Ball joint improvement and method

The invention pertains to a ball joint assembly which includes a ball stud received in a swivel socket of a supporting body. Some of such assemblies are classed as quick disconnects, meaning that the ball stud may be conveniently assembled and disassembled as desired. In another class, the bodies are substantially cylindrical with the sockets forming a pair of diametrically opposed feather edges. In drilling the sockets, it is not uncommon for a burr to be formed about the perimeter, and for this burr to be bent inwardly thereby obstructing the free insertion of the ball stud into the socket. Also it is not uncommon for the feather edges to be bent inwardly resulting in the same problem. By counterboring the socket, the burr is removed and the feather edges are flattened which not only solves the obstruction problem but may also provide other advantages.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to ball joints, and more particularly to improved 
ball joint assemblies of the quick disconnect and cylindrical body types. 
2. Description of the Prior Art 
Typical of both of the quick disconnect and cylindrical body type ball 
joint assemblies are those disclosed in U.S. Pat. No. 2,859,060. In this 
patent there is disclosed a stud member having a ball-shaped swivel 
element on one end which is adapted to be received in swiveling relation 
by a socket cross-drilled in a cylindrical supporting body. A moveable 
retaining sleeve is telescoped over the body for retaining the stud member 
assembled within the socket. 
The supporting body is cylindrical and the socket is cross-drilled therein 
to a diameter such that relatively sharp, feather edges are normally 
formed at the perimeter of the socket on diametrically opposite sides 
thereof, such feather edges being formed at the intersection of the socket 
wall with the body surface. 
In the manufacture of such assemblies, it not infrequently occurs that in 
drilling the socket, a small burr is formed either around the entire or a 
portion of the socket perimeter. During normal handling of such supporting 
bodies in bulk quantities or in the further processing thereof, such as in 
barrel plating, the drilling burr becomes peened or bent radially 
inwarding of the socket. The socket opening as a consequence becomes 
smaller such that the ball of the stud member sized to fit slidably into 
the socket now encounters the inturned burr as an obstruction. Insertion 
then becomes difficult, and in some instances leads to an increase in 
production time and expense. Further, it is not uncommon upon attempting 
to remove the stud, the ball encounters the obstruction causing 
inconvenience. 
As explained hereinabove, feather edges are formed on opposite perimetral 
sides of the socket opening. During bulk handling and barrel plating, for 
example, these feather edges may also become peened or bent inwardly 
thereby resulting in the same type of obstructions. Still further, such 
feather edges being sharp may lead to weakened stress regions in the 
supporting body. 
Different techniques were tried in solving the problem presented by the 
drilling burr, but none was found to be satisfactory. One of these was the 
use of abrasive in some form for grinding off the burr, and another was 
the use of a peening technique similar to shot peening. A third involved 
drilling the socket to a larger diameter or making the ball of the stud 
member smaller, but the dimensional tolerances resulting were too great. 
Also, tapering the socket was tried, but this also resulted in such a 
loose fit as to be unsatisfactory. 
SUMMARY OF THE INVENTION 
The present invention solves this problem in a manner which is the ultimate 
in simplicity and adds no cost to the manufacturing process. Simply 
stating, it involves counterboring the upper end of the socket which in 
effect cuts away the perimetral burr and/or feather edges. With the mouth 
of the socket therefore being larger, the insertion and withdrawal of the 
stud member is obstruction free. 
Not only was the burr problem solved, but also it was discovered that 
controlling the counterboring by an amount which flattened the feather 
edges may result in greater tensile strength of the socket body thereby 
providing an unexpected advantage without increasing cost of 
manufacturing. 
It is an object of this invention to provide an improved ball joint 
assembly wherein the ball of the stud member may be removably inserted 
into the socket of the supporting member without obstruction. 
