Sliding homokinetic transmission joint intended for motor vehicles

A sliding transmission joint intended for motor vehicles, which includes a tripod (1) locked in rotation with a driving shaft (2) and provided with three radial arms (3) capable of sliding axially on flat rolling tracks (22) provided inside a drum (5). The drum 5 is locked in rotation with a driven shaft, rows of needle rollers (7) are arranged between the arms (3) and the rolling tracks (22), and also cages (14) are provided for holding the rows of needle rollers (7). The cages (14) having projecting members (16) which are used for attaching the cages (14) to the drum (5) and which are accommodated in corresponding recesses (15) formed in the drum. The arrangement of the projecting members 16 and recesses 15 ensures that the cage (14) is guided perfectly as far as the end of the extension of the driving shaft (2), and reduces the weight of the joint by eliminating projecting parts (28) between two internal adjacent shoulders of the rolling tracks.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The present invention relates to a sliding homokinetic transmission joint 
intended for motor vehicles. 
2. Description of the Prior Art 
More particularly, the invention concerns joints of the type comprising a 
tripod locked in rotation with a driving shaft and provided with three 
radial arms capable of sliding axially on flat rolling tracks provided 
inside a drum locked in rotation with a driven shaft, rows of needle 
rollers arranged between the arms of the tripod and the rolling tracks, 
and also cages for holding the rows of needle rollers. The cages are 
guided laterally by parallel shoulders defining the upper and lower edges 
of the rolling tracks, such that the cages remain exactly aligned parallel 
to the general axis of the rolling track, itself parallel to the axis of 
the drum. Consequently, the needles, which are held by the cage so that 
they are perpendicular to the longitudinal axis of the latter, always roll 
precisely in their natural direction, i.e. without sliding and without 
giving rise to lateral frictional forces. Such a joint is described in 
French Pat. No. 2,506,872. 
So that there is sufficient angular clearance for the driving shaft, the 
internal guiding shoulder close to the edge of the drum must be 
eliminated, for which purpose a chamfer of large dimensions is machined in 
the latter. Consequently, at the end of the extension of the driving 
shaft, the cage is not guided properly and undesirable friction and 
frequent binding occur. 
SUMMARY OF THE INVENTION 
Therefore, the aim of the invention is to provide a joint of the 
abovementioned type, which is constructed such that the abovementioned 
drawbacks are overcome. 
According to the invention, the cages have projecting means comprising 
guiding members which are arranged on only one side of the cage, i.e. the 
side situated towards the outside of the drum, and which are slidingly 
engaged with case retaining means, such as a single longitudinal groove 
machined in the drum along the external edge of the rolling track or the 
cage retaining means can comprise adjacent members mounted on the interior 
of the drum. 
Due to the arrangement of such projecting means, an internal guiding 
shoulder for the cage formed by a projecting part along the entire length 
of the drum can be eliminated and the latter can thus be bored so as to 
have a larger diameter limited by the effective width of the rolling track 
corresponding to the length of the cylindrical part of of the needles. 
It is thus still ensured that the cages are perfectly guided, independently 
of the chamfer at the open end of the drum which is required in order to 
obtain maximum sliding at an angle. 
According to a first possible embodiment, the projecting means consist, in 
the case of each cage, of projecting guiding members provided at the ends 
or in the vicinity of the ends on one side of the cage.

DESCRIPTION OF THE PREFERRED EMBODIMENTS 
The prior art transmission joint shown in FIGS. 1b and 2 is intended for 
motor vehicles and comprises a tripod 1 locked in rotation with a driving 
shaft 2 and provided with three radial arms 3 capable of sliding axially 
on flat rolling tracks 4 provided inside a drum 5 locked in rotation with 
a driven shaft (not shown). Rows of needle rollers 7 and bearings or 
cup-shaped members 8 are arranged between the arms 3 and the rolling 
tracks 4, and cages 9 keep the rows of needles 7 on the tracks 4. The 
latter are each defined between two longitudinal shoulders 11, 12 arranged 
in such a way that the cages 9 remain exactly aligned parallel to the 
general axis A of the rolling track 4, itself parallel to the axis B of 
the drum 5. Consequently, the needles 7, which are held by the cage 9 so 
that they are perpendicular to the longitudinal axis A, always roll 
precisely in their natural direction, i.e. without sliding and without 
giving rise to lateral frictional forces. So that there is maximum angular 
clearance for the driving shaft 2, a chamfer 13 of large dimensions is 
machined in one end of drum 5. 
