Abstract:
A constant velocity counter track joint having an outer joint part with outer ball tracks having first tracks opening toward the aperture end and second tracks opening toward the attaching end. The center line of the second tracks, departs, radially inwardly, a first reference radius centered in the point of intersection of a perpendicular line on the tangent at the center line of the ball track and the longitudinal axis. In the inner joint part, the center line of the ball tracks departs, radially inwardly, a second reference radius centered in the point of intersection of a perpendicular line on the tangent at the center line of the ball track and the longitudinal axis. In the outer joint part, the center line of the ball tracks towards the aperture end, moves radially outwardly beyond said first reference radius. In the inner joint part, the center line of the ball tracks towards the attaching end, moves radially outwardly beyond said second reference radius.

Description:
TECHNICAL FIELD 
     The invention relates to a constant velocity joint in the form of a counter track joint with the following characteristics: 
     an outer joint part which comprises a longitudinal axis L 12  and an attaching end and an aperture end arranged so as to be axially opposite one another, and which is provided with outer ball tracks; 
     an inner joint part which comprises a longitudinal axis L 13  and attaching means for a shaft pointing towards the aperture end of the outer joint part, and which is provided with inner ball tracks; 
     the outer ball tracks and the inner ball tracks form pairs of tracks with one another, 
     the pairs of tracks each accommodate a torque transmitting ball; 
     an annular ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows which each accommodate at least one of the torque transmitting balls, 
     the centers of the balls are held by the cage in a joint center plane EM and, upon articulation of the joint, are guided onto the angle-bisecting plane between the longitudinal axes L 12 , L 13 , 
     for a first part of the pairs of tracks, the opening angle α 1  between the tangents T 22   1 ′, T 23   1 ′ at track base lines extending parallel to the tangents T 22   1 , T 23   1  at the center lines M 22   1 , M 23   1  of the ball tracks in the joint center plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13 , opens from the attaching end to the aperture end. For a second part of the pairs of tracks, the opening angle α 2  between the tangents T 22   2 ′, T 23   2 ′ at track base lines extending parallel to the tangents T 22   2 , T 23   2  at the center lines of the ball tracks in the joint center plane when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13  opens from the aperture end to the attaching end. With reference to the joint center plane EM, the center lines of pairs of tracks are substantially mirror-image like relative to one another. 
     BACKGROUND 
     Prior art counter track joints comprise an even number of pairs of tracks. The first half of said pairs of tracks opens towards the aperture end of the outer joint part. The other half of said pairs of tracks opens towards the attaching end of the outer joint part. The pairs of tracks of the first type and second type are arranged so as to alternate if viewed in the circumferential direction. The tracks are arranged on meridian planes R which, in the circumferential direction, comprise uniform pitch angles of 360°/n, with n being the number of pairs of tracks, e.g. 6, 8, 10. 
     The alternating pairs of tracks are curved in such a way that, in the joint center plane EM, they comprise a tangent angle α 1 , α 2  at the track base lines, which angles are identical in size, but differ in respect of orientation, and the track extensions of the alternating pairs of tracks are mirrored with reference to the joint center plane. 
     Prior art counter track joints permit only a relatively small articulation angle of 35°, which is due to the pairs of tracks opening towards the attaching end of the outer joint part and closing towards the aperture end and having to be relatively short towards the aperture end to allow the cage to be mounted in the outer joint part. 
     U.S. Publication No. 2004/0116192 proposes counter track joints wherein the second pairs of tracks are provided with different track shapes which also include track center lines extending in an S-shaped way and having a turning point in the outer joint part and in the inner joint part. The track center lines are defined as being the path of the centers of the balls in the ball tracks. 
     SUMMARY OF THE INVENTION 
     The present invention provides fixed joints of the above-described type with increased articulation angles. 
     A first solution provides a constant velocity joint in the form of a counter track joint having: 
     an outer joint part which comprises a longitudinal axis L 12  and an attaching end and an aperture end arranged so as to be axially opposite one another, and which is provided with outer ball tracks; and 
     an inner joint part which comprises a longitudinal axis L 13  and an attachment for a shaft pointing towards the aperture end of the outer joint part, and which is provided with inner ball tracks. 
     The outer ball tracks and the inner ball tracks form pairs of tracks with one another, the pairs of tracks each accommodate a torque transmitting ball. 
     An annular ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows which each accommodate at least one of the torque transmitting balls. 
     The centers of the balls are held by the cage in a joint center plane and, upon articulation of the joint, are guided onto the angle-bisecting plane between the longitudinal axes. The center lines M 22 , M 23  of the ball tracks of pairs of tracks are positioned in radial planes R through the joint. For a first part of the pairs of tracks, the opening angle α 1  between the tangents T 22   1 ′, T 23   1 ′ at track base lines extending parallel to the tangents T 22   1 , T 23   1  at the center lines M 22   1 , M 23   1  of the ball tracks in the joint center plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13  opens from the attaching end to the aperture end. 
     For a second part of the pairs of tracks, the opening angle α 2  between the tangents T 22   2 ′, T 23   2 ′ at track base lines extending parallel to the tangents T 22   2 , T 23   2  at the center lines M 22   2 , M 23   2  of the ball tracks  22   2 ,  23   2  in the joint center plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13  opens from the aperture end to the attaching end. The following applies to the center lines of the second pairs of tracks; 
     in the outer joint part, the center line M 22   2  of the ball tracks in the region from the joint center plane EM to the attaching end radially inwardly leaves a reference radius RB whose radius center MB is positioned in the point of intersection of a perpendicular line on the tangent T 22   2 ′ at the center line M 22   2  of the ball track in the joint center plane EM and of the longitudinal axis L 12 ;
 
in the inner joint part, the center line M 23   2  of the ball tracks in the region from the joint center plane EM to the aperture end radially inwardly leaves a reference radius RB′ whose radius center MB′ is positioned in the point of intersection of a perpendicular line on the tangent T 23   2 ′ at the centre line M 23   2  of the ball track in the joint center plane EM and of the longitudinal axis (L 13 ).
 
