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
METHOD OF PRODUCING A BALL AND SOCKET JOINT AND JOINT PRODUCED
ACCORDINGLY

2. APPLICANT(S)
a) Name
b) Nationality
c) Address

ZF FRIEDRICHSHAFEN AG GERMAN Company
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 invention relates to a method of producing a ball and socket joint. It further relates to a ball and socket joint produced by this method, and its joint shell respectively bearing shell is made in a specific way proposed by the invention.
Ball and socket joints transmit and absorb forces from several directions. They are used in automotive construction, for example in the steering system or in conjunction with the track rod. Bearings of the generic type essentially comprise a joint journal with a ball formed on one of its ends, a shell accommodating the ball of the journal and a joint housing accommodating the shell and parts of the ball journal. The ball of the ball journal slides in the permanently lubricated, pre-tensioned shell, which is protected from moisture and dirt by the housing. Furthermore, at its end which is open in order to accommodate the journal, the joint housing is additionally protected against dirt and against leakage of lubricant by means of a bellows seal. An opening of the joint housing often provided at the rear end is also closed by a closure cover. The above-mentioned joint components are usually manufactured separately and then assembled to form a joint in an assembly process. However, this is seen as a disadvantage in terms of assembly costs.
This being the case, patent specification DE 195 13 714 CI already discloses a method whereby the joint shell is placed on the ball of the joint journal and the entire arrangement obtained is subjected to an injection process in order to fix the components and form a joint housing. Based on the approach described in this publication, however, there is a risk of the joint shell being pushed onto the joint ball due to the pressure which occurs during the injection process to form the housing so that it lies on the latter with its full surface. The disadvantage of too large a contact surface, however, is that it undesirably increases the rotational and tilting moment.
Accordingly, the objective of the invention is to specify a method which offers a simple way of producing a fully assembled ball and socket joint and results in a functionally reliable ball and socket joint with a low friction moment and a low rotational and tilting moment, whilst ensuring that the sliding surfaces of the ball and socket joint and the


joint shell respectively bearing shell are sufficiently lubricated. Also described is a ball and socket joint which can be produced using this method.
This objective is achieved by a method based on the characterising features defined in the main claim. A ball and socket joint which achieves this objective is characterised by the first substantive claim. Advantageous embodiments and other versions of the invention are defined in the respective dependent claims.
Both the method proposed as a means of achieving the objective and the ball and socket joint produced as a result relate to a ball and socket joint of a type which is known in principle. It comprises a joint journal with a joint ball formed at one end of the joint journal, a joint housing open at one end accommodating this joint ball, a permanently lubricated, essentially spherical joint shell disposed between the joint ball and the joint housing, and a bellows seal sealing the open end of the joint housing in the region of the transition between the joint ball and the shaft of the joint journal projecting out of the joint housing. The way in which the corresponding ball and socket joint is produced is by employing an injection or casting process (for example pressure casting) to produce the joint housing, whereby the joint ball with the bearing shell placed on it is surrounded by a metal material or a plastic. For the purpose of the invention, however, the essentially spherical design of the joint shell is slightly modified. To this end, the joint shell is provided with a protuberance in at least one region, which flexes elastically when subjected to the pressure prevailing during the injection or casting process, and cambers slightly outwards from the otherwise spherical shape of the joint shell respectively bearing shell when the injection or casting process is terminated. This ensures that the joint shell does not lie with its full surface on the joint ball after the injection or casting process. In order to produce the ball and socket joint, the joint shell designed in the manner described above is placed on the joint ball of the joint journal and is subjected to an injection together with it. In an assembly process which takes place downstream of the injection or casting process, the sealing system with the bellows seal is finally added.


