FORM 2
THE PATENT ACT 1970 (39 of 1970)
&
The Patents Rules, 2003 COMPLETE SPECIFICATION
(See Section 10, and rule 13)
1. TITLE OF INVENTION BALL-AND-SOCKET JOINT
2. APPLICANT(S)

a) Name : ZF FRIEDRICHSHAFEN AG
b) Nationality : GERMAN Company
c) Address : 88038 FRIEDRICHSHAFEN
GERMANY
3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention and the manner in which it is to be performed : -

Description
The present invention relates to a ball and socket joint for a motor vehicle, in particular for a pendulum-type support of a motor vehicle, with a housing open on at least one side, in the interior of which a bearing shell is inserted, which in turn accommodates a joint ball of a ball journal so that it is able to effect a sliding movement.
Patent specification DE 43 06 006 Al discloses a ball and socket joint with an annular housing and a bearing shell inserted in it, in which a ball journal is mounted. The bearing shell has a contour on its external circumference, which engages in a complementary contour of the housing internal diameter in order to prevent twisting movements about the ball journal mid-axis.
With ball and socket joints known from the prior art, it may be that the contour of the bearing shell works loose from the complementary contour of the housing with increasing use of the ball and socket joint, so that the effect of preventing twisting can fail.
Accordingly, the objective of die invention is to propose a ball and socket joint of the type outlined above, which is better at preventing twisting than the prior art.
In a first variant, this objective is achieved by the invention on the basis of a ball and socket joint incorporating the characterising features defined in claim 1 and in a second variant on the basis of a ball and socket joint incorporating the characterising features of claim 11.
As regards the first variant, a ball and socket joint for a motor vehicle is proposed, in particular for a pendulum-type support of a motor vehicle, with a housing that is open on at least one side, in the interior of which a bearing shell is inserted, which in turn accommodates a joint ball of a ball journal so that it is able to effect a sliding movement, and the interior has raised areas along its internal casing surface which positively
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engage in the bearing shell. This being the case, the raised areas are provided in the form of triangular webs.
Twisting is reliably prevented as a result of the bearing shell proposed by the invention, because it has been found that the shell does not work loose from the housing. The ball and socket joint proposed by the invention can be manufactured inexpensively by a mass production process and the means whereby twisting is prevented is better than the prior art.
The triangular webs may extend at an angle with respect to the longitudinal mid-axis, i.e. along a zig-zag line. However, the triangular webs preferably extend parallel with the longitudinal mid-axis of the housing, thereby making it particularly easy to assemble the ball and socket joint by pushing the bearing shell into the interior on the basis of a plastic deformation of its external casing surface.
The triangular webs may extend across only a part of the length of the internal casing surface of the housing, but the triangular webs preferably extend across the entire length of the internal casing surface of the housing. This enables particularly strong torques to be transmitted between the bearing shell and housing.
The triangular webs may have the shape of an acute-angled triangle in cross-section. By preference, however, the triangular webs respectively have two identical side faces and the bisectrix of the angle subtended by the two identical side faces extends though the longitudinal mid-axis of the bearing. As a result of this design, the effect of preventing twisting works equally well in both possible directions of rotation about the longitudinal mid-axis.
The radial height of the triangular webs may be varied depending on the intended use and load of the ball and socket joint. However, a particularly effective anti-twisting effect is obtained if the radial height of the triangular webs is equal to the product of the shell thickness of the bearing shell and the elongation of the material used for the
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bearing shell.
By preference, the two identical side faces of each triangular web subtend a right angle. A larger opening angle could make the bearing shell susceptible to sliding off the triangular webs, whereas a smaller angle could increase the sensitivity of the material of the bearing shell to notching. However, other opening angles are naturally possible, provided the use and load of the ball and socket joint permit this.