The above-mentioned and other features and objects of this invention and 
the manner of attaining them will become more apparent and the invention 
itself will be best understood by reference to the following description 
of an embodiment of the invention taken in conjunction with the 
accompanying drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings and more particularly to FIGS. 1, 2 and 3, the 
ball joint assembly illustrated is of the quick disconnect type, meaning 
that the stud member may be manually inserted into or withdrawn from the 
socket as desired. This basic design is fully disclosed and claimed in 
U.S. Pat. No. 2,859,060. A cylindrical supporting body 12 has a 
cylindrical socket 14 crossbored therein, the relative diameters of the 
body 12 and socket 14 being substantially as shown. A stud member 16 is of 
conventional design and includes a ball shaped swivel portion 18 having a 
frusto-conical section 20. The diameter of the ball portion 18 
substantially equals that of the socket 14 such that the two have a 
sliding, swivel fit. 
For retaining the ball portion 18 within the socket 14, a retaining sleeve 
22 is telescopically fitted over the body 12. A helical compression spring 
24 is also fitted over the body 12 and bears at one end against the sleeve 
22 and at the other end against an enlargement 26 on the end of the body 
12. The opposite end of the body 12 may be staked to provide an abutment 
28 which prevents the sleeve from being pushed off the body 12 by means of 
the spring 24. 
As shown more clearly in FIG. 3, the sleeve 22 is provided with a wedge 
shaped notch 30 having a part circular portion 32 of a diameter smaller 
than that of the socket 14 but large enough to pass around the neck 
portion 34 of the stud member 16. The sleeve 22 may be moved toward the 
left to the dashed line position shown in FIG. 1 thereby fully exposing 
the socket 14. The ball portion 18 of the stud member is then inserted 
into the socket 14 following which the sleeve 22 is released permitting 
the spring 24 to move the sleeve 22 into captive engagement with the neck 
portion 34 of the stud member. Since the portion of the sleeve 22 is 
registry with the socket opening 14 is of smaller diameter than the ball 
portion 18, the stud member is thus locked into place. However, since the 
sleeve 22 is moveable on the body 12, any tilting movement of the stud 
member 16 is accommodated. 
Referring to FIGS. 4 through 5A, it is there shown that upon drilling the 
socket 14, a drilling burr 34 is formed around the socket mouth or 
perimeter. This burr may be as much as a 1/32nd of an inch in height but 
will vary depending upon the sharpness of the drill being used. In any 
event, since production quantities of the drilled bodies 12 are mass 
produced, it is conventional for them to be collected in trays or barrels 
in large numbers such that it is not uncommon for bodies thrown or 
otherwise dumped into such containers to engage forcefully or hammer 
against one another. In so doing, some of the burrs 34 are contacted and 
peened or bent over radially inwardly of the socket 14 as indicated by the 
numeral 34b, and if this peening is of the entire burr, an inner rim 
surrounding the socket perimeter will thus be produced. This same peening 
or bending can result from barrel-type, metal plating in which the bodies 
12 are tumbled for a relatively long period of time. 
Now if it is attempted to insert the ball 18 of the stud member 16 into the 
socket 14, it will at once be noted that the bent over burr 34b will 
constitute an obstruction. The strength and size of this obstruction will 
determine how difficult it is to insert the ball into the socket. The same 
applies to withdrawal of the ball from the socket, since the ball portion 
18 contacts the burr in the same manner as for insertion. In some 
instances it has been found that a tool, such as a pair of pliers or 
mallet, is required for inserting and withdrawing the stud member thereby 
defeating the objective of the quick disconnect feature of the assembly. 
Even though a burr 34 may not be formed, since the socket 14 is drilled 
into the side of the body 12 which is cylindrical, relatively sharp, 
feather edges will be formed on diametrically opposite sides of the socket 
opening as indicated by the numeral 36. During bulk handling, barrel 
plating or the like, such feather edges 36 can be bent inwardly of the 
socket 14 as indicated by the numeral 36a. Such bent over portions 36a 
thus become obstructions to the removable insertion of the ball stud into 
the socket 14. 
