Constant velocity joint

A constant velocity joint is provided with an outer part, in the inner surface of which tracks are provided, an inner part, on the outer surface of which corresponding tracks are provided, and with balls in a pivotable cage located in the space between the outer part and the inner part. Taking as a basis the particular axial displacement, caused by the torque, of the outer part and the inner part in relation to the cage, this displacement depending mainly on the amount of the respective axial clearances of the pairs of centering surfaces and/or on the brinelling of the window support surfaces by the balls in the running-in phase and also on the elastic flexibility of the parts, the running-in wear and the thermal expansion, the tracks of the outer part run in a mirror image with the corresponding tracks of the inner part in relation to the ball plane.

The invention relates to a constant velocity joint. 
The constant velocity joint concerned belongs to the track-steered 
ball-joint type, in which the homokinetic plane is controlled by the 
intersecting tracks of the outer and inner parts. U.S. Pat No. 2,046,584, 
FIG. 3 or FIG. 9, shows a design of this type as a fixed joint with tracks 
running in meridian planes, the control principle being shown in FIG. 1. 
To satisfy the requirement of constant velocity, this patent stipulates 
that the spherical centering surfaces of the inner part, outer part and 
cage be arranged concentrically with a common center point located in the 
ball plane. The centering surfaces extend on both sides of the plane of 
symmetry or ball plane. Furthermore, the axial distance between the center 
point of the centering surface of the outer part and the center point of 
the tracks of the outer part (called the outer-part offset) should be 
equal to the axial distance between the center point of the centering 
surface of the inner part and the center point of the tracks of the inner 
part (called the inner-part offset). When the center point of the track of 
one part is not located on its axis of rotation (for example, FIG. 5), the 
offset corresponds to the distance between the center point of the 
centering surface of this part and the point of intersection of the axis 
of rotation with the plane extending perpendicularly to the track and 
containing the ball center point (FIG. 5, point c and point b 
respectively.) The tracks of the outer part are therefore a mirror image 
of the tracks of the inner part, seen from the ball plane. 
However, the four spherical centering surfaces cannot basically be kept 
concentric, as long as there is a clearance fit between the pairs of 
mating surfaces, so that the condition of constant velocity can be 
guaranteed only with clearance-free mating surfaces. In fact, the parts 
are loaded axially as a result of torque transmission, more specifically 
the outer and inner parts in the direction of the transmission points and 
the balls and the cage in the opposite direction. If the centering 
surfaces are assembled with a clearance, as is absolutely unavoidable in 
practice, the parts are displaced correspondingly, so that the distance 
between the ball plane and the center point of the tracks of the outer 
part (called the outer-part lever arm) gets shorter, and the distance 
between the ball plane and the center point of the tracks of the inner 
part (called the inner-part lever arm) gets longer than the respective 
offset values. As a result, the tracks of the outer part are no longer a 
mirror image of the tracks of the inner part, seen from the ball plane, or 
the equality of the lever arms, which is, in fact, decisive for an 
accurate control of constant velocity, is already disturbed twice. The 
particular axial displacement depends primarily on the radial clearance 
and on the width of the centering surfaces, as measured from the ball 
plane in the direction of the respective points of contact; the smaller 
the width, the greater the axial displacement. To allow the joint parts to 
be assembled, the width of the parts must be kept within limits, as is 
known per se, and accordingly the particular axial displacement amounts, 
as a rule, to a multiple of the radial clearance. 
Because of the displaced mirror image or the unequal lever arms and the 
axially displaced centering surfaces, the control of the ball plane in the 
angle-bisecting plane is disturbed, with the result that, among other 
factors, the balls are loaded very unequally, or one-sidedly, when the 
joint is angled, in comparison with joints controlled accurately, and 
consequently the performance of the joint in terms of torque and endurance 
is reduced considerably. Moreover, the joint tends to produce clicking 
noises. 
