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 WITH SEALING RING

2. APPLICANT(S)
ZF FRIEDRICHSHAFEN AG GERMAN Company 88038 FRIEDRICHSHAFEN GELRMMTC
a) Name
b) Nationality
c) Address

3. PREAMBLE TO THE DESCRIPTION
The following specification particularly describes the invention
and the manner in which it is to be performed : -

The invention relates to a ball-and-socket joint, for example tor an axle system or a wheel suspension in a motor vehicle, in accordance with the pre-characterising clause of patent claim 1.
Ball-and-socket joints of the type initially mentioned are used, by way of example but in no way exclusively, in the field of wheel suspension or as bushing joints - for example for the articulating attachment of roll-stabilisers, shock-absorbers or spring-damper systems in motor vehicles.
The demands imposed upon ball-and-socket joints or bushing joints of this type include, in particular, a high specific load-bearing capacity and low bearing play in the case of both static and dynamic loads, and also a low maintenance requirement or freedom from maintenance, if possible over the working life of the motor vehicle or of the ball-and-socket joint, the lowest possible mass and a low requirement as regards installation space. In addition, their manufacture is to be as cost-effective as possible.
A ball-and-socket joint or bushing joint usually possesses a substantially annularly cylindrical or pot-shaped joint housing, in the interior of which the bearing socket or ball socket is arranged. In this connection, it is necessary for the ball socket to be anchored in the joint housing in a manner devoid of play and, in particular, secured against twisting, relative to said housing, since movements of the outer surface of the ball socket in relation to the inner surface of the joint housing would lead to abrasion and thus, prematurely, to unwanted play and a shortening of the working life of the ball-and-socket joint.
In the ball-and-socket joints or bushing joints which are known from the prior art, an attempt is made to counteract the unwanted twisting of the ball socket within the joint housing by providing the ball socket with a projecting ball-socket collar in the region of that end face of the joint housing which is on the cover side, said ball-socket collar coming to rest, when the ball socket and joint housing are joined
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together, in a circumferential step in the housing in the region of the cover of said housing, which step is complementary in shape to the ball-socket collar. When the cover of the joint housing is fitted, the projecting ball-socket collar is then clamped in between said cover and the circumferential step in the housing in such a way that relative movements - in particular twisting movements between the ball socket and the joint housing - are eliminated as far as possible.
Particularly in the context of the strict cost requirements which are also imposed upon ball-and-socket joints and bushing joints in mass production, critical consideration is to be given to the tool and production costs which are always linked with the manufacture of a ball-socket collar and also with the production of the circumferential step on the joint housing in the prior art.
Also, the increases in the particular chain of tolerances in the axial direction with respect to the joint housing which are linked with the circumferential step in the housing and the ball-socket collar, tend to lead to an increase in production wastage or else to the necessity to adhere to correspondingly higher requirements as regards accuracy in the production of the individual parts, which likewise tends to increase the production costs of ball-and-socket joints or bushing joints of this type. Finally, the requirements as regards accuracy in the manufacture of both the ball-socket collar and the circumferential step in the housing are comparatively high, since the desired twist-proofing can only be guaranteed if there is precise reproducibility of the clamping forces necessary for this purpose.
Against this background, it is the object of the present invention to provide a ball-and-socket joint by means of which the aforesaid drawbacks of the prior art are overcome. In particular, it is the intention, by means of the invention, to obtain effective twist-proofing between the ball socket and the joint housing, an improvement in the robustness of the chain of tolerances which is axial with respect to the housing, and also, at the same time, a reduction in the manufacturing costs.
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This object is achieved by means of a ball-and-socket joint having the features in patent claim 1. Preferred forms of embodiment form the subject of the subclaims.
First of all, the ball-and-socket joint according to the invention comprises, in a manner known per se, a substantially annular or pot-shaped joint housing. Said joint housing has a substantially cylindrical interior in which the ball socket of the ball-and-socket joint is arranged, said ball socket being fixed in the joint housing by means of a closing ring. The ball of the ball pin or the ball bush of the ball-and-socket joint is, in turn, accommodated in the ball socket so as to be capable of sliding movement.
According to the invention, however, the ball-and-socket joint is distinguished by the fact that the ball socket is substantially of smoothly cylindrical construction on the outside in its end region that adjoins the closing ring. Under these circumstances, the closing ring of the joint housing at the same time has toothing on its end face that faces towards the ball socket.
