Title of Invention

BALL AND SOCKET JOINT AND METHOD FOR PRODUCING THE SAME

Abstract

A ball and sleeve joint is proposed, in particular for chassis components and steering components of motor vehicles, comprising a joint housing made up of two housing halves and a ball sleeve with a rounded bearing surface, which bearing surface is accommodated in a bearing shell made from elastic plastic secured in an opening of the joint housing, and a method of producing a ball and sleeve joint of this type whereby the two housing halves (3a, 3b) are pressed together in the direction of the longitudinal axis of the ball and sleeve joint (1) with defined pressing forces during assembly of the ball and sleeve joint (1) and are retained in the assembly position defined by the pressing forces by means of at least one material joint (14) between the housing halves (3a, 3b).

Full Text

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 AND METHOD FOR PRODUCING THE SAME 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 invention relates to a ball and sleeve joint, in particular for chassis components and joint components of motor vehicles incorporating the generic features disclosed in claim 1, and a method of producing a ball and sleeve joint of this type as outlined in the introductory part of claim 11. Ball and sleeve joints are basically known from the prior art and are used in various different designs in all areas of engineering and in particular also in the automotive industry. In the applications for which they are used, they must be capable of transmitting very high dynamic radial loads as well as static initial loads, as a rule. In particular, two different types of construction are known in terms of the housing design of such ball and sleeve joints. Firstly, the housing may comprise an integral tube, preferably made from steel, in which the other components of the ball and sleeve joint are fitted as part of the production process. The production steps in this instance involve introducing a first locking ring into the housing, after which the unit comprising the ball sleeve and bearing shell is inserted in the housing and then finally secured in the housing by means of a second locking ring. Another known construction is a joint housing comprising two parts, which are latched to one another by means of elastic tooth elements in the assembled state. As a rule, shells made from plastic are used as bearing shells for both designs, and have a row of slots which fit with the bearing surface of the internally lying ball sleeve, enabling the bearing shell to be located on the ball surface. The disadvantage of the POM plastic material which is preferably used for this purpose is that the plastic material starts to creep when subjected to higher loads and migrates into the slits provided in the bearing shell. This results in a bigger clearance in the ball and sleeve joint, which leads to failure of the entire component within a short time. Experience has also shown that the ball and sleeve joints outlined above have a very low stiffness in the axial direction of the component because the plastic is able to flex 2 very easily in the axial longitudinal direction due to its creep properties and thus causes an axial clearance. This problem is further exacerbated by the fact that the joint locking system, especially in the case of single-part ball and sleeve joints which use locking rings made from sheet metal parts, must likewise be regarded as relatively flexible and the ball shell secured by the locking rings is not able to afford adequate support at a correspondingly higher load. In view of the disadvantages of ball and sleeve joints known from the prior art as outlined above, the objective of the invention is to improve a ball and sleeve joint of the generic type so that its service life is significantly longer than that of known designs, whilst at the same time keeping the cost of producing such a joint low. Another objective is to propose appropriate steps by simple means, whereby dimensional tolerances can be compensated, especially those induced between the bearing shell and joint housing, because the cost of the manufacturing process can be significantly reduced on the basis of a larger bandwidth of what are usually narrowly specified tolerance values of ball and sleeve joints. These objectives are achieved with regard to the ball and sleeve joint by means of the technical teaching disclosed in claim 1 in conjunction with the generic features. As regards the method, the manufacturing steps for a ball and sleeve joint of this type proposed by the invention are defined in claim 11. The technical teaching relating to the ball and sleeve joint is essentially based on the fact that the two housing halves are pressed together in the direction of the longitudinal axis of the ball and sleeve joint with defined pressing forces during assembly of the ball and sleeve joint and are retained in the assembly position defined by the pressing forces by means of at least one material joint between the housing halves. As a result of the defined pressing forces, an initial tension can be induced within the bearing shell and, by contrast with the existing prior art, the static characteristic values are not determined by the manufacturing tolerances of the individual parts and 3 optionally by the forming process used to secure the locking rings, but by the defined pressing forces applied between the housing halves during the assembly operation. This enables the joint stiffness to be produced by means of the initial tension applied with very small variations in values. Furthermore, the defined pressing forces to a certain extent enable higher initial tensions to be produced in the bearing shell, resulting in defined, low friction radii. In order to produce this effect, it is necessary for the ball mid-radii of the bearing shell and the housing halves surrounding it to be offset. As defined by the technical teaching in claim 11 relating to the method proposed by the invention, once the ball sleeve and bearing shell have been introduced into the opening of the joint housing, defined pressing forces are applied to the housing halves, in order to push them together, which are transmitted via the internal surface of the opening in the housing halves to the bearing shell, and the housing halves are held fixed to one another in the assembly position defined by the pressing forces by means of at least one material joint between the housing halves. Applying pressing forces to the housing halves is therefore an easy option in terms of production technology as a means of compensating for dimensional tolerances of the components assembled with one another in conjunction with the elastic properties of the bearing shell, and the defined pressing forces simultaneously guarantee a higher stiffness of the joint due to the controlled initial tension induced by the forces as a result of pressing the bearing shell halves together. The force-controlled initial tension can be achieved with low variation tolerances. Furthermore, as a result of the subsequent material joint, it can be guaranteed that no additional external forces will act on the bearing shell, such as occur for example if the bearing shell is secured by means of locking rings fixed by