These disadvantages can, in practice, be kept within limits only by pairing 
the centering surfaces with only very small clearance. However, a small 
clearance fit of the centering surfaces is incompatible with thermal 
expansion and also makes it necessary for the parts, expecially the outer 
part, to be made massive, so as to keep their elastic deformation within 
the given narrow clearance. Furthermore, a narrow clearance fit of the 
centering surfaces entails greater restrictions in the production 
accuracies of the joint parts. In the first place, the concentricity 
between the tracks and the centering surface of both the outer and the 
inner part must be kept within even narrower tolerances. In fact, the 
inner part is centered radially, in the main direction of the ball plane, 
with respect to the outer part mainly by the geometry of the tracks and 
balls, while under the influence of the torque, the centering is mainly 
decieded by the transmission forces on the balls. If, along the ball 
plane, the eccentricity between the tracks and the centering surface of 
the outer part and/or inner part is greater than the radial clearances of 
the centering surfaces, the cage is jammed radially on one side between 
the outer and inner parts. Centering is overdefined, and the balls are 
already loaded unequally even in the straight position. Exact 
concentricity of the centering surfaces of the cage is likewise necessary 
for the same reasons. 
A narrow clearance fit therefore means that the joint designs according to 
the state of the art also involve high production costs, cause high 
temperatures, which endanger to the lubricant film to a high degree, and 
are subject to a certain danger of seizure between the cage and the outer 
or inner part, which for example, may lead to fatal consequences in motor 
vehicles with front-wheel drive. 
A further feature of this known type of joint is the high point loading 
between the balls and the window support surfaces, which leads, during a 
relatively short running-in period to significant plastic deformation or 
brinelling of the window support surfaces. As a result, the ball plane is 
further displaced axially in the main loading direction, and is no longer 
symmetrical to the cage centering surfaces, after which the outer-part 
lever arm becomes even shorter and the inner-part lever arm becomes even 
longer, or the mirror images of the tracks are disturbed more seriously, 
with the result that the individual balls, tracks and window surfaces are 
subjected to an even more extreme load. 
Various methods of solving the problem of the point loading of the window 
support surfaces are known, such as those described in W. German Pat. Nos. 
2,430,109, 2,430,026 and 2,430,025. In the first two solutions, the 
natural shape of the balls is disturbed by the flattened portions or by 
cylindrical regions in the cage windows, with which they are prevented 
from rolling freely in the tracks of the outer and inner parts, resulting 
in an increase of the sliding friction, thus leading to an increase in 
temperature and to a reduction of the endurance. Additional parts are 
proposed according to W. German Patent Specification No. 2,430,025, but 
these involve extra costs, losses in accuracy and a further space 
requirement. 
Further inaccuracies in the mirror image of the tracks or in the equality 
of the control lever arms of the joints according to the state of the art 
arise as a result of the elasticity of the parts, running in wear or 
thermal expansion, whether momentary or at a constant temperature. 
The object of this invention is to substantially eliminate the 
disadvantages mentioned above, especially by providing accurate or more 
accurate control conditions. 
According to the invention, there is provided a constant velocity joint 
with a hollow outer part, in the inner surface of which tracks are 
provided, an inner part which is located in the outer part and on the 
outer surface of which corresponding tracks are provided, with balls each 
being received in a track of the outer and inner part for torque 
transmission, a cage which is located in the space between the outer and 
inner parts maintaining the balls in the homokinetic or ball plane by 
means of windows and which is pivotably fixed respectively centered to the 
inner and/or outer part, with a clearance fit, the tracks of the outer and 
inner parts not extending parallel to the main axis, at least in the low 
joint angle range, so that, with the joint in the straight position and 
under torque, the contact or transmission points of the balls in relation 
to the tracks of both the outer and inner parts are located on one side of 
the homokinetic plane, and that the balls are held axially on the other 
side of the homokinetic plane by means of window support surfaces or 
window surfaces, wherein, considering the respective axial displacement, 
caused by the torque, of the outer part and the inner part in relation to 
the cage in one direction and of the balls in the opposite direction, this 
displacement depending mainly on the amount of the respective axial 
clearances of the pairs of centering surfaces and/or on the brinelling of 
the window support surfaces by the balls in the running-in phase, further 
on the elasticity of the parts, the running-in wear and the thermal 
expansion, the tracks of the outer part run in a mirror image with the 
corresponding tracks of the inner part in relation to the ball plane. 
Thus, the accuracy of the track control is achieved after eliminating the 
sources of error irrespective of their individual magnitudes. For example, 
the clearances between the centering surfaces can be decided to their best 
possible values more freely and do not need to be minimized. Brinelling of 
the window support surfaces as such is then practically no longer a 
disadvantage, inasmuch as certain production inaccuracies of the window 
support surfaces or certain eccentricities of the functional surfaces can 
advantageously be corrected or compensated as a result of the plastic 
deformation. 
