Note: Descriptions are shown in the official language in which they were submitted.
aAc~GRouND OF T~ ILIVE~ITIC:;
This invention generally relates to fle~ible joints and more
particularly to a new improved housing and b~aring constructior
for ball joints such as are used in automoti-~e steering lin-
kages or the like.
PROBLE~S IN THE ART
It is presently the practice in the art to fabricate
ball joints from forged ~ousings provided with seperate interna
spherical bearing inserts for supporting the male ball studs.
In many instances the spherical bearing inserts have been
formed of synthetic resinous materials but a problem has been
present in that such plastic bearing materials have been lackin
in longevity under high stress operating conditions, particular-
ly when operated in high temperature environments. Operation of
automotive pivot joints in hot environments has only recently
been dictated by the required polution control fabricated with
spherical bearings formed of annular metal inserts which over-
come the heat problem but which require highly accurate machi-
ning operations both with respect to the fabrication of the
metal inserts and the required annular seat supporting surface
which must be accurately located and formed in the housing.
SU~MARY OF THE INVENTION
In general the present invention comprises a novel
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.
' ~
- 2 - pivot joint housing and bearing construction, as well as a
novel method of producing same, which can be fabricated at
high rates of production with such housings including integrally
formed spherical bearing surfaces which surfaces are located
and shaped simultaneously with the forging and internal ma-
chining of the housings~.
As another aspect of the present invention, the
novel pivot joint housing construction includes lubrication
grooves in the spherical bearing surface which form grease
reservoirs in the bearing surface without the presence of
aberations in the finished bearing surface.
As another aspect of the present invention the -;
above mentioned lubrication grooves are asymmetriccally loca-
ted with respect to the spherical bearing surface to prevent
machine tool chatter during the final machining of the surface.
As another aspect of the present invention, the
pivot joint in one of its embodiments includes a novel ball
stud construction wherein the lubrication grooves are formed
in the spherical bearing surface of the ball stud during the
forging thereof.
As still another aspect of the invention, the pivot
joint in one of its embodiments comprises a novel ball stud
construction which includes a forged head portion that includes
a refined spherical bearing surface devoid of surface film.
,
It is, therefore, an object of the present invention
to provide an improved pivot joint and method of making same
which includes a housing portion provided with an integral
spherical bearing surface.
'3.f~
3 - It is another object of the present invention to
provide a novel pivot joint and method of making same that
includes a housing portion provided with integral hardened
spherical bearing surface that include lubrication grooves
located in the bearing surfaces without the presence of spheri-
cal aberrations adjacent the grooves.
It is another object of the present invention to
provide a novel pivot joint and method of making same that
comprises a novel ball stud that includes lubrication grooves
in the spherical bearing surface thereof, said grooves being
integrally formed in the bearing surface during the forging
thereof.
It is still another object of the present invention
to provide a novel pivot joint and method of making same that
comprises a ball stud that includes a refined spherical bea-
ring surface that is devoid of surface film normally resulting
from the heat treating operation.
Further objects and advantages of the present inven-
tion will be apparent from the following description, reference
being had to the accompanying drawings wherein a preferred
form of embodiment o~ the invention is clearly shown.
BRIEF DESCRIPTION OF THE DRAWINGS
Fig. 1 is a side sectional view of a ball joint in-
cluding a housing constructed in accordance with the present
invention;
Fig. 2 is a partial side elevational view of a work-
piece used in forming the housing of Fig. l;
~0
- 4 - partially in section, of the workpiece of Fig. 2
in various steps of formation;
Fig. 6 is a bottom elevational view of the work-
piece corresponding to Fig. 5;
Fig. 7 is an end sectional view of the workpiece
of the preceding figures;
Fig. 8 and Fig. 9 are side and end elevational views
of a ball stud constructed in accordance with the present
invention; and
Fig. 10 and Fig. 11 are side and end elevational
views of a second ball stud constructed in accordance with
the present invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Referring in detail to the drawings, Fig. 1 illus-
trates a typical pivot joint including a housing constructed
in accordance with the present invention, with such housing r
being indicated generally at 10. The housing includes a cavity
12 that includes an inner wall surface 14 and a spherical bea-
ring surface 16.
With continued reference to Fig. 1, a ~all stud is
indicated generally at 10. The housing includes a cavity 12
that includes an inner wall surface 14 and a spherical bearing
surface 16.
With continued reference to Fig. 1, a ball stud in-
dicated generally at 18 includes a ball shaped end 20 which is
pivotally supported by bearing surface 16 as well as by a
bearing surface 22 formed on a removeable bearing insert 24.
Bearing surface insert 24 is urged inwardly by a
compression spring 26 which is interposed between and end
closure 28 and the bearing insert. The housing further in-
- 5 - cludes a shank portion 30 as well as a top opening 32 which
includes a tapered wall 34 the latter permitting angular
movement of the shank 36 upon pivoting thereof.
The assembly of Fig. 1 also includes a dust cover 38,
sleeve 40, and nut 42.
Referring next to Fig. 2, the above mentioned hou-
sing 10 is formed from a workpiece W which consists of a rod of
carbon steel. A suitable steel material is referred to as the
middle carhon type, such as SAE 10~0.
After the workpiece W has been sheared to length
from bar stock, it is heated and forged to the shape shown in
Fig. 3 wherein the housing 10, with the cavity 12, have been
forged to the shape illustrated.
