Note: Descriptions are shown in the official language in which they were submitted.
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This invention relates generally to clutches. More
particularly, it relates to a clutch for use in effecting
locking engagement between a front drive axle and a front
wheel of a four-wheel drive vehicle in response to the
application of power to the front drive axle. The clutch
automatically effects disengagement upon cessation of the
application of power to the front drive axle, together with
a direction reversal thereof.
Heretofore, various clutching mechanisms have been used
for engaging a front drive axle with its associated wheels
in a four-wheel drive vehicle. One such mechanism normally
is disengaged to allow the wheels to rotate independently of
the front drive system. This requires that the operator
lock each clutch manually to engage the front drive axle and
wheels, and to unlock them manually to disengage.
Another such mechanism provides an overrunning clutch
which engages automatically when power is applied to the
front drive axle and when operation is in the drive mode.
However, such an overrunning clutch disengages automatically
upon operation in the coast mode. In other words, the
overrunning clutch engages when the rotational speed of the
axle tends to exceed the rotational speed of the wheel, but
disengages when t~e rotational speed of the wheel tends to
overrun that of the axle. Such overrunning clutches generally
provide some means by which the operator may override manually
to insure locking engagement between the axle and wheels.
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Yet another such mechanism provides a clutch which
operates in response to the application of torque to the
front drive axle to move pins into slots so as to engage the
axle with its associated wheels, Although a Dechanism of
this type will effect engagement in either the drive or
coast mode of operation, there is the possibility tha~ the
pins will slip out of the slots during movement between
drive and coast, in which case the clutch would disengage
and then re-engage automatically. At normal operating
speeds such disengagement and re-engagement could cause
severe shocks to the clutch components and, indeed, to the
entire front drive line. This would result in a dangerous
and possibly destructive condition. Further, in a Lloat
condition wherein the axle is rotating but no torque is
transferred between the axle and wheels, an inadvertent
tendency for movement between the drive and coast modes of
operation could develop. This could cause the clutch to
disengage and then re-engage, and establish the same dan-
gerous condition.
There remains a need in the art for a clutch which will
automatically engage a front drive axle and an associated
wheel in response to engagement of the front wheel drive
system, which will maintain engagement positively in the
drive and coast modes of operation as well as during the
transition between drive and coast, which will maintain
engagement positively in forward and reverse operation as
well as during the transition between forward and revPrse,
and which will disengage automatically upon disengagement of
the front wheel drive system.
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A primary object of this invention is to provide an
improved automatic clutch which will meet the need noted
above. The invention is directed to an improved clutch for
automatically effecting engagement between dxiving and driven
members in response to rotation of the driving member.
According to the present invention there is
provided an automatic clutch in~luding first and second
rotatable members ana first and second clutch elements
respectively rotatable with the first and second elements,
the first element being movable relative to the first
member between first and second positions, the first and
second elements bei~g relatively rotata~le between engagement
in drive and coast modes when the first element is in the -
second position. Means is provided for biasing the first
element for movement toward the first position. Means
is responsive to rotation of the first member in one direction
for moving the first element to the first position and means
is provided for retaining the first element in the second
position so long as the first member is subject to rotation
in the one direction irrespective of the relative rotation ~-
of the first and second elements between engagement in
the drive and coast modes. Means is provided for maintaining
the first element in the second position as the direction
of rotation of the first member is changed from the one
~` direction to the opposite direction. The retaining means
also is effective for retaining the first element in the
second position so long as the first member is subject
to rotation in the opposite direction irrespective of the
relative rotation of the first and second elements between
engagement in the drive and coast modes.
The clutch maintains positive engagement between the -
members so long as the driving member rotates, and disengages
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automatically when rotation of the driving member is reversed.
The clutch of the present invention is adapted for use in
four-wheel drive vehicles where it is desirable to provide
automatic engagement of the front wheels when the operator
engages the front wheel drive system. The clutch is
operative when the vehicle is engagea in forward or reverse,
and maintains engagement positively until the operator
shifts out of four-wheel drive and reverses direction.