In principle, it is possible to provide any number nweb of triangular webs in order to produce the anti-twisting effect proposed by the invention. However, it has been found that this number nweb is optimum if it is greater than or equal to the ratio of the maximum torque Mmax to be transmitted and the product of the surface area of the webs Aweb, the ultimate shearing strength OSmax of the bearing shell material and the effective bearing shell radius r, rounded up to the next even number. This results in:

In this respect, the effective bearing shell radius r extends from the ball centre point to a region between the inner edge and the outer edge of the bearing shell, the radius to the inner edge of the bearing shell being denoted by Tinner and the radius to the outer edge of the bearing shell being denoted by router. Accordingly, the effective bearing shell radius r is based on the following equation:

and the optimum value of r depends on the depth to which the triangular webs engage in the bearing shell. It has been found mat a good value for r is obtained if r = router.
The bearing shell is preferably made from plastic, in particular polyoxymethylene, in which case the bearing shell can be introduced into the housing due to a plastic


deformation of its external circumferential surface, provided the recesses in which the triangular webs engage when the ball and socket joint is in the assembled state are not formed in the bearing shell prior to assembly.
In principle, a gap may be left free between the external circumferential surface of the bearing shell and the internal casing surface of the housing. By preference, however, the bearing shell has a dimension that is slightly bigger than the internal casing surface of the housing so mat it sits in the housing under a slight radial pressure. This avoids the air gap and thus prevents dirt from penetrating.
In a second variant of the invention, a ball and socket joint for a motor vehicle is proposed, in particular a pendulum-type support of a motor vehicle, with a housing open on at least one side, in the interior of which a bearing shell is inserted, which in turn accommodates a joint ball of a ball journal so that it is able to effect a sliding motion, and the interior has recesses along its internal casing surface in which the bearing shell positively engages. This being the case, the recesses are provided in the form of undercuts.
This variant also prevents the bearing shell from working loose from the housing and affords a particularly effective and durable anti-twisting effect. As with the first variant, the ball and socket joint based on the second variant can be manufactured inexpensively by a mass production process.
The undercuts may extend at an angle to the longitudinal mid-axis, e.g. along a zig-zag line. By preference, however, the undercuts extend parallel with the longitudinal mid-axis of the housing, thereby making it particularly easy to assemble the ball and socket joint.
In principle, the recesses may extend across the entire length of the internal casing surface of the housing. However, an adequate anti-twisting effect can still be obtained if the recesses, which are open towards an end face of the housing, extend across only a
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part of the length of the internal casing surface. This being the case, it has proved to be of advantage if the recesses have a rectangular or triangular profile by reference to a longitudinal section of the housing.
The bearing shell is preferably made from plastic, in particular polyoxymethylene, in which case the bearing shell can be formed into the recess by an ultrasound forming process.
The invention will be explained below on the basis of a preferred embodiment illustrated in the appended drawings. Of the drawings:
Fig. 1 shows a longitudinal section through a first embodiment of the ball and socket joint proposed by the invention in the partially assembled state;
Fig. 2 shows a longitudinal section of the embodiment illustrated in Fig. 1 in the fully assembled state;
Fig. 3 shows a cross-section of the first embodiment of the housing based on the first variant of the invention;
Fig. 4 shows the cross-section of a triangular web illustrated in Fig. 3;
Fig. 5 shows the longitudinal section of the housing illustrated in Fig. 3 along section surface A-A';
Fig. 6 shows the cross-section of the housing illustrated in Fig. 3 with a calibrating tool inserted;
Fig. 7 shows the cross-section of a second embodiment of the housing based on the second variant of the invention;
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Fig. 8 is a diagram on an enlarged scale showing an undercut from Fig. 7 with a projection of the bearing shell engaging in it and
Fig. 9 shows a longitudinal section through the housing illustrated in Fig. 7, along section surface B-B', two sub-variants of the profile for the undercut being illustrated.
As illustrated in Fig. 1, a bearing shell 2 is inserted in an annular housing 1, in which a ball journal 5 comprising a pin 3 and joint ball 4 are mounted so that they effect a sliding movement. Accordingly, the ball journal 5 extends out from the ball and socket joint through an orifice 6 provided in the bearing shell 2 and can be rotated about the longitudinal mid-axis 7 of the ball and socket joint and pivoted transversely to it about a pivot point in the joint ball 4. In the region of the orifice 6, the bearing shell 2 lies on an end face of the housing 1 by means of an external shoulder 8, whereas at the end of the bearing shell 2 remote from the external shoulder 8, an annular collar 9 projects out from the housing 1.
