IMPROVED DIFFERENTIAL HOLDOUT RING ARRANGEMENT
TITLE OF THE INVENTION
Title: Improved Differential Holdout Ring Arrangement
BACKGROUND OF THE INVENTION
FIELD OF THE INVENTION
A locking differential includes an annular center cam member freely rotatably
supported within an annular central driver member without the use of any keying
device, such as a snap ring, thereby to simply the construction and assembly of the
differential, and to reduce cost. The center cam member and the central driver
member have adjacent outer and inner circumferential surfaces, respectively, that are
smooth, continuous, and uninterrupted. The holdout rings are rotatably connected at
their remote ends with the clutch members by integral annular outer ribs that extend
within corresponding grooves contained in the counterbore wall surfaces.
DESCRIPTION OF RELATED ART
Locking differentials are well known in the patented prior art, as evidenced by
the patents to Knoblock No. 2,329,059, Bawks (the present inventor) No. 4,424,725,
and Edwards et al No. 4, 745, 818. In these prior art patents, the annular center cam
member is normally arranged concentrically within, and keyed to (by a snap ring or
the like), the annular central driver member, thereby to prevent relative axial
displacement between the two components. When one output shaft overruns the other
by a predetermined amount, the overrunning clutch member slidably mounted on the
side gear associated with the overrunning shaft is cammed out by the teeth on the
central driver member and on the clutch members, thereby to disengage the
overrunning output shaft as long as the overrunning condition exists.
These known differentials require a relatively large number of complicated
parts, and are difficult and expensive to manufacture and assemble. For example, in
the Bawks and Knoblock patents, the spring biasing means for the locking
differentials are arranged concentrically within the clutch members and the center
cam member, thereby complicating the assembly and servicing of the differential. In
the clutch members of the Edwards patent, the camming teeth are arranged in a
circular pattern adjacent the inner circumference of the opposed faces of the clutch
members, and the driving teeth are arranged in an outwardly spaced circular pattern
adjacent the outer circumferences of the clutch members, with the holdout rings being
mounted at their remote ends in grooves contained in the clutch member faces
between the cam teeth and the driving teeth.
[0005] Some of the known differentials present the problem that the holdout ring can
jump over the spider key during a speed variation between the spider and clutch,
thereby causing the clutch to be non-parallel with the spider. This will result in
damage to the clutch teeth and failure of the differential.
The present invention was developed to provide an improved less costly
locking differential that requires fewer parts, is easier to manufacture and assemble,
and is more durable in operation, and easier to service.
SUMMARY OF THE INVENTION
Accordingly, a primary object of the present invention is to provide an
improved locking differential that eliminates the need for key means between the
center cam member and the central driver members, such that the adjacent outer and
inner circumferential surfaces of the concentrically arranged center cam and central
driving members are smooth, continuous and uninterrupted. The biasing spring
means include a pair of helical compression springs arranged concentrically externally
about the side gears, respectively, thereby to bias the clutch members inwardly
together toward the central driving member arranged therebetween.
Another object of the invention is to provide a differential wherein the clutch
teeth at the adjacent ends of the clutch members are continuous and unitary, whereby
the cam teeth on the center cam member engage the clutch teeth adjacent the inner
circumferential portion of the clutch members, and the driving teeth on the central
driving member engage the corresponding clutch teeth adjacent the outer
circumference of the clutch members.
According to another object, the annular holdout rings are formed from bar
stock, forged powder metal or a sheet of resilient metal material and include at their
remote ends on their outer circumferential surfaces annular ribs that extend within
corresponding grooves contained in counterbore wall surfaces within the clutch
members, respectively. The holdout rings are provided at their other ends with a
plurality of circumferentially- spaced axially-extending integral lugs that normally
extend within corresponding through slots contained in the center cam member. The
holdout rings are resiliently biased radially outwardly into engagement with the
counterbore wall surfaces of the clutch members, respectively, whereby when one
overrunning clutch member is cammed out to the disengaged condition, the holdout
ring associated therewith is rotatabiy dragged through a small angle to cause a comer
extremity of the lug to be seated in a holdout notch provided at the free edge of the
associated center cam member through slot.
new differential design will prevent the holdout ring from jumping the
key. This is accomplished by moving the holdout ring locating surface from the
spider/central driver to the center cam, and by providing an additional length of
contact between the holdout ring lug and the center cam locating shoulder. The
holdout ring cannot climb over the center cam locating shoulder and therefore the
clutch cannot become non-parallel with the spider/central driver. This will prevent
tooth damage due to partial contact.