In the accompanying drawings:
FIGURE 1 is a sectional view showing details of the
improved automatic locking clutch;
FIGURE 2 is a sectional view taken along the line
2-2 of FIGURE 1 showing additional details of the clutch;
FIGURE 3 is a developed view taken along the line
3-3 of FIGURE 1 showing the clutch in its disengaged position;
FIGURE 4 is a developed view similar to FIGURE 3
showing the clutch in its forward drive position;
FIGURE 5 is a developed view similar to FIGURE 3
showing the clutch in its forward coast position;
FIGURE 6 is a developed view similar to FIGURE 3
showing the clutch in its reverse drive position;
FIGURE 7 is a developed view similar to FIGURE 3
showing the clutch in its reverse coast position; and
FIGURE 8 is a schematic view showing an associated
transfer case for use in conjunction with the clutch.
While this invention is susceptible of embodiment in
many different forms, there is shown in the drawings and
herein will be described in detail a preferred embodiment,
with the understanding that the present disclosure is to be
considered as an exemplification of the principles of the
invention, and is not intended to limit the invention to
this embodiment.
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Referring to the drawings now in greater detail, and
with particular reference to FIGURES 1, 2, and 3, thPre is
shown a driving member or shaft 10, which in one preferred
form of the invention is the front axle of a four-wheel
drive vehicle. A~le 10 is rotatably supported in a con-
ventional manner within an axle housing 12. Axle 10 extends
outwardly beyond the spindle of housing 12, and a spring
retainer 14 is secured to the outer end thereof by a bolt 16
or the like. A collar 18 is secured to axle 10 for rotation
therewith, and is oriented between the spindle of housing 12
and spring retainer 14.
A driven member 20, which in one preferred form of the
invention is ~he front wheel hub of a four-wheel drive
vehicle, is supported by a conventional bearing, not shown,
for rotation about housing 12. Lock nuts 22 and 24 secure
this bearing in the usual manner. However, lock nut 24
defines a smooth annular surface 26.
A hub extension sleeve 28 is secured to wheel hub 20
for rotation therewith. Hub extension 28 extends outwardly
beyond spring retainer 14 and bolt 16, and a suitable cap 30
close~ its outer end. Hub extension 28 defines a plurality
of clutch teeth 32.
An annular cam 34 is spaced from the spindle of housing
12 and from collar 18 so as to be rotatable relative thereto.
Cam 34 defines outwardly converging cam surfaces 36. A
pin 38 is secured to cam 34 and extends inwardly therefrom.
A drag ring 40 in frictional contact with surface 26 of
lock nut 24, is engaged by pin 38. Cam 34 also defines a
plurality of outwardly extending fingers 42.
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An axle clutch sleeve 44 is splined to collar 18 for
rotation therewith and sliding movement rela~ive thereto.
Sleeve 44 defines a plurality of clutch teeth 46 adap~ed for
meshing engagement with teeth 32 of hub extension 28.
A suitable spring 48 reacts against spring retainer 14 and
biases sleeve 44 inwardly such that teeth 46 normally are
out of meshing engagement with teeth 32. Sleeve 44 defines
a plurality of cam follower means comprising surfaces 50.
Surfaces 50 diverge inwardly toward an inner smooth surface
52. Sleeve 44 also supports a plurality of cam stop pins
54.
Cam surfaces 36 of cam 34 and cam follower surfaces 50
of sleeve 44 are complimentary. With sleeve 44 in the position
shown in FIGURE 1, surfaces 36 and 50 are in the position
shown in FIGURE 3. Teeth 32 and 46 are out of mesh, and
wheel hub 20 rotates freely about stationary axle 10 with
the associated vehicle in two-wheel drive.
When the operator desires to establish four-wheel drive,
he directs power to axle 10. Collar 18 and sleeve 44 rotate
with axle 10. The force developed by the frictional contact
of drag ring 40 with lock nut 24 is sufficient such that
rotation of cam 34 i~ retarded. Surfaces 50 ride outwardly
on surfaceQ 36, and sleeve 44 is moved outwardly against the
biasing force of spring 4~ from the position shown in FIGURE 3
to the position shown in FIGURE 4. Surface 52 rides along
the outwardmost point of surfaces 36 until pins 54 abutt
fingers 42, whereupon cam 34 is rotated with sleeve 44.