Since a full-surface contact between the joint shell and joint ball is prevented, the frictional moment between the joint shell and ball and socket joint and the rotational and tilting moment is restricted during operational use of the ball and socket joint. This ensures that the ball and socket joint has good running properties and its components exhibit a high degree of strength. In the case of a ball and socket joint with a metal joint housing, a metal overlap can advantageously be produced between the joint ball and the joint housing during the course of a casting process. This being the case, the joint housing is designed so that it extends virtually as far as the transition between the joint ball and the shaft of the joint journal, and the diameter of the joint housing in the region where the joint journal extends through the opening is smaller than the diameter of the joint ball. The metal overlap obtained as a result advantageously reduces the likelihood of the joint journal being pulled out.
In one advantageous embodiment of the invention, the joint housing is provided with a shaft, by injecting around an appropriately shaped tube or a rod during the process of producing the joint housing. An alternative option is to produce only a shaft stub on the joint housing during the injection or casting process and to fit a connecting tube or a rod to it by a cold or hot driving process.
With the ball and socket joint proposed by the invention, an outwardly cambered raised area is formed on the joint shell in the region of the pole of the joint ball. In this case, the joint or bearing shell is made from a plastic, which is elastically deformable at least in the region of this camber. During the injection or casting process used to produce the joint housing, the elastically deformable camber of the bearing shell placed on the joint ball beforehand is pressed onto the surface of the joint ball. However, due to the special shape and the choice of an appropriate, elastic material such as polyoxymethylene, polyamide, polyphenylene sulphide or polyphthalamide, for example, said protuberance cambers at least partially outwards again once the injection or casting process is terminated. As a result, a gap is left free at least in the region of the protuberance between the internal contour of the joint shell and the joint ball. A full-surface contact between the bearing shell and joint ball is therefore prevented, thereby


reducing the frictional moment and the rotational and tilting moment. In a preferred embodiment of the ball and socket joint proposed by the invention, the joint shell also has ribbing on its internal surface in the region of the outwardly cambering protuberance. This is provided to deal with the situation in which, due to tolerances relating to the pressure prevailing during the injection or casting process or tolerances relating to the material and shape of the joint shell, the region of the protuberance does not spring back in exceptional individual cases after the injection or casting process. In this case, the ribbing ensures that the joint shell still does not lie with its full surface on the joint ball.
In terms of geometry, said ribbing may be of different designs. Based on one option, several ribs extend radiating out from the pole of the essentially spherical geometry on the internal surface of the outwardly cambered region of the joint shell, and several ribs disposed parallel with one another and with the equator of the sphere of the joint ball extend transversely to these. In another embodiment, the joint shell has a plurality of ribs on its internal surface in the region of the outwardly cambered protuberance, which intersect at a right angle by reference to a surface projection of the spherical surface.
The ball shell preferably also has several longitudinally extending rib-shaped portions on its external surface, which prevent any twisting. They prevent the joint shell from twisting in the joint housing.
In another advantageous embodiment, a ring is inserted between the joint housing and the joint shell in the region of the opening of the joint housing, the portion of which projecting out of the opening of the joint housing serves as the bellows seat for the bellows seal. In the case of a metal joint housing, this advantageously further increases the metal overlap between the joint housing and the joint ball.
The invention will be explained again below with reference to examples of embodiments. Illustrated in the associated drawings are:
Fig. 1: a first embodiment of the ball and socket joint proposed by the invention with a tubular shaft,


Fig. 2: a ball and socket joint based on the embodiment illustrated in Fig. 1, the housing
of which is connected to a rod, Fig. 3: another embodiment with a tubular shaft, Fig. 4: an embodiment with a washer inserted between the joint shell and housing in
the region of the housing opening, Fig. 5: embodiments of the joint shell.
Fig. 1 illustrates one possible embodiment of the ball and socket joint proposed by the invention. In a known manner, it comprises a joint journal 3,4, the joint ball 4 of which is accommodated by a joint housing 7. Disposed between the joint housing 7 and the joint ball 4 is a permanently lubricated joint shell 1,1'. The embodiment illustrated is produced by placing the joint shell 1,1' on the joint ball 4 and then forming the joint housing 7 by injecting around or casting around the joint shell 1,1' and the joint ball 4. The sealing system with the bellows seal 8 was added during a subsequent assembly operation.
In order to prevent the joint shell 1,1' from lying with its full surface on the joint ball 4 after the injection process, the joint shell 1,1' is designed in a special way in keeping with the principle underlying the invention. As illustrated, in the region of the pole 5 of the joint ball 4, it has an outwardly cambered protuberance l1. In addition, ribbing 2 is provided on the internal surface of the joint shell 1,1' in the region of this protuberance 1'. Due to these features relating to the shape of the joint shell 1,1', a full-surface contact of the joint shell 1, 1' on the joint ball 4 is prevented. Although the joint shell 1,1' is pressed onto the surface of the joint ball 4 during the injection or casting process, the protuberance 1' provided on the joint shell 1, l1 cambers at least partially outwards again on termination of the injection or casting process. If, exceptionally, this desired result does not occur, however, a restriction in the frictional moment is achieved by at least the ribbing 2 provided on the internal contour. In the case of the ball and socket joint illustrated in Fig. 1, a shaft 12 forming an integral part of the joint housing 7 provides a connection to other elements. To this end, injection takes place around a metal tube 13 during production of the joint housing.