rolling. The material joint itself, whether it be produced by a welding operation, a soldering operation or a bonding operation, can be produced inexpensively in terms of the technical peripheral 4 conditions and using what is standard equipment these days, and the production costs incurred by the method proposed by the invention can therefore be kept significantly lower overall than has been the case in the past. Specific embodiments of both the ball and sleeve joint proposed by the invention and the associated production method are defined by the technical teaching of claims 1 and 7 in conjunction with the dependent claims relating back to each of these claims. With regard to the ball and sleeve joint, it has been found to be of particular advantage if the material joint is produced as a welded joint. This enables the joint to be tempered by the heat applied during the welding process, thereby creating a better contact pattern in the joint and preventing subsequent settling of the bearing shell. The fact that the bearing shells are provided with at least one retaining projection standing proud of the surface on their external surface in contact with the internal wall of the opening of the joint housing, for which a matching recess is provided in the opening of the joint housing, prevents any shifting or turning, and simultaneously affords a maximum possible support surface due to an otherwise constant wall thickness of the bearing shell. This being the case, the retaining projection may be provided in the form of a radially extending retaining collar which engages in a radially extending groove of the joint housing, and part of the groove is in turn recessed into each of the two housing halves. In one advantageous embodiment resulting from the teaching of the invention, the housing halves can be secured to one another by a laser welded joint, for example, which may comprise individual welded sections extending round the external contour of the joint housing or alternatively as a welded joint extending round the outer edges of the joint housing. It is of particular advantage to provide the welded joint by laser welding because laser welding offers an inexpensive and accurate option for producing tie welded joint. 5 The essential features of the invention relating both to the ball and sleeve joint and the associated production method will be described in more detail with reference to two design variants. Of the drawings: Figure 1 is a diagram showing a section through a ball and sleeve joint proposed by the invention during assembly, Figure 2 is a diagram showing a section of the ball and sleeve joint illustrated in Figure 1 once assembly has been completed and Figure 3 is a diagram showing a section of another embodiment of a ball and sleeve joint proposed by the invention. The ball and sleeve joint proposed by the invention, illustrated in two different design variants in Figures 1 to 3, essentially comprises a ball sleeve 1 provided with a continuous bore, a bearing shell 2 and a joint housing 3 surrounding the bearing shell, which is made up of two essentially symmetrically shaped housing halves 3a and 3b. The ball sleeve 1 has two symmetrical end regions 4, 5 and a middle region lying in between, which has a spherically shaped bearing surface 6 on its external contour, although bearing surfaces of different shapes, such as oval, would also be conceivable. The bearing surface 6 is surrounded by the bearing shell 2, which is likewise of a spherical shape corresponding to the contour of the bearing surface 6 and, in this embodiment illustrated as an example, is of an essentially constant thickness through its cross-section. Disposed on the external contour of the bearing shell 2 is a retaining projection 7 extending round the bearing shell in the form of a retaining collar. The bearing shell 2 is in turn surrounded by the joint housing 3 and has an opening 8 adapted to the external contour of the bearing shell 2 for this purpose. As indicated in Figure 1, the centre points of the ball radii of the bearing surface (Rs) and the opening of the joint housing (RG) are pushed towards one another in the direction of the mid-longitudinal axis 11. 6 As a result, the joint housing 3 is moved into abutment with the bearing shell 2 in the top and bottom end regions respectively, whereas a gap 9 is left free in the middle region of the spherical bearing shell between it and the internal surface of the opening of the joint housing 3. As explained above, the joint housing 3 is made up of two parts and the housing halves 3a and 3b each incorporate one half of a groove-shaped recess. During assembly, the housing halves 3a and 3b are push-fitted over the respective end region 4 respectively 5 of the ball sleeve 1 and pushed towards the middle of the ball and sleeve joint. As may be seen from Figure 1, a spacing area 10 is left free between the actual housing halves 3a and 3b. Once the ball and sleeve joint components have been assembled, the two housing halves 3a and 3b are subjected to defined pressing forces on their external face in the direction of the mid-longitudinal axis 11 corresponding to the force vectors F1 and F2. The pressing forces F1 and F2 thus act respectively on external shoulder surfaces 12 and 13 and are directed so that they oppose one another, causing the housing halves 3a and 3b to be pressed together. The result of applying the pressing forces F1 and F2 is illustrated in Figure 2. Both the gap 9 and the spacing area 10 have disappeared due to the flexibility of the bearing shell 2 as a result of the plasticity of the bearing shell induced by the plastic material. This therefore results in a full surface abutment of the bearing shell, both at the spherically shaped bearing surface 6 of the ball sleeve and at the internal contour of the opening 8 of the housing halves 3a and 3b. Any dimensional tolerances which might exist in the bearing shell 2, ball sleeve 1 and opening 8 of the joint housing 3 are therefore eliminated by the controlled action of pressing the housing halves 3a and 3b together. In the embodiment illustrated as an example, a different distribution of initial tension is 7 created by the different centre points of the ball radii Rs and RG within the bearing shell, leading to lower frictional torques due to the defined smaller friction radii. In the assembled relative position assumed by the housing halves 3a and 3b due to the pressing forces, the latter are then joined to one another by means of a material joint in the form of a welded joint 14. This being the case, the welded joint may have the shape of a V seam, as illustrated, or may be of some other shape. In the case of the embodiment illustrated as an example, laser welding has proved to be a particularly practicable and inexpensive welding method. The heat introduced into the metal housing halves 3a and 3b as a result of the welding operation offers the additional advantage of tempering the bearing shell of plastic, i.e. the heat transmitted causes an equalisation of the tensions in the bearing shell. This corresponds to an artificial ageing process, thereby imparting a very good contact pattern to the joint and ensuring that subsequent settling or ageing of the ball and sleeve joint can no longer take place. The advantage of