     In the outer joint part, the center line M 22   2  of the ball tracks in the region from the joint center plane EM to the aperture end moves radially outwardly beyond said reference radius RB. 
     In the inner joint part, the center line M 23   2  of the ball tracks in the region from the joint center plane EM to the attaching end moves radially outwardly beyond said reference radius RB′. 
     The track shape given here permits the maximum articulation angle to be increased relative to prior art track shapes. The characteristic mentioned first according to which the center lines leave the reference radii inwardly can start directly at the joint center plane or even at a later stage, and it can behave so as to increase progressively. The second characteristic mentioned according to which the center lines move outwardly beyond the reference radius includes a direct outward movement away from the reference radius as well as a later crossing of the reference radius and subsequent outward movement. 
     According to a further embodiment, the constant velocity joint is provided with the following further characteristics of the second pairs of tracks: 
     in the outer joint part, the local radius of curvature R 1  of the center line M 22   2  in the joint center plane EM is smaller than the reference radius RB; and 
     in the inner joint part, the local radius of curvature R 1 ′ of the center line M 23   2  in the joint centre plane EM is smaller than the reference radius RB′. 
     According to another embodiment, the constant velocity joint is provided with the following further characteristics of the second pairs of tracks: 
     in the outer joint part, the center line M 22   2  of the ball tracks extends from the joint center plane EM to the attaching end radially outside a reference radius RZ whose radius center is positioned in the joint center M; and in the inner joint part, the center line M 23   2  of the ball tracks extends from the joint center plane EM to the aperture end radially outside a reference radius RZ′ whose radius center is positioned in the joint center M. 
     A further advantageous embodiment refers to the following further characteristics of the second pairs of tracks: 
     in the outer joint part, the center line M 22   2  of the ball tracks extends from the joint center plane EM to the aperture end radially outside a reference radius RB and, 
     in the inner joint part, the center line M 23   2  of the ball tracks extends from the joint center plane EM to the attaching end radially outside a reference radius RB′. 
     According to a further embodiment, the following further characteristics are proposed: in the outer joint part, the center line M 22   2  of the ball tracks extends from the joint center plane EM to the aperture end radially inside a reference radius RZ around the joint center M; and 
     in the inner joint part, the center line M 23   2  of the ball tacks extends from the joint center plane EM to the attaching end radially inside a reference radius RZ′ around the joint center M. 
     According to a further embodiment, the following further characteristics of the second ball tracks are proposed: 
     the center lines M 22   2 , M 23   2  of the outer ball tracks and inner ball tracks each comprise at least two arched portions which are curved in opposite senses and which adjoin one another in a turning point. 
     The turning points W 22   2  of the outer ball tracks are positioned at a distance from the center plane EM towards the aperture end. 
     The turning points W 23   2  of the inner ball tracks are positioned at a distance from the center plane EM towards the attaching end. 
     The turning points W 22   2 , W 23   2  are each positioned below a maximum of the distance of the center lines M 22   2 , M 23   2  from the longitudinal axes L 12 , L 13 . A further embodiment comprises the following characteristics of the second pairs of tracks: 
     the track center lines M 22   2  of the outer ball tracks comprise a first arch with the radius R 1  whose center M 1  is offset by a first axial offset O 1   a  from the center plane EM of the joint towards the attaching end and by a first radial offset O 1   r  from the longitudinal axis L 12  outwardly towards the ball track and, in the region adjoining said arch, towards the attaching end. They comprise a second arch with the radius R 2  whose center M 2  is offset by a second axial offset O 2   a  from the center plane EM of the joint towards the aperture end and offset outwardly from the longitudinal axis L 12  by a second radial offset O 2   r  which is greater than the sum of the first radius R 1  and the first radial offset O 1   r.    
     The track center lines M 23   2  of the inner ball tracks comprise a first arch with the radius R 1 ′ whose center M 1 ′ is offset by a first axial offset O 1   a ′ from the center plane EM of the joint towards the aperture end and offset outwardly by a first radial offset O 1   r ′ from the longitudinal axis L 13  to the ball track and, in the region adjoining said arch, towards the aperture end, they comprise a second arch with the radius R 2 ′ whose center is offset by a second axial offset O 2   a ′ from the centre plane EM of the joint towards the attaching end and offset outwardly from the longitudinal axis L 13  by a second radial offset O 2   r ′ which is greater than the sum of the first radius R 1 ′ and the first radial offset O 1   r′.    
     More particularly, the following further characteristics of the second pairs of tracks are proposed: 
     the radius of curvature of the center lines M 22  of the outer ball tracks decreases in the extension from the center plane EM to the attaching end and the radius of curvature of the centre line M 23  of the inner ball tracks decreases in the extension from the center plane EM to the aperture end. 
     More particularly, the following further characteristics of the second pairs of tracks are proposed: 
     the track center lines M 22   2  of the outer ball tracks comprise a third arch with the radius of curvature R 3  which tangentially, while having the same sense of curvature, adjoins the first arch with the radius of curvature R 1  and whose radius of curvature R 3  is smaller than the radius of curvature R 1 , and
 
the track center lines M 23   2  of the inner ball tracks comprise a third arch with the radius of curvature R 3 ′ which tangentially, while having the same sense of curvature, adjoins the first arch with the radius of curvature R 1 ′ and whose radius of curvature R 3 ′ is smaller than the radius of curvature R 1 ′.
 
