described in
detail below, transmission disconnect system 12 is engaged when disconnect
shaft 14 has first
end 16 rotatably affixed to input coupler 18, and has a second end 20
rotatably affixed to output
gear 22. Thus, in the engaged position shown in Fig. 2A, disconnect shaft 14
rotatably fixes
input coupler 18 to output gear 22. By contrast, Fig. 2B illustrates a
disengaged configuration of
transmission disconnect system 12 in which force F has been applied to
disconnect shaft 14 to
axially displace shaft 14 toward input coupler 18. When so displaced, second
end 20 becomes
rotatably decoupled from output gear 22. Although coupler 18 (having internal
splines) and gear
22 (having external splines) are used for input and output torque transmitters
in the exemplary
embodiment illustrated in the figure, it is of course contemplated that any
combination of gears
and couplers may be used. For purposes of the present disclosure, "gearing
component" refers to
couplers or other gearing components with internal splines, gears or other
gearing components
with external splines, and/or components with both internal and external
splines.
[0024] As described in detail below, transmission disconnect system 12
includes cup-
shaped washer 24 to facilitate toggling of disconnect shaft 14 between the
engaged and
disengaged positions, while maximizing the capacity of disconnect shaft 14 to
transfer torque
between input coupler 18 and output gear 22.
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1. Wheel Drive Unit
100251 In the exemplary embodiment illustrated in Figs. 2A and 2B,
transmission
disconnect system 12 is used to selectively engage or disengage planetary gear
system 26 housed
within wheel drive transmission unit 10. Planetary gear system 26 is engaged
when disconnect
shaft 14 is rotatably fixed to output gear 22 (Fig. 2A), which in turn drives
wheel hub 28 with a
substantial gear reduction relative to input coupler 18 as described in
further detail below.
100261 Wheel drive transmission unit 10 may be mounted to a vehicle
frame via
mounting holes 30, establishing spindle 32 as the component of transmission
unit 10 that is
rotationally and axially fixed with respect to the other components thereof. A
powered shaft (not
shown) is rotatably fixed to input coupler 18 and operably connected to a
vehicle power source,
such as an engine, battery bank, or the like. Inner, female splines formed
along the bore of input
coupler 18 engage male outer splines 34 formed along a portion of the outer
surface of first end
16 of disconnect shaft 14, thereby rotatably fixing disconnect shaft 14 to
input coupler 18. When
disconnect shaft 14 is in the disengaged position shown in Fig. 2B, motive
force provided to
input coupler 18 serves only to rotate disconnect shaft 14. On the other hand,
when disconnect
shaft 14 is in the engaged position as shown in Fig. 2A, motive force provided
to input coupler
18 is transmitted to output gear 22 via disconnect shaft 14, thereby providing
driving torque to
wheel hub 28 via planetary gear system 26 (as further described below).
[0027] Second end 20 of disconnect shaft 14 includes male outer
splines 36, which are
sized and configured to intermesh with correspondingly formed female inner
splines within the
bore of output gear 22 (Fig. 2A). When so engaged, disconnect shaft 14 and
output gear 22 are
rotatably affixed to one another such that torque is transmissible to output
gear 22 from input
coupler 18. Output gear 22, in turn, acts as a sun gear in planetary gear
system 26, with outer
splines of sun gear 22 engaging correspondingly formed outer splines on a
plurality of planet
gears 38. As sun gear 22 rotates, planet gears 38 orbit sun gear 22 around
longitudinal axis A1 of
disconnect shaft 14 (which is coaxial with input coupler 18 and output gear
22), such that planet
gears 38 circumnavigate disconnect shaft 14. Planet gears 38, in turn, are
rotatably coupled to
gear carrier 40 via planet shafts 42, so that the circumnavigation of planet
gears 38 about sun
gear 22 rotates gear carrier 40 about axis Al.
