WO1995002773A1

WO1995002773A1 - Double cardan joint

Info

Publication number: WO1995002773A1
Application number: PCT/EP1994/002118
Authority: WO
Inventors: Wolfgang Huth
Original assignee: G. Elbe & Sohn Gmbh & Co.
Priority date: 1993-07-14
Filing date: 1994-06-29
Publication date: 1995-01-26
Also published as: DE4323503A1; DE4323503C2

Abstract

A double cardan joint (30) has two outer forks (31; 32), a middle piece (33) with two inner forks (34; 35) and two spiders (36; 37) coupled to each other in the usual manner. A centering device (38) aligns the outer forks (31; 32) so that their axes cross each other at a point located in the center plane (51) of the middle piece (33). This centering device (38) has two centering members (63; 64) that are rotatively mounted each on a centering pin (65) of the corresponding outer fork (31; 32). Both centering members (63; 64) are provided on their facing sides with meshing cylindrical tooth segments. Both centering members (63; 64) are further provided with a guiding device that guides them against each other in the direction of the surface line of their teeth.

Description

Cardan double joint

Gimbal double joints each have two outer fork parts, one of which is permanently or releasably connected to the drive shaft and the other to the output shaft. Between these two outer fork parts there is a middle piece, which has an inner fork part at each end. An articulated cross is arranged between an outer fork part and an inner fork part. Each joint cross is coupled on the one hand with an outer fork part and on the other hand with one of the inner fork parts. For the synchronism of the double joints, it is necessary that the pivot pins mounted in the inner fork parts of the center piece are aligned parallel to one another on the center piece.

A further condition for the synchronism of a double joint is that the intersection of the axes of the drive shaft and the output shaft is always in a plane which is perpendicular to the connecting straight line between the centers of the cross members and the same from the centers of the cross members Distance. It is referred to below as the middle level. The drive shaft and the driven shaft are collectively referred to below as shaft parts.

The latter synchronism condition is implemented in different ways. In a known double joint (DE-C2-28 33 149), a hollow spherical cap aligned with the axis of this shaft part is arranged for centering the axes of the shaft parts on an outer fork part, into which a ball section engages, which is centered on the axis of the other shaft part arranged centering pin sits. Because when the one shaft part is pivoted relative to the other shaft part, the spherical cap moves on a circular path that affects the center plane, the spherical section must follow this deviation from the center plane. It is therefore slidably guided in the longitudinal direction on the centering pin. However, the common intersection of the axes of the two shaft parts moves out of the center plane. This leads to irregularities in the rotational movement of the output shaft with respect to the drive shaft. As a result, the rotational movement of the devices driven by the double joint also becomes non-uniform. In addition, the mass forces that occur load all moving parts of the double joint and the parts connected to it. This double joint is therefore only quasi-homokinetic.

In order to avoid such irregularities, it was proposed (DE-A1-21 05 751) to use two centering bodies as the centering device, one of which is firmly connected to the outer fork part and is aligned centrally to the axis of one of the shaft parts. The centering bodies each have spherical ring teeth on the mutually facing end faces. This spherical ring toothing is arranged on a spherical surface section which is arranged on the axis of the shaft part in question and the center of which is simultaneously located in the center of the adjacent universal joint.

In the extended position of the two shaft parts, depending on the tooth play, line contact may be possible between the two spherical toothings. When one shaft part is pivoted relative to the other, the two spherical ring toothings roll on each other. In each swivel position of the two shaft parts there is only point contact between the two spherical ring toothings. This fact is disadvantageous because in the pivoted position of the two shaft parts, the centering device is transverse to it This circumstance is disadvantageous because, in the angled position of the two shaft parts, forces which are aligned by the centering transversely to their axis have to be absorbed. The centering parts are subjected to very high mechanical stresses due to the point contact of their surfaces. This causes the parts to wear out quickly.

With the features specified in claim 1, the object is achieved to create a cardan double joint that is free of

Is non-uniformity and has the favorable power transmission conditions.

