TITLE OF INVENTION
[0001] Mechanical Locking Differential Lockout Mechanism.
CROSS-REFERENCE TO RELATED APPLICATIONS
[0002] This application is a continuation-in-part (CIP) of co-pending
application U.S. Serial No. 11/354,627, filed February 15, 2006, in the name of
Robert J. Kyle, Keith E. Morgensai, Thomas L. Sape and Gregory L. Heatwole
for a "Mechanical Locking Differential Lockout Mechanism".
BACKGROUND OF THE DISCLOSURE
[0003] The present invention relates to differential gear mechanisms, and
more particularly, to such mechanisms of the type commonly referred to as
"locking differentials". More specifically, the present invention relates to
mechanisms of the type also referred to as "mechanical lockers", i.e., locking
differentials in which the locking function occurs in response to the operation of
a mechanical device, as opposed to hydraulic actuation or electromagnetic
actuation.
[0004] A conventional locking differential made by the assignee of the
present invention utilizes a flyweight mechanism to initiate the lock-up of the
differential clutch, wherein the flyweight mechanism then retards rotation of the
cam plate relative to the differential input (i.e., the ring gear and differential
case). Locking differentials of the type that utilize a flyweight mechanism to
initiate clutch engagement are now well known, and may be made in
accordance with the teachings of any one or more of U.S. Pat. Nos. 3,606,803;
5,484,347, and 6,319,166, all of which are assigned to the assignee of the
present invention and incorporated herein by reference. However, it should be
understood that the present invention is not limited to only locking differentials
that are made in accordance with the teachings of the cited patents.
[0005] The locking differentials of the type made and sold commercially by
the assignee of the present invention have been in widespread commercial

usage for many years, and have performed in an extremely satisfactory manner,
especially on vehicles which operate, for at least part of their duty cycle, on
rough, uneven terrain, or under conditions of poor traction. Such locking
differentials perform especially well when the vehicle is operating on what is
referred to as a "split- u" surface, i.e., wherein the drive wheel on one side of the
vehicle has fairly good traction, and the drive wheel on the other side of the
vehicle has very poor traction. In such operating conditions, the locking
differential will engage the locking clutch, thus driving both drive wheels at the
input speed to the differential case (i.e., the speed of rotation of the input ring
gear).
[0006] One situation that has been observed, in which the conventional
locking differential does not perform in a satisfactory manner, is when a vehicle
equipped with a mechanical locking differential is operating in a condition in
which "spin-out" of one of the driving wheels is inherent. For example, if the
vehicle is operating with a mini-spare (i.e., a spare tire which, for purposes of
saving space in the trunk, is substantially smaller than the "normal" tires), the
difference in tire diameter will cause operation of the differential flyweight
mechanism, and lock-up of the differential clutch pack, even as the vehicle is
operating in a "straight-ahead" mode.
BRIEF SUMMARY OF THE INVENTION
[0007] Accordingly, it is an object of the present invention to provide an
improved differential gear mechanism, of the "mechanical locker" type, in which
it is possible to, in some manner, control operation of the mechanical device
that normally initiates engagement of the differential clutch, wherein such
control is not dependent on only the normal mode of operation of the
mechanical device.
[0008] It is a more specific object of the present invention to provide such an
improved differential gear mechanism in which it is possible to "lock-out" or to
prevent the operation of, a flyweight mechanism which reacts to the speed
difference between the two differential side gears and initiates engagement of

the differential clutch.
[0009] The above and other objects of the invention are accomplished by the
provision of an improved differential gear mechanism comprising a gear case
defining a gear chamber, a differential gear set disposed in the gear chamber,
and including at least one input gear and a pair of output gears defining an axis
of rotation. A lock-up clutch is operable to retard differentiating action, and
included is an actuating means for actuating the lock-up clutch. The lock-up
clutch is operable between an engaged condition, effective to retard relative
rotation between the gear case and the output gears, and a disengaged
condition. The actuating means includes cam means operable to affect the
engaged condition of the lock-up clutch, and retarding means operable to
engage the cam means and retard rotation of one member of the cam means.
The retarding means comprises a flyweight mechanism rotatable about an axis
oriented generally parallel to the axis of rotation of the differential gear
mechanism, the flyweight mechanism being rotatable at a speed generally
representative of the extent of the differentiating action and defining a stop
surface moveable from a retracted position to an extended position in response
to a predetermined extent of differentiating action. The actuating means further
includes a latch surface disposed to engage the stop surface when the stop
surface is in the extended position.
[0010] The improved differential gear mechanism is characterized by a
lockout mechanism operably associated with the flyweight mechanism and
including a lockout member positionable, in response to an input signal,
between a normal condition and a lockout condition. In the normal condition,
the lockout member permits the stop surface to move from the retracted
position to the extended position. In the lockout condition, the lockout member
prevents the stop member from moving from the retracted position to the
extended position.
[0011] The improved differential gear mechanism is also characterized by a
lockout mechanism operably associated with the flyweight mechanism and
including a lockout member positionable, in response to an input signal,