An overall advantage of a control which can be realized with high accuracy 
is the fact that the lever-arm dimensions can simply be reduced, the 
consequence of which is that the minimum track depths of both the outer 
and inner parts can be increased, furthermore that the axial force vector 
is reduced, as a result of which the performance data of the joint as a 
whole are further improved. 
The main idea on which the invention is based is that the direction of the 
sum of all the forces acting on the window surfaces remains unchanged both 
in the straight position of the joint and in its angled position, and also 
that centering by means of a close clearance fit of the centering surfaces 
along the ball plane is superfluous. 
In one improved construction of the invention, to improve a constant 
velocity joint, in which the inner surface of the outer part and the outer 
surface of the inner part respectively as well as the outer and inner 
surfaces of the cage are predominantly spherical and in which the outer 
and inner surfaces of the cage are made concentric, wherein the outer-part 
offset is greater than the constructive nominal size of the lever arms, 
specifically by an amount corresponding to and compensating the sum of all 
the axial displacements essentially as a result of play and also as a 
result of elastic deformation, running-in wear and thermal expansion 
between the outer part and the cage, and/or the inner-part offset is less 
than the constructional nominal size of the lever arms, specifically by an 
amount corresponding to and compensating the sum of all the axial 
displacements mainly as a result of play and also as a result of elastic 
deformation, running-in wear and thermal expansion between the inner part 
and the cage, and/or the ball plane lies asymmetrically relative to the 
plane of symmetry of the centering surfaces of the cage by an amount 
corresponding to and compensating the axial displacement of the ball plane 
in relation to the cage essentially as a result of the brinelling as well 
as a result of the elastic deformation of the cage support surfaces. 
To maintain the centering or fixing accuracy of the joint even for 
relatively large angular ranges, one of the centering surfaces between the 
outer part and the cage has, on the side of the window support surfaces, 
or one of the centering surfaces between the cage and the inner part has, 
on the side of the transmission points a greater arc length than the 
respective opposing surface or bearing surface and serves as a guide 
surface, and wherein the guide surfaces are made exactly spherical with 
their center point in the ball plane. 
As a result of these measures, the relatively narrow counterpiece or 
relatively narrow joint part is guided accurately by the guide surface so 
as to be pivotable spherically. The guide surface can be both the outer 
surface (convex) or the inner surface (concave) of a pair of surface. By 
means of this embodiment , the axial clearance between the centering 
surfaces can be compensated by constructive means in the main loading 
direction. 
When the arc length of the guide surfaces on both sides of the bearing 
surface corresponds at least approximatey to an amount of about half the 
maximum operating joint angle, the bearing surfaces are always in contact 
with the guide surfaces over their full periphery, so that both the 
control accuracy and the support provided for the axially acting forces 
are guaranteed to the best possible extent over the entire angle range of 
the joint. 
The invention proposes, further, that the bearing surface be circular, so 
that linear contact with the guide surface is obtained. 
A very important and inventive design of the constant velocity joint 
envisages that the surface or surefaces of revolution adjacent to the 
bearing surface is finished, preferably produced in one chucking operation 
together with the bearing surface. 
By producing the adjacent surfaces in one operation, such as grinding, the 
accuracy of the bearing surface is increased. A chamfer or a plane surface 
can be assumed as an adjoining surface. This feature also results, 
independently of the mirror-image accuracy of the tracks, according to the 
invention, in an improvement in the steering conditions. 
If a line contact of this type adapts itself to be wider in the course of a 
certain running-in time, the corresponding axial displacement must be 
taken into account in the determination of the lever arms. 
It is proposed, according to a further feature of the invention, that the 
bearing surface be made spherical with the same radius as the guide 
surface. 
By this measure, surface contact is produced, whereby the surface pressure 
on the centering surfaces is reduced, furthermore the arc length of the 
guide surface can be shortened correspondingly. 
In some applications, for example at high speeds, it is advantageous to 
assure the lubricant film between the centering surfaces by means of a 
wedge effect of the lubricant. It is therefore also proposed that the 
bearing surface in the longitudinal section and/or cross-section is 
realised with a certain conformity to the guide surface. This measure 
likewise results, independently of the mirror-image design according to 
the invention, in an improvement in the control conditions. 