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[0028] The outer splines of planet gears 38 also engage correspondingly
formed inner
splines of ring gear 44, thereby causing ring gear 44 to rotate when sun gear
22 is rotating
(although at a much slower speed). Ring gear 44, in turn, is affixed to wheel
hub 28 (as well as
to transmission cover 46) via bolt 48. Thus, wheel hub 28 rotates at the same
rotational speed as
ring gear 44, thereby rotating a wheel connected to wheel hub 28 (i.e., by
wheel connector bolts
50).
[0029] Gear carrier 40 is also in splined engagement with outer splines
formed on idler
gear 52, such that rotation of gear carrier also rotates idler gear 52 as
planet gears 38
circumnavigate disconnect shaft 14. Idler gear 52, in turn, meshingly engages
outer splines of
secondary planet gears 54, which are rotatably coupled to secondary gear
carrier 56 via
secondary planet shafts 58. Secondary gear carrier 56 is rotatably coupled to
spindle 32, thereby
facilitating circumnavigation of secondary planet gears 54 about idler gear
52. Planet gears 38,
54 cooperate with idler gear 52 and ring gear 44 to provide substantial
reduction in the rotational
speed of ring gear 44, and therefore also wheel hub 28, as compared with the
rotational speed of
input coupler 18.
[0030] To reconfigure disconnect shaft 14 from the engaged to the
disengaged position,
force F (Figs. 2B and 3B) is applied along axis A1 to axially displace
disconnect shaft 14 out of
splined engagement with output gear 22 (and therefore also further into
splined engagement with
input coupler 18). In the illustrated embodiment, such application of force
may be provided
manually by the user of wheel drive transmission unit 10, i.e., by pushing on
the terminal end of
second end 20 of disconnect shaft 14. As used herein, "terminal end" refers to
the axial terminus
of a structure, (e.g., shaft 14, cup-shaped washer 24 or spring 68) beyond
which no material of
the structure extends. Exemplary embodiments of mechanisms which may be used
to facilitate
reconfiguration of disconnect shaft 14 between the engaged and disengaged
positions may be
found in U.S. Patent No. 6,607,049 to Cigal filed March 6, 2001 and entitled
"Quick Disconnect
for an Integrated Drive Unit" and U.S. Patent Application Publication No.
2012/0031212, filed
May 9, 2011 and entitled "Quick Disconnect for a Drive Unit," the entire
disclosures of which
are hereby expressly incorporated by reference herein.
[0031] Although transmission disconnect system 12 is illustrated in the
context of wheel
drive transmission unit 10 shown in Figs. 2A and 2B and described in detail
above, it is
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contemplated that transmission disconnect system 12 may also be used in other
systems in which
first and second torque transmitters axially spaced from one another are to be
selectively coupled
and decoupled from one another by disconnect shaft 14. Moreover, transmission
disconnect
system 12 may be used for any transmission application, where "transmission"
refers to any
mechanism for transferring motive force from an input to an output. Changes in
torque and
speed between the input and output, such as those changes accomplished by use
of planetary gear
system 26 described above, need not be performed by a transmission made in
accordance with
the present disclosure.
2. Transmission Disconnect System
100321 For example, turning to Figs. 3A and 3B, disconnect shaft 14 is
shown
independently of most components within wheel drive transmission unit 10,
illustrating only the
components which interact directly with disconnect shaft 14. Broadly speaking,
disconnect shaft
14 is rotatably fixed to input coupler 18 (i.e., a torque transmitter) and is
selectively rotatably
fixed to output gear 22 (i.e., a second torque transmitter). In the
illustrated exemplary
embodiment, disconnect shaft 14 includes central portion 60 having diameter Ds
(Fig. 6A)
larger than diameters DFs DSs (Fig. 6A) of first and second ends 16, 20
respectively, thereby
creating first shoulder 62 and second shoulder 64 at the axial ends of central
portion 60. As
illustrated, second shoulder 64 bears against washer 66 in the engaged
position. Washer 66, in
turn, is axially fixed within transmission unit 10, so that such abutment
defines the end of axial
travel of disconnect shaft 14 toward output gear 22. First shoulder 62
provides a bearing surface
for the output-side axial end of biasing element 68, while the opposing input-
side axial end of
biasing element 68 abuts cup-shaped washer (as described in greater detail
below).