between a normal condition and a lockout condition. In the normal condition,
the lockout member permits the stop surface to move from the retracted
position to the extended position. In the lockout condition, the lockout member
prevents the stop member from moving from the retracted position to the
extended position.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is an axial cross-section of a locking differential mechanism
("Prior Art") of the type with which the present invention may be utilized.
[0013] FIG. 2 is a somewhat fragmentary, transverse cross-section of the
locking differential mechanism shown in FIG. 1, and on approximately the same
scale.
[0014] FIG. 3 is an axial cross-section, similar to FIG. 1, but on a larger
scale, illustrating in somewhat greater detail the flyweight mechanism which
comprises an important part of the locking differential mechanism of FIG. 1.
[0015] FIG. 4 is a perspective view of a locking differential mechanism
according to an embodiment of the present invention.
[0016] FIG. 5 is a detail view of the flyweight mechanism and a lockout
mechanism, which comprise an important part of the locking differential
mechanism of FIG. 4.
[0017] FIG. 6 is a partial cross-sectional view of the locking differential
mechanism of FIG. 4, showing a lockout member in a normal condition.
[0018] FIG. 7 is a partial cross-sectional view of the locking differential
mechanism of FIG. 4, showing a lockout member in a lockout condition.
[0019] FIG. 8 is a perspective view illustrating a locking differential
mechanism according to an alternative embodiment of the present invention.
[0020] FIG. 9 is a detail view of the flyweight mechanism and a lockout
mechanism, which comprise an important part of the locking differential
mechanism of FIG. 8.
[0021] FIG. 10 is a cross-sectional view of a portion of the lockout
mechanism shown in FIG. 9.

[0022] FIG. 11 is a partial cross-sectional view of the flyweight mechanism
and the lockout mechanism shown in FIG. 9.
[0023] FIG. 12 is a partial cross-sectional view of the locking differential
mechanism of FIG. 8, showing a lockout member in a normal condition.
[0024] FIG. 13 is a partial cross-sectional view of the locking differential
mechanism of FIG. 8, showing a lockout member in a lockout condition.
[0025] FIG. 14 is a perspective view illustrating a locking differential
mechanism according to an alternative embodiment of the present invention.
[0026] FIG. 15 is a detail perspective view of the flyweight mechanism and a
lockout mechanism, which comprise an important part of the locking differential
mechanism of FIG. 14.
[0027] FIG. 16 is a plan view of the flyweight mechanism and a lockout
mechanism of FIG. 14.
[0028] FIG. 17 is a cross-sectional view of the locking differential mechanism
of FIG. 14, showing a latch member in a locking position.
[0029] FIG. 18 is a cross-sectional view of the locking differential mechanism
taken along line 18-18 in FIG. 17, showing the lockout mechanism in the normal
condition.
[0030] FIG. 19 is a cross-sectional view of the locking differential mechanism
of FIG. 14, showing the latch member in an unlocking position.
[0031] FIG. 20 is a cross-sectional view of the locking differential mechanism
taken along line 20-20 in FIG. 19, showing the lockout mechanism in the lockout
condition.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0032] Referring now to the drawings, which are not intended to limit the
invention, FIG. 1 is an axial cross-section of a locking differential gear
mechanism of the type that may advantageously utilize the present invention.
The overall construction and operation of the locking differential shown in FIG. 1
is already well known to those skilled in the art, and is illustrated and described
in greater detail in the above-incorporated patents. The differential gear

