Note: Descriptions are shown in the official language in which they were submitted.
1298097
BALL RETAINER
This invention relates to a retainer for holding a
swivel ball in the socket of a universal joint yoke.
U.S. Patent No. 4,650,439 discloses a centering
apparatus for a constant velocity universal joint in which a
pair of outer yokes are pivotally connected to a double inner
housing and a centering apparatus is positioned between the
outer yokes. The inner end of each yoke defines a ball
socket to mate in sliding contact with a swivel ball. The
swivel ball is held in the socket by a retainer ring which is
threaded to the yoke. Patent 4,650,439 also discloses that
it may be desirable in some applications to weld or bolt the
retainer ring to the yoke.
However, there were problems with threading, welding and
bolting the retainer ring to the yoke. Threading the
retainer ring to the yoke required that threads be formed on
the yoke and on the retainer ring. It also resulted in the
retainer ring having the opportunity to become loosened and
possibly removed from the yoke, which could result in failure
of the universal joint. Welding the retainer ring to the
yoke was also a relatively difficult production process and
could result in undesirable hardening of the areas of the
yoke and retainer ring adjacent to the weld bead. Hardening
not only could make the parts unacceptably brittle but also
could result in fatigue failure as the hardened areas were
subjected to many loading cycles. Bolting the retainer ring
to the yoke would require a relatively great additional mass
and space.
All of the retainers discussed above involved a rigid
connection to the yoke. However, such a rigid connection is
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not desirable where a preload is not to be applied to the
swivel ball by the retainer. With the threaded and welded
retainers, it was possible that the retainers could
inadvertently be made to apply a preload to the ball, which
would result in greater friction therebetween, generating
unwanted heat and accelerated wear.
The present invention provides a ball retainer for
the centering apparatus of a universal joint for a rotary drive
line, comprising: a yoke having a ball receiving cavity at one
end thereof; a first spherical surface formed in said ball
receiving cavity, said spherical surface defining an axial
direction and a radial direction in a plane normal to the axial
direction and opening in its substantially largest dimension in
the radial direction outwardly away from said yoke; a ball for
being retained in said cavity and slidably mating with the
first spherical surface; a ball retainer ring for keeping the
ball in the cavity, said retainer ring having an inner end and
an outer end; a second spherical surface on the ball retainer
ring for mating with the ball when the ball is mating with the
first spherical surface, said second spherical surface opening
in its substantially largest dimension in the radial direction
toward said yoke, said outer end of the ball retainer ring
intersecting said second spherical surface at said
substantially largest dimension in the radial direction of said
second spherical surface; and a circular retainer spring for
locking the retainer ring to the yoke; the ball receiving
cavity having at one end an enlarged circular opening coaxial
with the first spherical surface, said opening being defined by
a first shoulder facing outwardly in the axial direction and
having a radially inward edge and a radially outward edge, said
radially inward edge intersecting the first spherical surface
at said substantially largest dimension in the radial direction
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of said first spherical surface and said radially outward edge
intersecting a cylindrical sur~ace for engaging the outer
periphery of the ball retainer ring with a clearance, said
cylindrical surface having a groove formed therein which
defines a second shoulder facing in the axial direction toward
the first spherical surface; the ball retainer ring having a
groove around its outside circumference to receive the retainer
spring~ said groove having a side facing in the axial direction
toward the first spherical surface, said ball retainer ring
being insertable into said circular opening with said side of
said groove passing beyond the axial position of the second
shoulder of the circular opening and said groove allowing the
retainer spring to be substantially fully compressed into said
groove; wherein the retainer spring is compressed into the
groove in the retainer ring to insert the retainer ring into
the circular opening, and expands behind the second shoulder
after the retainer ring is inserted past the position where the
side of the groove is aligned with the second shoulder of the
ball receiving cavity when said retainer spring clears said
shoulder so that the retainer ring locks the ball in the ball
receiving cavity between the first and second spherical
surfaces with a space between the first shoulder and the inner
end of the ball retainer ring, a loose sliding fit between the
ball and the ball receiving cavity and with the retainer ring
freely rotatable in the circular opening.
Preferably, the second groove has a round cross
section and the retainer spring is rectangular, so that the
radially outer corners of the spring expand out against round
surfaces of the second groove. The round second groove endures
fatigue better than a rectangular groove and also cams the
corners of the spring in opposite directions to fix the spring
axially without any play in its axial position. Also, a
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retainer spring with a rectangular CL-OSS section is less
sensitive to axial misalignment than round cross section
springs.
In addition, in an especially preferred form, the
first groove is rectangular. With a rectangular retainer
spring, this minimizes the depth of the first groove required
to compress the spring far enough into the groove to insert it
into the opening of the ball receiving cavity.
