Title of Invention

COLD FORMING METHOD FOR PRODUCING BALL JOURNALS

Abstract

A cold forming method is proposed for producing ball journals with a spherical region, a conical region and a threaded region for fitting in ball and socket joints by cold forming, whereby a ball journal blank (1) with a formed cone region (3) and cylindrical regions for thread (2) and ball (5) is firstly produced by extrusion from a bar-shaped rod of semi-finished material. Following the extrusion process, a subsequent production sequence involves forming the ball region by means of a rolling method. The threaded region can be processed to its final shape at the same time. The ball journal as a whole is produced by cold forming only and permits a significant increase in the number of units which can be produced per unit of time compared with methods known from the prior art. At the same time, less expensive types of steel can be used because the ball journal is guaranteed to be sufficiently durable due to the cold forming process. Figure 4

Full Text

FORM 2 THE PATENT ACT 1970 (39 of 1970) The Patents Rules, 2003 COMPLETE SPECIFICATION (See Section 10, and rule 13) TITLE OF INVENTION COLD FORMING METHOD FOR PRODUCING BALL JOURNALS APPLICANT(S) a) Name b) Nationality c) Address ZF LEMFORDER METALLWAREN AG GERMAN Company POSTFACH 122 0, 4 9441 LAMFORDE, GERMANY PREAMBLE TO THE DESCRIPTION The following specification particularly describes invention and the manner in which it is to be performed : Cold forming method for producing ball journals Description The invention relates to a cold forming method for producing ball journals with a spherical region, a conical region and a threaded region for fitting in ball and socket joints. 5 Ball journals designed for fitting in ball and socket joints are primarily made by production methods which involve the removal of material and which do not involve the removal of material. Forming processes involving the 10 removal of material result in larger quantities of waste material, which then has to be disposed of. There is also the disadvantage that the waste material initially has to be acquired in the form of a semi-finished product. Another disadvantage is the fact that it is not possible 15 to run process cycles at a rate essentially in excess of 10 units per minute on the standard machines available today. In forming processes involving the removal of material, at least the threaded region also has to be processed by means of a roller or roll-forming process in 20 order to provide the requisite thread in this region. The cycle times at which such roller or roll-forming process operate also lie within the above-mentioned range of approximately 10 units per minute. 25 As an alternative to processes involving the removal of material, another approach to making ball journals known from the prior art is by cold or warm processing by pressing. The pressing operations may be performed in the O direction of the longitudinal axis of the ball journal, in which case a burr ridge is typically formed at one end of the ball journal blank, or horizontally in a two-part pressing tool, which results in a burr extending around 5 the entire pressed blank. The burrs which occur due to pressing are removed by an appropriate finishing process of removing material in the approach known from the prior art. This means that cost and time-intensive work operations are necessary before the ball journal is 10 finished, even if the ball journal is made by a forming process which does not involve the removal of material as such. Also known from the prior art are ball journals 15 comprising several parts, although the process by which they are manufactured will not be discussed in detail here because the method proposed by the invention relates to the production of one-piece ball journals. 20 The objective of the present invention is to propose a method of producing ball journals with a spherical region, a conical region and a threaded region, whereby the number of units per unit of time for producing individual ball journals can be significantly increased, 25 thereby enabling the requisite production costs to be decreased significantly. This objective is achieved by the invention on the basis of the technical teaching defined in claim 1. For the 30 purpose of the invention, a ball journal blank with a formed conical region and cylindrical regions for a thread and ball are firstly produced from a bar-shaped rod of semi-finished material by means of extrusion, and the pressing shoulder is disposed at the free end of the region intended for forming the ball, after which the spherical region is formed in another work operation by a process of rolling off forming bodies by means of a 5 rolling process triggered in synchronisation. Combining the method steps outlined above in this new way obviates the need for any forming which involves the removal of material. During both the pressing process and 10 during the downstream rolling process, cycle times can be run at approximately 100 units per minute in the case of pressing and in the range of approximately 50 units per minute in the case of rolling. 