As illustrated in Fig. 2, the annular collar 9 has been turned radially outwards by a material deformation in order to secure the bearing shell 2 axially in the housing 1, and this forming is preferably done using the ultrasound forming process. This embodiment of the ball and socket joint is designed to transmit a maximum torque Mtmax of 15 Nm between the housing 1 and bearing shell 2, and the bearing shell made from POM has a shell thickness Sd of 1.5 mm and an elongation es of approximately 10%. However, another embodiment might be designed to transmit a maximum torque Mtmax of 20 Nm between the housing 1 and bearing shell 2.
The housing 1 is of an integral design with a first motor vehicle part 10, and a threaded region 11 is provided on the pin 3 for attaching a second motor vehicle part. In order to prevent dirt and moisture from penetrating the interior of the ball and socket joint, a seal 12 made from an elastic material, in particular rubber, is disposed between the ball journal 5 and the bearing shell 2, although this seal 12 may also be disposed between the
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ball journal 5 and the housing 1.
The triangular webs 13 provided on the internal casing surface of the housing 1 based on the first variant proposed by the invention are illustrated in Fig. 3. The triangular webs 13 extend parallel with the longitudinal mid-axis 7 across the entire length lg of the housing 1 (see Figs. 1 and 5), which is 10 mm in this embodiment.
The cross-section of a triangular web 13 is illustrated on a larger sale in Fig. 4, where an angle a of a = 90° is subtended by the two equal side faces 14 and 15 of the triangular web 13. The bisectrix 16 of the angle a extends through the longitudinal mid-axis 7 of the ball and socket joint and the triangular web 13 has a radial height ha of 0.15 mm, which is derived from the product of the shell thickness Sd (1.5 mm) and elongation es (10%).
As a rule, the ball and socket joint housing 1 has to be calibrated once it has been manufactured, in other words widened to the correct diameter. A calibrating tool 18 made up of several segments 17 and illustrated in Fig. 6 is used for this purpose. The calibrating tool 18 has a continuous bore 19 at its centre, through which a conical pin (not illustrated) can be driven in order to push the segments 17 radially apart. As this happens, however, there is a risk that the triangular webs 13 might be broken. For this reason, the calibrating tool 18 may be designed so that it makes contact with the internal casing surface of the housing 1 at specific points only so that only the triangular webs 13 extending at these points can be broken. As illustrated in Fig. 6, the calibrating tool 18 touches the internal casing surface of the housing 1 at eight points, so that only eight of the sixteen triangular webs 13 provided in this instance can be broken during calibration. In the situation in which sixteen triangular webs have to be provided in the calibrated housing 1, therefore, it is necessary to provide twenty four triangular webs 13 in the housing 1 prior to calibration, to be on the safe side.
Naturally, the number of triangular webs 13 and the number of contact points of the calibrating tool 18 on the housing 1 may be varied. The optimum number, however, is
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sixteen triangular webs after calibration for an effective bearing shell radius of r = 9.5 mm.
After calibration, die bearing shell 2, which is of a slightly bigger dimension than the internal circumferential surface of the housing 1 is introduced into the housing 1 so that the triangular webs 13 dig into it due to a plastic deformation of the external circumferential surface of the bearing shell 2. This is a particularly effective way of preventing the bearing shell 2 from twisting relative to the housing 1 and, because the bearing shell 2 has a slightly larger dimension prior to assembly, also prevents dirt and moisture from penetrating the region between the bearing shell 2 and ball and socket joint housing 1.
Fig. 7 illustrates a cross-section of a second embodiment of a housing 1 based on the second variant of the invention, the same or similar features being denoted by the same reference numbers as those used in connection with the first embodiment. The second embodiment also corresponds to a ball and socket joint of the type illustrated in Figs. 1 and 2, but there are no triangular webs along the internal casing surface of the housing 1 and instead, sixteen undercuts 20 are provided, extending parallel with the longitudinal mid-axis 7, in which the bearing shell 2 engages to produce the anti-twisting effect.