mechanism as shown in FIG. 1 ("Prior Art") includes a gear case 11 that defines
therein a gear chamber, generally designated 13. Torque input to the locking
differential is typically by means of an input gear 15 (shown only in fragmentary
view in FIG. 1). The input gear 15 (also referred to as a "ring gear") is intended
to be in toothed engagement with an input pinion gear (not shown in FIG. 1),
which receives input drive torque from the vehicle driveline. The input gear 15
may be attached to the gear case 11 by means of a plurality of bolts 17.
[0033] Disposed within the gear chamber 13 is a differential gear set
including a plurality of pinion gears 19 (only one of which is shown in FIG. 1),
rotatably mounted on a pinion shaft 21 (only a portion of which is shown in FIG.
1). The pinion shaft 21 is secured to the gear case 11 by any suitable means,
not shown herein. The pinion gears comprise the input gears of the differential
gear set, and are in meshing engagement with a pair of side gears 23 and 25,
which comprise the output gears of the differential gear set. The side gears 23
and 25 are in splined engagement with a pair of axle shafts 27 and 29,
respectively. The gear case 11 includes annular hub portions 31 and 33,
surrounding the axle shafts 27 and 29, respectively. Typically, bearing sets (not
shown) are mounted on the hub portions 31 and 33 to provide rotational support
for the differential gear mechanism, relative to the main, outer differential
housing (also not shown herein).
[0034] During normal, straight-ahead operation of the vehicle, no
differentiating action occurs between the left and right axle shafts 27 and 29,
and the pinion gears 19 do not rotate relative to the pinion shaft 21. Therefore,
the gear case 11, the pinion gears 19, the side gears 23 and 25, and the axle
shafts 27 and 29 all rotate about an axis of rotation (A) of the axle shafts 27 and
29, as a solid unit.
[0035] Under certain operating conditions, such as when the vehicle is
turning, or theere is a slight difference in the size of the tires associated with the
axle shafts 27 and 29, it is permissible for a certain amount of differentiating
action to occur between the side gears 23 and 25, up to a predetermined level
of speed difference. Above that predetermined level (e.g., above a difference of

about 100 rpm between the side gears 23 and 25), indicating that a wheel spin-
out is imminent, it is desirable to retard the relative rotation between each of the
side gears 23 and 25 and the gear case 11, to prevont excessive differentiating
action between the axle shafts 27 and 29.
[0036] In order to retard differentiating action, the differential gear means is
provided with a lockup means for locking up the differential gear set, and an
actuating means for actuating the lockup means. The general construction and
operation of the lockup means and the actuating means are now well known in
the art, and will be described only briefly herein. For a more detailed
explanation of the lockup means and the actuating means, reference should be
made to the above-incorporated patents, and further, to U.S. Patent No.
RE 28,004 and U.S. Patent No. 3,831,462, both of which are assigned to the
assignee of the present invention.
[0037] In the subject embodiment, the lockup means comprises a clutch
pack, generally designated 35. As is now well known to those skilled in the art,
the clutch pack 35 includes a plurality of outer clutch disks splined to the gear
case 11, and a plurality of inner clutch disks splined to the side gear 23.
Referring still to FIG. 1, the lock-up means further includes a cam mechanism,
generally designated 41. As is well known to those skilled in the locking
differential art, the primary function of the cam mechanism 41 is to effect
movement of the clutch pack 35 from the disengaged condition, as shown in
FIG. 1, to an engaged, "loaded" condition (not specifically illustrated herein). In
the engaged condition, the clutch pack 35 is effective to retard relative rotation
between the gear case 11 and the side gear 23, thus retarding and minimizing
differentiating action between the side gears 23 and 25.
[0038] The cam mechanism 41 includes the side gear 23 and a main cam
member 43. The side gear 23 defines a cam surface 45, and the cam member
43 defines a cam surface 47. The cam member 43 also defines a set of
external teeth 49, the function of which will be described subsequently. During
normal, straight-ahead operation of the vehicle, with little or no differentiating
action occurring, the cam surfaces 45 and 47 remain in the neutral position

shown in FIG. 1, with the cam member 43 rotating with the side gear 23, at the
same rotational speed. Movement of the clutch pack 35 to the engaged
condition is accomplished by retarding rotation of the cam member 43, relative
to the side gear 23, to cause "ramping" of the cam surfaces 45 and 47, as is
well known to those skilled in the cam art. Such ramping results in axial
movement of the cam member 43, to the left in FIG. 1, thus initiating
engagement of the clutch pack 35.
[0039] In order to retard rotation of the cam member 43 relative to the side
gear 23, the locking differential gear mechanism includes a retarding
mechanism, generally designated 51, which comprises the actuating means for
actuating the lockup means. It should become apparent to those skilled in the
art that within the scope of the present invention, many different configurations
and types of retarding mechanisms may be utilized. In the subject embodiment,
and by way of example only, the retarding mechanism 51 is of the flyweight
type, illustrated and described in greater detail in the above-incorporated
patents and herein below. The retarding mechanism 51 is mounted within the
gear case 11 for rotation about its own axis, and includes a cylindrical flyweight
portion 53. The retarding mechanism 51 further includes an externally geared
portion 55, which is in engagement with the external gear teeth 49 of the cam
member 43.
[0040] Flyweight portion 53 is rotatable about an axis (a), shown in FIG. 5,
and oriented generally parallel to the axis of rotation (A), at a speed generally
representative of the extent of the differentiating action. Flyweight portion 53
includes a pair of flyweight members 56 each defining a stop surface 57. The
stop surface 57 is moveable from a retracted position (FIG. 2) to an extended
position (not shown) in response to a predetermined extent of differentiating
action. The flyweight member also defines a pivot portion 59 defining a pivot
axis generally parallel to and spaced apart from the axis (a) of the flyweight
portion 53. The stop surface 57 is generally oppositely disposed from the pivot
axis. The actuating means includes a latch surface 61 positioned to engage the
stop surface 57 when the stop surface is in the extended position.