15 The rolling process may be what might be termed a flat die rolling process or a round die rolling process. Combining said production sequences therefore enables a considerably higher number of units of ball journals to 20 be produced than has been the case up to now in the prior art. Amongst other things, this is due to the fact that in flat die rolling or round die rolling, several functional regions such as the ball region, the cone region and the threaded region for example, can be 25 processed by a single tool simultaneously. Furthermore, there is also no need to dispose of any waste material, which is necessarily the case if using production methods which involve the removal of material. 30 Since the capital outlay for a rolling machine falls within the same cost range as that of procuring a turning machine, the new solution proposed by the invention also offers cost advantages in terms of the initial investment /. needed for the production of ball journals, due to the higher output of workpieces. With the new method proposed by the invention, it has 5 also proved to be of advantage during the flat die or round die rolling process to form first of all a neck region between the cone region and the cylindrical region which is intended for forming the ball. Strength measurements taken as examples on ball journals produced 10 by the new method have shown that the durability of the ball journals can be increased by up to 50% if a neck region is formed by rolling. The fact that durability can be increased by rolling the neck means that it is possible to use steels with micro-alloying elements which 15 are significantly less expensive in terms of procurement costs than the high quality steels needed for heat treatments. Cold forming C-Mn steels containing micro-alloying elements is sufficient to produce adequate strength, especially in the neck region. Use can be made 20 of the increased strength properties to reduce the structural dimensions of ball journals accordingly for the same external stresses. In one particular embodiment of the method proposed by 25 the invention, it has also proved to be of particular practical advantage if a recess in the form of a blind bore open at an end face is pressed into the free end of the ball journal blank where the ball region is to be formed, prior to the rolling process. This being the 30 case, the blind bore-shaped recess can be formed by the upper die used for pressing purposes. The recess facilitates forming when it comes to imparting the final spherical shape to the cylindrical part-region of the ball journal where the ball region is to be formed. The recess naturally also results in a saving on material. If at least some of the blind bore-shaped recess or so-called pole bore remains in place once the ball region of 5 the ball journal has been produced, the recess can be used as a means of accommodating sensors or as a reservoir for grease, for example. In this connection, it would naturally also be conceivable to close off the pole bore by means of a plastic cover, for example. 10 The work sequences involved in both flat die rolling and round die rolling will be explained in more detail with reference to the appended drawings. Of these: 15 Figure 1 is a side view of a ball journal blank prior to forming the ball region by means of the rolling process triggered in synchronisation, Figure 2 is a schematic plan view of a flat die rolling 20 device with the ball journal disposed in it during the rolling process, Figure 3A is a diagram in section through the flat die rolling device at the start of the rolling 25 process along section line A-A indicated in Figure 2, Figure 3B is a diagram in section through the flat die rolling device during the rolling process along 30 section line B-B indicated in Figure 2, Figure 3C is a diagram in section through a flat die rolling device on terminating the forming £ process for the ball journal along section line C-C indicated in Figure 2, Figure 4 is a schematic diagram in section through a 5 round die rolling device with a ball journal blank disposed in it, Figure 5 is a plan view of the round die rolling device illustrated in Figure 4, 10 Figure 6 is a perspective diagram of another variant of a round die rolling device with a ball journal blank disposed in it, 15 Figure 7 is a schematic diagram through a round die rolling device with the ball journal blank disposed in it and 20 Figure 8 is a plan view of the round die rolling device illustrated in Fig. 7. The ball journal blank illustrated in Figure 1 is 25 produced by an extrusion process and essentially consists of several part-regions of differing three-dimensional shape disposed one after the other in the ball journal longitudinal direction. After extrusion, the different regions are formed to their final shape by the 30 combination of features incorporated in the method proposed by the invention, resulting in a ball journal shape corresponding to that illustrated in the diagram of Figure 3C on completion of the cold forming process -i proposed by the invention. As a whole, the ball journal blank denoted by reference 1 illustrated in the diagram of Figure 1 therefore consists 5 of a cylindrical region 2 disposed at a free end of the ball journal blank 1, adjoining which a thread is disposed for securing the ball