The invention will enable one to provide an improved
construction for retaining a swivel ball in a socket.
The invention will further enable one to provide such
a construction particularly for a universal joint yoke.
The invention will further enable one to provide such
a construction which is easy and economical to manufacture and
assemble.
The invention will also enable one to provide such a
construction which provides a loose connection with a retainer
ring and which cannot produce a preload on the ball.
The invention will also enable one to provide such a
construction which is compact and resists fatigue failure.
The invention will also enable one to provide such a
construction which resists tampering.
In drawings which illustrate the embodiments of the
invention,
Figure 1 is an exploded elevation view showing the
parts of a ball retainer assembly of the invention;
Figure 2 is an elevation view partially in section of
the ball retainer of Figure 1 assembled;
Figure 3 is an exploded elevation view in section of
a portion of the ball retainer of Figure 2 but without the ball
in place; and
Figure 4 is a side elevation view illustrating a
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retainer spring for the ball retainer.
Figure 1 illustrates a preferred embodiment of the
invention unassembled. Illustrated are a yoke 10, a swivel
ball 12, a retainer spring 14, and a ball retainer ring 16.
The assembly is to be used in a universal joint like that
disclosed in United States Patent No. 4,650,439, the disclosure
of which is hereby incorporated by reference. Aspects of the
yoke 10 other than those described herein are described in
United States Patent No. 4,966,488.
The yoke 10 includes a ball receiving recess 18
formed at its inner end 19. The ball receiving recess 18
includes
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an induction hardened spherical surface 20, indicated by
stippling, to mate with the ball 12 in sliding surface
contact and an enlarged circular opening 22 for receiving the
retainer spring 14 and the ball retainer ring 16.
The spherical surface 20 defines an axial direction 24.
The spherical surface 20 may be made so that its diameter at
its inner end 25 is slightly smaller than the largest
diameter of the ball 12 so that the ball 12 must be pressed
or popped into mating contact with the surface 20. Once
seated against the surface 20, however, the ball 12 can be
freely swiveled therein. Also, the force holding the ball 12
against the surface 20 by virtue of the pop fit is not
sufficient to rely upon under operating conditions to hold
the ball 12 against the surface 20. Hence, even if a pop fit
is used, a further retainer to lock the ball 12 against the
surface 20 is required.
After the ball 12 is inserted against the surface 20,
the retainer spring 14 is compressed into a groove 26 formed
around the outside circumference of the retainer ring 16.
The spring 14 can be compressed into the groove 26 by using a
tool (not shown) having an interior conical surface to
gradually compress the ring 14 into the groove 26 as the
retainer ring 16 and spring 14 are together pushed axially
through the tool. The diameter at the end of the tool where
the spring 14 and retainer ring 16 exit should be slightly
smaller than the diameter of the opening 22 so that the
spring 14 and retainer ring 16 can be pushed directly from
the end of the tool into the opening 22. Referring to Fig.
3, to facilitate this process, the end of the opening 22 can
be chamfered as at 27.
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To be able to assemble the retainer 16 in the opening
22, the outside diameter of the retainer ring 16 must be
slightly smaller than the smallest inside diameter of the
opening 22. The depth of the groove 26 also must be at least
substantially equal to the radial thickness of the retainer
spring 14 so that the spring 14 can be compressed far enough
into the groove 26 for the spring 14 to be inserted into the
opening 22. In the preferred embodiment, the spring 14 has a
square cross section and the groove 26 has a rectangular
cross section. Square corners 26a and 26b (Fig. 3) at the
- base of the groove allow the spring 14 to be compressed all
the way into the groove 26, thereby minimizing the size of
the groove 26 and ultimately the size of the entire ball
retainer.
15The ball retainer 16 has a second spherical surface 30
which, together with the spherical surface 20, forms a socket
for the ball 12. The surface 30 is spherical to mate with
the ball 12 and spread the forces therebetween over the area
of surface 30. The inner end 31 of the ball retainer ring 16
is chamfered at 32 for additional support to the inner end of
the surface 30.
A shoulder ~4 facing in the axial direction of the
spherical surface 20 is formed in the opening 22. The
shoulder 34 is alignable with side 26c of groove 26 which is
the side of groove 26 that is away from spherical surface 20.
As retainer ring 16 with spring 14 in groove 26 is inserted
in opening 22, surface 22a of opening 22 slides on the outer
circumference of spring 14 to maintain spring 14 compressed
in groove 26. When side 26c becomes aligned with shoulder
34, spring 14 expands radially outwardly to catch behind
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shoulder 34. Thereafter, forces tending to remove ring 16
from opening 22 are reacted against through side 26d of
groove 26, spring 14, and shoulder 34.