This improves the strength of the clutch cam teeth, which cause the clutch to
disengage from the spider/central driver drive teeth during a wheel speed variation.
This is accomplished by moving the holdout ring groove inward on the clutch,
allowing the clutch cam teeth to become an extension to the clutch drive teeth. By
eliminating the spider/central driver key, the corresponding manufacturing steps are
corresponding eliminated.
BRIEF DESCRIPTION OF THE DRAWINGS
Other objects and advantages of the invention will become apparent from a
study of the following specification, when viewed in the light of the accompanying
drawing, in which:
Fig. 1 is a sectional view of a differential mechanism of the prior art;
Fig. 2 is a plan view of the spider member of the prior art differential of Fig 1;
Fig. 3 is a detailed view taken along line 3 - 3 of Fig. 2;
Fig. 4 is an end view of the improved differential of the present invention, and Fig. 5
is a sectional view taken along line 5-5 of Fig. 4;
Fig. 6 is an end view of one of the side gears of Fig. 5, and Fig. 7 is a sectional view
taken along line 7-7 of Fig. 6;
Fig. 8 is an exploded view of the differential of Fig. 5;
Figs. 9 and 10 are side and end views, respectively, of the center cam member of Fig.
5;
Fig 11 is a sectional view taken along the line 11 of Fig. 10, and Fig. 12 is a
perspective view of the center cam member of Fig. 10;
Fig. 13 is an end view of one of the holdout rings of Fig. 5, and Fig. 14 is a sectional
view taken along the line 14-14 of Fig. 13;
Fig. 15 is an end view of the central driver member of Fig. 5, and Fig. 16 is a
sectional view taken along line 16-16 of Fig. 15;
Fig. 17 is an end view of one of the clutch members of Fig. 5, and Fig. 18 is a
sectional view taken along line 18-18 of Fig. 17.
DETAILED DESCRIPTION OF THE INVENTION
Referring first more particularly to Figs. 1-3 (which illustrate the differential
of the prior art Edwards et al patent No. 4,745,818), the collinearly arranged output
shafts 12 and 14 are splined at their adjacent ends within side gears 16 and 18 that are
journaled within openings contained in the opposed end walls of the differential
casifig 2. Slidably splined to the side gears are clutch members 20 and 22 that are
biased together by the compression springs to effect engagement between the clutch
teeth 20a, 22a with the driving teeth 10a at opposite ends of the central spider member
10. An annular center cam member 24 is keyed to the central spider member by
means of a conventional snap ring 26, thereby to prevent axial displacement of the
center cam member relative to the central driver member. The center cam member
has cam teeth 24a and 24b that engage a corresponding set of cam teeth 20b, 22b
provided on the clutch members. Arranged in the grooves contained in the clutch
members between the sets of driving teeth and cam teeth are split holdout rings 28, 30
that are operable to maintain a clutch member associated with an overrunning output
shaft in the cammed out disengaged condition, as is known in the art.
As shown in Figs. 2 and 3, the spider or central driver member 10 is provided
on its inner circumference with a key 10 that extends within the slits contained in the
holdout rings, thereby to limit the extent of angular displacement of each holdout ring
relative to the center cam member during the holdout ring operation. If this key is
jumped by the holdout ring during faulty holdout ring operation, damage to the
differential components can result.
Referring now to Figs. 4 and 5, according to the improved differential of the
present invention, the annular side gears 118 and 120, which are non-rotatably splined
to the collinearly arranged output shafts 104 and 106, are journaled in openings
contained in the opposed end walls of the rotatably driven casing 114, thereby to
define an axis of rotation R. Slidably splined for longitudinal sliding displacement on
the side gears are clutch members 122 and 124 that are biased together toward the
central driver member 116 by helical compression springs 144 and 146 that are
arranged externally in concentrically spaced relation about the side gears,
respectively. At their remote ends, the compression springs engage annular spring
retainer members 148, 150 that abut external integral annular shoulders 118c, 120c on
the side gears, respectively. The adjacent ends of the compression springs are in
engagement with the clutch members, respectively, thereby causing engagement
between the clutch teeth 122a and 124a and corresponding portions of driving teeth
116a at opposite ends of the central driver member, which portions are adjacent the
outer periphery of the central driver member.