Fig. 2 illustrates an embodiment of the ball and socket joint proposed by the invention that is in principle the same as that shown in Fig. 1. Unlike the embodiment described above, however, a rod 13' is provided instead of a tube 13 for producing the shaft 12, around which the injection takes place. Like the ball and socket joint illustrated in Fig. 1, the seating collar of the ball journal is provided in the form of a nut 14. This makes the component more service-friendly. In order to compensate for the reduction in contact surface obtained as a result, a washer 15 is additionally pressed onto the journal respectively shaft 3 of the ball journal 3, 4 underneath the nut 14.
Fig. 3 illustrates another embodiment, which is likewise similar in principal to the embodiment described above. In this instance, however, only a stub 12' is injected onto the joint housing 7 in order to produce a shaft and it is connected to a tube 13 by a cold driving process, for example.
Fig. 4 illustrates another embodiment of the ball and socket joint proposed by the invention, in which an additional ring 11 is inserted between the joint shell 1,1' and the joint housing 7 in the region of its opening and around at least part of which the injection also takes place. The overlap (in the case of a metal joint housing 7, this will be the metal overlap) between the joint housing 7 and the ball journal 4 is advantageously made larger as a result, thereby making it more resistant to being pulled out. As with all the embodiments described above, the ball and socket joint is sealed by a bellows seal 8 fitted after the injection or casting process to prevent ingress by dirt and leakage of lubricant.
Fig. 5 illustrates possible embodiments of the joint shell 1,1' of the ball and socket joint proposed by the invention. In conformity with the principle behind the invention, the joint shell 1,1' has a protuberance 1' cambering slightly outwards in the region of the pole 5'. Contouring is imparted to its internal surface in the form of ribbing 2 in the region of this protuberance. Examples of this ribbing 2 are shown adjacent to one another by a) and b). In the case of the ribbing 2 based on shape a), several ribs 2' extend radiating out from the pole 5'. Extending transversely to these are several ribs 2" parallel


with one another and with the equator of the ball. In the case of the embodiment illustrated by b), a plurality of ribs 2'" intersect at a right angle by reference to a surface projection of the spherical surface of the joint shell 1,1'. The rib structures illustrated merely represent examples and are shown separately from the external shape of the joint shell 1, V in the drawings purely with a view to obtaining better clarity. However, they are integral with the joint shell 1,1' in each case. The joint shell 1,1' illustrated in the drawings also has several ribs 10 or webs on its external surface, which are intended to prevent any twisting and prevent the joint shell 1,1' from twisting in the joint housing 7.


List of reference numbers

1,1' Joint respectively bearing shell
1' Protuberance
2 Ribbing
2', 2", 2'" Ribs
3 Shaft of the joint journal
4 Ball of the joint journal
5 Pole of the joint ball
5' Pole of the joint shell
6 Equator of the joint ball
7 Joint housing
8 Bellows seal
9 Gap
10 (External) ribs or webs
11 Ring
12 Shaft
12 Shaft stub
13 Tube
13' Rod
14 Nut
15 Washer


