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
JOINT ASSEMBLY FOR A VEHICLE

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

ZF FRIEDRICHSHAFEN AG GERMAN Company 88038 FRIEDRICHSHAFEN GERMANY

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 joint arrangement for a vehicle, having a joint that comprises a joint housing and a pivot pin mounted movably relative thereto, a rack that has a cavity and is connected to the joint, a ring element that is disposed between the joint and the rack, sealing bellows, which delimit an interior and in which the joint is at least partially disposed, and a gas-permeable connection that connects the cavity of the rack to the interior of the sealing bellows.
Such joint arrangements are known from the background art and used for example for rack-and-pinion steering systems, wherein the sealing bellows protect at least part of the joint arrangement from environmental influences and fouling. Movements of the gear rack may lead to pressure variations inside the sealing bellows that may be compensated by means of the gas-permeable connection.
From JP 5-37644 a connection between a hollow rack and a housing is known, a groove being introduced into the wall of the rack at the end face. On the inner wall of the rack, moreover, two mutually opposite grooves are formed in the region of a thread.
From DE 43 31 291 CI an articulated connection to a ball joint housing is known, the ball joint housing being connected integrally with an axial connection pin, which has an external thread and is screwed into a hollow gear rack having a corresponding internal thread. The gear rack after being assembled lies against a radial flange, into which the connection pin verges at the ball joint housing side. Vent grooves are introduced into the connection pin and run into the radial flange.
The drawback of this solution is that the radial regions of the vent grooves extend in the end face of the radial flange that may also be used simultaneously as a bearing surface during press moulding of the joint. As a result of the vent grooves this surface is reduced, leading in turn to design limitations.
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From JP 3-8066 a ball joint is known, the housing base of which has an axially stepped flange with an axially projecting pin that engages into a hollow rack. Radial grooves are introduced into the flange, which is provided with a key surface, and run into axial grooves formed in the lateral surface of the pin.
From JP 63-104173 a joint arrangement is known, having a joint that is connected by means of a pin by way of a screw joint to a hollow rack. An axial groove extending in a thread is formed in the pin and runs into a radial groove formed in a radial flange of the pin, wherein between the rack and the radial flange provided with a key surface a ring element is disposed.
The drawback of the last two solutions is that grooves combined with key surfaces lead to complicated contours where burrs or increased tool wear may arise. Furthermore, the sealing bellows according to JP 63-104173 may get caught on the ring element and suffer damage as a result.
Proceeding from this background art the underlying object of the invention is to develop the initially described joint arrangement in such a way that it is possible to reduce design limitations and avoid grooves in key surfaces.
This object is achieved according to the invention by a joint arrangement according to claim 1. Preferred developments are indicated in the sub-claims.
The joint arrangement according to the invention for a vehicle, in particular a motor vehicle, has a joint that comprises a joint housing and a pivot pin mounted movably relative thereto, a rack that has a cavity and is connected to the joint, a ring element that is disposed between the joint and the rack, sealing bellows, which delimit an interior and in which the joint is at least partially disposed, and a gas-permeable connection that connects the cavity of the rack to the interior of the sealing bellows, wherein at least part of the gas-permeable connection is formed by at least one
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groove, which is formed on and/or in the ring element and opens into the interior of the sealing bellows.
Since according to the invention the gas-permeable connection opens via the groove formed in the ring element into the interior of the sealing bellows, in the connection region between the joint and the rack the formation of air guide grooves in an end face of the joint facing the rack may be avoided. Since the ring element moreover forms a separate component disposed between the joint and the rack, it is equally possible to avoid having the gas-permeable connection pass through a key surface. In particular, the ring element is disposed in the interior delimited by the sealing bellows.
The ring element has an edge that surrounds a recess extending through the ring element. In this case, the ring element may be designed as a ring or as a sleeve that regularly has a larger longitudinal extent than a ring. The ring element is however preferentially designed as an annular disc. The ring element may further have a round or circular external circumferential contour. It is equally possible that the recess extending through the ring element is of a round or circular design.
The groove may open out into the recess extending through the ring element. In particular, the groove is formed in an end face of the ring element and extends preferably from the inner, continuous ring recess up to the lateral surface of the ring. In this case, the groove may be formed in an end face of the ring element facing the rack, thereby keeping the gas-permeable connection as short as possible. Furthermore, a plurality of grooves may be formed in the ring element.