Characterized in that the centering device has two centering elements which are rotatably mounted on a centering pin of the associated outer fork part and which are provided on their mutually facing end faces each with a cylindrical tooth segment, the teeth of which mesh with one another, the cylinder axis being in the center of the adjacent one Joint cross is located, the axes of the shaft parts coupled to each other via the centering device always intersect at a point which is located on the central plane of the double joint. This double joint is actually homokinetic. Because the toothing of the centering elements is arranged on a circular cylinder surface, line contact occurs in the toothing not only in the extended position but also in any swiveled position of the shaft parts. Even higher transverse forces can be transmitted without problems using this centering device. Because of the cylindrical shape of the toothings and due to the rotatable mounting of the centering elements on the associated outer fork part, no rotating or drilling relative movement occurs between the centering elements and their toothings. When the shaft parts are brought into a certain swivel position relative to one another, the centering elements are also swiveled against one another in the same swivel plane, their toothings rolling against one another. The centering elements remain in their Swiveling position at rest, even if the shaft parts with the outer fork parts and the center piece with the inner fork parts rotate constantly. Because of the line contact, the Hertzian pressure between the two toothings is considerably smaller than that of the centering elements with spherical ring toothing. Constant circumferential relative movements with the associated drilling movement are omitted anyway. Therefore there is no wear of the toothings.

Even if the pivoting angle of the shaft parts is changed while the shaft is rotating, the centering elements only change their mutual pivoting position in the same pivoting plane without - in absolute terms - executing a rotary movement.

The guide device absorbs the swelling forces occurring during the rotational movement of the shaft parts, which act in the direction of extension of the toothing of the toothed segments, and thus prevents corresponding relative movements of the two toothings from occurring. In addition, when the shaft is pivoted in a horizontal plane and stands still, the guide device prevents one shaft part from sinking under the effect of gravity and thereby the two tooth segments in the

Direction of extension of their teeth can be shifted against each other.

By an embodiment according to claim 2, the bearing of the centering elements on the associated outer fork part is designed to be low-maintenance and low-wear. The further development according to claim 3 creates a very simple and, according to experience, sufficiently resistant and low-wear axial guide. By an embodiment according to claim 4, the guide device can be realized in a relatively simple and inexpensive manner. This applies even more to a further development according to claim 5. Further developments according to one of claims 6 to 12 enable the guide device to be implemented just as easily and cheaply in another way, with the guide device also being able to serve as a driver device in these embodiments .

By means of an embodiment according to claim 13 or 14, the toothing of the centering elements also assume the function of the guide device due to their special design.

By an embodiment according to claim 15 it is achieved that whenever the shaft is at a standstill in the extended position and the direction of extension of the toothing of its centering elements is located randomly in the plane in which the shaft parts are to be pivoted against each other, the centering elements when starting the shaft immediately and without difficulty turn into the rotational position in which the direction of extension of their teeth is oriented normal to the swivel plane, so that the teeth can roll against each other in the course of the pivoting of the shaft parts. For this, simple further developments are given in claims 16 and 17.

With an embodiment according to claim 18 it is achieved that when the shaft is at a standstill in the extended position and the direction of extension of the toothing of its centering elements is located randomly in the plane in which the shaft parts are to be pivoted against each other and also this pivoting movement While the shaft is at a standstill, the toothed segments can be pivoted by a small swivel angle due to the convex curvature, especially in the Sym, until the centering elements can be pivoted by the subsequent start of the shaft adjust to the rotary position in which they can follow the swiveling movement of the shaft parts without jamming. This applies in particular to a further development according to claim 19. In the further development according to claim 20 it is achieved that the forces acting with increasing pivoting angle of the shaft parts in the transverse direction on the centering device and also increasing forces are exerted by the gears which are then straight again with line contact ¬ can be taken.

With an embodiment according to claim 21, a very simple and inexpensive to manufacture holder for the spring is created. In a further development according to claim 22, manufacturing tolerances can be compensated for very easily and at the same time a vibration-free fit of the holder can be created.

In an embodiment according to claim 23, the holder for the spring also creates a protective housing for the centering elements. In a further development according to claim 24, the protective housing lies all around on the outer edge regions of the centering elements, so that a certain sealing effect against the penetration of dirt particles and against the escape of lubricants is also achieved.

With an embodiment according to claim 25, in particular with a further development according to claim 26, another type of protective device is created, which also protects the parts of the guide device which are moved relative to one another against the ingress of dirt and against the loss of lubricants.

Through an embodiment according to claim 27, the parts of the centering device and, for example, other device parts interacting therewith can be mounted more easily. The longitudinal sections can be joined together simply and precisely by means of coordinated guide surfaces. After this If the two longitudinal sections have been set in the axial direction to the cheapest tooth play of the toothing of the two centering elements, the two longitudinal sections are permanently connected to each other to form the center piece, in particular welded together.