WE CLAIM:
1. Method of producing a ball and socket joint comprising a joint journal (3,4) with
a joint ball (4) formed at one end, a joint housing (7) accommodating the joint
ball (4) and an essentially spherical joint shell (1, l1) disposed between the joint
ball (4) and the joint housing (7), which joint housing (7) is made by an injection
or casting process, whereby the joint ball (4) with the joint shell (1,1') placed on it
is surrounded with a metal material or a plastic and completed by means of a
sealing system with a bellows seal (8) in an assembly process downstream of the
injection or casting process,
characterised in that the joint shell (1,1') is provided with a protuberance (l1) in at least one region, which flexes elastically when subjected to the pressure prevailing during the injection or casting process and cambers outwards from its otherwise spherical shape once the injection or casting process is terminated so that the joint shell (1,1') does not lie with its full surface on the joint ball once the joint housing (7) has been produced.
2. Method as claimed in claim 1, whereby the ball and socket joint is surrounded by a metal joint housing (7), characterised in that a metal overlap is formed between the joint ball (4) and the joint housing (7) during the course of the injection or casting process.
3. Method as claimed in claim 1 or 2, characterised in that the joint housing is provided with a shaft (12) for connecting to other units during the course of the injection or casting process by also injecting around a tube (13) or a rod (131).
4. Method as claimed in claim 1 or 2, characterised in that a shaft stub (12') is injected onto the joint housing and once the injection or casting process has been completed, it is connected to a tube (13) or a rod (13') by a cold driving process or a hot driving process.


5. Ball and socket joint comprising a joint journal (3,4) with a joint ball (4) formed
on one end, a joint housing (7) open at one end accommodating the joint ball (4)
made from metal or plastic and produced by an injection or casting process, a
permanently lubricated, essentially spherical joint shell (1,1') disposed between
the joint ball (4) and the joint housing (7) and a bellows seal (8) sealing the open
end of the joint housing (7) in the region of the transition between the joint ball
(4) and the shaft (3) of the joint journal (3,4) extending out from the joint housing
(7),
characterised in that the joint shell (1, 1') has an outwardly cambered protuberance (l1) in the region of the pole (5) of the joint ball (4), in the region of which a gap (9) is also left free between the internal contour of the joint shell (1, 1') and the joint ball (4) on termination of the injection or casting process during which an injection takes place around the joint ball (4) and the joint shell (1,1') placed on it together with the joint housing (7).
6. Ball and socket joint as claimed in claim 5, characterised in that the joint shell (1, 1') has ribbing (2) on its internal surface facing the joint ball (4) in the region of the protuberance (I1).
7. Ball and socket joint as claimed in claim 5 or 6, characterised in that several ribs (21) extend on the internal surface of the outwardly cambered protuberance (I1) of the essentially spherical joint shell (l1) radiating out from its pole (5'), and several other ribs (2") disposed parallel with one another and with the ball equator (6) of the joint ball extend transversely to these ribs (21).
8. Ball and socket joint as claimed in claim 5 or 6, characterised in that the joint shell (1,1') has a plurality of ribs (2"') on the internal surface of the outwardly cambered protuberance (l1) which intersect at a right angle by reference to a surface projection of the spherical surface.


9. Ball and socket joint as claimed in claim 7 or 8, characterised in that one or more ribs (10) are provided on the external surface of the joint shell (1, l1) remote from the joint ball (4) to form a means of preventing twisting.
10. Ball and socket joint as claimed in one of claims 5 to 9, characterised in that a ring (11) is inserted between the joint housing (7) and the joint shell (1, l1) in the region of the opening of the joint housing (7), the portion of which extending out from the opening of the joint housing (7) serves as the bellows seat for the bellows seal (8).

ABSTRACT:
The invention relates to a method of producing a ball and socket joint and a joint produced accordingly. The intention is to offer a simple way of producing a fully assembled ball and socket joint with a low rotational and tilting moment. The described ball and socket joint is made by producing the joint housing using an injection or casting process, whereby the joint ball with the bearing shell placed on it is surrounded by a metal material or a plastic. For the purpose of the invention, the essentially spherical shape of the bearing shell is slightly modified. The joint shell is provided with a protuberance in at least one region which flexes elastically when subjected to the pressure prevailing during the injection or casting process and cambers slightly outwards on termination of the injection or casting process. This ensures that the joint shell does not lie with its full surface on the joint ball after the injection or casting process.
To,
The Controller of Patent,
The Patent Office
Mumbai
Figure 1