The rack may be connected to the pivot pin, so that the ring element is disposed between the rack and the pivot pin and is for example seated on the pivot pin. Preferably however the rack is connected to the joint housing, wherein the ring element is disposed between the joint housing and the rack and in particular is in contact with the joint housing and/or the rack. In this case, the ring element may lie
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with an end face facing the joint housing against an end face of the joint housing facing the rack. Furthermore, the ring element may lie with an end face facing the rack against an end face of the rack facing the joint housing.
The ring element may have an outside diameter that is smaller than or equal to the outside diameter of the joint housing. In particular, the ring element has the same outside diameter as the rack. In this way it is possible to reduce the risk of the sealing bellows getting caught on the ring and suffering damage as a result.
The end face of the joint housing facing the rack may be provided at a housing base that is formed in particular integrally with the joint housing. The joint housing moreover preferably has a housing recess, which is delimited by a housing wall and in which the pivot pin is seated. The base in this case may be remote from, or lie opposite, a housing opening, through which the pivot pin mounted in the joint housing extends out of the joint housing.
The joint housing preferably has an axial pin, which is formed in particular integrally with the joint housing and engages into the cavity of the rack. The ring element in this case may be slipped onto, or seated on, the axial pin so that the axial pin extends through the continuous recess provided in the ring element. The pin is preferably provided with an external thread and screwed into the rack, which for this purpose has in particular an internal thread that engages with the external thread one into the other. The pin may be connected to the base or be formed integrally therewith.
The gas-permeable connection preferably comprises at least one second groove, which at least indirectly adjoins the groove and extends at least in sections or entirely inside the rack and opens out into the cavity of the rack. In this case, the two grooves are in gas-permeable connection with one another in particular inside or in the region of the continuous recess formed in the ring element, wherein this recess or a part thereof may be interposed.
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The second groove may be formed in the inner wall of the rack. As the joint housing however preferably has the pin that engages into the cavity, the second groove may alternatively be formed in the lateral surface of the pin. The second groove in this case extends for example from an in particular free end of the pin remote from the joint housing up to or over the ring element. If the joint and the rack are screw-connected to one another, the second groove preferably extends in or in the region of the external thread of the pin or of the internal thread of the rack. Furthermore, a plurality of grooves may be formed on the pin and/ or on the inner wall of the rack.
The (first) groove formed in the ring element and the second groove in particular do not extend parallel to one another. Preferably, the second groove extends in the direction of and/or parallel to a longitudinal direction of the rack (axial direction), whereas the first groove may extend transversely of, in particular at right angles to this longitudinal direction (radial direction). A spiral course of the first and/ or second groove is further possible.
The rack may be connected to a steering gear and moved by means of the steering gear, in particular may be displaced in longitudinal direction of the rack. In this case, the rack is preferably designed as a gear rack, which together with the steering gear forms a rack-and-pinion steering system and/or a rack-and-pinion steering gear. The sealing bellows may lie sealingly at one end against the steering gear or against a housing of the steering gear and at the other end against the pivot pin or against a coupling element connected thereto.
The joint is preferably a ball joint, so that the pivot pin takes the form of a ball pin that is mounted by its joint ball rotatably and pivotably in the joint housing.
The cavity formed inside the rack runs in particular in longitudinal direction thereof and extends preferably up to the end face of the rack facing the joint. Inside the rack the cavity may be axially delimited and/or take the form of a blind hole.
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Alternatively, the cavity may extend through the rack. Furthermore, a plurality of cavities may be provided in the rack.
It is equally possible for the rack to be connected to a second joint and extend between these two joints. In this case, there may be disposed between each of the joints and the rack a ring element having a groove that opens out into the interior, wherein the two joints are in particular of an identical style of construction.
As the grooves described here are part of, or form, a gas-permeable connection, they are preferably free grooves.
There now follows a description of a preferred embodiment of the invention with reference to the drawings. The drawings show:
Fig. 1: a partial sectional view of a rack-and-pinion steering system,
Fig. 2: a sectional view of a ball joint for the rack-and-pinion steering system according to an embodiment of the invention,
Fig. 3: a plurality of groove profiles,
Fig. 4: a plurality of groove courses and
Fig. 5: different numbers of grooves.