The invention is based on several in the following

Drawing illustrated exemplary embodiments explained in more detail.

1 shows a side view of the cardan double joint, shown partly in section;

Fig. 2 is a partially sectioned plan view of the double joint in the extended position;

Fig. 3 is a partially sectioned plan view of the double joint in an angled

Position;

Fig. 4 is a plan view of a pair of centering elements of the double joint in the extended position;

FIG. 5 shows a top view of the centering element pair according to FIG. 4 in a kink position; FIG.

Fig. 6 is a side view of the pair of centering elements;

7 shows an end view of the one centering element;

8 is an end view of the other centering element;

9 shows a simplified top view of one of the centering elements;

FIG. 10 shows a simplified vertical section of the centering element according to FIG. 9;

FIG. 11 shows a top view of the centering element pair according to FIG. 5 with a protective device; FIG. 12 shows a partially sectioned end view of the pair of centering ducks with a protective device according to FIG. 11;

Fig. 13 is a schematically illustrated perspective

View of the toothed end face of the centering elements;

14 shows a vertical section of a modified pair of centering elements; Fig. 15 each a horizontal section of another modified and 16 converted centering element pair with one

Guide and protective housing in extended or kinked position;

17 shows a plan view of a centering element according to FIG. 15;

18 shows a vertical section of the centering element according to FIG. 17;

19 shows a rear view of the centering element according to FIGS. 15 and 16;

20 is an end view of the guide and protective housing of the centering element pair according to FIGS. 15 and 16;

21 shows a vertical section, shown as a detail, of a converted center piece of the double joint;

FIG. 22 shows a horizontal section of the center piece according to FIG. 21, shown in sections.

The apparent from Fig. 1 to Fig. 3 Kärdan double joint, which is hereinafter referred to only as a double joint 30, has two main fork parts 31 and 32, a middle piece 33 with two inner fork parts 34 and 35, two joint crosses 36 and 37 and a centering device 38.

In Fig. 1, a shaft part 41 is indicated by dash-dotted lines, with which the fork part 31 is welded. On the other side, a shaft part 42 is indicated by dash-dotted lines which, like the shaft part 42, is provided with a flange, by means of which the shaft part 42 is detachably connected to the fork part 32.

The outer fork part 31 has two mutually aligned cylindrical through holes 43 and 44, into the two mutually aligned pivot pins 45 and 46 of the one

Intervene joint cross 36 and are rotatably supported therein by means of a roller bearing 47 or 48 (FIG. 2). In a similar manner, the inner fork part 34 has at one end of the Center piece 33 has two cylindrical through holes 51 and 52, which are aligned with one another, into which the other two joint pins 53 and 54 of joint cross 36 engage and are rotatably supported therein by means of roller bearings 55 and 56 (FIG. 1). Thus, the outer fork part 31 and thus also the shaft part 41 is coupled to the middle piece 33 in a rotationally fixed manner but pivotable about two axes.

In the same way as the one outer fork part 31 coupled to the middle piece 33, the other outer fork part 32 is also coupled to the middle piece 33, one of the synchronizing conditions for the double joint 30 being the articulated pin of the two articulated crosspieces articulated to the middle piece 33 36 and 37 must be aligned parallel to each other (Fig. 1).

As a second synchronism, both in the extended position and in any pivot position of the two shaft parts 41 and 42, the axes 57 and 58 of the two fork parts 31 and 32 must always intersect at a point which is located on the center plane 59, which is normal to Connection line of the centers 61 and 62 of the two crosses 36 and 37 is aligned and has the same distance from the centers 61 and 62 (Fig. 1 and

Fig. 3). This condition is met by means of the centering device 38.

The centering device 38 has two centering elements 63 and 64. The centering element 63 is rotatably mounted on a centering pin 65 which is arranged on the outer fork part 31 and is centered on its axis 57. The centering element 64 is rotatably mounted on a centering pin 66 which is arranged on the outer fork part 32 and is aligned with the axis 57 thereof. A needle bearing 67 and 68, the needles of which directly on the assigned pivot pins 65 and 66 run. The needle bearings 67 and 68 have a closed bottom 69, which rests on the end face of the centering pin 65 and 66 in question and takes over the axial guidance of the centering element in the manner of a plain bearing.