     According to a further embodiment, in the second pairs of tracks, along the extension of the center line M 22   2  of the outer ball tracks, towards the aperture end, the second arch is adjoined by an axis-parallel straight line G 3  and, along the extension of the center line of the inner all tracks M 23   2 , towards the attaching end, the second arch is adjoined by an axis-parallel straight line G 3 ′. 
     According to an alternative embodiment, in the second pairs of tracks, along the extension of the centre line M 22   2  of the outer ball tracks, towards the aperture end, the second arch is adjoined by a straight line which approaches the longitudinal axis L 12  and that, along the extension of the center line M 23   2  of the inner ball tracks, towards the attaching end, the second arch is adjoined by a straight line which approaches the longitudinal axis L 13 . 
     According to a further characteristic in the second pairs of tracks, the center lines M 22 , M 23  of the ball tracks in the joint center plane EM intersect one another at an angle of 4 to 32°, wherein the tangents T 22 , T 23  at the center lines M 22 , M 23  of the ball tracks of all pairs of tracks when the joint is in the aligned condition form identical opening angles α. 
     Preferably, first pairs of tracks and second pairs of tracks are arranged so as to alternate around the circumference. The radial planes R 1  of the first pairs of tracks and the radial planes R 2  of the second pairs of tracks, in the circumferential direction, can, more particularly, comprise identical pitch angles. In a special embodiment, the first pairs of tracks and the second pairs of tracks do not extend symmetrically relative to the joint center plane EM. More particularly, the first pairs of tracks—analogously to the pairs of tracks of UF joints—can be designed to be undercut-free when viewed from the joint aperture end. 
     According to a further embodiment, the pitch circle radius PCR 1  of the balls of the first pairs of tracks is smaller than the pitch circle radius PCR 2  of the balls of the second pairs of tracks. 
     A second solution provides a constant velocity joint in the form of a fixed joint with the following characteristics: 
     an outer joint part which comprises a longitudinal axis L 12  and an attaching end and an aperture end arranged so as to be axially opposite one another, and which is provided with outer ball tracks, 
     an inner joint part which comprises a longitudinal axis L 13  and an attachment for a shaft pointing towards the aperture end of the outer joint part, and which is provided with inner ball tracks, 
     the outer ball tracks and the inner ball tracks form pairs of tracks with one another, the pairs of track each accommodate a torque transmitting ball; and 
     an annular ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows which each accommodate at least one of the torque transmitting balls. 
     The centers of the balls are held by the cage in a joint center plane EM and, upon articulation of the joint, are guided onto the angle-bisecting plane between the longitudinal axes L 12 , L 13 . 
     The center lines M 22 , M 23  of the ball tracks of pairs of tracks are positioned in pairs of track planes BE, BE* which extend parallel relative to one another and symmetrically relative to radial planes R 1 , R 2  through the longitudinal axes L 12 , L 13 . 
     For a first part of the pairs of tracks, the opening angle α 1  between the tangents T 22   1 ′ T 23   1 ′ at track base lines extending parallel to the tangents T 22   1 , T 23   1  at the center lines M 22   1 , M 23   1  of the ball tracks in the joint center plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13  opens from the attaching end to the aperture end. 
     for a second part of the pairs of tracks, the opening angle α 2  between the tangents T 22   2 ′, T 23   2 ′ at track base lines extending parallel to the tangents T 22   2 , T 23   2  at the centre lines M 22   2 , M 23   2  of the ball tracks in the joint centre plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13  opens from the aperture end to the attaching end, and the following applies to the centre lines of the second pairs of tracks; in the outer joint part, the centre line M 22   2  of the ball tracks in the region from the joint centre plane EM to the attaching end radially inwardly leaves a reference radius RB whose radius centre MBE is positioned in the point of intersection of a perpendicular line on the tangent T 22   2  at the centre line M 22   2  of the ball track in the joint centre plane EM and of a parallel axis PE, PE* relative to the longitudinal axis L 12  through a track plane BE, BE*,
 
in the inner joint part, the centre line M 23   2  of the ball tracks in the region from the joint centre plane EM to the aperture end radially inwardly leaves a reference radius RB′ whose radius centre MBE′ is positioned in the point of intersection of a perpendicular line on the tangent T 23   2 ′ at the centre line M 23   2  of the ball track in the joint centre plane EM and of a parallel axis PE, PE* relative to the longitudinal axis L 13  through a track plane BE, BE*,
 
in the outer joint part, the centre line M 22   2  of the ball tracks in the region from the joint centre plane EM to the aperture end moves radially outwardly beyond said reference radius RB, and
 
in the inner joint part, the centre line M 23   2  of the ball tracks  23   2  in the region from the joint centre plane EM to the attaching end moves radially outwardly beyond said reference radius RB′.
 