100331 In the illustrated embodiment, biasing element 68 is a compression
spring which
is slightly compressed in the engaged position of Fig 3A and more fully
compressed in the
disengaged position of disconnect shaft shown in Fig 3B. Thus, spring 68 urges
disconnect shaft
14 toward its engaged position, and reconfiguration of disconnect shaft 14
into the disengaged
position requires that force F (Fig. 3B) overcomes such biasing force (as well
as any frictional
forces which may be present on disconnect shaft 14).
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,
[0034] Cup-shaped washer 24 is illustrated in Figs 4 and 5. Washer
24 includes sidewall
70 having a generally arcuate configuration, such as a cylindrical or a
slightly conical shape,
such that sidewall 70 defines longitudinal axis A2 of washer 24. However, it
is appreciated that
sidewall could take any cross-sectional profile while still defining a
generally longitudinal
structure having axis A2. At one axial terminal end of sidewall 70 (i.e., the
output-side axial
end), mounting flange 72 extends radially inward toward axis A2 and defines
washer bore 74.
Bore 74 includes a plurality of gear splines formed around the periphery
thereof, which are sized
and configured to engage outer splines 34 at first end 16 of disconnect shaft
14 as described in
further detail below.
[0035] At the opposing (i.e., input-side) axial terminal end of
sidewall 70, seating flange
76 extends radially outwardly away from axis A2. This outward extension of
seating flange 76
provides a generally planar seating surface 84 (Fig. 5) which bears against
thrust washer 78 (Fig.
3B) and thereby maintains proper alignment and coaxiality of longitudinal axis
A1 of disconnect
shaft 14 and longitudinal axis A2 of cup-shaped washer 24 as shaft 14 moves
axially through
bore 74. More particularly, when seating surface 84 of seating flange 76 bears
against the
adjacent surface of thrust washer 78, the planar configuration of seating
surface 84 and the
perpendicularity of such plane with respect to longitudinal axes A1, A2
ensures that axes AI, A2
remain parallel and coincident, and thereby ensures that first end 16 of
transmission shaft 14
remains able to smoothly slide within bore 74 of washer 24 without binding or
creating undue
friction.
[0036] Mounting 86 (Fig. 5) of mounting flange 72 provides the
bearing surface for the
input-side axial terminal end of spring 68. As best seen in Fig. 5, sidewall
70 of washer 24
defines cavity 80 extending axially from inner surface 82 of mounting flange
72 and seating
surface 84 of seating flange 76, which provides a space for axial travel of
lock ring 90 (as shown
in Figs. 3A and 3B, and described in detail below).
[0037] In the exemplary embodiment illustrated in Fig. 5, cup-shaped
washer 24 defines
overall axial extent E of 0.65 inches between opposing axial terminal ends
thereof. Major
diameter Dmw, defined by the radial extent of seating flange 76, is 1.72
inches. Diameter Dsw=
defined by sidewall 70, is 1.50 inches. In this exemplary embodiment,
thickness T is 0.0897
inches throughout the material of cup-shaped washer 24. Accordingly, this
exemplary
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embodiment of washer 24 is sized and configured for use in a standard
commercial wheel drive,
such as transmission unit 10 shown in Fig. 2A. One such exemplary transmission
unit is the
Model 8 Power Wheel Planetary Gear Drive available from Auburn Gear, Inc. of
Auburn,
Indiana. Power Wheel is a registered trademark of Auburn Gear, Inc. of
Auburn, Indiana.
[0038] Moreover, the exemplary thickness T specified above facilitates
production of
cup-shaped washer 24 by a stamping process, thereby facilitating production of
washer 24 in
large volumes at low cost, while also imparting sufficient strength and
rigidity to washer 24 to
ensure minimal material deformation and long service life in use. When
produced by stamping,
sidewall 70 includes a slight amount of draft, such that sidewall 70 is
slightly conical (with
diameter Dsw decreasing slightly toward mounting flange 72). In this exemplary
stamped
embodiment, washer 24 is made from steel, such as 1010 carbon steel.
