Universal joint

A universal joint for small articulation angles, especially, an intermediate joint in a propeller shaft of motor vehicles, has an outer joint part (11) with longitudinally extending first ball tracks (14) which, between stop faces, include an axial length with an unchanged cross-section; an inner joint part (31, 51) with longitudinally extending second ball tracks (36, 56) whose axial length is greater than that of the first ball tracks (14); and torque transmitting balls (15) guided in the radially opposed first and second ball tracks (14, 36, 56). The outer joint part (11), at least in the axial region of the ball tracks (14) is produced as a formed plate metal part with an approximately constant wall thickness. The ball tracks (14), in the outer joint part (11), are formed by circumferentially distributed formations (13) axially closed at both ends by stops (16, 17).

SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a universal joint of 
the initially mentioned type which can be more simply produced. 
In the present invention, at least in the axial region of the ball tracks, 
the outer joint part is produced by a formed plate metal part. The part 
has an approximately constant wall thickness and the ball tracks in the 
outer joint part are formed by circumferentially distributed formations 
axially closed at both ends by integral stops. Such a shape simplifies the 
production of the outer joint part. The ball tracks and stops, which are 
produced integrally with the component, leads to a high degree of 
mechanical strength. 
According to a preferred embodiment, at least in the axial region of the 
ball tracks, the outer joint part includes one piece and the ball tracks 
in the outer joint part are formed seamlessly from the material of a 
tubular member or circular blank. A joint component is produced simply by 
introducing a tubular member or circular blank into a suitable die. 
Expanding fingers, of an inner tool, press the axially limited ball tracks 
outwardly. However, a particularly advantageous and adapted production 
method may include introducing a tube into a die, with the tube sealingly 
closed at both ends and filled with a hydraulic pressure agent through a 
supply line, so that the track portions are produced in corresponding 
recesses in the die. In each case it is possible to produce seamless and 
accurately dimensioned ball tracks in the outer joint part. 
According to a modified embodiment, in the region of the ball tracks, the 
outer joint part includes two longitudinal sections. Halves of the ball 
tracks, if viewed axially, are formed out of tube ends, respectively, with 
production taking place by mechanically deforming two circular blanks or 
tubular portions. This method is particularly advantageous in that the 
respective inner tools may be rigid and undercut-free. The two tube ends 
provided with the ball track halves may be connected by a suitable welding 
method, and if a suitable welding technology is chosen, there is no need 
for remachining the transverse seam in the region of the ball tracks. 
According to a third embodiment, in the region of the ball tracks, the 
outer joint part is composed of two half-tubes. One half of the ball 
tracks, if viewed circumferentially, is formed out of one of the 
half-tubes, respectively. In this case, it is possible to use two planar 
plates or two half-round tubular shells to form the tracks as 
trough-shaped formations by applying a suitable forming technology, with 
the two half-tubes subsequently welded together to form a tube. As the 
connections are preferably provided between two tracks, the question of 
any projections at the welds is of subordinate significance. The tracks 
themselves can be produced seamlessly from the material. Apart from using 
mechanical means for forming purposes, which again have to have expandable 
elements, it is possible to consider explosion forming technologies or 
forming technologies involving the use of hydraulic pressure agents. 
Preferred embodiments which have been selected to consistently further 
develop the chosen plate metal design include the outer joint part 
comprises an inserted cover. The cover closes the inner cross-section and 
if viewed from the shaft connection for the inner joint part, is 
positioned axially behind the ball tracks. The cover also forms an axial 
stop for the inner joint part to prevent axial pushing in of the inner 
joint part. The inserted cover includes at least partially internally 
spherical or internally conical guiding faces whose centers are positioned 
on the joint axis. If the joint is a fixed joint, the outer joint part 
comprises a further inserted cover. The cover partially closes the inner 
cross-section and comprises a central aperture for a shaft connection of 
the inner joint part. The cover, if viewed from the shaft connection for 
the inner joint part, is positioned axially in front of the ball tracks 
and forms an axial stop for the inner joint part to prevent axial 
extraction of the inner joint part. The further inserted plate metal cover 
includes at least partially internally spherical or internally conical 
guiding faces whose center is positioned on the joint axis. 