Fig. 8 provides a view of such an undercut 20 on a larger scale, where the bearing shell 2 engages in this undercut 20 by means of a projection 21. The undercuts 20 are open towards an end face of the housing 1 and do not extend across the entire length Ig of the internal casing surface of the housing 1 but only across a partial length It, which is illustrated in Fig. 9. The anti-twisting effect between the bearing shell 2 and housing 1 in this instance is designed so that the annular collar 9 of the bearing shell 2 projecting out from the housing 1 in the partially assembled state is bent radially outwards in a forming process and, as it is so, is simultaneously formed into the undercuts 20. An ultrasound forming process is specifically used for this purpose, whereby the material of the bearing shell 2 is heated. After forming, a so-called material shrinkage occurs as the bearing shell material cools, which causes the projections 21 of the bearing shell 2
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formed in the undercuts 20 to pull radially inwards against the side walls 22 and 23 of the undercuts 20, thereby forming a durably effective anti-twisting means for the bearing shell 2 relative to the housing 1.
As schematically illustrated in Fig. 9, the undercuts 20 may have a rectangular profile (24) or a triangular profile (25) for this purpose by reference to a longitudinal section of the housing (1) along section surface B-B' illustrated in Fig. 7.
Although only sixteen undercuts 20 are illustrated in this embodiment, it has been found that a particularly effective anti-twisting effect is achieved by providing twenty four undercuts.
As with the first variant, the bearing shell 2 of the second variant of the invention may
have a slightly bigger dimension than the internal circumferential surface of the housing
1 prior to assembly, thereby enabling dirt and water to be prevented from penetrating
the region between the bearing shell 2 and housing 1.
Both variants of the invention prevent the bearing shell 2 from working loose from the housing 1. In the case of the first variant, the bearing shell may be introduced into the interior of the housing 1 by plastic deformation of its external circumferential surface. Since this deformation can take place without specifically heating the material, a contraction of the bearing shell material which might leave the bearing shell 2 susceptible to loosening can be avoided. Furthermore, it is not necessary for the external diameter of the bearing shell 2 to be bigger than the internal diameter of the housing 1. However, a slight extra dimension may be of advantage with a view to producing a sealing effect between the bearing shell 2 and housing 1. Accordingly, the bearing shell
2 can be introduced into the housing 1 without or with only a slight radial initial
tension, thereby avoiding the undesired effects of a high radial initial tension which
could have a detrimental effect on the friction torques of the ball journal in the bearing
shell. Such a high radial initial tension is also dependent on time, due to the behaviour
of the plastic, which means that the friction torques of the ball journal can be set as a
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function of time solely on the basis of the high initial tension. This detrimental effect can also be avoided by the ball and socket joint proposed by the invention. In the case of the second variant, the projections 21 of the bearing shell 2 contract firmly into the undercuts 20 due to the shrinkage of the bearing shell material after the forming process and the shrinkage effect in this case does not impair but improves the anti-twisting effect.
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List of reference numbers
1 Housing
2 Bearing shell
3 Pin
4 Joint ball
5 Ball journal
6 Orifice in the bearing shell
7 Longitudinal mid-axis
8 External shoulder
9 Annular collar
10 First motor vehicle part
11 Thread
12 Sealing bellows
13 Triangular web
14 First side face of the triangular web
15 Second side face of the triangular web
16 Bisectrix
17 Segments of the calibrating tool
18 Calibrating tool
19 Bore in the calibrating tool
20 Undercut
21 Projection of the bearing shell
22 First side wall of the undercut
23 Second side wall of the undercut
24 Rectangular profile
25 Triangular profile
Ig Length of the housing
hd Radial height of the triangular webs
Sd Thickness of the bearing shell
r Effective bearing shell radius
a Angle
It Length of the undercut (partial length)
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WE CLAIM:
1. Ball and socket joint for a motor vehicle, in particular a pendulum-type support of a motor vehicle, with a housing (1) open on at least one side, in the interior of which a bearing shell (2) is inserted, which in turn accommodates a joint ball (4) of a ball journal (5) so that it is able to effect a sliding movement, characterised in that the interior has raised areas along its internal casing surface, which positively engage in the bearing shell (2), and the raised areas are provided in the form of triangular webs (13).