journal to a machine or chassis component once the ball journal is finished.. Directly adjoining the cylindrical region 2 is a cone- 10 shaped region 3. After the extrusion process, this cone-shaped region 3 has in principle already assumed its finished dimensions, in which case the cone surface can be smoothed in a downstream work operation. In turn, adjoining the cone-shaped region 3, is another 15 cylindrical region 4, which encompasses the so-called neck portion of the finished ball journal and in which a cut is made, as illustrated in the diagram of Figure 3C, constituting the transition to the adjoining region. The terminal region of the ball journal blank 1 is another 20 cylindrical region 5 disposed at its second free end, which may have a hemispherical part-region 6 where it merges with the cylindrical region 4. As an alternative to the hemispherical shape of the part region 6, it would also be conceivable for the transition to the cylindrical 25 region 4 to be cone-shaped. The latter-mentioned cylindrical region 4 is spherically formed as part of the context of the method proposed by the invention, resulting in the ball head 18 on the top free end of the ball journal illustrated in Figure 3C. In order to 30 facilitate the forming process, a likewise essentially cylindrical recess 7 in the form of a blind bore may be introduced into the top free end in the cylindrical region 5. This may be done as part of the upstream fc extrusion process and may be undertaken using the top die of the extrusion press. This being the case, the two pressing tool halves are shaped so that the dividing line of the two halves lies in the region of the dividing line 5 8 so that the die dividing plane and hence any accumulations of burrs which might be attached lie outside of the cylindrical region 5 to which a spherical shape is to be imparted. 10 To complete forming of the ball journal blank 1 by a process of rolling off forming bodies by means of a rolling process triggered in synchronisation, three different possible rolling methods may be used in principle. These three different methods will be 15 explained below with reference to the drawings. Firstly, one possible rolling method is the so-called flat die rolling method. With this rolling method, the co-operating roller device has two flat dies 9 and 10, in 20 which case one of the flat dies, and in the diagram of Figure 2 the one denoted by reference 9, is a stationary flat die, whereas the oppositely lying flat die 10 is designed to move in translation in the direction of arrow P. Disposed between the flat dies 9 and 10 is the roll 25 gap 11 with an inlet region 12 and an outlet region 13. At the start of the flat die rolling method, the ball journal blank 1 is introduced into the roll gap 11 in the region of section line A-A and the displaceable roller die 10 assumes a position indicated by dotted-dashed 30 lines in the drawing. By displacing the displaceable flat die 10 and due to the resultant rolling off movement of the ball journal blank 1, the latter is transported through the roll gap 11. Forming of both the ball journal a and the adjoining neck region takes place as the ball journal blank is moved within the roller gap 11. For forming purposes, the flat dies 9 and 10 at the start of the actual rolling operation have a contour as 5 illustrated in Figure 3A, which essentially corresponds to that of the ball journal blank 1. This is illustrated by the ball journal blank 1 together with the flat die 9 in Figure 3A. The contour of the other flat die 10 illustrated in Figures 3A, 3B and 3C in principle 10 corresponds to that of the flat die 9 illustrated in said figures. The contour of the flat dies 9 and 10 continuously changes at the mutually facing end faces 14 and 15 until the finished contour of the finished ball journal is obtained in the outlet region 13, as 15 illustrated in Figure 3C. Due to the translating movement of the displaceable flat die 10, the initial contour of the flat die 9 illustrated in Figure 3A may naturally be found on the flat die 10 at the bottom region in the area of point C in the diagram of Figure 2, whereas the final 20 contour of the flat die 9 illustrated in Figure 3C is disposed in the region of point A in the case of the flat die 10. Consequently, the flat dies 9 and 10 are of a symmetrical design in the region of section line B-B in Figure 2. From the change in the contours of the end 25 faces 14 respectively 15 of the flat dies 9 and 10, it may be seen that the contour of the shaping of the ball head as well as the neck region takes place in phases, one after the other. After introducing the ball journal blank 1 into the roll gap 11, the neck shoulder 16 is 30 formed first of all and forming takes place simultaneously in the head region 17 of the cylindrical region 5, which is facilitated as a result of the recess 7 at the free end of the ball journal blank 1 explained in connection with Figure 1. The shaping of the neck shoulder 16 by means of the rolling method leads to a significant increase in strength in this region because, unlike cutting processes, no material is removed and 5 instead, the material of the ball journal blank is reshaped in said region. As the rolling operation