The embodiment constituting a formed plate metal part with a substantially 
constant wall thickness as proposed in accordance with the invention for 
the outer joint part may, analogously, also be used for the inner joint 
part to the extent that the tracks, on the one hand, and the guiding faces 
opposite the outer joint part, on the other hand, are concerned. In this 
context, in a first preferred embodiment, at least in the axial region of 
the ball tracks, the inner joint part is produced in one piece. The ball 
tracks in the inner joint part are formed seamlessly out of the material 
of a tubular member or a circular blank. In this case, too, it is possible 
to carry out a forming operation against an outer tool by expanding means, 
but preferably by closing the tube ends and supplying a hydraulic pressure 
agent. 
According to an alternative embodiment, in the region of the ball tracks, 
the inner joint part includes two semi-dishes. One half of each ball 
track, if viewed circumferentially, is fully formed in one of the 
half-dishes. Again, analogously to the above, the seamless track regions 
may be formed out of two plates or half-dishes, with the two half-dishes 
subsequently welded together to form an annular member. 
Additional objects and advantages of the invention will be apparent from 
the detailed description of the preferred embodiment, the appended claims 
and the accompanying drawings, or may be learned by practice of the 
invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
The Figures show a constant velocity universal joint for small articulation 
angles. The outer joint part 11 is produced in one piece out of a tubular 
member 12. Preferably, the outer joint part has a short length and is 
suitable to weld to a tubular shaft of the same diameter, or it may form 
itself a complete tubular shaft of a greater length. At a small distance 
from the illustrated end of the tubular member 12, circumferentially 
distributed, trough-like formations 13 are provided whose inner faces form 
ball tracks 14 in which balls 15 are axially movable between different 
planes M. The movement of the balls is limited by inner stops 16, 17 in 
the formations 13. At the free end of the tubular member 12 a thin-walled 
portion 26 is provided to which a rolling boot 27 is secured by means of a 
securing ring 28. The rolling boot 27 is also secured to a shaft part by 
means of an annular bead 29. 
In FIGS. 1 and 2, covers 18, 19 are inserted into the tubular member 12. 
The covers are formed plate metal parts with the cover 19 including a 
central through-aperture 20. Otherwise the covers are largely identical 
and arranged symmetrically relative to one another. At both ends, the 
covers are arranged at a distance from the ball tracks 14 in the outer 
joint part. The covers 18, 19 include outer beaded portions 22, 23 resting 
against the inner wall of the straight tubular member 12. The parts 12, 
18, 19 are welded or soldered to one another. Furthermore, the covers 18, 
19 include partially spherical or conical inner faces 24, 25 which form 
guiding faces for the inner joint part 31, 51. 
FIGS. 3 and 4 only show the cover 18 in the above-described embodiment, but 
there is no part corresponding to the cover 19. 
In FIGS. 1 and 3, the inner part 31, 31' is a solid formed part and 
includes an inner aperture 32 into which a shaft journal 33 is inserted. 
The journal 33, in FIG. 1, passes through the aperture 20 of cover 19. The 
connection between the outer joint part 31, 31' and the shaft journal 33 
includes shaft teeth 34 and a securing ring 35. The inner joint part 31 is 
shown to have axial ball tracks 36 which enable a greater axial distance 
for the balls 15 than the tracks 14 in the outer joint part 11. 
Furthermore, in FIG. 1, the inner joint part 31, 31' includes externally 
spherical surface portions 37, 38 which, in a supporting and guiding way, 
cooperate with the internally spherical or conical surface 24, 25 of the 
cover 18 when the inner joint part is articulated around the joint center 
Z. In FIG. 3, only the surface portions 37 function in such a way. An 
axially opposed end face 40 of the inner joint part 31, 31' is 
contact-free relative to the outer joint part. 
In FIGS. 2 and 4, the inner joint part 51 is integrally formed out of the 
end of the tubular member 53. The tubular member 53 may be welded to an 
adjoining tubular shaft of the same diameter or itself constitutes a 
complete tubular shaft. Formations 59 in the shape of longitudinal ribs, 
which form the track 56 in the inner joint part 51, are formed out of the 
material. Otherwise, the end portion of the tubular member 53 in FIG. 2 
shows the same outer shape as the inner joint part according to FIG. 1. 
Again, externally spherical surfaces 57, 58 are shown which cooperate with 
the internally spherical or internally conical surfaces 24, 25 of the 
cover 18, 19. The surfaces 24, 25 provide axial support and guidance when 
the inner joint part is articulated around the joint center Z. In FIG. 4, 
only the surface portions 57 function in this way. A transition portion 60 
of the inner joint part 51 is contact-free relative to the outer joint 
part. 
While the above detailed description describes the preferred embodiment of 
the present invention, the invention is susceptible to modification, 
variation and alteration without deviating from the scope and fair meaning 
of the subjoined claims.