2. Ball and socket joint as claimed in claim 1,
characterised in that the triangular webs (13) extend parallel with the longitudinal mid-axis (7) of the housing (1).
3. Ball and socket joint as claimed in claim 1 or 2,
characterised in that the triangular webs (13) extend across the entire length (lg) of the internal casing surface of the housing (1).
4. Ball and socket joint as claimed in one of the preceding claims, characterised in that the triangular webs (13) each have two identical side faces (14,15) and the bisectrix (16) of the angle (a) subtended by the two identical side faces (14,15) extends through the longitudinal mid-axis (7) of the bearing.
5. Ball and socket joint as claimed in claim 4,
characterised in that the radial height (hd) of the triangular webs (13) is equal to the product of the shell thickness (Sd) of the bearing shell (2) and the elongation of the material used for the bearing shell (2).
6. Ball and socket joint as claimed in claim 3 or 4,
characterised in that the two identical side faces (14,15) of each triangular web (13) subtend a right angle (a).
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7. Ball and socket joint as claimed in one of the preceding claims, characterised in that the number of triangular webs (13) is greater than or equal to the ratio of the maximum torque to be transmitted between the housing (1) and the bearing shell (2) and the product of the surface area of the triangular webs (13), the ultimate shearing strength of the bearing shell material and the effective bearing shell radius (r), rounded up to the next even number.
8. Ball and socket joint as claimed in one of the preceding claims, characterised in that the bearing shell (2) is made from plastic.
9. Ball and socket joint as claimed in claim 8,
characterised in that the bearing shell (2) is made from polyoxymethylene
(POM).
10. Ball and socket joint as claimed in one of the preceding claims,
characterised in that the bearing shell (2) has a bigger dimension than the
internal casing surface of the housing (1).
11. Ball and socket joint for a motor vehicle, in particular a pendulum-type support of a motor vehicle, with a housing (1) open on at least one side, in the interior of which a bearing shell (2) is inserted, which in turn accommodates a joint ball (4) of a ball journal (5) so that it is able to effect a sliding movement, characterised in that the interior has recesses along its internal casing surface, in which the bearing shell (2) positively engages, and the recesses are provided in the form of undercuts (20).
12. Ball and socket joint as claimed in claim 11,
characterised in that the undercuts (20) extend parallel with the longitudinal
mid-axis (7) of the housing (1).
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13. Ball and socket joint as claimed in claim 11 or 12,
characterised in that the undercuts (2), open towards an end face of the housing (1), extend across only a part (It) of the length (lg) of the internal casing surface of the housing (1).
14. Ball and socket joint as claimed in claim 13,
characterised in that the undercuts (20) have a rectangular profile (24) or a triangular profile (25) by reference to a longitudinal section of the housing (1).
15. Ball and socket joint as claimed in one of preceding claims 11 to 14, characterised in that the bearing shell (2) is made from plastic.
16. Ball and socket joint as claimed in claim 15,
characterised in that the bearing shell is made from polyoxymethylene (POM).
17. Ball and socket joint as claimed in claim 15 or 16,
characterised in that the plastic is suitable for ultrasound forming.
Dated this 26th day of February, 2007



ABSTRACT
Ball and socket joint for a motor vehicle, in particular a pendulum-type support of a motor vehicle, with a housing (1) open on at least one side, in the interior of which a bearing shell is inserted, which in turn accommodates a joint ball of a ball journal so that it is able to effect a sliding movement.
In a first variant, the interior has raised areas along its internal casing surface, which positively engage in the bearing shell. To this end, the raised areas are provided in the form of triangular webs (13).
In a second variant, the interior has recesses along its internal casing surface, in which the bearing shell positively engages, whereby recesses are provided in the form of undercuts.
To,
The Controller of Patents,
The Patent Office,
Mumbai