The problems posed by the bent over burrs 34b and feather edges 36a are 
easily solved by counterboring the socket 14 as indicated by the numeral 
38, the counterbore 38 being to a depth which cuts off the feather edges 
36 and produces instead an annular shaped flattened portion of shoulder 40 
which surrounds the mouth of the socket 14. The size of this flat in 
radial dimension may be made to about 0.015 inches for a body diameter of 
about 0.436 inches and a socket diameter of about 0.350 inches. This may 
be accomplished by making the counterbore 38 to a diameter of about 0.380 
inches. 
Preferably, the shoulder 40 is flat and defines a plane at right angles to 
the axis 42 of the socket 14, this axis also being perpendicular to the 
axis 44 of the body 12. The depth of the socket 14 in this working 
embodiment is as shown in FIGS. 8 and 9 as will assure engagement along 
the full extent of the frusto-conical portion 20 with the wall of the 
socket 14, as shown in FIG. 9, when the stud member 16 is tilted to the 
extreme. This arrangement is the preferred; however, for some sizes of 
ball and sockets, the wall of the socket may be slightly shallower than 
shown. Nevertheless, full engagement between the ball and socket sides is 
still achieved. This serves in providing maximum strength in the parts so 
engaged as a stop against further tilting of the stud member 16. 
By counterboring, the drilling burr 34 will be cut off as will be the 
feather edge 36. This results in the socket 14 being unobstructed such 
that the ball portion 18 of the stud member may be easily inserted and 
withdrawn. 
While providing such counterbore solves the problem of the drilling burr 
and feather edge becoming an obstruction, an unexpected benefit may be 
derived therefrom which is in the form of increased tensile strength of 
the body 12 in the region of the socket 14. This is explained by reference 
to FIGS. 6 and 10. The feather edge 36 is relatively sharp and may be 
characterized by an angle "a" (FIG. 6) formed between the tangent 46 and 
the side 48 of socket 14. By comparison, the angle "b" (FIG. 6) formed 
between the plane of shoulder 40 and the tangent 50 is a great deal 
larger, this tangent 50 coinciding with the intersection 52 between the 
plane of shoulder 40 and the body surface. Since the feather edge 36 is 
defined by a small angle "a" and is sharp, a region of localized stress 
with consequent structural weakness is produced. By converting this sharp 
feather edge 36 to the flattened ledge or shoulder 40, the localization of 
stress is spread out over a corresponding area thereby providing greater 
strength in the region. There are actually two such regions, these being 
on diametrically opposite sides of the socket 14. 
Actual tests reveal that the mean tensile strength of the body may be 
enhanced by reason of the presence of the counterbore 38. These tests were 
conducted on ten different samples, each of the assemblies in a category 
having feather edges 36 and the counterbores 38, respectively. A 
cylindrical stud member was used instead of the ball stud 16 and a force 
was applied to this stud and to the supporting body in a direction 
longitudinally of the latter up to the point of failure. At failure, 
cracks would appear on diametrically opposite sides of the socket opening 
or in other words at the locations of the feather edges. FIG. 10 shows the 
results of these tests wherein, for the old style body having the feather 
edges 36, the load ranges extended from 1000 pounds to 1282 pounds but for 
the counterbored version as denoted in FIGS. 7 through 9, from 1100 to 
1205 pounds. The mean strength of the feather edge style was calculated in 
this test run to be at 1150 pounds with the mean strength of the 
counterbored style to be 1170 pounds indicating the counterbored version 
to be stronger. It should be observed that a reduction in the range of 
ultimate failure load of the socket by approximately 60% has been achieved 
through counterboring the cavity. 
While there have been described above the principals of this invention in 
connection with specific apparatus, it is to be clearly understood that 
this description is made only by way of example and not as a limitation to 
the scope of the invention.