The workpiece is next subjected to a coining opera-
tion to form the grease grooves 46 with such grooves being
eccentrically located so as not to be directly opposite each
other as seen in Fig. 6.
In accordance with the present invention the work-
piece W is subjected to an internal machining operation using
a circular milling cutter so as to machine away the surface
decarboni~ation and accurately locate and finally shape and
finish the previously mentioned spherical bearing surface 16.
Inner wall portion 14 is also machined at the same time to
remove the taper left by the forging die.
A bottom hole 32 is also formed in the housing as
well as a groove 52 for receiving the end closure 28. Such
bobtom hole 32 and groove 52 can be cut at the same time the
wall surface 14 and bearing surface 16 are machined.
It should further be mentioned that during the internal machi-
ning the grease grooves 46 are cut down in length and any
6 - surface aberrations present in Fiy. 3 are machined away such
that the bearing curvature will be accurately produced. As
still another operation, a radial hole 54 is formed through
the wall of the housing for the subsequent mounting of a
grease fitting.
Reference is next made to Fig. 5, which illustrates
the machining of the outwardly tapered surface 34 at the
opening 32.
Reference is next made to Figs. 8 and 9 which illus-
trate a ball stud constructed in accordance with a modifi-
cation of the present invention, with such being indicated
generally at 118. In this embodiment the head portion 120 ~s
provided with longitudenally extending lubrication grooves 124,
instead of forming such lubrication grooves in the spherical
bearing surface 16 of the housing portion as was the case with
the previously described embodiment of Figs. 1-6.
Figs. 10 and 11 show a modified ball stud construc-
tion similar to the embodiment of Figs. 8 and 9 except that
the lubrication grooves 134 are~Qf~spirally ex~e~dIng~configura-
tion.
In both of the ball stud embodiments illustrated the
spiral grooves are positioned so as not to be diametrically
opposite one from another so as to eliminate vibratory machine
chatter during a finish machin~ning operation later to be des-
cribed.
Reference is next made to Figs. 8 and 9 which illus-
trate a ball stud constructed in accordance with a modifica-
tion of the present invention and indicated generally at 118.
In this embodiment the lubricating grooves 46 are eliminated
from the housing seat 22 and instead are formed in the spherical
- 7 - outer surface of the ball stud.
Ball stud 118 is formed from a carbon steel blank
which is cold headed to form an enlarged head portion on a
shank portion 122 with the head portion including a spherical
outer surface 120.
A plurality of spaced lubricating grooves 124 are
formed in spherical outer surface 120 during the cold heading
operation which forms the head portion on the ball stud. Such
lubricating grooves 124 serve as cavities for retaining grease
that maintains a film of lubricant at the confronting spherical
bearing surfaces 120 on the stud and 22 on the housing.
It has been determined that in the production of
certain designs of pivot joints, which include raised bottom
shells, or webs, in the bottom of the housing forging, it is
; also possible to hot forge the flare or tapered wall 34 of the -
top opening 32 simultaneously with the hot forging of the
housing portion 10. This eliminates the need for a seperate
machining operation to provide the flare 34 needed for angular-
ityof stud movement. However, in such pivot joint design where
the flare 34 can be hot forged, it is not possible to also
simultaneously forge the lubricating grooves 46. Hence, it
becomes economically desireable to form the lubricating grooves
124 in the spherical outer surface 120 of the ball stud 118.
In accordance with the present invention, the ball
stud 118 of Figs. 8 and 9 can be economically and accurately
produced by the following production steps:
1. A carbon steel blank is upset in a cold heading
machine fo form the shank portion 122 and enlarged
head portion that includes the spherical outer surface
- 8 - 120, with the longitudinally extending lubricating grooves
124 being forged into surface 120 by a suitable shaped
forging die
2. The spherical outer surface 120 is next subjec-
ted to a machining operation, such as grinding, to accurate-
ly establish the spherical radius to specified tolerances for
the particular job requirement. For example, with a one inch
diameter ball a typical tolerance for automotive applications
would be .5265 - .5}65 spherical radius after grinding.
3. The workpiece is next heat treated to case harden
the outer surface. A typical heat treatment would be to carbo-
nitride in an atmosperic furnace with a temper at 400 degrees
for one hour minimum at heat after quench. This will result in
a case depth of .00~ - .014 with the spherical surface file
hard for the typical one inch diameter ball mentioned above.
4. The spherical outer surface 120 is next refined,
preferably by a vibratory-slurry treatment wherein the heat
treated workpieces are tumbled in a drum type container in the
presence of a slurry of water and ceramic pellets. This polish-
ing operation serves to refine thespherical surface hy remoV~
-ing~surface film which resulted from the above described heat
treating operation.
After the finished ball studs 118 have been subjected
to the above mentioned steps th0y are ready to be assembled
into the pivot joint, as seen in Fig. 1, with the spherical
outer surface 120 pivotally supported on the spherical bearing
surface 22 of the housing portion 10.
Figs. 10 and 11 illustrate a modified ball stud 128
which is identical to the previously described embodiment of
Figs. 8 and 9 except that the lubricating grooves 134 are of
spiral configuration instead of straight as was the case with the prior
embodiment.
It will be noted that in the case of both ball stud constructions
the lubricating grooves are circumferentially spaced at a 120 degrees so as
to not be located diametrically opposite one another. It has been determined
that this spacing arrangement eliminates the possibility of vibratory chatter
during the machining step.