Fig. 1 shows a partial sectional view of a rack-and-pinion steering system 1, wherein there is mounted in a housing 2 of a steering gear 3 a gear rack 4 that is displaceable in the direction, and counter to the direction, of the arrow 5 by means of the steering gear 3. The gear rack 4 has a recess 6 and is connected at one end to a ball joint 7. The ball joint 7 comprises a joint housing 8 and a ball pin 9, which is mounted rotatably and pivotably in the joint housing 8 and seated by a joint ball 18 (see Fig. 2)
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in a housing recess 16 (see Fig. 2), which is formed in the joint housing 8 and delimited by a wall 17 (see Fig. 2) of the joint housing 8. The ball pin 9 in this case extends out of the ball joint housing 8 through an opening 19 (see Fig. 2) provided therein, wherein outside of the ball joint housing 8 sealing bellows 10 lie with one end sealingly against the ball pin 9. The sealing bellows 10 lie with their other end sealingly against the housing 2 of the steering gear 3, thereby forming between the two ends of the sealing bellows 10 an interior 11, which is delimited by the sealing bellows 10 and in which the ball joint housing 8, an end region of the gear rack 4 and part of the ball pin 9 are disposed. The longitudinal axis of the gear rack 4 is denoted here by the reference character 12, wherein the arrow 5 extends parallel to and/or in the direction of the longitudinal axis 12.
Tf the gear rack 4 is displaced counter to the direction of the arrow 5 by means of the steering gear 3, the sealing bellows 10 are compressed and/ or upset, which may lead to an increase of the pressure of the air in the interior 11 of the sealing bellows 10. If, on the other hand, the gear rack 4 is displaced in the direction of the arrow 5 by means of the steering gear 3, the sealing bellows 10 in the form of expansion bellows are extended and/ or expanded, which may lead to a drop in the pressure of the air in the interior 11 of the sealing bellows 10. So that such pressure variations may be compensated, the rack-and-pinion steering system 1 has a gas-permeable connection 13 (see Fig. 2) that connects the cavity 6 of the gear rack 4 in an air-permeable manner to the interior 11 of the sealing bellows 10. This allows air to be removed from the interior 11 through the cavity 6 or allows air to be supplied to the interior 11. If the cavity 6 does not extend through the gear rack 4, the air may be for example diverted via the housing 2 of the steering gear 3.
Fig. 2 shows the ball joint 7 of the rack-and-pinion steering system 1 according to an embodiment of the invention in a sectional view, wherein the cavity 6 is connected by the gas-permeable connection 13 in an air-permeable manner to the interior 11 of the sealing bellows 10 (not shown here) that is disposed outside of the ball joint housing 8.
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The joint housing 8 has an axial pin 20 formed in particular integrally therewith, which is provided with an external thread and engages into the cavity 6 of the gear rack 4. In this case, an internal thread is formed in the region of the end of the gear rack 4 facing the ball joint 7, in the inner wall of the gear rack 4, and engages into the external thread of the pin 20. Thus, the ball joint housing 8 and the gear rack 4 are connected to one another by a screw joint.
Disposed between the ball joint housing 8 and the gear rack 4 is a ring 21, which in particular takes the form of an annular disc that is slipped onto, or seated on, the pin 20, wherein an end face of the ring 21 facing the joint housing 8 lies against the joint housing 8. An end face of the ring 21 facing the gear rack 4 further lies against the gear rack 4.
The gas-permeable connection 13 comprises at least one groove 14, which is formed in the lateral surface of the pin 20, and at least one groove 15, which is formed in the ring 21 and is in air-permeable connection with the groove 14 in the region of and/or in a continuous recess 22 formed in the ring 21 (see Fig. 4). In this case, the in particular axially extending groove 14 preferably extends from an end face of the joint housing 8 facing the gear rack up to an end face of the pin 20 remote from the joint housing 8 and opens out into the recess 6. The groove 14 further extends at least in sections in and/or in the region of the external thread of the pin 20. The at least one groove 15 extends in particular from the ring recess 22 up to the outer lateral surface of the ring 21 and opens out, on the one hand, into the ring recess 22 and, on the other hand, into the interior 11 of the sealing bellows 10 (not shown here).