The centering elements 63 and 64 have a hub 71 or 72 on the side facing the centering pin, which receives the outer ring of the needle bearing 67 or 68. On the side facing away from the assigned fork part, the

Centering elements 63 and 64 on a toothed segment 73 or 74, which is at least approximately designed as a cylindrical surface section. Their mutually coordinated teeth 75 and 76 are aligned parallel to the surface lines of the cylindrical tooth segments 73 and 74. So that the tooth segments can be aligned with one another, a tooth is present in the symmetry plane in one tooth segment and a tooth gap is present in the other tooth segment. The radius of the cylindrical toothed segments 73 and 74 is at least approximately equal to half the distance between the centers 61 and 62 of the two articulated crosses 36 and 37, the pitch circle radius of the toothings 75 and 76 being exactly equal to this half the distance. The centering elements 63 and 64 are arranged on the associated centering pin 65 and 66 in the axial direction so that the center point of the cylinder axis of the partial cylinder of the toothings 75 and 76 passes through the center 61 and 62 of the cross members 36 and 37. When the centering elements 63 and 64 swivel around the center 61 or 62 of the adjacent universal joint 36 or 37, the toothings 75 and 76 mesh with one another and the toothed segments 73 and 74 roll on one another.

The centering elements 63 and 64 are provided with a guide device 77 which prevents the tooth segments 73 and 74 from partially or completely disengaging in the direction of extension of their toothing 75 or 76 due to a force acting in the same direction devices. This guide device 77 has two guide rims 78 and 79, which are arranged together on the one centering element 63, on both sides of the end faces 81 and 82, which are oriented normally to the direction of extension of the toothing 75 (FIG. 7) .

The guide ribs 78 and 79 protrude sufficiently far beyond the lateral surface of the toothed segment 73, so that at least a portion of the guide ribs 78 and 79 extend into the extension projection as well as in each pivoting position of the two centering elements 63 and 64 Tooth segment 74 of the other centering element 64 extends out. The mutually facing side surfaces of the guide rims 78 and 79 serve as guide surfaces 83 and 84, respectively. They interact with a further guide surface 85 and 86, both of which are arranged together on the other centering element 64 and practically through the end faces of the toothed segment 76 of this centering ¬ element 64 are formed. The clear distance between the guide surfaces 83 and 84 is slightly larger than the outer distance between the guide surfaces 85 and 86.

The two centering elements 63 and 64 are also provided with a driver device 87 (FIGS. 5 and 8). It has two driver surfaces 88 and 89, which are arranged together on the centering element 64. They are oriented toward one of the two sides in the direction of extent of the toothing 76. These guide surfaces 88 and 89 are formed here by the corresponding section of the peripheral surface of a driver pin 91 and 92, respectively, which are inserted into a recess of an extension 93 and 94 of the centering element 64. Two further guide surfaces interact with the guide surfaces 88 and 89, which are arranged on the centering element 63 and are formed there by the end faces 81 and 82 of the toothed segment 75. If the two guide rims 78 and 79 of the guide device 77 are arranged in the plane of symmetry of the associated centering element 63, it is expedient for the driver surfaces 88 and 89 of the driver device 87 to be outside the ones extending in the direction of extension of the toothing 76 of the centering element 64 Symmetry planes are arranged.

The tooth segments 73 and 74 were previously shown as cylinder surface sections. So that in the extended position of the two shaft parts 41 and 42 when the double joint is stationary and in an unfavorable rotational position of the centering elements 63 and 64 when a pivoting movement of the shaft parts 41 and 42 is initiated, the teeth of the centering elements 63 and 64 do not jam with one another before the start of a rotational movement of the shaft parts and if they and the other interacting parts are even damaged or destroyed, it is expedient to extend the theoretically purely cylindrical reference surface of the toothings 75 and 76 in the direction of extension of the spanned by the pitch circle

To curve gears partially convex. It is sufficient if this convex curvature is present mainly in the region of the plane of symmetry of the centering elements and is at the same time largest there, whereas it can become smaller on both sides, and it is even advantageous that it is zero again in the region of the edge of the centering elements has become. The maximum value of the curvature of the toothing 76 is illustrated in FIG. 10. For the radii of curvature indicated in FIG. 9, R1 <R2 <R3 <R4 applies, where R4 = oθ. These geometrical relationships are illustrated in perspective in FIG. 13, where the "distortion" of the theoretically cylindrical reference plane of the toothing is most clearly recognizable when the representation along the chain line 95 and in particular is viewed from a small angle to the plane of the drawing. In FIGS. 1 to 3, the centering elements 63 and 64 are surrounded by a protective device 96, which is shown as a simple bellows for the sake of clarity in the drawing. Because the required movement space of the centering elements is relatively large, it is expedient to use a bellows with a larger number of folds, namely an accordion bellows 97, as protective device 96, as can be seen from FIGS. 11 and 12 . The ring flanges 98 and 99 of the bellows 97 are pushed onto the hubs 71 and 72 of the centering elements 63 and 64 and, if necessary, clamped thereon by means of tensioning straps or tensioning rings.