Teeth 46 are moved outwardl~ into meshing engagement with
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~eeth 32, and a positive driving engagement is established
between axle 10 and wheel hub 20. Teeth 32 and 46 are constructed
such that the backlash therebetween is smaller than the
distance between the inner end of each cam follower surface
50 and an adjacent pin 54 along surface 52.
When the vehicle shifts from drive to coast, as for
example when the operator lifts his foot off of the accelerator,
hub 20 tends to overrun axle 10. In this condition teeth 32
shift from the position shown in FIGU~E 4 to the position
shown in FIGURE 5. In effect, an engine braking condition
is established. Pins 54 continue to abutt fingers 42, and
sleeve 44 continues to rotate cam 34 and drag ring 40
relative to lock nut 24. The vehicle may shift back and
forth between drive and coast, but teeth 32 and 46 will
remain in meshing engagement, thus ensuring that four-wheel
drive operation is maintained.
When the operator desires to move the vehicle in reverse,
he stops the vehicle, shifts the transmission out of a
forward gear and into reverse gear7 and then starts the
vehicle once again, all the while remaining in four-wheel
drive. Because the backlash between teeth 32 and 46 is
smaller than the distance between surfaces 50 and pins 54,
tooth contact i5 established before surfaces 50 come into
contact with surfaces 36. Sufficient pressure is established
between teeth 32 and 46 such that sleeve 44 i~ held against
the biasing force of spring 48 as it moves from the position
shown in FIGURE 4, for example, to the position shown in
FIGURE 6. Cam follower surfaces 50 do not ride down cam
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surfaces 36, and four-wheel drive operation is maintained.
When in reverse, the vehicle may shift between the drive
mode shown in FIGURE 6 and the coast mode shown in FIGURE
7 while remaining positively engaged for four-wheel drive
operation.
An important advantage of the arrangement disclosed
herein is that a positive drive condition is maintained in
both the drive and the coast modes, either in forward or
reverse. This positive drive is established automatically,
thereby eliminating any need for manually locking the wheel
hubs.
When the operator desires to establish two-wheel drive,
he stops the vehicle, discontinues the transfer of power to
axle 10, and moves the vehicle in the reverse direction
sufficiently to align surfaces 36 and 50. Spring 48 biases
sleeve 44 inwardly to the position shown in FIGURES 1 and 3.
The operator may then proceed in either direction in two-
wheel drive.
In one preferred form of the invention, direct drive
may be e~tablished from an engine to a rear drive axle, with
offset drive being established to a front drive axle. As
shown in FIGURE 8, one example of such an arrangement
includes a transfer case having an input 56 adapted to
receive power from the transmission of a four-wheel drive
vehicle~ A rear output 58 is connected directly to input
56, and is connected through a rear propeller shaft to the
rear axle. A sprocket 60 is journaled for rotation relative
to input 56, and a complimentary sprocket 62 is secured to a
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front output 64 which is connected through a front propeller
shaft to front axle 1~. A suitable chain ~6 couples sproc~ets 60
and 62 for power transfer therebetween. A clutch 68 is
controllable by the vehicle operator through a suitable
actuating mechanism 70. In one position, clutch 68 disengages
sprocket 60 from input 56 such that power is transferred
from input 56 to output 58, but not to output 64. Two-wheel
drive is established. In another position, clutch 68
engages sprocket 60 with input 56 such that power is trans-
ferred from input 56 to both outputs 58 and 64. With clutch
68 engaged and power transferred to output 64, front axle 10
will rotate and four-wheel drive will be established auto-
matically.
Thus it will be seen that positive drive is established
automatically in both the drive and coast modes of operation
when four-wheel drive is engaged. The automatic feature
eliminates any necessity for manual lock-up in order to
insure positive drive. The automatic feature maintains
four-wheel drive in either the drive or coast modes, and
during the transition between drive and coast. Similarly,
four-wheel drive is maintained in either forward or reverse
gears, and during the shift between forward and reverse.
It should be apparent that although the invention
provides a novel arrangement for clutching the front drive
axle and its associated wheels in a four-wheel drive vehicle,
it is readily available for use in any environment where
automatic clutching between driving and driven members is
desired.
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