continues, between the region of section lines B-B and C-C, the ball head 18 is then 10 finally formed to its ultimate shape and, once the rolling operation has been completed, the displaceable flat die 10 assumes position III indicated by dotted lines in Figure 2. During the entire rolling operation, the surface of the cone-shaped region 3 of the ball 15 journal blank 1 can be smoothed simultaneously due to appropriate shaping of the contour of the end faces 14 respectively 15 of the flat dies 9 and 10. Furthermore, the requisite thread may also naturally be imparted to the cylindrical region 2 at the bottom free end of the 20 ball journal blank 1. Consequently, by shaping the flat dies accordingly, the entire ball journal can optionally be shaped accordingly during a translating movement of the displaceable flat die 10, without the need to remove and dispose of material as is the case with a cutting 25 process to remove material. In addition, the rolling operation results in an increase in the strength of the surface overall, thereby obviating the need for subsequent hardening measures. 30 As an alternative to using the flat die rolling method, the illustrated sequence of the rolling process for producing the finished ball journal may also be operated using devices, the rolling dies of which have a curved shape. Starting with the diagrams of Figures 4 and 5, a first embodiment of the round die rolling operation will be explained. As illustrated in Figures 4 and 5, the round die rolling device consists of two roll cylinders 5 21 and 22 disposed adjacent to one another on parallel axes of rotation 19 and 20. As with the flat die rollers, a roll gap 11 results between the two roll cylinders into which the ball journal blank 1 is introduced. The two roll cylinders 21 and 22 have on their external surface 10 the negative shape of the contour of both the ball journal blank 1 and, in another angular region which may be offset on the circumference by approximately 270°, the contour of the finished ball journal. The rolling operation is effected by rotating the roll cylinders 21 15 and 22 in opposite directions, whilst the ball journal itself remains stationary in the roll gap 11. The diagrams of Figures 4 and 5 illustrate a position of the roll cylinders immediately after introducing the ball 20 journal blank 1 into the roll gap 11. As may also be seen from the diagram in section shown in Figure 4, a contour is formed at the circumference of the roll cylinders 21 and 22 offset by 180° in the region of points PI and P2, which essentially corresponds to that of the flat die 9 25 illustrated in Figure 3B. In the region of points P3, respectively P4 on the circumference of the roll cylinders 21, respectively 22, a contour corresponding to that of the flat die 9 illustrated in Figure 3C is formed in the circumferential surface. The rolling operation of 30 the ball journal blank through to its ultimate shape therefore takes place during a 270° rotation of the roll cylinders 21 and 22. Again with the so-called round die rolling method, the cone-shaped region 3 of the ball journal blank 1 may likewise be simultaneously smoothed and the requisite thread imparted to the cylindrical region 2. 5 Another suitable variant of a so-called round die rolling method is one with devices in which one rolling die is provided in the form of a roll cylinder 23 similar to that of the first variant described above but the second rolling die is provided in the form of a roll hollow 10 cylinder 24 concentrically enclosing the roll cylinder. In the same way as with the alternative rolling method described above, a roll gap 11 is created between the roll cylinder 23 and the roll hollow cylinder 24 surrounding it, as illustrated in Figure 6, into which 15 the ball journal blank 1 to be formed is introduced. The inner jacket surface of the roll hollow cylinder 24 and the external jacket surface of the roll cylinder 23 are stamped with the changing shape of the contour structure of the ball journal blank 1 to be rolled. The actual 20 rolling operation takes place by counter-rotating the roll cylinder 23 and roll hollow cylinder 24 with respect to one another, and the relative movement of the roll cylinder 23 and the roll hollow cylinder 24 is decisive to the imparted shape. One option, therefore, is to 25 rotate only one of the cylinders 23 or 24, whilst the other remains stationary. Again with this method, both the ball head and the neck shoulder, optionally in addition to the cone-shaped region and the threaded region of the finished ball journal, can be shaped. 30 Consequently, this other variant of the round die rolling method also offers corresponding advantages in terms of high production rates and increased strength compared with the methods known from the prior art. )*> The ball journal may also be re-shaped with a round die rolling device which is known per se, as illustrated by way of example in figures 7 and 8. 