Patent Publication Number: US-11020784-B2

Title: Method for producing a moulded body comprising a hub and device for carrying out the method

Description:
BACKGROUND AND SUMMARY OF THE INVENTION 
     Exemplary embodiments of the invention relate to a method for producing a molded body having a hub and an axially adjoining, bell-shaped lower part. 
     Such molded bodies are used in particular as axle pins or pivot pins and are part of a connecting joint to transmit torques to components disposed mutually angularly to each other, especially shafts. 
     German patent document DE 10 2013 101 555 B3 disclose producing the molded body consisting of metal, in particular steel, from a tube as a semi-finished product, forming an integrally formed hub and an adjoining bell-shaped lower part, with an inner contour. 
     This inner contour consists of circumferentially alternately arranged ball raceways and cage raceways, which are arched concavely in the axial direction of the molded body, wherein the ball raceways are formed deeper than the cage raceways. 
     The introduction of the inner contour in a bulbous region of the lower part is characteristic in this case, which lower part is constricted to some extent on its side opposite the hub. That is, the inside diameter in this region is smaller than the diameter at the apex of the bulbous region. At this constriction, i.e., in continuation of the bulbous region, a conically widening section adjoins as an apron, which deviating from it can also be aligned radially outwards. 
     Although the use of a round blank as a semi-finished product is mentioned in the aforementioned German patent document, further details cannot be found there. 
     In the known method, the bell-shaped lower part is produced by pressing by means of a suitable pressing tool or by pressing with the aid of a pressure roller, while the subsequent inner contouring is effected by an outwardly contoured pressure roller, with which the bulbous region of the lower part is pressed against a multi-part inner contour tool having contour segments. 
     However, a desired dimensional accuracy required for the purpose in the known method can only be achieved with a considerable manufacturing effort, which is particularly disadvantageous in that such molded bodies are produced as series parts in large quantities. 
     U.S. Pat. No. 5,970,776 A discloses the production of a bell-shaped molded body with inner contours shaped in the manner of ball and cage raceways, which are formed by the interaction of inner contour segments with outer pressure pieces. 
     By means of the device provided for this purpose, however, only one molded part can be produced whose wall, in relation to the size of the bulbous region, in particular of the diameter, is very small. In that regard, this literature is not suitable to provide evidence of a molded body, which in terms of its loading capacity can be used as axle pin or pivot pin, regardless of that an essential configuration, namely the molded hub, is not provided. 
     Exemplary embodiments are directed to a method for producing a molded body having a hub and an axially adjoining, bell-shaped lower part so that the dimensional accuracy of the molded body and its usability are improved. 
     The essence of the invention is to bring, by means of at least one pressure roller, both the hub and the bell-shaped lower part into a preform in which the inner contours, i.e., the cage and ball raceways, are partially formed with respect to their depth. 
     Thus, the possibility of centering and securing anti-rotation of the preform for subsequent finishing is achieved, in which then the inner contour is brought to its final dimensions. 
     While in the preforming of the lower part by means of the at least one pressure roller the outer surface of the lower part remains with a smooth surface, the outer shell surface is similarly formed according to the progression of the curvature of the inner contour according to the invention by means of a forming die consisting of die parts, wherein the concave curvatures both in the axial direction as well as the ball raceways and the cage raceways transversely thereto are represented again as convex curvatures on the outer surface. 
     According to an advantageous embodiment of the method according to the invention, the material is heated to form the hub and/or for the production of the preform and/or the final molded body preferably to a temperature of about 400° to 1000°, preferably about 600° C. to 700° C. 
     As a result of the so-called forced centering of the preform in the further processing to form a final molded body, dimensionally accurate production of the inner contour is achieved, which equally affects the predetermined pitch, i.e., the arrangement of rolling ball raceways and the cage raceways. 
     Moreover, compared to the prior art, a significantly faster production of the molded body is possible, wherein the hub may be formed either as a hollow or solid body. 
     Furthermore, as a result of the spin forming by means of the pressure rollers for the completion of the preform, lower parts with relatively thick walls in relation to the diameter of the lower part are possible, so that in principle a load-optimized molded body can be provided in principle. 
     A device for carrying out the method comprises, for the formation of the preform, a first, rotatable inner contour tool, with radially movable, separate contour segments which are each associated with a ball raceway and a cage raceway and which lie against each other without a gap in the functional position. 
     Functionally, the contour segments for forming the preform are identical to those for the formation of the final molded body and only differ in their dimensional configuration. 
     Except for the contour segments, the structure of the device is comparable for both applications. In contrast to the first, rotatable contour tool, however, the second inner contour tool is held in a rotation-proof manner. 