[0039] Bore 74 of washer 24 is sized to allow first end 16 of disconnect
shaft 14 (and
outer splines 34) to be received therein upon assembly and use of transmission
disconnect system
12. In the exemplary embodiment illustrated in Figs. 3A and 4, bore 74
includes inner splines 88
formed around the periphery thereof which matingly engage outer splines 34 to
rotatably fix
washer 24 to disconnect shaft 14, while also having a clearance fit that
allows free axial travel of
washer 24 with respect to disconnect shaft 14. This rotatably fixed
arrangement prevents any
relative rotation of washer 24 with respect to spring 68 during operation of
transmission unit 10,
thereby protecting spring 68 from friction and/or torsional movement at its
area of contact with
mounting flange 72. However, it is contemplated that bore 74 may exclude
splines 88.
[0040] Whether including or excluding splines 88, the smallest diameter
defined by bore
74, i.e., minor diameter Dgw' (Fig. 5), is larger than the minor diameter DFsi
of first end 16 of
disconnect shaft 14 (Fig. 6A), while the largest diameter defined by bore 74,
i.e., major diameter
Dgw, is also larger than major diameter DFs of first end 16. This allows cup-
shaped washer 24 to
axially slide over the outer surface of first end 16 freely. In an exemplary
embodiment, major
diameter DFs of first end 16 of shaft 14 (i.e., at the lands of outer splines
34) is between 0.994
inches and 0.998 inches, and the corresponding major diameter of bore 74 is
equal to 1.0 inches
or greater. The clearance between the respective minor diameters DFS1, Dgw' of
first end 16 and
bore 74 may be the same or similar.
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[0041] In an exemplary embodiment, second end 20 of disconnect shaft 14
defines major
diameter Dss with a corresponding minor diameter Dss' defined by the depth of
outer splines 36.
Diameters Dss, Dss' may be any diameters as appropriate to allow outer splines
36 to mate with
the corresponding inner splines of output gear 22, and may be the same or
different from
diameter DFs of first end 16. In one exemplary embodiment diameter Dss is
between 0.854 and
0.859 inches.
[0042] Diameter Dcs (Fig. 6A) of central portion 60 may be any diameter
larger than
diameters DFS and Dss, such as 1.30 inches in the above-described exemplary
embodiment. The
overall axial length L of disconnect shaft 14 may be about 9 inches in this
exemplary
embodiment, with first and second ends 16, 20 and central portion 60 occupying
whatever
portion of overall length L is needed as required or desired for a particular
application. Of
course, it is contemplated that disconnect shaft 14 may take on other sizes
and configurations for
larger or smaller applications or other alternative designs.
[0043] Lock ring 90 is provided to constrain the axial travel of cup-
shaped washer 24
toward input coupler 18, as illustrated in Fig. 3A. With disconnect shaft 14
in the engaged
position as shown in Fig. 3A, spring 68 is extended and cup-shaped washer 24
is biased into
abutting engagement with lock ring 90 as illustrated. The axial position of
lock ring 90 is
designed to ensure that gap 92 is maintained between seating surface 84 of
seating flange 76 and
the adjacent surface of thrust washer 78 as illustrated in Fig. 3A. In an
exemplary embodiment,
extent EG of gap 92 is between 0.010 inches and 0.016 inches. Gap 92 allows
washer 24 to
rotate together with disconnect shaft 14 without frictional interference from
thrust washer 78,
which is axially and rotationally fixed to the adjacent structures of
transmission unit 10.
[0044] To retain lock ring 90 in the desired axial position upon first end
16, notch 94
may be provided along the outer surfaces or lands of outer splines 34 as shown
in Fig. 6B. In an
exemplary embodiment, notch 94 is 1.4 inches from the axial terminal end of
first end 16, which
provides proper axial spacing to create gap 92 in the engaged position of
shaft 145 as described
above. Notch 94 may be small, as it accommodate a relatively small lock ring
90 (e.g., a lock
ring having a nominal inside diameter of 0.925 inches with a nominal thickness
of 0.042 inches).