Rotatably arranged concentrically within said central driver member is an
annular center cam member 130 provided at each end with a circular arrangement of
cam teeth 130a that are arranged to engage portions of the associated driving teeth
116a adjacent the inner circumference of the central driver member 116. In
accordance with a characterizing feature of the present invention, the adjacent inner
and outer circumferential surfaces of the central driver member 116c and the center
cam member 130b, respectively, are smooth, continuous and uninterrupted, since the
necessity of the snap ring of the prior art has been eliminated. The center cam
member is provided on its inner circumference with a plurality of circumferentially-
spaced longitudinal through slots 142 that terminate at each end with a pair of lateral
hold-out notches 144, as will be described below.
pair of longitudinally-spaced coUinearly-arranged holdout rings 132 and
134 are provided that extend at their remote ends concentrically within counterbores
125 contained in the adjacent ends of the clutch members 122 and 124, respectively.
In order to prevent relative longitudinal displacement between the holdout rings and
their associated clutch members, the holdout rings are provided on their outer
peripheries with annular ribs 132a and 134a that extend within corresponding grooves
140 contained in the counterbore wall surfaces. The holdout rings are formed from
bar stock, forged. Powder metal or a resilient sheet metal material, are longitudinal
split by slits 135, and are resiliently biased outwardly into frictional engagement with
the associated clutch member, respectively. At their adjacent ends, the holdout rings
are provided with a plurality of circumferentially-spaced axially-extending integral
lug portions 132b and 134b that extend into opposite ends of the corresponding
through slots 142 contained in the center cam member.
In operation, the output shafts 104 and 106 are normally driven at the same
rotational velocity from the main drive shaft via the casing 114, central driving
member 116, the clutch members 122 and 124, and the side gears 118 and 120,
respectively. When the rotational velocity of one output shaft exceeds that of the
other above a predetermined rotational velocity (such as occurs during a turn of the
vehicle), the clutch member associated with the overrunning shaft is cammed out by
the cooperation between the clutch teeth on the overrunning clutch member and the
associated cam teeth 130a on the center cam member, thereby to disengage the clutch
teeth of that clutch member from the driving teeth of the center cam member. The
associated holdout ring is slightly dragged to cause the comer extremities of the
holdout ring lugs to enter the associated notches 144 on the center cam member,
thereby to maintain the clutch member in the disengaged condition. When the
overrunning output shaft condition ends upon the completion of the turn, the holdout
rings is rotationally dragged to its initial position, and the spring biasing force causes
the lugs to again enter the cam slots, whereupon the clutch member is returned to
reengage the clutch teeth with the driving teeth of the central driver member. The ring
gear torque will again flow through the clutch member and the side gear into the
output shaft.
While in accordance with the provisions of the Patent Statutes the preferred
forms and embodiments of the invention have been illustrated and described, it will be
apparent to those skilled in the art that changes may be made without deviating from
the invention described above.
