Ball coupling device for keeping two sliding shafts articulated

1. A device for coupling an inner shaft and a concentrically arranged tubular outer shaft sliding one within the other in the direction of a common axis, said inner and outer shafts having adjacent peripheral surface containing axially extending concave portion,

said coupling device including a plurality of balls, each of said balls being disposed between a concave portion of the inner shaft and a concave portion of the outer shaft and moving on two rolling tracks disposed one on each side of a median plane passing through the common axis and through centers of said balls;

each of the two rolling tracks cooperating with the concave portion of one of the shafts and pivots about an articulation axis parallel to the common axis, said articulation axis being situated between a sliding face and the concave portion of one of said inner shaft and outer shaft, so that each rolling track pivots at a junction of the sliding face and the concave portion;

each of the two rolling tracks being pushed against each of said balls by a spring member disposed in and bearing on said concave portion of the inner shaft;

each of said balls rolling directly against the concave portion of the outer shaft, wherein the balls are arranged in a plurality of axial rows:

each row of balls being disposed in a concave portion of the outer shaft in the form of an axial groove whose section includes two concave faces inclined to each other which come into contact with the balls of said each row:

each row of balls being disposed in a concave portion of the inner shaft in the form of an axial groove whose section includes a bottom and two flanks, the bottom being substantially perpendicular to the median plane passing through the common axis and through the axis of the centers of the balls of said each row;

two rolling tracks for each row of balls being disposed one on each side of the median plane and cooperate with the concave portion in the form of the axial groove of the inner shaft and each rolling track takes the form of an axial bar whose section has:

a bearing portion with a face adapted to come into contact with the balls of said each row:

a pivot portion in the form of a fork with a concave face that cooperates with a conjugate convex shape of a junction face disposed between the face of the inner shaft and the corresponding flank of the axial groove, the concave face and the junction face having a substantially cylindrical shape whose axis is the articulation axis; and

each of the two rolling tracks is pushed by a spring member that bears on said bottom of the axial groove of the inner shaft, so that:

at rest, when there is no transmission of torque, and when active, when there is transmission of torque,

each of said balls is always in contact on each side of the median plane, via one bearing area, with the corresponding rolling track disposed in one of the two shafts, and through another bearing area with the concave portion of the other shaft, and

the center of each of said balls, a &enter of the bearing area with the rolling track, and a corresponding center of the articulation axis of said rolling track are always aligned.

2. A coupling device according to claim 1 , wherein each of the two rolling tracks is pushed by a respective spring member, said two spring members being connected to each other to constitute a double spring member.

3. A coupling device according to claim 1 , wherein spaced male and female conjugate profiles affording a certain degree of play are formed on the inner shaft and the outer shaft so that torque still is transmitted between the inner shaft and the outer shaft in the event of breakage of the balls.

4. A coupling device according to claim 1 , wherein the spring members are disposed in the inner shaft and push the two rolling tracks which cooperate with the inner shaft.

5. A coupling device according to claim 1 , wherein the balls are arranged in a plurality of axial rows:

each row of balls is disposed in a concave portion of one of said inner shaft and outer shaft in the form of an axial groove whose section includes two concave faces inclined to each other which come into contact with the balls of said each row;

each row of balls being is disposed in a concave portion of the other of said inner shaft and outer shaft in the form of an axial groove whose section includes a bottom and two flanks, the bottom being substantially perpendicular to the median plane passing through the common axis and through the axis of the centers of the balls of said each row;

two pivoting rolling tracks for each row of balls are disposed ore on each side of the median plane and cooperate with the concave portion in the form of the axial groove of said other of said inner shaft and outer shaft and each rolling track takes the form of an axial bar; and

each of the two pivoting rolling tracks is pushed by a respective spring member, said two spring members being connected to constitute a double spring member in the form of a double axial spring member which has a thin section with a rounded central portion that bears on the bottom of the axial groove of said other of said inner shaft and outer shaft and two curved ends which act on said two pivoting rolling tracks.

6. A coupling device according to claim 1 , wherein the balls are arranged in three axial rows transverse at 120° to each other:

said three axial ball rows are respectively disposed in three axial grooves of one of said inner shaft and outer shaft which are transverse at 120° to each other, the axial groove of each of said three axial ball rows having a section including two concave faces inclined to each other which come into contact with the balls of said each row;

said three axial ball rows are respectively disposed in three axial grooves of the other of said inner shaft and outer shaft which are transverse at 120° to each other, the axial groove of each of said three axial ball rows of said other of said inner shaft and outer shaft having a section including a bottom and two flanks, the bottom being substantially perpendicular to the median plane passing through the common axis and through the axis of the centers of the balls of said each row; and

two pivoting rolling tracks for each row of balls are disposed one on each side of the median plane and cooperate with the concave portion in the form of the axial groove of said other of said inner shaft and outer shaft and each rolling track takes the form of an axial bar.

7. A coupling device according to claim 1 , wherein the balls are arranged in three axial rows transverse at 120° to each other;

the outer shaft has three axial grooves transversely at 120° to each other which slide respectively on the rows of balls, the axial grooves having the length required to allow a required axial sliding of the outer shaft and the inner shaft,

each axial groove of the outer shaft has a section including two concave faces inclined to each other which come into contact with the balls of the respective row;

the inner shaft has three axial grooves transverse at 120° to each other, and an axial spring member and two rolling tracks in the form of axial bars are mounted in each axial groove of the inner shaft;

each axial groove of the inner shaft has a section including a bottom and two flanks, the bottom being substantially perpendicular to the median plane passing through the common axis and through the axis of the centers of the balls of the respective row;

two rolling tracks for each row of balls are disposed one on each side of the median plane and cooperate with the concave portion in the form of the axial groove of the inner shaft and each rolling track takes the form of an axial bar whose section has a bearing portion with a face adapted to come into contact with the balls of said each row and a pivot portion;

each of the two rolling tracks is pushed by one of said spring members that bears on said bottom of one of said the axial groove of the inner shaft; and

the combination of the balls, the rolling tracks and the spring members is closed at each end by a shoulder and a retaining ring that engages in each of the axial grooves of the inner shaft.

8. A coupling device according to claim 1 applied to an intermediate part of an automobile vehicle steering column.

9. A coupling device according to claim 1 applied to a top part of an vehicle steering column.