[0041] During operation, if differentiating action begins to occur between the
axle shafts 27 and 29, the sidegear 23 and cam member 43 will begin to rotate
in unison at a speed different than that of the gear case 11, causing the
retarding mechanism 51 to begin to rotate about its axis (a) at a rotational
speed which is a function of the extent of the differentiating action. As the
speed of rotation of the retarding mechanism 51 increases, centrifugal force
causes the flyweights 56 to move outward until one of the flyweights stop
surface 57 engages the latch surface 61, preventing further rotation of the
retarding mechanism 51. When the retarding mechanism 51 stops rotating, the
engagement of the geared portion 55 and the gear teeth 49 causes the cam
member 43 to rotate at the same speed as the gear case 11 (which is different
than the speed of rotation of the sidegear 23), resulting in ramping, and
initializing of engagement of the clutch pack 35.
[0042] Referring to FIGS. 4-7, a differential gear mechanism is shown that is
substantially similar to the mechanism shown in FIG. 1 with at least one
exception, namely, a lockout mechanism 63 is operably associated with the
retarding mechanism 51. The lockout mechanism 63 allows the retarding
mechanism 51 to be selectively deactivated when automatic locking of the
differential is not desired (e.g., when the vehicle is operating with a mini-spare).
[0043] Lockout mechanism 63 includes a lockout member 65 that is
positionable, in response to an input signal, between a normal condition (FIG.
6) and a lockout condition (FIG. 7). In the normal condition, the lockout
member 65 permits the stop surface 57 to move from the retracted position to
the extended position. In the lockout condition, the lockout member 65
prevents the stop member 57 from moving from the retracted position to the
extended position.
[0044] In an embodiment illustrated in FIGS. 4-7, the lockout member 65 is
generally cylindrical, having a cup-shaped body moveably supported on the
retarding mechanism 51 between the externally geared portion 55 and the
flyweights 56. In the lockout condition (FIG. 7), the lockout member 65 at least
partially surrounds the flyweight mechanism 53 to prevent the flyweight

members 56 from pivoting outward as the flyweight mechanism rotates. In the
normal condition (FIG. 6), the lockout member 65 is retracted toward the
externally geared portion 55 leaving the flyweights 56 free to pivot outward.
[0045] The lockout mechanism 63 also comprises a first, generally annular
member 69 having an electromagnetic coil 71 that may be energized to produce
a magnetic field. A second, generally annular member 73 of known magnetic
properties is positioned around the first annular member 69 and includes a ramp
75. First annular member 69 is stationary with respect to the gear case 11,
such that the gear case 11 rotates relative to the first annular member 69 during
operation. The second annular member 73 is free to rotate with the gear case
11 when the coil 71 is de-energized and is inhibited from rotating with the gear
case 11 when the coil 71 is energized by virtue of the second annular member's
interaction with the magnetic field generated by the coil. The coil 71 is
energized by an electrical input signal, which is selectively transmitted to the coil
71 through an electrical connector 77. The connector is provided in
communication with a controller (not shown), such as the vehicle electronic
control unit (ECU), which controls communication of the electrical input signal to
coil 71.
[0046] Referring still to FIGS. 4-7, lockout mechanism 63 also includes a
movable, elongated pin 79 connected to the lockout member 65 and adapted to
engage the ramp 75 when the coil 71 is energized to move the lockout member
65 toward the lockout condition. The pin 79 is supported by the gear case 11
for movement along an axis generally parallel to axis (a). The pin 79 is laterally
offset from retarding mechanism 51 and connected to the lockout member 65
by a connecting member 81. The pin 79 extends through and exits the gear
case 11 adjacent the second annular member 73, and includes an end portion
83 orthogonally positioned with respect to a portion of the pin 79 supported
within the gear case 11. The end portion 83 engages the ramp 75 when the coil
71 is energized and rotation of the second annular member 73 is inhibited. As
the end portion 83 travels up the ramp 75 during engagement, the pin 79 is
drawn out of the gear case 11 (to the right in FIG. 5) and the lockout member 65