As is known per se, the application of conformity entails a reduction in 
production accuracies. 
Since according to this invention no special requirements apart from the 
guide or bearing surfaces are imposed for the joint, the adjoining 
remaining surfaces not serving as a guide nor as a bearing surface on the 
outer surfaces or inner surfaces in the region of the pivoting movement of 
the joint parts can be at a distance from the center point of the guide 
surfaces which in the case of convex surfaces is less than and in the case 
of concave surfaces is greater than the radius of the guide surfaces. 
A free design of the surfaces not involved in the function of fixing or 
centering can, depending on the particular embodiment, lead to optimise 
the construction , to a considerably easier production of the parts, and 
to a simpler assembly and will contribute to a potential improvement and 
reduction in the cost of the joints. As a rule, only the requirements of 
the track depth have to be considered.

FIG. 1 shows a joint of known design with a relatively large clearance fit 
between the outer part (120) and the cage (340) and between the cage (340) 
and the inner part (560). The four centering surfaces (2') on the outer 
part, (3' and 4') on the cage and (5') on the inner part are predominantly 
spherical, that is to say, in the straight position of the joint, the 
spherical surfaces are located on both sides of the plane of symmetry (3", 
4") or the ball plane (7") respectively. The tracks (1') of the outer part 
(120) and (6') of the inner part (560) are located in the plane of cross 
section and have their center points (1 and 6) on the main axis of 
rotation. The track bottoms are designated by (10) and (60). The balls 
(70) are retained axially between cage window surfaces (72) and 
cage-window support surfaces (71). The cage windows are made symmetrically 
to the concentric centering surfaces (3' and 4') of the cage, so that the 
ball plane (7") originally coincides with the plane of symmetry (3" and 
4") of the centering surfaces (3' and 4'). The points (701 and 706) are 
the contact point of the ball in relation to the track surfaces (100, 600) 
of the outer part and inner part respectively and are each located on the 
plane (1" and 6"), which pass through the ball center point (0) and the 
track center points (1 and 6) respectively or are perpendicular to the 
ball track. In the straight position of the joint, both points are located 
on one side of the ball plane, with the result that an axial force vector 
is produced by each ball. With an increasing joint angle, the axial force 
vector of each ball varies during one revolution. From a specific joint 
angle onwards, the contact points of individual balls located on one side 
of the periphery in the region of the pivot axis of the joint, could lie 
on the other side of the ball plane, so that the window surface (72) is 
loaded at this interval, but this occurs with a lower intensity and 
frequency than the loading between the balls and the window support 
surfaces (71). This angle depends on the inclination of the plane (1" and 
6" respectively) and on the position of the contact points as well as on 
the inclination on the ball-track plane in relation to the meridian plane, 
if the tracks are not in the meriodian plane. In a typical application in 
the front-wheel drive of a motor vehicle, the loading on the window 
surface (72) and on the dents arising thereby is quite insignificant. On 
the opposite, the dents (7') on the window support surface (71) are 
significant and, for example in the case of balls with a diameter of 15 
mm, attain a depth which can amount to several tenths of a millimeter, 
depending on the loading. However, the sum of all the forces on the window 
support surfaces (71) always remains greater than those on the window 
surfaces (72), so that contact between the centering surfaces lies always 
on one side. 
The joint is shown under the effect of torque, so that the axial 
displacement of the outer part (120) and the inner part (560) in relation 
to the cage (340) in the direction Z is evident. As a result of this axial 
displacement, the center points (2) of the centering surface (2') and (5) 
of the centering surface (5') are likewise displaced according to the 
clearance conditions. 
The high point-loading of the ball (70) on the window support surface (71) 
gives rise to a running-in brinelling (7'). The balls shift in the 
direction of the brinelling, so that the ball plane (7") is no longer 
identical to the planes of symmmetry (3" and 4" respectively) of the cage 
centering surfaces and intersects the main axis at the point (7). As a 
result of the displacements illustrated, the distance between the ball 
plane and the center point of the tracks of the outer part (7-1) is less 
than the axial offset of the outer part "A" by the amount (2-7). The lever 
arm (6-7) of the inner part becomes greater than the axial offset "I" of 
the inner part by the amount (5-7). The large difference between the lever 
arms gives rise to great inaccuracy of the steering. The centering 
surfaces are no longer symmetrical in relation to the ball plane, with the 
result that constrained running occurs as the deflection angle increases. 