     To remove the lower part, whether as a preform or as a final molded body of the contour tool, the contour segments, as mentioned, are movable radially inwardly, i.e., to the axis of rotation, namely by means of a positive guide. For this purpose, the contour segments are held on a cone ring, which tapers towards the hub and on the outside has sliding surfaces on which the contour segments are supported. 
     This cone ring is axially relatively displaceable to the contour segments, wherein each contour segment has an undercut longitudinal groove in which a cap screw or a sliding block connected to the cone ring is guided. 
     For an obstruction-free radial movement of the adjoining contour segments associated with the cage raceways and the ball raceways, in particular of the second contour tool, the guide surfaces of the cone ring, which abut the contour segments for the ball raceways, are flatter in their inclination than the guide surfaces on which the contour segments associated with the cage raceways are supported. 
     The contour segments are so far radially movable towards the axis of rotation of the molded body that the lower part, whether as a preform or as a final molded body, can travel over the contour segments even with the smallest clear diameter in the part limiting the bulbous region, which adjoins an outwardly facing conical apron. 
     Moreover, the device is distinguished by its high stability and concentricity due to the formation of the upper end of the guide column near the hub, so that the forces occurring during the deformation of the round blank to a finished molded body can be easily absorbed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING FIGURES 
       The method according to the invention and exemplary embodiments of a device according to the invention are described below with reference to the attached drawings, wherein: 
         FIG. 1  shows a molded body in a perspective view; 
         FIG. 2  shows a longitudinal section through a first embodiment variant of a device according to the invention for forming a preform according to the line B-B in  FIG. 3 ; 
         FIG. 3  shows a cross-section through the device according to  FIG. 2  along the line A-A; 
         FIG. 4  shows a longitudinal section through the device for forming the final molded body, corresponding to the line B-B; 
         FIG. 5  shows a cross-section through the device according to the line C-C in  FIG. 4 ; 
         FIG. 6  shows a longitudinal section through a second embodiment variant of a device according to the invention for forming a preform according to the line B-B in  FIG. 7 ; 
         FIG. 7  shows a cross-section through the device of  FIG. 6  according to the line A-A; 
         FIG. 8  shows a longitudinal section through the second embodiment variant of the device for forming the final molded body, corresponding to the line B-B in  FIG. 9 ; and 
         FIG. 9  shows a cross-section through the device according to the line C-C in  FIG. 8 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a substantially rotationally symmetrical molded body  30 , having a hub  2  and a lower part  31  adjoining the hub and being integrally formed thereon without cutting. 
     Such a molded body  30  already known from the prior art has in its lower part  31  an inner contour  32 , consisting of ball raceways  24 , between each of which a cage raceway  23  is formed, wherein the ball raceways  24  and the cage raceways  23  are distributed evenly over the circumference of the lower part  31 . 
     The cage raceways  23  and the ball raceways  24  are curved in a concave manner in the axial direction, with respect to an axis X, as well as transverse thereto. The ball raceways  24  visibly extend to a lower end region of the lower part opposite the hub  2 , while the cage raceways  23  extend shorter than the ball raceways  24  into the region of an apron  14 , which in the example, as shown in particular in  FIG. 2 , expands conically to the outside. It is also conceivable to form the apron  14  up to a radial orientation. 
     In  FIG. 2 , it can be seen that from a rotating, preferably flat, round blank  3 , which is shown with a dashed line and is made of metal a hub  2 , is integrally formed by means of at least one rotatable pressure roller, which is immersed in the material of the round blank, and then moved radially from outside to inside, this occurring with a reduction in thickness. 
     For further processing, i.e., for forming the lower part  31 , first as a preform  13 , the round blank  3  is pressed by a presetter  1  as a clamping element against an axially fixed, guide column  8  held in a base plate  12 , which simultaneously performs the centering function. In this case, the guide column  8  comprises at its end facing the hub a support plate  27  on which the round blank  3  is supported. 
     The guide column  8  is part of a first inner contour tool, which furthermore has a cone ring  9 , which is held against rotation, but axially displaceable on the guide column  8 . The security against rotation is preferably carried out, as shown in  FIG. 3 , by a spline  22 A, also referred to as spline connection, between guide column  8  and cone ring  9  in order to enable the absorbance of the high torque occurring during this step. 
     By means of at least one pressure roller  4 , the plan area of the round blank  3  radially adjoining the hub  2  is pressed against the first inner contour tool, i.e., against contour segments  10 ,  11  of the first inner contour tool, wherein the pressure roller  4  is advanced radially and axially. The first inner contour tool rotates with the round blank  3  in this case. 
     As a result, a preform  13  is provided whose outer jacket surface is contoured only in the axial direction, as shown according to the illustration in  FIG. 2 . On the inside, however, cage raceways  23  and ball raceways  24  are preformed by the contour segments  10 ,  11 , i.e., only in its axial contour progression, but not with respect to their width and depth corresponding to the final molded body, which is shown particularly clearly in  FIG. 3 . 