In this way, because of the substantially smoothly cylindrical construction of that end region of the ball socket which adjoins the closing ring, simplification of the geometry of the socket comes about, first of all, through the fact that the ball-socket collar can be dispensed with, a fact which already saves initial tool and manufacturing costs. Furthermore, the circumferential step in the joint housing can also be dispensed with, as a result of which it is possible to save further tool and production costs. What is more, because of the elimination of the circumferential step in the joint housing yet another additional reduction in the diameter of said joint housing is also possible, and this contributes to the reduction in installation space and diminution in weight which are always desirable from the design point of view. Finally, as a result of the configuration according to the invention, the chain of tolerances in the axial direction with respect to the joint housing is also shortened or simplified, and this additionally contributes to further cost savings and also to a reduction in wastage.
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Under these circumstances, the twist-proofing, which is necessary as before, of the ball socket within the joint housing is obtained, according to the invention, through the fact that the closing ring has toothing on its end face that faces towards said ball socket. The toothing on the closing ring is able to penetrate, at the moment when the joint housing is closed by the closing ring, into that end face of said joint housing which is on the cover side. In this way, a secure, form-locking connection between the ball socket and the housing cover, and therefore also between the ball socket and the joint housing, is produced, which ensures the necessary twist-proofing.
Under these circumstances, the precise construction and arrangement, design-wise, of the toothing on the closing ring may, according to the invention, first of all be of any desired kind, so long as secure form-locking between the housing cover and the ball socket can be guaranteed by the penetration of the toothing into the ball socket when the housing cover is fitted. According to one particularly preferred form of embodiment of the invention, however, provision is made for the toothing to be arranged only in an inner circular-ring-shaped partial region of the end face of the closing ring.
What is particularly made possible in this way is that an outer circular-ring-shaped partial region of the closing ring can be employed as a sealing arrangement for fastening the closing ring relative to the joint housing, the connection between said closing ring and joint housing preferably taking place by rolling/pressing.
It is therefore possible to dispense with the toothing in the outer circular-ring-shaped partial region of the closing ring, as a result of which costs can, once again, be saved in the manufacture of said closing ring.
According to another, likewise preferred, form of embodiment of the invention, the toothing is constructed in the form of knurling. In this case, the knurling is preferably constructed from a large number of elevations which are constructed so as to be sharp-edged on the ball-socket side, extend substantially radially and are
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substantially prismatic in shape. Knurling which is constructed in this way can be produced on the closing ring in a cost-effective and, in particular, non-cutting manner, merely requires low forces for pressing it into the ball socket, and at the same time leads - for the purposes of effective twist-proofing - to high transmissible torques between the ball socket and the closing ring.
According to another preferred form of embodiment of the invention, the closing ring has a substantially C-shaped cross-sectional contour in axial longitudinal section with respect to the joint housing. This configuration of the closing ring first of all provides savings on material in manufacture and, in addition, permits advantageous combining both of the functions of the joint-housing cover or joint-housing cap, the anchoring and twist-proofing of the ball socket, and the fastening of a joint-sealing gaiter, and optionally also, in addition, of the function of an angular stop for the ball pin or for the ball bush of the ball-and-socket joint. What is more, a closing ring which is designed in this way can be manufactured in a simple and cost-saving manner, particularly as a pressed part.
For the purpose of putting the invention into practice, the way in which the connection between the joint-housing cover and the joint housing takes place is, first of all, not essential. According to one preferred form of embodiment of the invention, however, the closing ring is flanged into the joint housing at the end face. In this way, particularly leak-proof and durable closure of the joint housing is achieved without any other components. Furthermore, closure by flanging can be defended as cost-effective and reliable from the process point of view.
According to other forms of embodiment of the invention, provision is made for the interior of the joint housing to have a shoulder as an axial stop for the ball socket in the region of the opposite side of the joint housing from the housing cover; or for the interior of said joint housing to have a diameter which decreases continuously in the axial direction with respect to the latter in the region of the opposite side of said joint housing from said housing cover.
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With the aid of a shoulder, which is arranged in the interior of the joint housing, as an axial stop for the ball socket, the latter can be simply pushed in, as far as the shoulder in the joint housing, from the cover side, and said joint housing can then be closed by the housing cover. In this way, simple assembly and defined positioning of the ball socket in the joint housing is thus achieved. A diametral contour which is present, additionally or alternatively, in the interior of the joint housing and which becomes continuously smaller, can likewise be employed as an axial stop when ball socket is fitted in the joint housing; it is also possible, in this way, to achieve increased stiffness of the ball socket, which is desirable in some individual applications, with the aid of the wall thickness of the ball socket, which wall thickness is lower in this region.