Because of the axial loading, contact between the centering surface (3') of 
the cage and the centering surface (2') takes place at the cylindrical 
orifice (21) in the outer part. To guarantee contact over the entire 
periphery, especially in the case of relatively large clearance fits, the 
surface (21) should be produced according to the invention concentrically 
with the centering surface (2'), preferably in one chucking operation. The 
same applied to the chamfer (51) and the centering surface (5') of the 
inner part. When the joint angle is relatively large, contact over the 
entire periphery is no longer possible, so that certain concentricity 
errors between the centering surfaces are also unavoidable, especially 
with larger clearance fits. The surfaces (31 and 41) adjoining the 
centering surfaces (3' and 4') are likewise to be produced preferably 
concentrically with the adjacent centering surfaces. 
Under load, there arises in each case an approximately elliptical contact 
surface between the balls (70) and the track surfaces (100 and 600), the 
main axes of which are located on the plane (1" and 6") extending 
perpendicularly to the track. The contact points (701 and 706) are the 
center points of the ellipses. 
FIG. 2a shows a diagrammatic representation of a joint according to FIG. 1, 
showing the bottom of the tracks (10), the ball tracks (1') and the center 
point of the tracks (1) of the outer part (120), and also the bottom of 
the tracks (60), the ball track (6') and the center point of the tracks 
(6) of the inner part (560), as well as the balls (70). The lever arm of 
the outer part (1-7) is less than that of the inner part (6-7). The 
broken-line contour (560) of the inner part would correspond to equal 
lever arms with a center point (6). The clearance between the balls and 
the tracks mainly takes the form, in practice, of rotational play. However 
the loading on the balls remains uniform. The meriodional planes are 
slightly distorted as a result of the rotational play. 
In FIG. 2b, the axis of rotation AA of the outer part is pivoted in one 
direction about the pivot axis (7) by an angular amount of .beta./2, and 
the axis of rotation II of the inner part is pivoted in the other 
direction by the same amount. The deflection angle of the joint amounts to 
.beta., and the pivot axis lies in the ball plane (7"). KK is the axis of 
the cage, unchanged. The center points (1) of the tracks and (2) of the 
centering surface of the outer part as well as the center points (6) of 
the tracks and (5) of the centering surface of the inner part, and also 
the common center point (3,4) of the cage centering surfaces are shown 
enlarged. The state of eccentricity of the guide surfaces, caused by the 
axial displacement of the respective center points, becomes evident. The 
centering-surface center point (5) of the inner part is located above the 
axis of rotation of the cage or above the centering center point of the 
cage (3,4) whereas the centering-surface center point (2) of the outer 
part is located underneath this, so that the centering surfaces and 
likewise the balls above the axis of rotation of the cage experience less 
radial play and those underneath the axis of rotation of the cage 
correspondingly more radial play. This forced eccentricity worsens the 
degree of uniformity of the load on the balls and centering surfaces to a 
great extent. Errors of a few hundredths of a millimeter in the approach 
to the contact surfaces of a joint with 15 mm balls can already result in 
a considerable reduction in the performance of such a joint. 
FIG. 3 shows a joint according to the invention in a state under torque, 
after running-in, the control accuracy being assured up to the maximum 
joint angle. The outer surface (3') of the cage (340) and the outer 
surface (5') of the inner part (560) serve as control surfaces with their 
center points (3 and 5) on the ball plane (7"). (7") is virtually the end 
position of the ball plane after the running-in brinelling has occurred. 
The hollow spherical surfaces (2') of the outer part (120) and (4') of the 
cage (340) are provided as bearing surfaces. The offset of the center 
point (2) from the center point (3) is a product of the radial clearance 
fit between (2' and 3') and of the distance of the contact point between 
(2' and 3') from the ball plane considering the thermal expansion and the 
elasticity of the parts. The same applies to the center point (4). 