Alternatively, the at least one groove 15 emanating from the ring recess 22 may terminate at a radial distance from the external circumferential contour or the external lateral surface of the ring 21. In this case, the groove 15 takes the form of a delimited groove that may extend in radial direction beyond an external circumferential contour of a contact surface, with which the rack 4 lies against the
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ring 21. Thus, the delimited groove terminates preferably between the external circumferential contour of the contact surface and the external circumferential contour of the ring.
The at least one groove 15 extends in particular in radial direction and may in this case have one of the groove profile shapes 23, 24, 25 or 26 shown in Fig. 3 and/or one of the groove courses shown in Fig. 4. In particular, it is evident from Fig. 4 that the groove 15 in accordance with a modification of the embodiment may alternatively have a spiral course. Fig. 5 further reveals that a different number of grooves 15 may be formed in the ring element 21. In this case, for the at least one groove 14 the groove profile shapes, groove courses and/or numbers of grooves evident from Figs. 3,4 and 5 are correspondingly possible.
Although this is not shown, inside the recess 16 between the joint ball 18 and the housing wall 17 a bearing shell may be disposed, in which the joint ball 18 is mounted.
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List of reference characters
1 rack-and-pinion steering system / joint arrangement
2 housing of steering gear
3 steering gear
4 gear rack
5 arrow
6 recess in gear rack / cavity
7 ball joint
8 ball joint housing
9 ball pin
10 sealing bellows
11 interior of sealing bellows
12 longitudinal axis of gear rack
13 air-permeable connection
14 axial groove
15 radial groove
16 recess in housing
17 housing wall
18 joint ball
19 opening in ball joint housing
20 pin on joint housing
21 ring
22 recess in ring
23 groove profile
24 groove profile
25 groove profile
26 groove profile
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WE CLAIM:
1. Joint arrangement for a vehicle, having a joint (7) that comprises a joint housing
(8) and a pivot pin (9) mounted movably relative thereto, a rack (4) that has a
cavity (6) and is connected to the joint (7), a ring element (21) that is disposed
between the joint (7) and the rack (4), sealing bellows (10), which delimit an
interior (11) and in which the joint (7) is at least partially disposed, and a gas-
permeable connection (13) that connects the cavity (6) of the rack (4) to the
interior (11) of the sealing bellows (10),
characterized in that
- at least part of the gas-permeable connection (13) is formed by at least one
groove (15), which is formed in the ring element (21) and opens out into
the interior (11) of the sealing bellows (10).
2. Joint arrangement according to claim 1, characterized in that the groove (15) is formed in an end face of the ring element (21) facing the rack (4).
3. Joint arrangement according to claim 1 or 2, characterized in that the gas-permeable connection (13) comprises at least one second groove (14), which at least indirectly adjoins the groove (15) and extends at least in sections inside the rack (4) and opens out into the cavity (6) of the rack (4).
4. Joint arrangement according to claim 3, characterized in that the joint housing (8) has a pin (20), which extends through the ring element (21) and engages into the cavity (6) of the rack (4) and in the lateral surface of which the second groove (14) is formed.
5. Joint arrangement according to claim 4, characterized in that the pin (20) has an external thread that engages with an internal thread formed in the rack (4), wherein the second groove (14) is formed in or in the region of the external thread.
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6. Joint arrangement according to one of claims 3 to 5, characterized in that the groove (15) formed in the ring element (21) extends transversely of the longitudinal axis (12) of the rack (4) and the second groove (14) extends parallel to the longitudinal axis (12) of the rack (4).
7. Joint arrangement according to one of the preceding claims, characterized in that the rack (4) is connected to a steering gear (3) and is movable by means of the steering gear (3).
8. Joint arrangement according to claim 7, characterized in that the sealing bellows (10) lie sealingly at one end against the steering gear (3) or against a housing (2) of the steering gear (3) and at the other end against the joint pin (9) or against a coupling element connected thereto. '
9. Joint arrangement according to one of the preceding claims, characterized in that the rack (4) is a gear rack.
10. Joint arrangement according to one of the preceding claims, characterized in
that the joint (7) is a ball joint and the pivot pin (9) is a ball pin that is mounted by its joint ball (18) rotatably and pivotably in the joint housing (8).

HIRAL CHANDRAKANT JOSHI
AGENT FOR ZF FRIEDRICHSHAFEN AG
Dated this 24th day of September, 2008
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