Moreover, lock ring 90 may be a relatively small, thin component because lock
ring 90 needs
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,
only to restrain the minimal biasing force placed upon lock ring 90 by spring
68 in its nearly
fully extended configuration.
[0045] In an exemplary embodiment, notch 94 is between 0.046 and
0.052 inches wide
and reduces the major diameter of splines 34 by between 0.035 and 0.045
inches. This minimal
reduction in diameter and minimal overall size of notch 94 minimizes any
stress riser effect
which may result from the addition of notch 94, and ensures that the overall
minor diameter of
first end 16 of disconnect shaft 14 is the minor diameter of splines 34 rather
than the minor
diameter created by notch 94. Stated another way, notch 94 extends into the
material of shaft 14
less than splines 34. Accordingly, the maximum torsional strength of first end
16 is the same or
nearly the same both before and after notch 94 is formed in shaft 14.
[0046] When force F is applied to disconnect shaft 14 as shown in
Fig. 3B, shaft 14 is
reconfigured into the disengaged position. As the reconfiguration begins,
axial displacement of
first end 16 of shaft 14 (and therefore, also of lock ring 90) toward input
coupler 18 allows
seating flange 76 to come into contact with the adjacent surface of thrust
washer 78. Thereafter,
further axial movement of disconnect shaft 14 toward the fully disengaged
position of Fig. 3B
compresses spring 68, which is captured between mounting flange 72 of washer
24 and shoulder
62 of shaft 14 and constrained against axial displacement toward input coupler
18 by washer 24.
As this compression occurs, lock ring 90 axially traverses the annular space
96 formed between
an inner surface of sidewall 70 of washer 24 and the adjacent outer surface
defined by the lands
of splines 34 on first end 16 of shaft 14. Overall axial extent E (Fig. 5) of
washer 24, and more
particularly the axial extent of cavity 80, are sufficient to allow sufficient
axial travel of lock ring
90 to fully disengage outer splines 36 of second end 20 of shaft 14 from the
corresponding inner
splines of output gear 22. More particularly, the axial extent of cavity 80
allows lock ring to
remain within annular space 96 as disconnect shaft is reconfigured from the
engaged position of
Fig. 3A to the disengaged position of Fig. 3B. Meanwhile, washer 24 axially
travels up outer
splines 34, thereby allowing first end 16 to protrude more deeply into the
bore formed within
input coupler 18 while seating flange 76 remains seated upon thrust washer 78.
[0047] When force F is removed from disconnect shaft 14, spring 68
is allowed to bias
outer splines 36 of second end 20 back into engagement with output gear 22.
Provided such
splines are properly aligned, the biasing force of spring 68 will return
disconnect shaft 14 to the
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BDDBOI 9483443v2
CA 02791767 2012-10-05
,
engaged position. As this return to the engaged position completes, lock ring
90 comes into
contact with inner surface 82 of mounting flange 72, and lock ring 90 draws
cup-shaped washer
24 out of engagement with thrust washer 78. This frees washer 24 to rotate
without frictional
interaction with thrust washer 78.
[0048] Moreover, rotation of cup-shaped washer 24 with respect to
thrust washer 78
while disconnect shaft 14 is in the disengaged configuration of Fig. 3B will
not occur in normal
operation, as there is no normal need or benefit to apply motive force to
input coupler 18 when
such motive force cannot be transmitted to output gear 22. Although some such
rotation may
occur during maintenance or diagnostic procedures, no significant wear of cup-
shaped washer 24
or thrust washer 78 will occur during operation of transmission unit 10
because no contact
therebetween occurs when disconnect shaft 14 is positioned to transmit torque
between input
coupler 18 and output gear 22.
[0049] While this disclosure has been described as having exemplary
designs, the present
disclosure can be further modified within the spirit and scope of this
disclosure. This application
is therefore intended to cover any variations, uses, or adaptations of the
disclosure using its
general principles. Further, this application is intended to cover such
departures from the present
disclosure as come within known or customary practice in the art to which this
disclosure
pertains and which fall within the limits of the appended claims.
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BDDBOI 9483443v2