The arc length of the guide surface (5') on both sides of the points of 
contact with (4') corresponds approximately to half the maximum deflection 
angle of the joint in each case, so that guidance of the bearing surface 
is always guaranteed over the entire periphery. Contact is, of course, 
interrupted by the ball tracks. The remaining outer surface (52) of the 
inner part can be designed as desired from the point of view of control 
and is, in this case, made spherical with the center point (6) which is 
also the center point of the tracks of the inner part, so that the track 
depth remains constant in this region. In this case, the spherical guide 
surface (5') does not extend up to the ball plane. The arc length of the 
guide surface (3') is likewise designed for the maximum deflection angle 
of the joint. The center point (1) of the tracks of the outer part is at 
the same distance from the ball plane as the center point (6) of the inner 
part, so that the mirror image of the tracks is ensured both in the 
straight position and at any joint angle. 
The offset (1-2) of the outer part is greater here than the offset (5-6) of 
the inner part, but the two lever arms (1-7" and 6-7") are equal, this 
being the prerequisite for constant velocity behavior. It is worthy of 
note that the outer and inner centering surfaces (3' and 4') of the cage 
do not run concentrically. According to the teaching of the invention, the 
center points (3 and 5) of the guide surfaces (3' and 5') are located on 
the ball plane (7"). Because of the desired clearances, the ball radii of 
the bearing surfaces (2' and 4') are each greater than those of the 
associated guide surface, thus resulting in an offset of the center points 
(2 and 4) in relation to (3 and 5). 
Since the guide surfaces (3' and 5') touch the bearing surfaces (2' and 4' 
respectively) at the end of their width, the adjoining surfaces of 
revolution (21 and 41) are preferably to be produced coaxially with the 
adjacent bearing surfaces, in one chucking operation, for example by means 
of grinding. It is also possible, of course, to produce only the parts of 
the bearing surfaces directly in contact with the guide surface with the 
necessary accuracy, for example by means of grinding, otherwise lower 
accuracy, for example, turning, would be sufficient. 
The joint in FIG. 4 is similarly shown after the necessary running-in of 
the window support surfaces (71) and under torque. In contrast to FIG. 3, 
the hollow spherical surfaces (2') of the outer part (120) and (4') of the 
cage (340) are designed as guide surfaces here, their center points (2 and 
4) being located on the ball plane (7"). The respective bearing surfaces 
(3' and 5') are designed, in longitudinal section, with a conformity to 
their guide surfaces, so that their profile center points (3 and 5) are 
located on the radii connecting the contact points to the guide center 
points. Otherwise, the remaining surfaces (32 and 52) which do not have to 
perform any control functions are appropriately made concentric with (2 
and 4). 
A further interesting design is shown in FIG. 5, 20 and in which the 
bearing surfaces (3' and 4'), being basically linear as edges on the outer 
and inner surfaces of the cage (340), are as far as possible from the ball 
plane. The guide surfaces (2' and 5') are, of course, shown spherical with 
their center points on the ball plane (7"). Here also is the brinelling of 
the window surfaces taken into account. Any flattening or adaptation of 
the bearing surfaces must be allowed for in the calculation of the 
functional dimensions. An advantage of this design is the rapid and 
accurate production of the bearing surface. In this design, the balls are 
introduced in the cage window with a prestress which is so high that it 
corresponds approximately to the expected depth of the brinelling (7'), so 
that, even after the running-in process which mainly takes place on the 
window support surface (71), the balls remain free of play. To improve the 
minimum track depth on the outer part, the ball track (1') of the outer 
part consists of a circle with the center point (1) on the main axis, and 
then of a tangent which is also evident from the path of the track bottom 
(10) with the portions (11 and 12). Because of the mirror image of the 
ball tracks (1' and 6'), the improvement in the track depth in the region 
(12) of the outer part (120) naturally involves impairment of the 
corresponding track parts (62) of the inner part (560), but in a place 
where there is, anyhow, abundant track depth on the inner part. The 
conical surface (311), adjacent to the bearing surface (3'), and the plane 
surface (312) are produced preferably in one chucking operation, and the 
same applies to the conical surface (411) and the cylindrical surface 
(412) of the inner contour of the cage. 
A bearing surface on the cage guarantees, because it always extends 
parallel to the ball plane irrespective of the joint deflection angle, 
that the sum of the axially acting forces in the direction of the window 
support surface remains perpendicular to the bearing surface. 