     The solution proposed here differs from the solution proposed first wherein the center lines of the pairs of tracks are positioned in radial planes through the center axes of the joint in that, in the present case, the center lines of pairs of tracks of two adjoining balls extend in two parallel track planes BE, BE* which extend parallel to and symmetrically to a radial plane R. As in the case of the first solution, the radial plane R is defined by the longitudinal axes L 12 , L 13  when the joint is in the aligned condition. With the track shape, in principle, being the same as in the first solution, the track shapes of the second solution, however, refer to parallel axes PE, PE* which are positioned in a reference plane EX through the longitudinal axes L 12 , L 13 , which reference plane EX is positioned perpendicularly on the radial plane R. The track shapes of the second solution also refer to reference centers ME which are positioned on said parallel axes PE, PE* and in the point of intersection of the parallel axes with the joint center plane EM. 
     A third solution provides a constant velocity universal joint in the form of a fixed joint with the following characteristics: 
     an outer joint part which comprises a longitudinal axis L 12  and an attaching end and an aperture end arranged so as to be axially opposite one another, and which is provided with outer ball tracks, 
     an inner joint part which comprises a longitudinal axis L 13  and an attachment for a shaft pointing towards the aperture end of the outer joint part, and which is provided with inner ball tracks, 
     the outer ball tracks and the inner ball tracks form pairs of tracks with one another; and the pairs of tracks each accommodate a torque transmitting ball, 
     an annular ball cage is positioned between the outer joint part and the inner joint part and comprises circumferentially distributed cage windows which each accommodate at least one of the torque transmitting balls. 
     The centers of the balls are held by the cage in a joint center plane and, upon articulation of the joint, are guided onto the angle-bisecting plane between the longitudinal axes L 12 , L 13 . 
     The center lines M 22   1 , M 23   1  of adjoining ball tracks in the outer joint part are positioned in pairs of first track planes BE, BE* which extend parallel relative to one another and symmetrically relative to radial rays RS 1 , RS 2  through the joint center M. 
     The center lines M 23   1 , M 23   2  of adjoining ball tracks in the inner joint part are positioned in pairs of second track planes BE′, BE*′ which extend parallel relative to one another and symmetrically relative to radial rays RS 1 , RS 2  through the joint center M. 
     The first track planes BE, BE* and the second track planes BE′, BE*′, together with radial planes RP 1 , RP 2  through the longitudinal axes L 12 , L 13 , form identically sized angles y, y′ which extend in opposite directions. 
     For a first part of the pairs of tracks, the opening angle α 2  between the tangents T 22   1 ′, T 23   1 ′ at track base lines extending parallel to the tangents T 22   1 ′, T 23   1 ′ at the center lines M 22   1 , M 23   1 , of the ball tracks in the joint center plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13 , opens from the attaching end to the aperture end. 
     For a second part of the pairs of tracks, the opening angle α 2  between the tangents T 22   2 ′, T 23   2 ′ at track base lines extending parallel to the tangents T 22   2 , T 23   2  at the center lines M 22   2 , M 23   2  of the ball tracks in the joint center plane EM when the joint is in the aligned condition with coinciding longitudinal axes L 12 , L 13  opens from the aperture end to the attaching end. The following applies to the center lines of the second pairs of tracks. In the outer joint part, the center line M 22   2  of the ball tracks in the region from the joint center plane EM to the attaching end radially inwardly leaves a reference radius RB whose radius center MBE is positioned in the point of intersection of a perpendicular line on the tangent T 22   2  at the centre line M 22   2  of the ball track in the joint center plane EM and of a reference axis PE, PE* through a track plane BE, BE*. In the inner joint part, the center line M 23   2  of the ball tracks in the region from the joint center plane EM to the aperture end radially inwardly leaves a reference radius RB′ whose radius center MBE′ is positioned in the point of intersection of a perpendicular line on the tangent T 23   2  at the center line M 23   2  of the ball tracks in the joint center plane EM and of a reference axis PE′, PE*′ through a track plane BE′, BE*′. 
     In the outer joint part, the center line M 22   2  of the ball tracks in the region from the joint center plane EM to the aperture end moves radially outwardly beyond said reference radius RB. 
     In the inner joint part, the center line M 23   2  of the ball tracks in the region from the joint center plane EM to the attaching end moves radially outwardly beyond said reference radius RB′. 
     According to the third solution proposed here, the center lines of pairs of tracks of two adjoining balls in the outer joint part extend in two parallel planes BE, BE* which extend symmetrically to and parallel to a reference plane EB through the joint center, which reference plane EB, together with a radial plane R, forms an angle γ positioned in a second reference plane EX arranged perpendicularly on the radial plane, and in the inner part they extend in two parallel reference BE′, BE*′ which extend symmetrically to and parallel to a reference plane EB′ through the joint center, which reference plane EB′, together with a radial plane R, forms an angle γ′ positioned in a second reference plane EX arranged perpendicularly on the radial plane. Said radial plane R, as in the case of the second solution, is defined by the longitudinal axes L 12 , L 13  when the joint is in the aligned condition. With, in principle, the same track shape as in the second alternative, the track shapes according to the third solution, however, refer to parallel axes in the inner joint part and outer joint part, which axes are arranged so as to extend, in parallel, relative to one another in pairs, which intersect one another in pairs and which are positioned in a second reference plane EX through the longitudinal axes L 12 , L 13  which is arranged perpendicularly on the radial plane R; they also refer to reference centers which are positioned on said parallel axes and in the point of intersection of the parallel axes with the joint center plane EM. 
     Joints according to the above-described second and third solutions comprise a number of track pairs which can be divided by two if only one track is positioned in each track plane BE, BE*, BE′ BE*′. They comprise a number of track pairs which can be divided by four if each of the track planes BE, BE*, BE′, BE*′ contains two symmetrically shaped pairs of tracks arranged substantially opposite one another. 
     As explained above, the further embodiments of joints according to the second and third solutions—while the respective reference places are changed—substantially correspond to joint embodiments according to the first solution. This results in the following: 
     A first advantageous embodiment comprises the following further characteristics of the second pairs of tracks: 
     in the outer joint part, the local radius R 1  of the centre line M 22   2  in the joint center plane EM is smaller than the reference radius RB, and 
     in the inner joint part, the local radius R 1 ′ of the center line M 23   2  in the joint centre plane EM is smaller than the reference radius RB′. 
     A first advantageous embodiment comprises the following further characteristics of the second pairs of tracks: 
     in the outer joint part, the center line M 22   2  of the ball tracks extends from the joint center plane EM to the attaching side radially outside a reference radius RZ whose radius center is positioned in the joint center plane EM on one of the reference axes PE, PE*, and
 
in the inner joint part, the center line M 23   2  of the ball tracks extends from the joint center plane EM to the aperture end radially outside a reference radius RZ′ whose radius center is positioned in the joint center plane EM on one of the reference axes PE, PE*, PE′, PE*′.
 