is moved toward the lockout condition. When the lockout member 65 is in the
lockout condition and the pin 79 is fully extended (FIGS. 5 and 7), the second
annular member 73 is forced to rotate with the gear case 11 and the pin 79
against the anti-rotative magnetic force created by the coil 71. The ramp 75
includes first and second ramp portions 85a and 85b, either of which are
engageable by the end portion 83 of the pin 79 depending on the direction of
rotation of the gear case 11.
[0047] The pin 79 and the lockout member 65 are urged toward the normal
condition by a compression spring 87 positioned between a window surface
defined by the gear case 11 and a flange 89 on the pin 79. As the end portion
83 moves away from the gear case 11 due to engagement with the ramp 75, the
spring 87 is compressed. When the coil 71 is de-energized and rotation of the
second annular member 73 is uninhibited, the spring 87 will force the pin 79 and
the lockout member 65 toward the normal condition as the end portion 83
moves down the ramp 75.
[0048] Referring to FIGS. 8-13, another embodiment of the present invention
is shown. In the illustrated embodiment, the lockout mechanism 90 comprises a
two-piece shaft having a first shaft portion 91 and a second shaft portion 93
upon which flyweight mechanism 53 is supported for rotation therewith. The
first and second shaft portions 91, 93 are rotatable about the axis (a) oriented
generally parallel to the axis of rotation (A), at a speed generally representative
of the extent of the differentiating action. The first shaft portion 91 includes the
externally geared portion 55 that meshes with the external teeth 49 of the cam
member 43. A first end 95 of first shaft portion 91 is supported by the gear case
11 in the conventional manner and a second end 97 of the first shaft portion 91
is supported by the second shaft portion 93. A first compression spring 99 is
disposed between the first and second portions 91, 93 to urge the first shaft
portion 91 away from the second shaft portion 93.
[0049] The first shaft portion 91 includes a lockout member 101 adapted to
be received in a receptacle 103 of the second shaft portion 93. Lockout
member 101 comprises a generally polygonal-shaped (when viewed in cross-

section) protrusion that mates with the correspondingly-shaped receptacle 103
when properly oriented. In the normal condition, the lockout member 101 is
received in the receptacle 103, locking the first and second shaft portions 91, 93
together for common rotation and permitting the stop surface 57 to move from
the retracted position to the extended position. In the lockout condition (FIGS.
9-11), the lockout member 101 is not positioned in the receptacle 103, allowing
the first shaft portion 91 to freely rotate relative to the second shaft portion 93
and preventing the stop member 57 from moving from the retracted position to
the extended position. The lockout member 101 and receptacle 103
configuration illustrated in FIGS. 9-12 is provided by way of example only. It will
be appreciated that many different lockout member and receptacle
configurations may be employed, including, for example, those configurations
where lockout member comprises a different polygonal-shaped protrusion (e.g.,
hexagon, octagon, etc) or a spline, and those configurations where the lockout
member 101 is provided on the second shaft portion for receipt in a receptacle
in the first shaft portion.
[0050] Referring still to FIGS. 8-13, lockout mechanism 90 also includes an
electric solenoid 105 attached to the second shaft portion 93 and supported on
the gear case 11 for rotation therewith. The solenoid 105 is selectively operable
in response to an electric input signal to move the second shaft portion 93
axially between a position in which the lockout member 101 is in the normal
condition (i.e., received in receptacle 103) and a position in which the lockout
member 101 is in the lockout condition (i.e., withdrawn from receptacle 103).
An electric slip-ring mechanism 107 may be used to transfer the electric input
signal from a remote source (e.g., vehicle ECU) to the solenoid 105. The slip-
ring mechanism 107 includes a first annular member 109 that is stationary
relative to the gear case 11 and a second annular member 111 that is free to
rotate with the gear case 11 and the solenoid 105. The second annular
member 111 is electrically connected to the solenoid 105 by one or more wires
113, and contacts the first annular member 109 during rotation to permit the
electrical input signal to pass from the first annular member 109, through the