In FIG. 6 the guide surface (2') of the outer part (120) and the bearing 
surface (3') on the cage (340) are located in the region of the main axis 
of rotation. As a result, the supporting forces between (2') and (3') are 
minimal and correspond to the axial force vector caused as a result of the 
track inclination. Furthermore, a radial eccentricity of the guide surface 
(2'), for example in relation to the tracks of the outer part (120), will 
have a very slight effect on the position of the ball plane (7") which can 
otherwise be pivoted out of its desired position as a result of 
eccentricities of the guide or bearing surfaces. Here also, the inner 
contour (22) of the outer part and the outer contour (32) of the cage are 
appropriately arranged with a large amount of play, concentrically to the 
center of rotation of the joint, because according to the invention 
guiding along the ball plane is not necessary. The remaining outer contour 
(33) of the cage (340) is set back, to allow the cage to be introduced in 
the outer part into a position pivoted 90.degree., as is known per se. The 
joint referred to here is a six-ball joint. The center points (2 and 3) of 
the centering, fixing or positioning surfaces (2' and 3') are located on 
the ball plane (7"). The same applies to the bearing surface (4') and the 
guide surface (5') with their center points (4 and 5). In both cases, 
there is two-dimensional or surface contact. The bearing surface (4') of 
the cage (340) has an arc length of A and a minimum distance U from the 
ball plane. U is intended to correspond to the arc length of the maximum 
friction angle between (4') and (5') and should preferably be greater than 
the maximum friction angle, which is the dimension for self-locking. The 
arc length of the guide surface (5') outside the region A is calculated as 
F in each case. Here also, minimum contact between the bearing surface and 
guide surface should always be assured up to the maximum joint angle, half 
the deflection angle corresponding to an arc length of F+A. In this case, 
the brinelling (7' and 7a) on the window support surfaces (71) and window 
surfaces (72) in incorporated in the cage. The shape of (7') and (7a) can 
be derived from the kinematics of the particular joint on the basis of the 
movement of the ball in relation to the cage, but corresponds 
approximately to a spherical cup with a radius greater than the ball 
radius. Due to the fact that, especially when the running angle of the 
joint is small, the cage can rotate about its main axis in the scope of 
the cage window length, it is recommended to produce the brinelling dents 
by means of cold extrusion, milling or grinding, etc, whereby they extend 
in a peripheral direction in the form of a groove with a cross section 
which approximates to a radius greater than the ball radius. Here, the 
inner surface (42) of the cage is set back and made spherical. 
The special feature of the joint in FIG. 7 is that the guide surface (5') 
of the inner part (560) is provided on the separate element (562) which is 
fitted in the inner member (561) after the inner member has been inserted 
into the cage (340). The bearing surface of the cage (4') has its center 
point (4) on the main axis which has a greater radius than the spherical 
surface (5'), the center point of which is located on the ball plane, so 
that point contact is obtained (theoretically). The outer surface (3') of 
the cage serves as a guide surface with its center point (5') which is 
likewise located on the ball plane (7"). The bearing surface (2') on the 
outer part (120) is made with a conformity, so that the radius of this 
surface is greater, in longitudinal section, than that of the guide 
surface and is located at the point (2). However, the bearing surface (2') 
can also be made spherical, likewise with a center point (2), so that 
conformity is obtained in all directions, which can have an advantageous 
effect on the relative movement of the centering surfaces (2' and 3') in 
relation to one another. The remaining inner surface (22) of the outer 
part is set back, to prevent any contact with the guide surface, even 
under the effect of thermal expansion, elasticity, wear, etc. The distance 
U between the bearing surface (2) and the ball plane also guarantees that 
there is no jamming or self-locking at this point, even in emergency 
running, for example, in the case of a lack of lubrication, because U is 
at least equal to the friction angle of the pairs of surfaces (2' and 3') 
in the dry state. The outer contour (52) of the inner piece (561) runs 
parallel to the track bottom (60), so that both have one center point (6), 
with the result that the track depth on the inner part is constant over 
the entire deflection angle range. 
FIG. 7a illustrates another alternative form of the inner part (560) of 
FIG. 7. The guide surface (5') is located at the end of the drive shaft 
(780) which is connected to the inner piece (561) by means of a spline. 