According to the invention shown in FIG. 1a, cages 14 have projecting means 
extending towards the outermost surface of the drum and beyond a plane 
defined by the rolling track surface comprising guiding members 16 on the 
drum 5, which are accommodated by cage retaining means associated with the 
drum comprising corresponding longitudinal recesses or grooves 15 formed 
in the drum 5 for slidingly engaging each projecting means to allow the 
cages to move axially along the rolling tracks, these guiding members 
being formed solely on the side of the cage 14 situated towards the 
outside of the drum 5, i.e. the side of the cage located closest to the 
outermost surface of the drum. 
In the embodiment shown in FIGS. 3 to 5 and 8, these projecting means or 
guiding members consist, in the case of each cage 14, of blade-like 
arcuate shaped guiding members or extensions 16 provided at the ends of an 
external longitudinal side piece 17 of the cage, this longitudinal side 
piece being connected to the opposite longitudinal side piece by 
crosspieces 18. 
By way of a variation (FIG. 7), the blade-like arcuate shaped guiding 
members 16a are arranged in the vicinity of the ends of the longitudinal 
side piece 17. 
In the case of each cage 14, these projecting means or guiding members may 
also be formed as single parts and extend along the entire length of the 
cage. The abovementioned blade-like arcuate shaped guiding members 16 or 
extensions of each cage 14 are curved inwards with a convex portion 23 
facing away from the opposite side of the cage, for example in the form of 
a quarter or half bend, and rest by means of another convex portion 19 
facing toward the opposite side of the cage against an internal side wall 
15a of the recess 15, this internal side wall leading to a corresponding 
rolling track 22. In line with each blade-like arcuate shaped guiding 
member 16 or 16a, the corresponding longitudinal side piece 17 is 
connected to the blade-like member by means of the convex rear portion 23 
sliding against a shoulder 24 defining, together with the internal side 
wall 15a, the recess 15 associated with the rolling track 22, the bottom 
of the recess 15 being preferably circular (FIG. 3). 
The cage 14 is provided, at its ends, with folded back transverse flanges 
10 which serve as end-of-travel stops for the cage, by means of contact 
with the ends of the cup-shaped members 8 (FIG. 8). 
With the internal shoulders 12 of the joint according to the prior art 
(FIG. 2) eliminated, the drum 5 of the joint according to the invention 
has a bore 25 (FIGS. 1a and 3), the diameter of which is clearly greater 
than that of the bore 26 (FIG. 1b) required in the prior art, the bore 25 
being limited by the effective width of the rolling track 22 corresponding 
to the length of the cylindrical part of the needles 7. A chamfer 27 (FIG. 
1a), provided at the end of the drum, obviously does not hinder in any way 
guiding of the needles 7. Due to the arrangement of the bore 25, the 
fragile projecting parts 28 located, in the prior art, between the 
internal shoulders 12 of two continguous rolling tracks (FIG. 1b) can be 
eliminated. 
The sliding homokinetic joint according to the invention has the following 
technical advantages: 
(1) due to the arrangement of projecting means comprising the guiding 
members 16, 16a retaining the cages 14 and their needles 7, and also the 
cage retaining means comprising the longitudinal grooves or recesses 15 
for these guiding members 16, 16a, perfect guiding of the cages 14 is 
ensured, independently of the chamfer required in order to obtain maximum 
sliding at an angle; this essential characteristic feature of the 
invention also makes it simpler and less costly to manufacture the 
homokinetic joint, while reducing its weight, in particular due to 
elimination of the fragile parts 28; 
(2) due to the enlarged bore 25, forged blanks which are less complicated 
and lighter than those of joints according to the prior art can be used; 
(3) high wear resistance surface hardening of the rolling tracks 22, which 
is generally performed after rapid heating by means of induction, no 
longer gives rise to problems of stress cracks, since the fragile part 28 
is eliminated; 
(4) finally, it is possible to obtain a simple blank which is very similar 
to the drum 5 and consists of a profiled tube 29 (shown in FIG. 9); 
machining thus consists in cutting the profiled parts 29 to the required 
length, broaching which defines at the same time the profiles of the 
rolling track 22, recess 15, shoulder 24 and a flat surface 31 adjacent to 
the edge of the shoulder 24, and turning of the inside chamfer 27 at the 
end of the drum 5. 
Consequently, machining is simplified, using a simpler and sturdier 
broaching tool, surface-hardening of the rolling tracks 22 is made easier, 
and the weight of the material used is reduced, while perfect guiding of 
the cage 14 is ensured over the entire distance of extension. 
FIG. 10 shows a third embodiment of a variation of the present invention in 
which only end parts 32 of blade-like arcuate shaped guiding members 33 
are engaged inside recesses formed in the drum 5 which consist of grooves 
35, formed by side walls 36, 37 against which the said end parts 32 bear. 