second annular member 111, and into the solenoid 105.
[0051] The second shaft portion 93 is urged toward the first shaft portion 91
by a second compression spring 115 positioned between the solenoid 105 and
a flange 117 on the second shaft portion 93. When the solenoid 105 moves the
second shaft portion 93 away from the first shaft portion 91, and the lockout
member 101 is in the lockout condition, the spring 115 is compressed. When
the solenoid is de-energized, the spring 115 will force the second shaft portion
93 toward the first shaft portion 91, returning the lockout member 101 to the
normal condition. The spring force generated by the second compression
spring 115 is greater than the spring force generated by the first compression
spring 99 to permit return to the normal condition.
[0052] Referring to FIGS. 14-20, another embodiment of the present
invention is shown. In the illustrated embodiment, the latch surfaces 61 form a
portion of a latch member 119, which is movable (e.g., rotatable) about an axle
121 attached for rotation with the gear case 11. The latch member 119 includes
a relatively massive body 123 that is influenced by centrifugal force during
rotation of the gear case 11 to rotate the latch member 119 about the axle 121
toward an unlocking position shown in FIG. 19. A spring 125, such as a torsion
spring, is wrapped around the axle 121 and biases the latch member 119
toward a locking position shown in FIG. 17. In an embodiment, one end of the
spring 125 engages a cylindrical member 126 on the shaft 67 supporting the
flyweight mechanism 53, and a second end of the spring 125 engages a flange
127 (FIGS. 17 and 19) on the latch member 119. The biasing force produced
by the spring 125 and/or the mass of body 123 may be sized such that the
centrifugal force required to move the latch member 119 exceeds the applied
spring force when the gear case 11 rotates above a predetermined speed. In
application, this permits the differential gear mechanism to be locked at
relatively low vehicle speeds when differentiation occurs, but prohibits locking of
the differential gear mechanism at relatively high vehicle speeds when locking
the differential is not desired.
[0053] A lockout mechanism 129 is operably associated with the latch

member 119 and includes a lockout member 131 positionable, in response to
an input signal, in a normal condition and a lockout condition. In the normal
condition, the lockout member 131 permits the latch member 119 to move freely
between the locking position (FIG. 17) and the unlocking position (FIG. 19).
However, in the lockout condition, the lockout member 131 prevents the latch
member 119 from moving into the locking position, even at relatively low vehicle
speeds.
[0054] In an embodiment, the lockout member 131 includes a shaft portion
133 that extends generally parallel to the axle 121. An end 135 (FIGS. 18 and
20) of the shaft portion 133 adjacent the latch member 119 is slightly offset from
the remainder of the shaft portion 133, such that the body 123 is free to move
about the axle 121 when the lockout member 131 is moved to the normal
condition (FIG. 18), and engages the shaft portion 133 when the lockout
member 131 is moved to the lockout condition (FIG. 20) to prohibit movement of
the latch member 119 toward the locking position (FIG. 19).
[0055] Referring still to FIGS. 14-20, the lockout mechanism 129 also
includes an electric solenoid 137 attached to the shaft portion 133 and
supported on the gear case 11 for rotation therewith. The solenoid 137 is
selectively operable in response to an electric input signal to move the shaft
portion 133 axially. An electric slip-ring mechanism 139 may be used to transfer
the electric input signal from a remote source (e.g., vehicle ECU) to the solenoid
137. The slip-ring mechanism 139 includes a first annular member 141 that is
stationary relative to the gear case 11 and a second annular member 143 that is
free to rotate with the gear case 11 and the solenoid 137. The second annular
member 143 may be electrically connected to the solenoid 137 by one or more
wires 145, and contacts the first annular member 141 during rotation to permit
the electrical input signal to pass from the first annular member 141, through the
second annular member 143, and into the solenoid 137.
[0056] The invention has been described in great detail in the foregoing
specification, and it is believed that various alterations and modifications of the
invention will become apparent to those skilled in the art from a reading and

understanding of the specification. It is intended that all such alterations and
modifications are included in the invention, insofar as they come within the
scope of the appended claims.

What is claimed is:
1. A differential gear mechanism comprising a gear case (11) defining a
gear chamber (13), a differential gear set disposed in said gear chamber
(13), and including at least one input gear (15) and a pair of output gears
(23, 25) defining an axis of rotation (A); a lock-up clutch (35) operable to
retard differentiating action, and actuating means for actuating said lock-
up clutch (35); said lock-up clutch being operable between an engaged
condition, effective to retard relative rotation between said gear case (11)
and said output gears (23, 25), and a disengaged condition; said
actuating means including cam means (41) operable to effect said
engaged condition of said lock-up clutch (35), and retarding means (51)
operable to engage said cam means (41) and retard rotation of one
member of said cam means (41), said retarding means comprising a
flyweight mechanism (53) rotatable about an axis (a) oriented generally
parallel to said axis of rotation (A), at a speed generally representative of
the extent of said differentiating action, and defining a stop surface (57)
moveable from a retracted position to an extended position in response
to a predetermined extent of differentiating action; said actuating means
further including a latch surface (61) disposed to engage said stop
surface (57) when said stop surface is in said extended position;
characterized by:
(a) a lockout mechanism (63, 90) operably associated with said
flyweight mechanism (53) and including a lockout member (65,
101) positionable, in response to an input signal, in a normal
condition and a lockout condition;
(b) in said normal condition, said lockout member (65, 101) permits
said stop surface (57) to move from said retracted position to said
extended position; and
(c) in said lockout condition, said lockout member (65, 101) prevents
said stop surface (57) from moving from said retracted position to