The spring ring (781) guarantees that the part (561) is fixed to the shaft 
(780) and that the guide surface (5') is positioned exactly with its 
center point (5). The position of the guide surface (5') can be influenced 
by means of the width of the spring ring, because the guide surface (5') 
is always loaded by the axial force component. The turned groove (782) 
serves for retaining the inner part when the intermediate shaft (780) is 
introduced or assembled. 
In FIG. 8, both bearing surfaces (2' and 4') are made on separate parts 
(122 and 342). The outer surfaces (3' and 5') of the cage piece (341) and 
of the inner part (560) form, here, the guide surfaces with the common 
center point (7) in the ball plane (7"). The part (342) is screwed into 
the threaded bore (43) on the cage part (341). The bearing surface (4') is 
spherical and is adapted to the guide surface (5'). The hollow spherical 
bearing surface (2') of the setscrew (122) touches the guide surface (3') 
with all-round conformity inasmuch as the radius of this plane surface is 
greater than that of the guide surface (3') with a center point (2) 
located on the longitudinal axis of the setscrew. The additional part 
(342) can be screwed into the cage (341) after the inner part (560) has 
been fitted axially. The same applies to setscrews (122) which are screwed 
into the outer piece (121) after the axial fitting of the inner part 
together with the cage (340) including the balls. To make this axial 
fitting possible, the inner contour of the outer piece (121) consists of a 
spherical surface (23) and then of a cylindrical surface (22), and the 
track path is also designed in a corresponding way, as is evident from the 
track bottom (10) with a circular track piece (11) having a center point 
(1), followed by a track piece (12) parallel to the axis. The tracks of 
the inner part are made in a mirror image and are likewise necessarily 
free of undercuts. 
The two separate parts (122) and (342) allow axial adjustment of 
readjustment of the lever arms (1-7) and (6-7) respectively. 
The tracks (1') of the outer part (120) of the joint in FIG. 9 are located 
in meridional planes, run in a straight line and extend obliquely to the 
main axis, but in alternate directions, so that the number of tracks (1') 
is provided in pairs and so that the tracks (1') located opposite one 
another extend parallel to one another. The corresponding tracks (6') of 
the inner part (560) run in a mirror image to these, and therefore in 
pairs likewise. As a result, the inner part can be displaced in relation 
to the outer part of both in the straight position and in the angled 
position; the cage (340) is displaced half the distance. Consequently, the 
cage support surfaces (71) are located on one side of the ball plane (7") 
for half the balls (70) and on the other side of the ball plane (7") for 
the other half. The position of the contact points of the particular ball 
is located on the side of the cage window surface (72) irrespective of the 
direction of torque. 
The oblique angle of all the tracks is essentially equal, so that the axial 
force components on the cage support surfaces (71) and on the outer and 
inner parts cancel each other out, so that there is no displacement of 
these parts in relation to one another as a result of torque, except in 
the region of elastic deformation. The inner surface (25) of the outer 
part is essentially cylindrical and the outer surface (35) of the cage is 
essentially spherical, so that the cage (340) is centered radially in the 
outer part. According to the idea of this invention, the tracks (1' and 
6') mirror one another in relation to the ball plane, after the brinelling 
(7') has been engraved on the cage support surfaces (71) during the 
running-in phase. To achieve this, the window support surface is offset, 
during production, by the amount of brinelling. In the present design, the 
cage window surfaces (71 and 72) of the balls located opposite one another 
are produced so as to be inclined by this amount, so that the window 
surfaces located opposite one another can be produced by means of a simple 
broaching operation R. 
Track-controlled sliding joints basically in the design according to FIG. 9 
are known, but in these the tracks are not located in meridional planes, 
but in planes running parallel to the main axis or in the manner of a 
screw, and in these joints the tracks of one part are also arranged 
obliquely in alternate directions. In these designs, the contact points of 
the balls are located on one side of the ball plane or the other depending 
on the direction of rotation, so that the measures mentioned above apply 
only to those joints which are mainly loaded in one direction of rotation. 
For example, drive joints in motor vehicles run mainly in one direction 
(forwards). 
When such joints are used, for example in machine engineering, for both 
directions of rotation, the correction of the brinelling of the case 
windows can be compensated only by incorporating the brinelling and/or by 
increasing the prestress between the ball window and cage window so as to 
neutralise the brinelling.