the method proposed by the invention essentially resides in the fact that the defined pressing forces F1 and F2 can be predefined depending on the predefined tolerances of the components to be joined to one another, as a result of which an initial tension of the bearing shell can be induced within the bearing shell cross-section, optionally with a different distribution of tension simultaneously, in addition to compensating the tolerances by pressing the housing halves 3a and 3b together accordingly. By contrast with standard methods of assembling ball and sleeve joints, the subsequent process of forming the material joint by means of a welding operation, a soldering operation or a bonding operation does not lead to any change in the initial tension within the bearing shell because welding itself does not involve applying any additional force to the joint 8 The welding operation itself may be limited to individual welded sections on the circumference of the joint housing 3 or may extend entirely around the joint housing 3. Figure 3 illustrates a different embodiment of the ball and sleeve joint proposed by the invention in which the joint region between the housing halves 3a and 3b is of a different design. The housing half 3b in this instance overlaps the other housing half in its external region facing the housing half 3a, resulting in an externally lying flange. This flange also serves as a guide for the housing halves 3a and 3b during assembly, thereby dispensing with the need for any other devices to keep the housing halves 3a and 3b positioned relative to one another during the assembly process when the forces Fi and F2 are being applied. 9 List of reference numbers 1 Ball sleeve 2 Bearing shell 3 Joint housing 3a Housing half 3b Housing half 4 End region 5 End region 6 Bearing surface 7 Retaining projection 8 Opening 9 Gap 10 Spacing area 11 Mid-longitudinal axis 12 Shoulder surface 13 Shoulder surface 14 Welded joint 10 WE CLAIM: 1. Ball and sleeve joint, in particular for chassis components and steering components of motor vehicles, comprising a joint housing made up of two housing halves and a ball sleeve provided with a rounded bearing surface, which bearing surface is accommodated in a bearing shell made from an elastic plastic secured in an opening of the joint housing, characterised in that the two housing halves (3a, 3b) are pressed together in the direction of the mid-longitudinal axis (11) of the ball and sleeve joint (1) with defined pressing forces during assembly of the ball and sleeve joint (1) and are retained in the assembly position predefined by the pressing forces by means of at least one material joint (14) between the housing halves (3a, 3b). 2. Ball and sleeve joint as claimed in claim 1, characterised in that the material joint is a welded joint, in particular a laser welded joint. 3. Ball and sleeve joint as claimed in claim 1, characterised in that the material joint is a soldered joint. 4. Ball and sleeve joint as claimed in claim 1, characterised in that the material joint is a bonded joint. 5. Ball and sleeve joint as claimed in one of claims 1 to 4, characterised in that the bearing shells (2) have at least one retaining projection (7) on their external surface in contact with the internal wall of the opening (8) of the joint housing (3) standing proud of the surface, for which a matching recess is provided in the opening (8) of the joint housing (3). 6. Ball and sleeve joint as claimed in claim 5, characterised in that the retaining projection (7) is provided in the form of a radially extending retaining collar which engages in a radially extending groove of the joint housing (3). 11 7. Ball and sleeve joint as claimed in claim 5, characterised in that part of the recess is provided in each of the two housing halves (3a, 3b). 8. Ball and sleeve joint as claimed in one of claims 1 to 7, characterised in that the material joint consists of individual welded sections extending around the external contour of the joint housing. 9. Ball and sleeve joint as claimed in one of claims 1 to 8, characterised in that the material joint (14) between the housing halves (3a, 3b) extends around the external edges of the joint housing (3). 10. Ball and sleeve joint as claimed in one of claims 1 to 9, characterised in that the centre points of the ball radii Rs of the bearing surface (6) and RG of the opening (8) of the joint housing (3) are pushed towards one another in the direction of the mid-longitudinal axis (11) before applying the pressing forces (Fl, F2). 11. Method of producing a ball and sleeve joint, in/particular for chassis components and steering components of motor vehicles, whereby the ball and sleeve joint comprises a metal joint housing and a ball sleeve with a rounded bearing surface, which bearing surface is accommodated in a bearing shell made from elastic plastic, and the bearing shell is in turn secured in an opening of the joint housing, characterised in that once the ball sleeve (1) and bearing shell (2) have been fitted in the opening (8) of the joint housing (3), defined pressing forces (F1, F2) are applied to the housing halves (3a, 3b) in order to push them together in the direction of the mid-longitudinal axis, which are transmitted via the internal face of the openings (8) in the housing halves (3a, 3b) to the bearing shell (2), and the housing halves (3a, 3b) are secured against one another in the assembly position defined by the pressing forces (Fl, F2) by means of at least one material joint (14) between the housing halves (3a, 3b). 12 12. Method of producing a ball joint as claimed in claim 11, characterised in that the material joint (14) between the housing halves (3a, 3b) is produced by a laser welding operation. 13. Method of producing a ball joint as claimed in claim 10, characterised in that the material joint (14) between the housing halves (3a, 3b) is produced by a soldering operation. 14. Method of producing a ball joint as claimed in claim 10, characterised in that the material joint (14) between the housing halves (3a, 3b) is produced by a bonding operation. 15. Method of producing a ball joint as claimed in one of claims 11 to 14, characterised in that the centre points of the ball radii Rs of the bearing surface (6) and RG of the opening (8) of the joint housing (3) are pushed towards one another in the direction of the mid-longitudinal axis (11) during production. 13 Dated this 8th day of February, 2007 ABSTRACT A ball and sleeve joint is proposed, in particular for chassis components and steering components of motor vehicles, comprising a joint housing made up of two housing halves and a ball sleeve with a rounded bearing surface, which bearing surface is accommodated in a bearing shell made from elastic plastic secured in an opening of the joint housing, and a method of producing a ball and sleeve joint of this type whereby the two housing halves (3a, 3b) are pressed together in the direction of the longitudinal axis of the ball and sleeve joint (1) with defined pressing forces during assembly of the ball and sleeve joint (1) and are retained in the assembly position defined by the pressing forces by means of at least one material joint (14) between the housing halves (3a, 3b) To, The Controller of Patents, The Patent Office, Mumbai