5 In this case, the ball journal blank 1 is processed by rolling off the symmetrical roll cylinders 25 and 26 rotating about their axes of rotation. The ball journal blank 1 is disposed in the roll gap 11 between the roll 10 cylinders 25, 26. The spherical shape is imparted to the ball journal blank 1 by the correspondingly shaped circumferential geometry of the roll cylinders 25, 26. A negative contour is imparted to the external surface 27 respectively 28 of the roll cylinders 25, 26, which may 15 also form the cylindrically shaped region 5 of the ball journal blank 1. The rotating roll cylinders 25, 26 in this instance are firstly moved towards the ball journal blank 1. This infeed movement may be operated by means of a hydraulic cylinder, for example. 14 List: of reference numbers 1. Ball journal blank 2. Cyli ndrical region 3. Cone- -shaped region 4. Cylindrical region 5. Cyli ndrical region 6. Hemi: spherical part-region 7. Recess 8. Divi ding line 9. Flat die 10. Flat die 11. Roll gap 12. Inle t region 13. Outlet region 14. End : face 15. End : face 16. Neck shoulder 17. Head region 18. Ball head 19. Axis of rotation 20. Axis of rotation 21. Roll cylinder 22. Roll cylinder 23. Roll cylinder 24. Roll hollow cylinder 25. Roll cylinder 26. Roll cylinder 27. External surface 15 Cold forming method to produce ball journals WE Claims '( — 1. Cold forming method to produce ball journals with a spherical region, a conical region and a threaded region for fitting in ball and socket joints, whereby a ball journal blank (1) with a formed cone 5 region (3) and cylindrical regions for thread (2) and ball (5) are firstly produced by extrusion from a bar-shaped rod of semi-finished material, and the pressing shoulder is disposed at the free end of the ball region (5) intended for forming the ball and 10 the ball region is formed in at least one other subsequent work operation by means of a rolling method by rolling off forming bodies. 2. Method as claimed in claim 1, 15 characterised in that the rolling method is a triggered synchronised rolling method. 3. Method as claimed in claim 1 or 2, 20 characterised in that the threaded region is simultaneously formed as the ball region is formed to its end shape. 4. Method as claimed in one of claims 1 to 3, 25 characterised in that the cone region (4) formed in the upstream pressing method is simultaneously smoothed as the ball region r£ is formed to its end shape. 5. Method as claimed in claim 1 to 4, characterised in that 5 prior to the rolling operation at the free end of the ball journal blank (1) intended for forming the ball region, an end-face open blind bore-shaped recess (7) is pressed in. 10 6. Method as claimed in claim 5, characterised in that the recess (7) is formed by the top die during pressing. 15 7. Method as claimed in one of claims 1 to 6, characterised in that, during rolling, a cylindrical neck region (4) is firstly formed between the cone region (3) and the cylindrical region (5) intended for forming the 20 ball. 8. Method as claimed in one of claims 1 to 7, characterised in that a flat die rolling method is used as the rolling 25 method. 9. Method as claimed in one of claims 1 to 7, characterised in that a round die rolling method is used as the rolling 30 method. 10. Method as claimed in claim 9, \^ characterised in -that the round die rolls are provided in the form of roll cylinders (21, 22) disposed adjacent to one another on parallel axes of rotation (19, 20), the external 5 contours of which respectively have a half negative shape of the contour of the ball journal to be rolled, and the ball journal is disposed in a roll gap (11) between the roll cylinders (21, 22 respectively 25, 26) during the rolling process. 10 11. Method as claimed in claim 9 or 10, - characterised in that the round die rolls are provided in the form of a roll cylinder (23) on the one hand and a hollow 15 cylinder concentrically surrounding the roll cylinder (24) on the other, and the external contour of the roll cylinder (23) and the internal contour of the hollow cylinder (24) respectively form a half negative shape of the contour shape of the ball 20 journal to be rolled which changes across the external respectively internal contour, and the ball journal is disposed in the roll gap (JL1) between the external and internal contour of the roll cylinder (23) and roll hollow cylinder (24) during the rolling process. Dated this 8th day of June, 2006. HIRAL CHANDRAKANT JOSHI AGENT FOR ZF LEMFORDER METALLWAREN AG 1% Cold forming method for producing ball journals Abstract A cold forming method is proposed for producing ball journals with a spherical region, a conical region and a threaded region for fitting in ball and socket joints by cold forming, whereby a ball journal blank (1) with a 5 formed cone region (3) and cylindrical regions for thread (2) and ball (5) is firstly produced by extrusion from a bar-shaped rod of semi-finished material. Following the extrusion process, a subsequent production sequence involves forming the ball region by means of a rolling 10 method. The threaded region can be processed to its final shape at the same time. The ball journal as a whole is produced by cold forming only and permits a significant increase in the number of units which can be produced per unit of time compared with methods known from the prior 15 art. At the same time, less expensive types of steel can be used because the ball journal is guaranteed to be sufficiently durable due to the cold forming process. Figure 4 20 !^;