said extended position.
2. A differential gear mechanism as claimed in claim 1, characterized by
said flyweight mechanism (53) including a flyweight member (56) defining
said stop surface (57), said flyweight member defining a pivot portion (59)
defining a pivot axis parallel to and spaced apart from said axis (a) of
said flyweight mechanism (53), said stop surface being generally
oppositely disposed from said pivot axis.
3. A differential gear mechanism as claimed in claim 1, characterized by
said lockout member (65) being generally cylindrical, said normal
condition comprising said cylindrical lockout member (65) being disposed
axially adjacent said flyweight mechanism (53), and said lockout
condition (FIG. 7) comprising said cylindrical lockout member at least
partially surrounding said flyweight mechanism (53).
4. A differential gear mechanism as claimed in claim 1, characterized by
said lockout mechanism (63) comprises a first annular member (69)
having an electromagnetic coil (71), a second annular member (73) of
known magnetic properties positioned around said first annular member
and including a ramp (75), and a movable pin (79) connected to said
lockout member (65) and adapted to engage said ramp (75) when said
coil (71) is energized to move said lockout member toward said lockout
condition (FIG. 7).
5. A differential gear mechanism as claimed in claim 4, characterized by
said first annular member (69) being stationary with respect to said gear
case (11), such that said gear case (11) rotates relative to said first
annular member (69).
6. A differential gear mechanism as claimed in claim 4, characterized by
said second annular member (73) being free to rotate with said gear case
(11) when said coil (71) is de-energized and is inhibited from rotating with

said gear case (11) when said coil (71) is energized.
7. A differential gear mechanism as claimed in claim 4, characterized by
said coil (71) being energized by said input signal.
8. A differential gear mechanism as claimed in claim 4, characterized by
said pin (79) being supported by said gear case (11) for movement along
an axis generally parallel to said axis (a).
9. A differential gear mechanism as claimed in claim 4, characterized by
said pin (79) being laterally offset from said flyweight mechanism (53)
and connected to said lockout member (65) by a connecting member
(81).
10. A differential gear mechanism as claimed in claim 4, characterized by
said pin (79) extending through and exiting said gear case (11) adjacent
said second annular member (73), said pin including an end portion (83)
orthogonally positioned with respect to a portion of the pin (79) supported
within said gear case (11), said end portion (83) engages said ramp (75)
when said coil (71) is energized and rotation of said second annular
member (73) is inhibited.
11. A differential gear mechanism as claimed in claim 4, characterized by
said ramp (75) including first and second ramp portions (85a) and (85b),
either of which are engageable by said pin (79) depending on the
direction of rotation of said gear case (11) and said pin (79).
12. A differential gear mechanism as claimed in claim 4, characterized by
said pin (79) and said lockout member (65) being urged toward the
normal condition (FIG. 6) by a spring (87).
13. A differential gear mechanism as claimed in claim 1, characterized by
said lockout mechanism (90) comprises a two-piece shaft having a first
shaft portion (91) and a second shaft portion (93) upon which said

flyweight mechanism (53) is supported for rotation therewith, a first end
(95) of first shaft portion (91) is supported by said gear case (11) and a
second end (97) of said first shaft portion (91) is supported by said
second shaft portion (93), said first shaft portion (91) or said second shaft
portion (93) including said lockout member (101), which is adapted to be
received in a receptacle (103) of the other of said first shaft portion (91)
and said second shaft portion (93).
14. A differential gear mechanism as claimed in claim 13, characterized by
said lockout member (101) comprises a protrusion that mates with a
correspondingly-shaped receptacle (103), whereby in the normal
condition (FIG. 12), said lockout member (101) is received in said
receptacle (103), locking said first and second shaft portions together for
concurrent rotation and permitting said stop surface (57) to move from
said retracted position to said extended position, and in said lockout
condition (FIG. 13), said lockout member (101) is withdrawn from said
receptacle (103), allowing said first shaft portion (91) to freely rotate
relative to said second shaft portion (93) and preventing said stop surface
(57) from moving from said retracted position to said extended position.
15. A differential gear mechanism as claimed in claim 13, characterized by
said lockout mechanism (90) including a compression spring (99)
disposed between said first and second shaft portions (91) and (93) to
urge said first shaft portion (91) away from said second shaft portion (93).
16. A differential gear mechanism as claimed in claim 13, characterized by
said lockout mechanism further comprising an electric solenoid (105)
operably associated with said second shaft portion (93) and supported on
said gear case (11) for rotation therewith, and a compression spring
(115) that urges the second shaft portion (93) toward the first shaft
portion (91), whereby when said solenoid (105) moves said second shaft
portion (93) away from said first shaft portion (91) and said lockout