     A further advantageous embodiment is characterised by the following further characteristics: 
     in the outer joint part, the center line M 22   2  of the ball tracks extends from the joint center plane EM to the aperture end radially outside the reference radius RB and in the inner joint part, the center line M 23   2  of the ball tracks extends from the joint center plane EM to the attaching end radially outside the reference radius RB′. 
     Furthermore, the following further characteristics are proposed for the second pairs of tracks: 
     in the outer joint part, the center line M 22   2  of the ball tracks extends from the joint center plane EM to the aperture end radially inside a reference radius RZ whose radius center is positioned in the joint center plane EM on one of the parallel axes PE, PE*. 
     In the inner joint part, the center line M 23   2  of the ball tracks extends from the joint center plane EM to the attaching end radially inside a reference radius RZ′ whose radius center is positioned in the joint center plane EM on one of the parallel axes PE, PE*, PE′, PE*′. 
     A further proposal concerns the following characteristics of the second pairs of tracks: the center lines M 22   2 , M 23   2  of the outer ball tracks and inner ball tracks each comprise at least two arched portions which are curved in opposite senses and which adjoin one another in a turning point. 
     The turning points W 22   2  of the outer ball tracks are positioned in a track plane BE, BE* at a distance from the center plane EM towards the aperture end. 
     The turning points W 23   2  of the inner ball tracks are positioned in a track plane BE, BE*, BE′, BE*′ at a distance from the center plane EM towards the aperture end, the turning points W 22   2 , W 23   2  are each positioned below a maximum of the distance between the center lines M 22   2 , M 23   2  and the parallel axes PE, PE*, PE′, PE*′. 
     A further embodiment comprises the following characteristics of the second pairs of tracks: 
     the track center lines M 22   2  of the outer ball tracks comprise a first arch with the radius R 1  whose center M 1  in a track plane BE, BE* is offset by a first axial offset O 1   a  from the center plane EM of the joint towards the attaching end and by a first radial offset O 1   r  outwardly from a parallel axis PE, PE* and, in the region adjoining said arch, towards attaching end, they comprise a second arch with the radius R 2  whose center M 2  in the track plane BE, BE* is offset by a second axial offset O 2   a  from the center plane EM of the joint towards the aperture end and is outwardly offset from the parallel axis PE, PE′ by a second radial offset O 2   r  which is greater than the sum of the first radius R 1  and the first radial offset O 1   r.    
     The track center lines M 23   2  of the outer ball tracks comprise a first arch with the radius R 1 ′ whose center M 1 ′ in a track plane BE, BE*, BE′, BE*′ is offset by a first axial offset O 1   a ′ from the center plane EM of the joint towards the aperture end and is offset outwardly by a first radial offset from a parallel axis PE, PE*, PE′, PE*′ and, in the region adjoining said arch, towards the aperture end, they comprise a second arch with the radius R 2 ′ whose center M 2 ′ in the track plane BE, BE*, BE′, BE*′ is offset by a second axial offset O 2   a ′ from the center plane EM of the joint towards the attaching end and is outwardly offset from the parallel axis PE, PE*, PE′, PE*′ by a second radial offset O 2   r ′ which is greater than the sum of the first radius R 1 ′ and the first radial offset O 1   r′.    
     A further proposal comprises the following characteristics of the second pairs of tracks: the radius of curvature of the center lines M 22  of the outer ball tracks decreases in the extension from the center plane EM towards the attaching end and the radius of curvature of the center plane M 23  of the inner ball tracks decreases in the extension from the center plane EM to the aperture end. 
     A further proposal comprises the following characteristics of the second pairs of tracks: the track center lines of the outer ball tracks  22   2  comprise a third arch with the radius R 3  which, tangentially, while having the same sense of curvature, adjoins the first arch with the radius R 1  and whose radius R 3  is smaller than the radius R 1 . 
     The track center lines M 23   2  of the inner ball tracks comprise a third arch with the radius R 3 ′ which, tangentially, while having the same sense of curvature, adjoins the first arch with the radius R 1 ′ and whose radius R 3 ′ is smaller than the radius R 1 ′. 
     Furthermore, in the second pairs of tracks, along the extension of the center line M 22  of the outer ball tracks, towards the aperture end, the second arch is adjoined by an axis-parallel straight line G 3  and that, along the extension of the center line M 23  of the inner ball tracks, the second arch, towards the attaching end, is adjoined by an axis-parallel straight line G 3 ′. 
     According to an alternative embodiment, in the second pairs of tracks along the extension of the center line M 22   2  of the outer ball tracks, towards the aperture end, the second arch is adjoined by a straight line which approaches the parallel axis PE, PE′ and that along the extension of the center line M 23   2  of the inner ball tracks, the second arch, towards the attaching end, is adjoined by a straight line which approaches the parallel axis PE, PE*, PE′, PE*′. 
     In this case, too, in the second pairs of tracks, the center lines M 22 , M 23  of the ball tracks in the joint center plane EM intersect one another at an angle of 4 to 32°, wherein the tangents T 22 , T 23  at the center lines M 22 , M 23  of the ball tracks  22 ,  23  of all pairs of tracks form identical opening angles α when the joint is in the aligned condition. 
     A joint of the shape described here comprises a number of pairs of balls which can be divided by four. More particularly, the balls of two adjoining pairs of tracks positioned in parallel track planes BE, BE′ are received in a common cage window of the ball cage. 
     As already explained above, the track planes BE, BE*, according to the second solution, can extend parallel to the longitudinal axes L 12 , L 13  and the track planes BE, BE*, BE′ BE*′, according to the third solution, can extend at a helix angle y, y′ relative to the longitudinal axes L 12 , L 13 . 
     According to a further embodiment, the pitch angle 2φ between the pairs of tracks whose balls are received in a common cage window is smaller than the pitch angle between adjoining pairs of tracks whose balls are received in different windows. 
     Between the helix angle y and the pitch angle 2φ there can exist the relation y=α/2 tans, with α/2 being the track inclination angle and half the opening angle respectively. 
     Furthermore, of two directly adjoining pairs of tracks, one constitutes a first pair of tracks and one a second pair of tracks. In addition, of two pairs of tracks positioned in one track plane, one constitutes a first pair of tracks and one a second pair of tracks, i.e. two substantially radially opposed tracks open towards the aperture end on the one hand and towards the attaching end on the other hand. 
     The invention will be explained in greater detail with reference to the drawings which show preferred embodiments of inventive joints as compared to a joint according to the state of the art. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an inventive joint according to the first solution:
         a) in a cross-section;   b) in a longitudinal section along sectional line A-A; and   c) in a longitudinal section along sectional line B-B.       
         FIG. 2  shows an inventive joint according to the second solution:
         a) in a cross-section;   b) in a longitudinal section along sectional line A-A; and   c) in a longitudinal section along sectional line B-B.       
         FIG. 3  shows an inventive joint according to  FIG. 2  of the third solution:
         a) in a cross-section; and   b) in a longitudinal section along sectional line A-A.       
         FIG. 4  shows geometric relations with reference to a pair of balls in a joint according to  FIG. 3 :
         a) in a cross-section;   b) in a longitudinal section through a track plane; and   c) in a longitudinal section through a pair of balls.       
         FIG. 5  shows the longitudinal axes and the track centre lines of the second tracks of an inventive joint in a first embodiment:
         a) for the outer joint part; and   b) for the inner joint part.       
         FIG. 6  shows the longitudinal axes and the track centre lines of the second tracks of an inventive joint in a second embodiment:
         a) for the outer joint part; and   b) for the inner joint part.       
     
    
    