In the following, modified centering elements 101 and 102 are explained with reference to FIGS. 14 to 19, which at the same time interact with a modified guide and driver device 103.

The centering elements 101 and 102 have a compact base body which has on one side the cylindrical recess 104 and 105, respectively, which holds the roller bearings for the rotatable mounting of the centering elements 101 and 102 on the centering pins 65 and 66 of the outer fork parts 31 and 32 records. On the other hand, the centering elements 101 and 102 again have the shape of a cylindrical surface section, which serves as tooth segment 106 or 107 and is provided with teeth 108 or 109. The tooth segments 106 and 107 and their toothings are otherwise designed and arranged in the same way as the tooth segments 63 and 64, which is why their explanations also apply here.

The guide device 103 is designed as a tongue and groove combination which has a tongue 111 and two grooves 112 and 113. The grooves 112 and 113 are arranged in the plane of symmetry of the toothed segments 106 and 107 which is normal to the direction of extension of the toothings 108 and 109 (FIGS. 14 and 19). You follow that Curvature of the tooth segments 106 and 107. The grooves 112 and 113 are shown with a rectangular cross section. You can also have a trapezoidal plan projection with a small spreading angle of the groove side walls from the groove base. These groove side walls can also have a slightly convex curvature.

The spring 111 is straight and has a rectangular cross section. It engages on both sides in the two mutually aligned grooves 112 and 113. As a result, it guides the two centering elements 101 and 102 in the direction of extension of their toothings. Since the spring 111 is in the stretched position of the shaft parts and thus also the centering elements 101 and 102 with a larger surface area on the groove flanks (FIG. 15), the tongue and groove combination can also serve as a driver device which, when a Pivoting movement of the shaft parts and simultaneous occurrence of a torque ensures that the two centering elements 101 and 102, which can rotate independently on the centering pin, rotate into the rotational position in which their spring 111 is located in the pivoting plane of the shaft parts, in which a mutual rolling of the Gears 108 and 109 is possible.

The spring 111 is held in the correct axial position between the two centering elements 101 and 102 by means of a holder 114. In the simplest case, the holder 114 is formed by a bracket each, which rests on the adjacent side edges of the centering elements 101 and 102, the spring 111 protruding through a recess through the bracket and being secured on the outside thereof by a spring clip. In the exemplary embodiment according to FIGS. 14 to 16, the holder 114 is at the same time designed as a protective housing which surrounds the centering elements 101 and 102 on their peripheral sides. For this purpose, the two upper and lower wall parts 115 and 116 serving as retaining brackets for the spring 111 have a width that is larger than the width of the centering elements 101 and 102. On the side edges of these wall parts 115 and 116, one side wall 117 and 118 adjoin each other, which together form the box-like protective housing 114 (FIG. 20).

So that the protective housing 114 can not only perform the holding function but also the protective function perfectly, the edge surfaces 121 and 122 of the centering element 101, which run parallel to the direction of extension of the teeth 108 and 109, and the corresponding edge surfaces 123 and 124 of the centering element 102 are sections formed a cylindrical surface, the cylinder axis intersects the axis 57 and 58 of the outer fork parts 31 and 32. As a result, the centering elements 101 and 102 each externally represent a cylinder section with flat parallel end faces 125 and 126. The top and bottom wall parts 115 and 116 of the protective housing 114 have a clear distance which is equal to the cylinder diameter of the centering elements 101 and 102. The clear distance of the side walls 117 and 118 is equal to the outside distance of the

End faces 125 and 126 of the centering elements 101 and 102 (FIG. 19). In this way, the centering elements 101 and 102 are tightly enclosed by the protective housing 114 and at the same time the spring 111 is always held in the correct position relative to the centering elements 101 and 102.