member is in said lockout condition (FIG. 13) said spring (115) is
compressed, and when said solenoid (105) is de-energized, said spring
(115) forces said second shaft portion (93) toward said first shaft portion,
returning said lockout member to said normal condition (FIG. 12).
17. A differential gear mechanism comprising a gear case (11) defining a
gear chamber (13), a differential gear set disposed in said gear chamber
(13), and including at least one input gear (19) and a pair of output gears
(23, 25) defining an axis of rotation (A); a lock-up clutch (35) operable to
retard differentiating action, and actuating means for actuating said lock-
up clutch (35); said lock-up clutch being operable between an engaged
condition, effective to retard relative rotation between said gear case (11)
and said output gears (23, 25), and a disengaged condition; said
actuating means including cam means (41) operable to effect said
engaged condition of said lock-up clutch (35), and retarding means (51)
operable to engage said cam means (41) and retard rotation of one
member of said cam means (41), said retarding means comprising a
flyweight mechanism (53) rotatable about an axis (a) oriented generally
parallel to said axis of rotation (A), at a speed generally representative of
the extent of said differentiating action, and defining a stop surface (57)
moveable from a retracted position to an extended position in response
to a predetermined extent of differentiating action; said actuating means
further including a latch surface (61) disposed to engage said stop
surface (57) when said stop surface is in said extended position;
characterized by:
(a) said latch surface (61) forming a portion of a latch member (119)
movable between a locking position, wherein said latch surface
(61) is engageable with said stop surface (57) and an unlocking
position, wherein said stop surface (57) is unable to engage said
latch surface (61);
(b) a lockout mechanism (129) operably associated with said latch
member (119) and including a lockout member (131) positionable,

in response to an input signal, in a normal condition and a lockout
condition;
(c) in said normal condition, said lockout member (131) permits said
latch member (119) to move freely between said locking position
and said unlocking position; and
(d) in said lockout condition, said lockout member (131) prevents said
latch member. (119) from moving into said locking position.

18. A differential gear mechanism as claimed in claim 1, characterized by
said flyweight mechanism (53) including a flyweight member (56) defining
said stop surface (57), said flyweight member defining a pivot portion (59)
defining a pivot axis parallel to and spaced apart from said axis (a) of
said flyweight mechanism (53), said stop surface being generally
oppositely disposed from said pivot axis.
19. A differential gear mechanism as claimed in claim 17, characterized by
said latch member (119) including a body (123) supported on an axle
(121) and including a spring (125) biasing said latch member (119)
toward said locking position, wherein a biasing force produced by said
spring (125) is sized such that the centrifugal force required to move said
latch member (119) exceeds the biasing spring force when said gear
case (11) rotates above a predetermined speed.
20. A differential gear mechanism as claimed in claim 19, characterized by
said lockout member (131) including a shaft portion (133) that extends
generally parallel to said axle (121), said shaft portion (133) having an
end (135) positioned adjacent said latch member (119) that is slightly
offset from the remainder of said shaft portion (133), such that said body
(123) is free to move about said axle (121) when said lockout member
(131) is moved to the normal condition and engages said shaft portion
(133) when said lockout member (131) is moved to the lockout condition

to prohibit movement of said latch member (119) toward said locking
position.
21. A differential gear mechanism as claimed in claim 17, characterized by
said lockout mechanism (129) further comprising an electric solenoid
(137) operably associated with said lockout member (131) and supported
on said gear case (11) for rotation therewith, said electric solenoid (137)
being selectively operable in response to an electric input signal to move
said lockout member (131) axially between said normal condition and
said lockout condition.
22. A differential gear mechanism as claimed in claim 21, characterized by
said lockout mechanism further comprising an electric slip-ring
mechanism (139) configured to transfer the electric input signal from a
remote source to said electric solenoid (137), said slip-ring mechanism
(139) including a first annular member (141) that is stationary relative to
said gear case (11) and a second annular member (143) that is free to
rotate with said gear case (11) and said solenoid (137), said second
annular member (143) being electrically connected to said solenoid (137)
and contacting said first annular member (141) during rotation to permit
the electrical input signal to pass from said first annular member (141),
through said second annular member (143), and into said solenoid (137).

An improved differential gear mechanism is
characterized by a lockout mechanism (63, 90, 129) operably associated with a flyweight mechanism (53), or a latch member (119) that cooperates with the flyweight mechanism (53), to retard differentiating acting in the
differential gear mechanism.