     DETAILED DESCRIPTION 
       FIGS. 1   a  to  1   c  will be described jointly below. A joint  11  comprises an outer joint part  12 , an inner joint part  13 , torque transmitting balls  14  as well as a ball cage  15 . The cage comprises a spherical outer face  16  which is guided in the outer joint part and a spherical inner cage face  17  which is guided on the inner joint part, with said second contact not being compulsory. The balls  14  are held in circumferentially distributed cage windows  18  in the ball cage  15  in a joint center plane EM. The outer joint part  12  is shown to comprise a longitudinal axis L 12  and the inner joint part is shown to comprise a longitudinal axis L 13 . The point of intersection of the longitudinal axes L 12 , L 13  with the joint center plane EM forms the joint center M. The outer joint part  12  comprises a base  19  which can change into an attaching journal for example, as well as an aperture  20  into which it is possible to insert a journal connectable to the inner joint part. For this purpose, the inner joint part  13  comprises an insertion aperture  21 . Hereafter, the position of the base  19  indicates the axial direction “towards the attaching end” and the position of the aperture  20  indicates the axial direction “towards the aperture end”. These terms are also used with reference to the inner joint part, with the actual attachment of a shaft to the inner joint part not being taken into account. 
     Starting from the center plane EM, the ball contact angles β max /2 have been entered for the maximum articulation angle β max /2 of the inner joint part  13  relative to the outer joint part  12  in both directions. First pairs of tracks  22   1 ,  23   1  with first balls  14   1  and second pairs of tracks  22   2 ,  23   2  with second balls  14   2  have been arranged so as to alternate around the circumference. The shape of the first pairs of tracks  22   1 ,  23   1  can be taken from section A-A and the shape of the second pairs of tracks  22   2 ,  23   2  from section B-B. The first balls  14   1  are in contact with first outer ball tracks  22   1  in the outer joint part and first inner ball tracks  23   1  in the inner joint part. The center lines M 22   1 , M 23   1  of said tracks are of the type as used in UF tracks and are composed of a circular arch and a tangentially adjoining straight line. In the aligned position as illustrated, the tangents T 22   1 ′, T 23   1 ′ at the balls  14   1  in the contact points with the tracks  22   1 ,  23   1  form an opening angle α 1  which opens towards the aperture end. The second balls  14   2  are guided in outer ball tracks  22   2  in the outer joint part and inner ball tracks  23   2 , in the inner joint part. The balls  14   2  are shown to be in contact with the track base of the ball tracks, which contact does not necessarily have to be provided. In the aligned position as illustrated, the tangents T 22   2 ′, T 23   2 ′ at the balls  14   2  in the contact points with the tracks  22   2 ,  23   2  form an opening angle α 2  which opens towards the attaching end. For describing the ball tracks  22 ,  23 , reference is made below to the center lines M 22   2 , M 23   2  of the ball tracks. The center plane EM is shown to comprise tangents T 22   2 , T 23   2  at the center lines which tangents are positioned parallel to the above-mentioned tangents T 22   2 ′, T 23   2 ′. The angle α 2  between said tangents T 22   2 , T 23   2  ranges between 4 and 32°. 
     It can be seen that each pair of tracks is positioned with its center lines M 22 , M 23  in a radial plane RP 1 , RP 2  through the joint, that said radial planes R are at identical angular distances from one another and that one ball  14  each is accommodated by a cage window  18  in the ball cage  15 . 
     The pitch circle radius of the first balls  14   1  and the pitch circle radius of the second balls  14   2  can differ in size with their size ratio ranging from 0.8 to 1.0. 
       FIGS. 2   a  to  2   c  will be described jointly below. They show a joint  11  in an embodiment which has been modified as compared to the embodiment according to  FIG. 1 . Nevertheless, identical details have been given the same reference numbers as in  FIGS. 1   a  to  1   c . An inventive joint  11  in said second embodiment comprises ball tracks  22 ,  23  which are positioned in track planes BE, BE* which are arranged in pairs symmetrically relative to radial planes R through the joint.  FIG. 2   b  shows an angled section according sectional line A-A, which angled section, on the one hand, extends through the track plane BE and a first pair of tracks  22   1 ,  23   1  with a first ball  14   1  and, on the other hand, through a radial plane between two pairs of tracks.  FIG. 2   c  shows a bent section according to sectional line B-B, which bent section extends through a track plane BE* and a second pair of tracks with second ball tracks  22   2 ,  23   2  on the one hand and through a radial plane between two pairs of tracks on the other hand. It is possible to see pairs of track pairs which are distributed around the circumference and which comprise a first pair of tracks  22   1 ,  23   1  and a second pair of tracks  22   2 ,  23   2  and which are held in a common cage window  18 . The pitch angle of said pairs of track pairs is smaller than that between two adjoining pairs of tracks which are not associated with a pair of track pairs. In the embodiment shows here, first pairs of tracks and second pairs of tracks alternate around the circumference. 