Documents:

200-mumnp-2007-abstract(08-02-2007).doc

200-mumnp-2007-abstract(08-02-2007).pdf

200-mumnp-2007-abstract.doc

200-mumnp-2007-abstract.pdf

200-mumnp-2007-cancelled pages(08-02-2007).pdf

200-mumnp-2007-claims(granted)-(08-02-2007).doc

200-mumnp-2007-claims(granted)-(08-02-2007).pdf

200-mumnp-2007-claims.doc

200-mumnp-2007-claims.pdf

200-mumnp-2007-correspondence(08-01-2008).pdf

200-mumnp-2007-correspondence(ipo)-(24-10-2008).pdf

200-mumnp-2007-correspondence-others.pdf

200-mumnp-2007-correspondence-received.pdf

200-mumnp-2007-description (complete).pdf

200-mumnp-2007-drawing(08-02-2007).pdf

200-mumnp-2007-drawings.pdf

200-mumnp-2007-form 1(08-01-2008).pdf

200-mumnp-2007-form 18(08-02-2007).pdf

200-mumnp-2007-form 2(granted)-(08-02-2007).doc

200-mumnp-2007-form 2(granted)-(08-02-2007).pdf

200-mumnp-2007-form 26(12-03-2007).pdf

200-mumnp-2007-form 3(08-02-2007).pdf

200-mumnp-2007-form 5(08-02-2007).pdf

200-mumnp-2007-form-1.pdf

200-mumnp-2007-form-2.doc

200-mumnp-2007-form-2.pdf

200-mumnp-2007-form-3.pdf

200-mumnp-2007-form-5.pdf

200-mumnp-2007-form-pct-ib-301.pdf

200-mumnp-2007-form-pct-ib-304.pdf

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