The end parts 32 include convex rear portions 34 which face away from the 
opposite side of the cage and form an extension of the latter which is 
located outside the grooves 35. Thus, the convex rear portions 34 are no 
longer used for guiding the cage, this being ensured solely by the 
attaching ends 32 which allow movement both axially and in the direction 
of translation towards the inside and the outside of the drum 5, without 
the need for the shoulders 11 or 24 of the drum 5 (FIGS. 1a, 1b and 3). 
Consequently, the shape of the drum is simplified and the latter can be 
provided with a profile having a practically constant thickness and hence 
can be manufactured at a low cost from pressed, rolled or folded sheet 
steel. 
In the fourth embodiment shown in FIGS. 11 and 12, each cage 50 has side 
pieces 38a, 38b for attaching the cage to the drum 5, one of which 38a 
comprises the projecting means which penetrates inside a corresponding 
groove 39 which comprises the cage retaining means and which is machined 
or cold-formed in the inner wall 41 of the drum. The groove 39 ensures 
lateral and axial guiding of the cage 50, and the longitudinal side pieces 
38a, 38b have conical holes 40 inside which the ends 42 of the needles 43 
revolve. The cage 50 is provided, at its ends and between the side pieces 
38a, 38b, with folded flanges 44 serving as stops for limiting the travel 
of the cage, by means of contact with opposite edges 45 of cup-shaped 
members 46 arranged between the needles 43 and the associated arm 3. 
Penetration of the side pieces 38a into the groove 39 ensures perfect 
guiding of the cage 50 in the direction of lateral translation and in the 
axial direction. The side pieces 38a, 38b are made by means of folding 
after cutting up and boring of a sheet-steel blank, at the end of which 
operations the cage 50 shown in FIG. 12 is obtained. 
The fifth embodiment is an example of embodiment of the invention, shown in 
FIGS. 13 and 14 in which the longitudinal grooves comprising the cage 
guiding means for guiding the cage are no longer machined in the drum, but 
rather the cage guiding means are formed by means of adjacent members 
mounted on the drum. 
Thus the invention provides here for a star-shaped clip 52 with the members 
comprising six radial arms 53, the clip 52 being made preferably from 
hardened sheet steel and having a base 52a which bears against the bottom 
or inner axial end surface 54 of the drum 60. Each arm or member 53 bears 
against the drum 60 and has an internal surface 55 forming a rolling track 
for the needles 56 contained inside the cages 57, while the edges 58 of 
the arms or members 53 situated towards the outside of the drum 60 form 
one of the two side walls of guiding grooves 59 receiving the projecting 
means comprising guiding members 61 of the cages 57, the second outer side 
wall 62 of which is machined in the drum 60 and spaced from the edge 58 
located closest to the outermost surface of the drum 60. 
Thus, the single guiding groove or slide 59, located on the outer side of 
the rolling track 55, is mounted inside the drum 60. 
Means are provided for fixing or securing the clip 52 axially to the drum 
60. In the example described, these recovery means consist of a 
sheet-metal or plastic cap 63 which encloses the free edge of the drum 60 
onto which it is crimped or snap-engaged at 64, and which performs a dual 
function. In fact, on the one hand, it prevents untimely disengagement of 
the movable members (not shown) made in a manner known per se, and, on 
other hand, it retains the clip 52 axially by means of contact with the 
free ends 65 of the six arms or members 53 of the latter. The base 53a of 
the clip 52 may be perforated so as to guide and hold an elastic stop 66 
for determining the end of compressive travel of the shaft (not shown). 
The cage 57, the outer side wall 61 of which comprises the projecting means 
which is guided by the groove 59, is of the type where the needles 56 
revolve individually inside the holes 40 formed in its two longitudinal 
side pieces (cage 50 in FIG. 12), but it may obviously be replaced by a 
cage of the type having blade-like members, such as the cage 14 (FIG. 6). 
The ends of the arms or members opposite the base 52a are cut in the shape 
of bevels 66 so as not to project beyond the cone formed by the chamfer 67 
of the drum 60, itself provided so as to increase the sliding length and 
angle of the joint. 
Despite the chamfer 67, when the joint is in the fully extended position, 
the needle cages 57 or 14 are positively guided by the cage retaining 
means comprising the slides or grooves 59 located on the radially 
outermost side of the rolling track 55, this single groove or guide for 
each cage 57, 14 extending as far as the edge of the drum 5, 60. 
While the invention has been fully described by way of example with 
reference to the accompanying drawings, it should be understood that 
various changes and modifications will be apparent to those skilled in the 
art. Therefore, unless otherwise such changes and modifications depart 
from the scope of the present invention, they should be constructed as 
being included therein.