Preferably, shoulder 34 is defined by a groove 36. The
groove 36 has no inside corners but is rounded and nearly
semicircular in cross section. For groove 36, a groove of a
rectangular cross section is not desirable, because it has
been found to result in possible fatigue failure of the yoke
in the vicinity of the groove 36. This is particularly the
case where portions of the ball receiving cavity 18 are
surface hardened, as is surface 20 in the preferred
embodiment.
Preferably, the spring 14 presses outward radially
against the groove 36 with a force of about 20-30 pounds.
This force is suitable to hold the spring 14 stationary in
the groove 36 under normal conditions because the square
corners of the spring 14 press out against the curved portion
of the groove 36 to capture the spring in the groove.
However, even with the spring 14 stationary, the retainer
ring 16 can still move slightly back and forth in the axial
direction because there is a small clearance between the
spring 14 and the sides of the groove 26 for the spring 14 to
be compressed into and expanded out of the groove 26. Also,
the retainer ring 16 is not held firmly against shoulder 38
of the cavity 18 so that shoulder 38 does not restrain it
against all axial movement. Preferably, as shown in Fig. 4,
the spring 14 is of the type that has a gap between its ends
so that it can be compressed. The spring 14 can be made from
a hard drawn, oil tempered steel (e.g., HD spring steel).
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This construction assures a loose connection of the
retainer 16 to the yoke lO. Firm seating of the retainer 16
against the ball 12 is undesirable because it increases
friction between the retainer 16 and the ball 12 which
results in excess heat and wear. Assembly of a ball retainer
of the preferred embodiment is not possible unless the
assembly results in a loose connection so that no preload on
the ball 12 is possible with this connection. This is
because, as the spring 14 drags on the surface 22a during
insertion, the retainer 16 must be moved slightly past the
position where the side 26c is in alignment with the shoulder
34 for the spring 14 to expand behind the shoulder 34. After
the spring 14 expands behind the shoulder 34, the retainer 16
will be moved back in the direction opposite to that of
insertion by the spring seating behind the shoulder 34.
Thus, the retainer 16 must actually be pushed slightly beyond
its final farthest-in position before the spring 19 will seat
in the groove 36. Thus, firm seating against either the
shoulder 38 or the ball 12 is prevented by this assembly.
As the spring 14 expands into groove 36, its radially
outer corners cam on the round surfaces of groove 36 until it
finds a static seated position. In this position, the spring
is axially stationary without any play in its axial position.
Thus, the looseness of the retainer connection is not
determined by the clearance between the sides of the spring
14 and groove 36. Thereby, one manufacturing variable which
could otherwise result in the connection being too loose is
eliminated. Note, however, that when using a rounded groove
36, the sprins 14 and the radius of the groove 36 must be
chosen so that the spring is not cammed further into the ball
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receiving cavity than the position where the spring first
began expanding into the second groove. Otherwise, a slight
preload could conceivably be applied to the ball 12 by the
retainer ring 16.
Although a spring 14 having a round cross section
could be used, a spring 14 having a rectangular or
square cross section is preferable for the disclosed
embodiment. It has been found that a round cross
section spring requires that its axial center line be
precisely coaxial with the centers of the groove 36 and
retainer 16. Otherwise, the retainer 16 can become
jammed against the spring or even be removed from the
circular opening 22. Also, if the groove 36 is slightly
shallow, a round cross section spring can be pushed out
of the groove 36.
Once installed, the retainer ring 16 cannot practically
be removed. This helps prevent tampering with the ball joint
which may otherwise cause a problem in the operation of the
universal joint.
In some applications, it may be desirable to provide a
retainer joint like that of the preferred embodiment but
which applies a preload to the ball 12. This could be
accomplished by providing a clearance between corner 14a and
groove 36. Then, in expanding outwardly, corner 14b of
25 spring 14 would cam along groove 36 and urge spring 14 and
retainer ring 16 toward spherical surface 20. Of course, an
appropriate clearance would also have to be provided between
shoulder 38 and retainer ring 16 so that the camming action
was stopped by the ring 16 abutting the ball 12, rather than
by abutting the shoulder 38.
097
Dimensions which have been found suitable for the
preferred embodiment are as follows: inside diameter, recess
22: 1.251"; outside diameter, ring 16: 1.249'; spring 14:
.063" square; width of groove 26: .0675"; width of groove 36:
.070"; ball 12 diameter: .998".
A low cost and effective ball retainer particularly
adapted for a universal joint yoke has now been described.
Many modifications and variations to the preferred embodiment
will be apparent to those of ordinary skill in the art but
which will still embody the invention. Therefore, it is not
intended that the invention be limited by the scope of the
drawings or the detailed description thereof, but only by the
claims which follow.