     As can be seen in  FIG. 2   b , the first balls  14   1  are guided in first pairs of tracks consisting of outer tracks  22   1  and inner tracks  23   1  which are of the type as contained in UF joints, which means that the center lines M 22 , M 23  of said pairs of tracks are composed of radii and adjoining tangential straight lines. The tangents T 22   1 , T 23   1 ′ at the balls in the tracks form a first opening angle α 1  which opens towards the aperture end of the outer joint part. 
       FIG. 2   c  shows a second ball  14   2  which is held in second outer ball tracks  22   2  and second inner ball tracks  23   2 . Tangents T 22   2 , T 23   2 ′ at the balls  14   2  form an opening angle α 2  with one another which opens towards the attaching end of the outer joint part. As far as the track extension is concerned, reference will be made below to the center lines M 22   2 , M 23   2 . In the joint center plane EM, the tangents T 22   2 , T 23   2  at the center line M 22   2 , M 23   2  intersect one another at the above-mentioned angle α 2 . 
     The track planes BE, BE* contain parallel axes PE, PE* extending relative to the longitudinal axes at the shortest distance, which thus form sectional lines between the track planes and a reference plane EX 1 , EX 2  positioned perpendicularly relative to the respective radial plane RP 1 , RP 2 . On the parallel axes PE, PE*, there are positioned track centers ME, ME* at the shortest distance from the joint center M. If there are arranged four pairs of tracks symmetrically to three or four radial planes R with identical pitch angles relative to one another, there are obtained joints with twelve or sixteen pairs of tracks  22 ,  23  and, accordingly, with twelve or sixteen balls  14 . In accordance with  FIG. 2   a , the center ME 1 , ME 1 * shown in  FIGS. 2   b  and  2   c  is not the joint center, but the track curve center in one of the track planes BE 1 , BE 1 *. 
       FIGS. 3   a  and  3   b  will be described jointly below, where like details have been give like reference numbers accompanied by a “′”. In principle,  FIG. 3   a  corresponds to  FIG. 2   a , but in this case, the sectional line A-A extends parallel to a reference plane EX 1  through the balls of a pair of track pairs.  FIG. 3   b  shows a first reference plane EB for outer ball tracks, which is positioned perpendicularly on said reference plane EX 1  and contains a radial ray RS through the joint centre M. Said reference plane EB′, together with the radial plane R extending through the longitudinal axes L 12 , L 13 , forms a helix angle γ. Parallel to the reference plane EB, there are positioned the reference planes BE and BE* in which there extend the center lines of the outer ball tracks of a pair of tracks. Furthermore,  FIG. 3   b  shows a first reference plane EB′ for inner ball tracks which is also positioned perpendicularly on said reference plane EX and contains the radial ray RS through the joint center M. Said reference plane EB′, together with the radial plane R through the longitudinal axes L 12 , L 13  forms a helix angle γ′ which is identical in size and extends in the opposite direction to y. The track planes BE′, BE*′ containing the center lines of the inner ball tracks of a pair of tracks extend parallel to the reference plane EB′. The center lines of each pair of tracks intersect one another in the joint center plane EM. 
       FIGS. 4   a  and  4   c  will be described jointly below, where like details have been give like reference numbers accompanied by a “′”.  FIG. 4   a  shows a cross-section through a ball assembly which consists of four pairs of balls  141 ,  142  according to  FIG. 3  and which is positioned in the joint centre plane. The pitch angle between the balls  141 ,  142  of a pair of balls and the radial plane RP  1  positioned therebetween amounts to φo and φo′ respectively. The ball tracks are arranged at a distance from a reference plane EX 1 , which distance corresponds to the pitch circle radius PCR multiplied by the cosine of φo. The perpendicular distance of the balls of a pair of balls from said radial plane RP 1  has been given the symbol a. The track planes BE 1 ′BE 1 * as shown represent the passage of the track planes BE′, BE*′ of the inner ball tracks through the joint center plane. 
     In  FIG. 4   b , in the section through one of the track planes BE 1 ′ BE 1 *, the track opening angle between the tangents T 22 , T 23  at the track center lines of a second pair of tracks has been given as α 2 , with the drawn-in angle legs representing the tangents T 22 ′, T 23 ′ at the track base lines of the track. α 2 / 2  thus corresponds to half the opening angle and track inclination angle respectively. 
       FIG. 4   c  shows a pair of balls  14   1 ,  14   2  with the outer track planes EB, EB* and the inner track planes EB′, EB*′. The penetration points D 1 , D 2  as shown in  FIG. 4   b  are also given. 
     The following equations apply to the ideal case wherein said track tangents T 22 , T 23  penetrate the radial planes R in the axes L 12 , L 13 , i.e. the penetration points D 1  and D 2  are positioned on the longitudinal axes L 12 , L 13 . 
     The following relations apply: 
                   α   ⁢           =       PCR   ·   sin     ⁢           ⁢     φ   0   1               (   1   )                     PCR   ·   cos     ⁢           ⁢     φ   0   1       x     =       tan   ⁢           ⁢     α2   2     ⁢           ⁢   with   ⁢           ⁢   x     =       PCR   ⁢           ⁢   cos   ⁢           ⁢     φ   0   1         tan   ⁢           ⁢     α2   2                   (   2   )                 a   x     =     sin   ⁢           ⁢   μ             (   3   )                   i   .   e   .           ⁢   sin     ⁢           ⁢   μ     =         PCR   ·   sin     ⁢           ⁢     φ   0   1           PCR   ·   cos     ⁢           ⁢     φ   0   1                                 
for small angles
 