The invention will be explained in greater detail below with the aid of drawings which merely represent exemplified embodiments and in which:
fig. 1 shows, in a diagrammatic representation, an example of a ball-and-
socket joint according to the prior art, in isometric longitudinal section;
fig. 2 shows a bushing joint according to one form of embodiment of the
invention, in longitudinal section;
fig. 3 shows a closing ring of a bushing joint according to one form of
embodiment of the invention, in longitudinal section;
fig. 4 shows the closing ring according to fig. 3, in plan view;
fig. 5 shows, in a diagrammatic, enlarged representation, the closure region
of a bushing joint according to the prior art;
fig. 6 shows, in a representation corresponding to fig. 5, the closure region of
the bushing joint according to fig. 2; and
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fig. 7 shows, in a representation which is further enlarged, a detail from the
knurled surface of the closing ring of the bushing joint according to fig. 6.
Fig. 1 shows a ball-and-socket joint according to the prior art, in a diagrammatic representation in longitudinal section. It is possible to make out the substantially pot-shaped joint housing 1 with the bearing socket or ball socket 2 arranged therein. Arranged, in turn, within the interior of the ball socket 2 is the ball 3 of a ball pin 4.
It can also be seen, in fig. 1, that the ball socket 2 is anchored in the joint housing 1 by means of a closing ring 5 which is merely indicated diagrammatically, said ball socket 2 having, for anchoring purposes, in particular for twist-proofing said ball socket 2, a projecting ball-socket collar 6 which points radially outwards in the region of that end face of said ball socket which adjoins the closing ring. This being the case, said ball-socket collar 6 is accommodated in a step 7 in the joint housing 1 which is likewise circumferential and is complementary in shape to said ball-socket collar 6, at which point said ball-socket collar is clamped fast between the closing ring 5 and the joint housing 1.
In the example from the prior art which is represented, however, the ball-socket collar 6 and the step 7 in the joint housing 1 are, as has already been mentioned initially, comparatively cost-intensive to produce, lead to prolongation of the particular chain of tolerances in the axial direction of the joint housing and, in addition, take up installation space, particularly in the radial direction in the region of that end face of the joint housing which is on the cover side.
Another example from the prior art, which example is identical to the representation from fig. 1 as regards anchoring and twist-proofing of the ball socket 1, is represented in an enlarged manner in fig. 5. In fig. 5, it is, once again, also possibe.
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to make out the mouth of the joint housing 1 at the end face, part of the joint-housing cover 5, and the appertaining end-face region of the ball socket 2. It is also possible to make out the circumferential ball-socket collar 6, which is present in this example from the prior art too, as well as the appertaining step 7 which is arranged in the joint housing 1, the said collar and step still being necessary, in this case too, for anchoring and particularly twist-proofing the ball socket 2, with the disadvantages which have already been mentioned, particularly as regards production expense and manufacturing costs, installation space and weight.
Represented in figs. 2 to 4 and also 6 and 7 are forms of embodiment for ball-and-socket joints or bushing joints according to the present invention, by means of which the above-described disadvantages and limitations of the prior art are overcome.
Fig. 2 shows one form of embodiment of a bushing joint according to the present invention. It is possible to make out, first of all, the ball bush 9, the joint housing 10 and the ball socket 11 which is arranged between said ball bush 9 and joint housing 10. In the form of embodiment represented, the bushing joint also possesses a closing cover 12 which is of substantially C-shaped construction in cross-section. The closing cover 12 closes the joint housing 10, anchors the ball socket 11 in said joint housing 10, also accommodates that end of a sealing gaiter 13 which is on the joint side, and may finally - with a view to an advantageous combining of functions - also additionally form the angular stop for limiting the angular deflection of the joint bush 9 relative to the joint housing 10.
It further emerges, from figure 2, that the interior of the joint housing 10 has, in the region of that side of said joint housing 10 which lies axially opposite the housing cover 12, a diameter which decreases continuously in the axial direction of the joint housing. In this way, defined positioning of the ball socket 11 within the joint housing 10 is achieved when the bushing joint is assembled, and increased stiffness
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of the ball socket 11 is also obtained with the aid of the wall thickness of said ball socket 11, which is reduced in certain regions with this configuration.