A modified center piece 127 can be seen from FIGS. 21 and 22. It is composed of two length sections 128 and 129, each of which has an inner fork part which corresponds to fork parts 34 and 35, respectively. At their connection point 131, the length sections 128 and 129 are each provided with a circular cylindrical guide surface 132 and 133, which are coordinated with one another. On the basis of these guide surfaces 132 and 133, the longitudinal sections 128 and 129 can be adjusted to a certain extent in alignment with one another in the direction of their longitudinal axis in the axial direction. This allows the Positioning elements 63 and 64 are set to the correct mutual distance for their toothing. The two length sections 128 and 129 are then welded to one another at the connection point 131.

Further modifications are possible to the exemplary embodiments explained so far.

The guide device for the centering elements can be formed as a tongue and groove combination with a tongue and a groove, in which the tongue is formed as a rib on the one centering element. This tongue can also be manufactured as a separate part, which is firmly inserted into a matching groove of the other centering element. In the guide device with an independent spring held by means of a holder and two grooves interacting with it, the spring can have a circular cross section. The grooves then accordingly have a cross-sectional surface with a semicircular surface section and with a rectangular surface section adjoining the base of the semicircle.

The toothed segments of the centering elements can, instead of the straight toothing explained so far, have an arch toothing which is expediently arranged symmetrically to the plane of symmetry of the centering element. Instead of the curved toothing, an arrow toothing or a double helical toothing can also be provided, both of which are likewise expediently arranged symmetrically on the centering elements. Because these gears are bilateral

Inherent leadership property, a separate guide device can be omitted when used. LIST OF REFERENCE SIGNS E 13. 12. PC 2

30 cardan double joint

31 outer fork part

32 outer fork part

33 center piece

34 inner fork part

35 inner fork part

36 universal joint

37 joint cross

38 centering device

41 shaft part

42 shaft part

43 through hole

44 through hole

45 pivot pins

46 pivot pins

47 rolling bearings

48 rolling bearings

51 through hole

52 through hole

53 pivot pins

54 pivot pins

55 rolling bearings

56 rolling bearings

57 axles (of 31)

58 axles (of 32)

59 middle level

61 middle

62 middle

63 centering element

64 centering element

65 centering pins

66 centering pin

67 needle bearings

68 needle bearings

69 floor

71 hub

72 hub

73 tooth segment

74 tooth segment

75 toothing

76 gearing

77 guide device

78 Guide board

79 leader board

81 end face

82 end face

83 guide surface

84 guide surface

85 guide surface

86 guide surface

87 Driver device and 88 driving surface

89 driving surface

91 drive pins

92 drive pins

93 continuation

94 continuation

95 dash-dot line

96 protection device

97 accordion bellows

98 ring flange

99 ring flange

101 centering element

102 centering element

103 Guide and driver device

104 recess

105 recess

106 tooth segment

107 tooth segment

108 gearing

109 gearing

111 spring

112 groove

113 groove

114 holder, protective housing

115 calf section

116 wall part

117 side wall

118 side wall

121 edge surface

122 edge surface

123 edge surface

124 edge surface

125 end face

126 end face

127 center piece

128 length section

129 length section

131 connection point

132 guide surface

133 guide surface

134 longitudinal axis

Claims

Cardan double joint with the features:

- There are two outer fork parts (31; 32),

- Of which one fork part (31) is permanently or detachably connected to the drive shaft as a shaft part (41) and is flush with it and

- - Of which the other fork part (32) with the

Output shaft as another shaft part (42) is permanently or detachably connected and aligned with it,

- there is a middle piece (33),

- - That in the axial direction between the two outer ones

Fork parts (31; 32) is arranged and

- - An inner one at each of its two end areas

Has fork part (34; 35),

- there are two articulated crosses (36; 37),

- of which the one hinge cross (36) is coupled on the one hand to the outer fork part (31) of the one shaft part (41) and on the other hand to the one inner fork part (34) of the middle piece (33),

- - of which the other joint cross (37) is coupled on the one hand to the outer fork part (32) of the other shaft part (42) and on the other hand to the other inner fork part (35) of the middle piece (33),

- There is a centering device (38) by means of which the two outer fork parts (31; 32) can be aligned so that their axes (57; 58) intersect at a point on the center plane (59) of the center piece (33 ) is located, which is normal to the connecting line of the centers (61; 62) of the two articulated crosses (36; 37) and is at the same distance from the centers (61; 62) of the articulated crosses (36; 37), characterized by di e feature e:

- The centering device (38) has two centering elements (63; 64), - - Of which the one centering element (63) on one

Centering pin (65) is rotatably mounted, which is arranged on an outer fork part (31) and aligned with the axis (57) thereof,