We claim:
1. A locking differential mechanism for driving a pair of spaced collinearly arranged
output shafts (104, 106) from a main drive shaft, comprising:
(a) a casing (114) driven by the drive shaft for rotation about a given axis (R)
collinear with the output shaft axis, said casing containing a chamber defining
a pair of opposed end walls containing aligned shaft openings for receiving the
adjacent ends of the output shafts;
(b) an annular central driver member (116) non-rotatably mounted in said
chamber concentrically about said given axis, said central driver member
having at each end an end surface provided with a circular arrangement of
radially- extending continuous drive teeth (116a);
(c) a pair of annular side gears (118, 120) mounted in said chamber for
rotation about said given axis adjacent said shaft openings, respectively, said
side gears being internally splined for non-rotatable connection with the
adjacent ends of the output shafts, respectively;
(d) a pair of annular clutch members (122, 124) concentrically mounted
about, and splined for non-rotatable longitudinal displacement relative to, said
side gears, respectively, the adjacent ends of said clutch members including a
plurality of circularly spaced radially-extending clutch teeth (122a, 124a)
arranged for engagement with portions of corresponding drive teeth (116a)
adjacent the outer circumference of said central driver member, respectively;
(e) spring means normally biasing said clutch members toward engaged
positions relative to said central driver member, said spring means including a
pair of compressions springs (144, 146) arranged externally concentrically
about said side gears, respectively;
(f) center cam means operable when the rotary velocity of one output shaft
exceeds that of the other output shaft above a predetermined value for axially
displacing toward a disengaged position the clutch member associated with
said one overrunning output shaft, said disengagement means including:
(1) an annular center cam member (130) rotatably mounted
concentrically within said central driver member;
(2) said center cam member and said central drive member having
adjacent continuous smooth circumferential surfaces (130b, 116c);
(3) said center cam member having at opposite ends a plurality of cam
teeth (130a) arranged for engagement with corresponding portions of
the clutch teeth adjacent the inner circumference of the adjacent clutch
members, respectively;
(4) said center cam member having an inner circumferential surface
containing a plurality of longitudinally-extending circumferentially-
spaced through slots (142);
(g) holdout means operable from an inactive position to a lock-out position to
retain the overrunning clutch member associated with the ovemmnlng output
shaft in the disengaged condition as long as the rotational velocity of the
overrunning output shaft exceeds said given value, said holdout means
including;
(1) a pair of resilient annular holdout rings (132, 134) arranged
concentrically about said given axis, each of said holdout rings
containing a longitudinal slit (135);
(2) said holdout rings each including a body portion having a smooth
uninterrupted internal circumferential surface, said holdout rings
having remote first ends the outer circumferential surfaces of which are
provided with integral circumferential generally-annular rib portions
(132a, 134a) that extend within corresponding grooves (140) contained
within the associated clutch member, respectively, thereby to prevent
longitudinal displacement of said holdout rings relative to said clutch
members, respectively;
(3) said holdout rings having adjacent ends provided with a plurality
of circumferentially-spaced axially extending lug portions (132b,
134b) that normally extend into said center cam member through slots,
respectively;
(4) said holdout rings being resiliently biased radially outwardly into
frictional engagement with the associated clutch member, such that
when the clutch member associated with an overrunning output shaft is
longitudinally displaced toward the disengaged position, subsequent
relative rotational movement of said clutch member causes the
associated holdout ring to be rotationally dragged toward said lock-out
position in which extremities of said holdout lugs are seated within
lock-out notches (144) provided at each end of, and on opposite sides
of, said through slots.
2. A locking differential mechanism as defined in claim 1, wherein the adjacent ends
of said clutch members contain central counterbores (125) which define counterbore
walls, said grooves being contained in said counterbore walls, respectively.
3. A locking differential mechanism as defined in claim 2, wherein each of said side
gears is provided with an integral outer annular flange portion (118c, 120c); and
further wherein said spring means includes:
(1) a pair of annular spring retainer members (148, 150) mounted
concentrically about said side gears between said side gear flange
portions and said clutch members, respectively, said spring retainer
members being in abutting engagement with said side gear annular
flange portions, respectively; and
(2) a pair of compression springs (144, 145) mounted concentrically
about said side gears between said spring retainers and the associated
clutch members, respectively.
4. A locking differential mechanism as defined in claim 3, wherein said central driver
member is provided on its outer circumferential surface with spline teeth (116b) that
non-rotatably connect said central driver member with said casing.

A locking differential includes an annular center cam
member freely rotatably supported within an annular
central driver member without the use of any keying
device, such as a snap ring, thereby to simply the
construction and assembly of the differential, and to
reduce cost. The center cam member is longitudinally
maintained in place by the biasing forces applied to
the clutch members arranged on opposite sides of the
central driver member by helical compression springs
arranged externally concentrically about the side
gears, respectively, and by the holdout rings that are
connected with the clutch members. The center cam
member and the central driver member have adjacent
outer and inner circumferential surfaces, respectively,
that are smooth, continuous, and uninterrupted. The
holdout rings are rotatably connected at their remote
ends with the clutch members by integral annular outer
ribs that extend within corresponding grooves contained
in the counterbore wall surfaces.