Represented in figs. 3 and 4 is the housing cover 12 of another form of embodiment of a ball-and-socket or bushing joint according to the invention. The housing cover 12 according to figs. 3 and 4 is also designed for flanging into a joint housing 10 and also for accommodating a sealing gaiter 13. In the representations according to figs. 3 and 4, it is possible to make out, in particular, the toothing 14 on the closing ring 12, which toothing is present in the form of knurling which is applied in the shape of a circular ring in certain regions. Under these circumstances, it can be seen, with the aid of figs. 3 and 4, that the toothing 14 on the closing ring 12 consists, in this case, of a large number of sharp-edged elevations which extend substantially radially and are substantially prismatic and which are arranged inside the circular-ring-shaped region 15.
The toothing 14 or knurling on a closing ring 12 according to one form of embodiment for a bushing joint according to the present invention is also, once again, represented in figs. 6 and 7, in an enlarged representation in each case. In fig. 6, it can be seen that the joint-housing cover 12 is connected to the joint housing 10 by means of a flanged portion 8. It is also possible to see, particularly by viewing figs. 5 and 6 together, that the geometry of the ball socket 11 and also of the joint housing 10 can be of considerably simpler design, in the region of connection to the housing cover 12 in the ball-and-socket joint according to the invention illustrated in fig. 6, and therefore also of more cost-effective and space-saving design, than in the prior art illustrated in fig. 5, since, as a result of the invention, both the ball-socket collar 6 which is present on the ball socket 2 in the prior art illustrated in fig. 5 and also the step 7 in the joint housing 1 are eliminated.
As a result, therefore, it becomes clear that, because of the invention, a ball-and-socket joint or bushing joint is provided, which offers advantages over the ball-and-
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socket joints or bushing joints which are known from the prior art, particularly with regard to minimising the manufacturing costs and also with respect to savings on installation space and reductions in weight. The invention therefore contributes to improving cost-effectiveness and also to increasing the possible range of application of ball-and-socket joints or bushing joints, particularly with regard to their use in the field of axle systems, wheel suspensions or for the articulating attachment of spring-damper systems to a motor vehicle.
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List of reference numerals

1 joint housing
2 ball socket
3 joint ball
4 ball pin
5 closing ring without toothing
6 ball-socket collar
7 step in housing
8 flanged portion
9 ball bush
10 joint housing
11 ball socket
12 closing ring with toothing
13 sealing gaiter
14 toothing, knurling
15 circular-ring-shaped knurled region
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WE CLAIM:
1. Ball-and-socket joint, for example for an axle system in a motor vehicle,
having a substantially annular or pot-shaped joint housing (10), in the
substantially cylindrical interior of which a ball socket (11) is arranged and is
fixed by means of a closing ring (12) in said joint housing (10), wherein the
ball (3) of a ball pin (4) or of a ball bush (9) is accommodated in the ball socket
(11) so as to be capable of sliding movement,
characterised in that
the ball socket (11) is substantially of smoothly cylindrical construction on the outside in its end region that adjoins the closing ring (12), said closing ring
(12) having toothing (14) on its end face that faces towards the ball socket (10).
2. Ball-and-socket joint according to claim 1,
characterised in that
the toothing (14) is arranged only in an inner circular-ring-shaped partial region (15) of the end face of the closing ring (12).
3. Ball-and-socket joint according to claim 1 or 2,
characterised in that
the toothing (14) is constructed in the form of knurling, said knurling consisting of a large number of elevations which are sharp-edged on the ball-socket side, extend substantially radially and are substantially prismatic.
4. Ball-and-socket joint according to one of claims 1 to 3,
characterised in that
the closing ring (12) has a substantially C-shaped cross-sectional contour in axial longitudinal section with respect to the joint housing.
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5. Ball-and-socket joint according to one of claims 1 to 4,
characterised in that
the closing ring is flanged (8) into the joint housing at the end face.
6. Ball-and-socket joint according to one of claims 1 to 5,
characterised in that
in the region of the opposite side of the joint housing from the housing cover, the interior of the joint housing (10) has a shoulder as an axial stop for the ball socket (11).
7. Ball-and-socket joint according to one of claims 1 to 6,
characterised in that
the interior of the joint housing (10) has a diameter which decreases continuously in the axial direction with respect to said joint housing in the region of the opposite side of said joint housing (10) from the housing cover.
Dated this 15th day of June, 2009
HIRAL CHANDRAKANT JOSHI AGENT FOR ZF FRIEDRICHSHAFEN AG
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