- - Of which the other centering element (64) on one

Centering pin (66) is rotatably mounted, which is arranged on the other outer fork part (32) and aligned with the axis (58) thereof,

the bearing part (67; 68) matched to the centering pin (65; 66) on the side facing the assigned outer fork part (31; 32),

- - On the side facing away from the assigned outer fork part (31; 32) have an at least approximately cylindrical tooth segment (63; 64), the mutually coordinated toothing (75; 76) parallel to the surface lines of their cylindrical Tooth segment (63; 64) is aligned,

- The radius of the cylindrical toothed segments (63; 64) is at least approximately equal to half the distance between the centers (61; 62) of the two articulated crosses (36; 37),

- The centering elements (63; 64) are arranged on the centering pin (65; 66) of the associated outer fork part (31; 32) in the axial direction so that the cylinder axis of their tooth segment (63; 64) through the middle ( 61; 62) of the associated articulated cross (36; 37) passes through.

- The centering elements (63; 64) are provided with a guide device (77), by means of which the one centering element (63) with respect to the other centering element (64) in the direction of the surface lines of their tooth segments (63; 64) in is guided in both directions. 2. Double joint according to claim 1, characterized by the features:

the centering elements (63; 64) are mounted on the centering pin (65; 66) by means of a roller bearing, preferably in the form of a needle bearing (67; 68),

- Preferably, the needles of the nail bearings (67; 68) run directly on the centering pin (65; 66).

Double joint according to claim 2, g e k e n n z e i c h n e t by the feature:

- In the axial direction aligned with the assigned fork part (31; 32), the centering elements (63; 64) are guided by means of the bottom (69) of the outer ring of the roller bearing (67; 68).

Double joint according to one of claims 1 to 3, g e k e n n z e i c h n e t by the feature:

- The guide device (77) has two guide rims (78; 79),

- - which are arranged together on the one centering element (63),

- - The side surfaces facing each other as

Guide surfaces (83; 84) serve and

- Of which in the extended position and in each swivel position at least one section extends into the Aufriß¬ projection of the other centering element (64) over,

- The guide device (77) has two further guide surfaces (85; 86),

- - Which are present together on the other centering element (64) and

- - Which are arranged in such a way that the

Guide surfaces (83; 84) on which one centering element (63) are at least closely adjacent or bear against it. 5. Double joint according to claim 4, characterized by the features:

- The guide rims (78; 79) are arranged on both sides of the one toothed segment (73) on the end faces thereof,

- The further guide surfaces (85; 86) are formed by the end faces of the toothed segment (74) of the other centering element (64).

the guide device is designed as a tongue and groove combination which has a tongue and a groove,

- The spring is arranged in the region of the cylindrical tooth segment of the one centering element and is aligned in the circumferential direction and

- The groove is arranged in the region of the cylindrical tooth segment of the other centering element and is also aligned in the circumferential direction.

Double joint according to one of claims 1 to 3, g e k e n n z e i c h n e t by the features:

the guide device (103) is designed as a tongue and groove combination which has a tongue (111) and two grooves (112; 113),

one of the grooves (112; 113) is arranged in the area of the cylindrical tooth segment (106; 107) of each of the two centering elements (101; 102) in a common plane and aligned in the circumferential direction,

- The spring (111) is straight and engages on both sides in the two grooves (112; 113) and is held in this position in the axial direction by means of a holder (114). 8. Double joint according to claim 6, characterized by the feature: - The spring is integrally formed on the associated centering element as a rib.

9. Double joint according to claim 6, characterized by the feature: - The spring is designed as a separate part which is inserted into a matching groove in the cylindrical tooth segment of the centering part.

10. Double joint according to claim 7, g e k e n n z e i c h n e t by the feature:

- The spring (111) and the grooves (112; 113) have a regular polygonal cross section, preferably a rectangular cross section.

11. Double joint according to claim 7, characterized by the feature: the spring has a circular cross section,

- The grooves have a cross section with a semicircular surface section and with a rectangular surface section adjoining the base of the semicircle.

12. Double joint according to claim 11, characterized by the feature: - the guide device (103) is arranged in the plane of symmetry of the tooth segments (106; 107).

13. Double joint according to one of claims 1 to 12, characterized by the features: - the tooth segments of the Zeήtrierelemente have an arch toothing, - preferably the arch toothing is arranged symmetrically on the centering element. 14. Double joint according to one of claims 1 to 12, characterized by the features:

the toothed segments of the centering elements have an arrow toothing or a double helical toothing, the helix angle of which is preferably the same size in opposite directions,

- The arrow teeth or the double helical teeth on the centering elements are preferably arranged symmetrically.