Documents:

674-mumnp-2006-abstract(27-5-2008).pdf

674-mumnp-2006-abstract(9-6-2006).pdf

674-mumnp-2006-abstract(granted)-(30-3-2009).pdf

674-mumnp-2006-abstract.doc

674-mumnp-2006-abstract.pdf

674-mumnp-2006-cancelled pages(27-5-2008).pdf

674-mumnp-2006-claims(9-6-2006).pdf

674-mumnp-2006-claims(granted)-(30-3-2009).pdf

674-mumnp-2006-claims.doc

674-mumnp-2006-claims.pdf

674-mumnp-2006-correspondance-received-ver-090606.pdf

674-mumnp-2006-correspondance-received-ver-290606.pdf

674-mumnp-2006-correspondence(27-5-2008).pdf

674-mumnp-2006-correspondence(ipo)-(31-3-2009).pdf

674-mumnp-2006-description (complete).pdf

674-mumnp-2006-description(complete)-(9-6-2006).pdf

674-mumnp-2006-description(granted)-(30-3-2009).pdf

674-mumnp-2006-drawing(27-5-2008).pdf

674-mumnp-2006-drawing(9-6-2006).pdf

674-mumnp-2006-drawing(granted)-(30-3-2009).pdf

674-mumnp-2006-drawings.pdf

674-mumnp-2006-form 1(14-6-2006).pdf

674-mumnp-2006-form 1(20-9-2006).pdf

674-mumnp-2006-form 18(14-6-2006).pdf

674-mumnp-2006-form 18(9-6-2006).pdf

674-mumnp-2006-form 2(complete)-(9-6-2006).pdf

674-mumnp-2006-form 2(granted)-(30-3-2009).pdf

674-mumnp-2006-form 2(title page)-(9-6-2006).pdf

674-mumnp-2006-form 2(title page)-(granted)-(30-3-2009).pdf

674-mumnp-2006-form 26(21-5-2008).pdf

674-mumnp-2006-form 3(14-6-2006).pdf

674-mumnp-2006-form 5(14-6-2006).pdf

674-mumnp-2006-form-1.pdf

674-mumnp-2006-form-18.pdf

674-mumnp-2006-form-2.doc

674-mumnp-2006-form-2.pdf

674-mumnp-2006-form-3.pdf

674-mumnp-2006-form-5.pdf

674-mumnp-2006-specification(amended)-(27-5-2008).pdf

674-mumnp-2006-wo international publication report(9-6-2006).pdf

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