               α   ⁢           ⁢   2     2         
and γ the following approximation applies:
 
     
       
         
           
             sin 
             ⁢ 
             
                 
             
             ≈ 
             arc 
           
         
       
       
         
           
             tan 
             ≈ 
             arc 
           
         
       
       
         
           
             
               arc 
               ⁢ 
               
                   
               
               ⁢ 
               μ 
             
             ≈ 
             
               tan 
               ⁢ 
               
                   
               
               ⁢ 
               
                 
                   φ 
                   0 
                   1 
                 
                 · 
                 arc 
               
               ⁢ 
               
                 α2 
                 2 
               
               ⁢ 
               uldsomiL 
             
           
         
       
       
         
           
             μ 
             ≈ 
             
               
                 
                   
                     α 
                     ⁢ 
                     
                         
                     
                     ⁢ 
                     2 
                   
                   2 
                 
                 · 
                 tan 
               
               ⁢ 
               
                   
               
               ⁢ 
               
                 φ 
                 0 
                 1 
               
             
           
         
       
     
       FIG. 5   a  shows the track center line M 22  of an outer ball track  22  according to any one of  FIGS. 1 to 3 , which track center line M 22  extends parallel to a track base line. The center line M 22  of a track in the outer part is composed of a first arched portion with a first radius R 1  around a center M 1  with the first axial offset O 1   a  and a radial offset O 1   r  as well as of a second arched portion with a second radius R 2  with a second axial offset O 2   a  and a second radial offset O 2   r . Second radial offset O 2   r  is greater than the sum of the first radius R 1  and the first radial offset O 1   r . The transition is indicated by a turning point W 22 . The second radius R 2  is tangentially adjoined by a straight line G 3  extending parallel to the axis L 12 , PE, PE*. The center plane EM is shown to comprise the tangent T 22  and the center line M 22  which intersects a longitudinal axis L 12 , PE, PE* at an angle α/2. A perpendicular line on the tangent T 22  intersects the longitudinal axis L 12 , PE; PE* in the reference center MB, MBE of a reference radius RB. First radius R 1  is smaller than reference radius RB. A further reference radius RZ is entered around the track center M, ME. To the left of the center plane EM, towards the attaching end  19 , the center line M 22  extends inside the radius RB and outside the radius RZ. To the right of the center plane EM, towards the aperture end  20 , the center line M 22  extends substantially outside the radius RB. The radial ball movement of a ball on its path along the ball track with reference to the track center M, ME has been given the reference symbol e. This corresponds to the minimum thickness of the ball cage in the region of the cage window, with a safety allowance being required to avoid edge bearing. 
       FIG. 5   b  shows the track center lines M 23  of the associated inner ball tracks  23  according to any one of  FIGS. 1 to 3 , which track center lines M 23  extend parallel relative to the track base lines. The center line M 23  of a track  23  in the inner part  13  is composed of a first arched portion with a first radius R 1 ′ around a center M 1 ′ and of a second arched portion with a second radius R 2 ′ around a centre M 2 ′. The transition is indicated by a turning point W 23 . The second radius R 2 ′ is adjoined by a straight line G 3 ′ which extends parallel relative to the axis L 13 , PE, PE*, PE′, PE*′. The center M 1 ′ comprises an axial offset O 1   a ′ and a radial offset O 1   r ′ and the center M 2 ′ comprises an axial offset O 2   a ′ and a radial offset O 2   r ′. Second radial offset O 2   r ′ is greater than the sum of the first radius R 1 ′ and the first radial offset O 1   r ′. In the center plane EM, there is shown the tangent T 23  at the center line M 23 , which intersects a longitudinal axis L 13 , PE, PE*, PE′, PE*′ at the angle α/2. A perpendicular line at the tangent T 23  intersects the longitudinal axis L 13 , PE; PE*, PE′, PE*′ in the reference center MB′, MBE′ of a reference radius RB′. Second radius R 1 ′ is smaller than reference radius RB′. A further reference radius RZ′ has been entered around the track center M, ME. To the right of the center plane EM, towards the aperture end  20 , the center line M 23  extends inside the radius RB′ and outside the radius RZ′. To the left of the center plane EM, towards the attaching end  19 , the center line M 23  extends at least predominately outside the radius RB′. The radial ball movement of a ball on its path along the ball track with reference to the track center M, ME has been given the reference symbol e. The two center lines M 22 , M 23  of  FIGS. 5   a ,  5   b  intersect one another in the joint center plane EM at the angle α and extend mirror-symmetrically relative to said centre plane. 
     According to an alternative embodiment, in the second pairs of tracks, along the extension of the center line M 22   2  of the outer ball tracks, towards the aperture end, the second arch is adjoined by a straight line which approaches the longitudinal axis L 12  and that, along the extension of the center line M 23   2  of the inner ball tracks, towards the attaching end, the second arch is adjoined by a straight line which approaches the longitudinal axis L 13 . 
       FIG. 6   a , in a modified embodiment, shows the track center line M 22  of an outer ball track  22 , which track center line M 22  extends parallel to a track base line. The center line M 22  of a track in the outer joint part is composed of a first radius R 1  around a center M 1  with a first axial offset O 1   a  and a radial offset O 1   r  as well as of a second radius R 2  with a second axial offset O 2   a  and a second radial offset O 2   r  as well as of a third radius R 3  which adjoins the radius R 1  opposite to the radius R 2 , which is smaller than the radius R 1  and is curved in the same direction, with the position of its center M 3  not being given detailed dimensions. The transition between the first and second radius is indicated by the turning point W 22 . The second radius R 2  is tangentially adjoined by a straight line G 3  which extends parallel to the axis L 12 , PE, PE*. In the center plane EM, there are shown the tangent T 22  and the center line M 22  which intersects a longitudinal axis L 12 , PE, PE* at the angle α/2. A perpendicular line on the tangent T 22  intersects the longitudinal axis L 12 , PE; PE* in the reference center MB, MBE of a reference radius RB. A further reference radius has been entered around the track center M, ME. To the left of the center plane, towards the attaching end  19 , the center line M 22  extends inside the radius RB and outside the radius RZ. To the right of the center plane EM, towards the aperture end  20 , the center line M 22  extends predominately outside the radius RB. The radial ball movement of a ball on its path along the ball track with reference to the track center M, ME has been given the reference symbol e. This corresponds to the minimum thickness of the ball cage in the region of the cage windows, with a safety allowance having to be provided to avoid edge bearing. 
       FIG. 6   b , in a modified embodiment, shows the track center line M 23  of an inner ball track  23 , which track center line M 23  extends parallel to a track base line. The center line M 23  of a track  23  in the inner joint part  13  is composed of a first radius R 1  around a center M 1 ′, of a second radius R 2 ′ around a center M 2 ′ as well as of a third radius R 3 ′ which adjoins the radius R 1 ′ opposite to the radius R 2 ′, which is smaller than said radius R 1  and is curved in the same direction. The second radius R 2 ′ is adjoined by a straight line G 3  which extends parallel to the axis L 13 , PE, PE*, PE′. PE*′. The center M 2 ′ comprises an axial offset O 1   a ′ and a radial offset O 1   r ′ and the center M 2 ′ comprises an axial offset O 2   a ′ and a radial offset O 2   r ′. The position of the center M 3 ′ has not been given detailed dimensions. In the center plane EM, there are shown the tangent T 23  and the center line M 23  which intersects a longitudinal axis L 13 , PE, PE*, PE′, PE*′ at the angle α/2. A perpendicular line on the tangent T 23  intersects the longitudinal axis L 12 , PE; PE*, PE′, PE*′ in the reference center MB′, MBE′ of a reference radius RB′. A further reference radius RZ′ has been entered around the track center M, ME. To the right of the center plane EM, towards the aperture end  20 , the center line M 23  extends inside the radius RB′ and outside the radius RZ′. To the left of the center plane EM, towards the attaching end  19 , the center line M 23  extends predominately outside the radius RB′. The radial ball movement of a ball on its path along the ball track with reference to the track center M, ME has been given the reference symbol e. The two center lines M 22 , M 23  of  FIGS. 6   a ,  6   b  intersect one another in the joint center plane EM at the angle α and extend mirror-symmetrically relative to said center plane. 
     Counter Track Joint for Large Articulation Angles 
     
       
         
               
             
               
               
               
             
           
               
                   
               
               
                 List of reference numbers 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                 11 
                 joint 
               
               
                   
                 12 
                 outer joint part 
               
               
                   
                 13 
                 inner joint part 
               
               
                   
                 14 
                 ball 
               
               
                   
                 15 
                 cage 
               
               
                   
                 16 
                 outer cage face 
               
               
                   
                 17 
                 inner cage face 
               
               
                   
                 18 
                 cage window 
               
               
                   
                 19 
                 base 
               
               
                   
                 20 
                 aperture 
               
               
                   
                 21 
                 insertion aperture 
               
               
                   
                 22 
                 outer ball track 
               
               
                   
                 23 
                 inner ball track 
               
               
                   
                 24 
                 track base of outer ball track 
               
               
                   
                 25 
                 track base of inner ball track 
               
               
                   
                 26 
                 track flank 
               
               
                   
                 27 
                 track flank 
               
               
                   
                 EM 
                 joint centre plane 
               
               
                   
                 L12 
                 longitudinal axis of outer part 
               
               
                   
                 L13 
                 longitudinal axis of inner part 
               
               
                   
                 M22 
                 centre line of track 22 
               
               
                   
                 M23 
                 centre line of track 23