15. Double joint according to one of claims 1 to 14, g e k e n n z e i c h n e t by the e features:

- there is a driver device (87),

- which is arranged outside the plane of symmetry of the centering elements (63; 64) running in the direction of the toothing (75; 76) of the centering elements (63; 64),

- The driver device (87) has two driver surfaces (88; 89), - - which are arranged together on the one centering element (64) and

- which are oriented in the direction of extension of the toothing (75; 76) of the toothed segment (64) in each of the two directions, - the driver device (87) has two further driver surfaces (81; 82),

- - which are oriented opposite to the first two driving surfaces (88; 89), and

- - Which are arranged on the other centering element (63) in such a way that they are at least in the extended position of the

Shaft parts (41; 42) are each at least closely adjacent to one of the first two driving surfaces (88; 89) or abut against it. 16. Double joint according to claim 14, characterized by the features:

the driver surfaces are arranged on a driver part, which is designed as a projection, preferably in the form of a nose or a pin,

- The two other driver surfaces are arranged on a recess matched to the driver part.

17. Double joint according to claim 16, g e k e n n z e i c h n e t by the features:

one of the two first driver surfaces is arranged on one of two driver parts of one centering element, one of the two other driver surfaces is arranged on one of two driver parts of the other centering element,

- - Which are matched to the driver parts on the one centering element in terms of design and arrangement.

18. Double joint according to one of claims 1 to 17, g e k e n n z e i c h n e t by the feature:

- At least on one tooth segment (74) the reference surface of the toothing (76) is at least partially convexly curved in the direction of extension of the toothing, the curvature being greatest in the plane of symmetry of the centering element and smaller towards the edge on both sides becomes.

19. Double joint according to claim 18, g e k e n n z e i c h n e t by the features:

on both tooth segments (73; 74) the reference surface of the toothing (75; 76) is at least partially convex in the direction of extension of the toothing,

- The maximum curvature is the same in both tooth segments (73; 74). 20. Double joint according to claim 18 or 19, characterized by the feature: - In the edge region of the tooth segment (73; 74) on both sides of the plane of symmetry, the curvature is zero.

21. Double joint according to claim 6, characterized by the feature: - The holder (114) of the spring (111) is formed by a bracket (115; 116), which is aligned in the direction of the connecting line of the two cross members (36; 37) and extends on both sides of the spring (111) at least up to the centering elements (101; 102) and rests on their edge (121, 122; 123, 124).

22. Double joint according to claim 21, which is characterized by the feature: the bracket is designed to be flexurally elastic transversely to its longitudinal extension.

23. Double joint according to claim 21, g e k e n n z e i c h n e t by the features:

the bracket (115; 116) has a width which is at least equal to the width of the centering elements (101; 102) transversely to the connecting line of the two cross members (36; 37),

- On the side edges of the bracket (115; 116) each have a side wall (117; 118) that extends from the side edge of one bracket (115) to the side edge of the other bracket (116) and forms a protective housing ( 114) is connected. 24. Double joint according to claim 23, characterized by the features:

- The edge areas (121, 122; 123, 124) of the centering elements (101; 102) facing the brackets (115; 116) are designed as sections of a cylindrical surface, preferably a circular cylindrical surface.

- The clear dimensions of the bracket (115; 116) and the two side walls connecting them (117; 118) are matched to the outer dimensions of the centering elements (101; 102).

25. Double joint according to one of claims 1 to 20, characterized by the feature: there is a protective device (96) for the centering elements (63; 64),

- - Which completely envelops the centering elements (63; 64) and

- - Which is held by the centering elements (63; 64).

26. Double joint according to claim 25, g e k e n n z e i c h n e t by the features:

- The protective device (96) is formed by a bellows (97),

- The bellows (97) is preferably designed in the manner of an accordion bellows.

27. Double joint according to one of claims 1 to 26, g e k e n n z e i c h n e t by the features:

- The middle piece (127) is composed of two longitudinal sections (128; 129) produced separately from one another,

- - Of which each length section (128; 129) has one of the inner fork parts (34; 35) and - which are preferably provided at their connection point (131) with coordinated cylindrical guide surfaces (132; 133),

- The two longitudinal sections (128; 129) are permanently connected to one another, in particular welded to one another, after the centering device (38) has been installed and adjusted.