     After completion of the use of the pressure roller  4 , which is otherwise pressed against the rotating round blank  3  or the preform  13 , the cone ring  9  is moved downwards in the arrow direction, into a position corresponding to the dashed illustration, wherein the cone ring  9  is connected to a pressure plate  5  via axially movable pressure dies  7 . 
     The guide column  8 , however, is fixed in a base plate  12 , which is held stationary and on which a support ring  6  is fixed, which serves as an abutment for the contour segments  10 ,  11  when the cone ring  9  is pulled downwards, i.e., in the direction facing away from the hub  2 . 
     As already mentioned, with the axial displacement of the cone ring  9  into a final shaping position, the contour segments  10 ,  11  are moved radially in the direction of the guide column  8 , for which purpose a sliding block  18  is fixed in each case in guide surfaces  27  of the cone ring  9 , on which the contour segments  10 ,  11  are displaceably mounted, the sliding block engaging in a slotted guide  19  of the respective contour segment  10 ,  11 . This sliding block  18  may, for example, consist of a cap screw. 
     As a result of the radial displacement of the contour segments  10 ,  11  into one position shown in  FIG. 2  in dashed lines, the preform  13  is exposed to such an extent relative to the contour tool that it is easily removeable. 
     In a subsequent method step, the preform  13  is further processed into a final molded body, namely the lower part  30 . This process step is shown in  FIGS. 4 and 5 . 
     In principle, the structure of the second inner contour tool is comparable to that of the first inner contour tool for forming the preform  13 . In this case, however, contour segments  20 ,  21  are used, which differ in dimension from the contour segments  10 , 11  of the first inner contour tool, namely such that ball raceways  24  and cage raceways  23  are given their final shape. 
     For their embossment, radially advanceable die parts  17  are provided on the outer jacket surface of the preform, which are a segmental component of a die  16  and which are pressed against the outer jacket surface of the now non-rotating preform  13 , wherein the die parts  17 , of which each is assigned a ball raceway  24 , have a concave shape adapted to the convex shape of the contour segment  21 , so that there is a corresponding outer contour of the final molded body forming the lower part  31 . 
     For placing the preform  13  on the second inner contour tool, the contour segments  20 ,  21  are held in a non-functional position, i.e., the cone ring  9  is brought into an end position that is displaced relative to the guide column  8  in the direction of the base plate, in combination with forced radial movement of the contour segments  20 ,  21  inwardly to the guide column  8 . 
     After placing the preform  13  on the guide column  8  formed at the end side as a support plate  27 , the cone ring  9  is displaced in the direction of the hub  2  or the integrally attached support plate  27  of the guide column  8  and as a result of the cone surfaces acting as a wedge, the contour segments  20 ,  21  are moved to an end position in which these rest against each other in a gap-free or almost gap-free manner. 
     To prevent rotation of the cone ring  9  with the guide column  8 , as clearly shown in  FIG. 5 , feather keys  22  are provided that engage in the guide column  8  and the cone ring  9 . 
     By pressing the die parts  17 , corresponding to the direction of the arrow in  FIG. 4 , the ball raceways  24  and the cage raceways  23  are formed. 
       FIGS. 6 to 9  show an alternative embodiment variant of a device according to the invention. In contrast to the device according to  FIGS. 2 to 5 , in the case of the first inner contouring tool, the contour segment  10 ′ for forming the ball raceways  24  is formed integrally with the cone ring  9 . 
     As can further be seen in  FIG. 6 , in this variant as well, the plan area of the round blank  3  radially adjoining the hub  2  is pressed against the first inner contour tool, i.e., against contour segments  10 ′,  11  of the first inner contour tool, wherein the pressure roller  4  is advanced radially and axially. The shape of the contour segments  10 ′ here is such that the radius of the jacket surface of the contour segments  10 ′ never increases upwardly, i.e., counter to the direction of the final shape, but is formed to decrease or remain upwardly constant, so that after completed pressing of the round blank  3  against the first inner contour tool the preform  13  can be removed easily relative to the contour tool. 
     As a result, a preform  13  is created whose outer jacket surface is contoured only in the axial direction, corresponding to the illustration in  FIG. 2 . 
     For simplified processing, in particular with regard to the material deformation, the round blank or the preform, as already stated, can be heated. To increase the service life of the tools involved in the deformation, they can be cooled, wherein corresponding cooling channels can be provided. 
     Although the invention has been illustrated and described in detail by way of preferred embodiments, the invention is not limited by the examples disclosed, and other variations can be derived from these by the person skilled in the art without leaving the scope of the invention. It is therefore clear that there is a plurality of possible variations. It is also clear that embodiments stated by way of example are only really examples that are not to be seen as limiting the scope, application possibilities or configuration of the invention in any way. In fact, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete manner, wherein, with the knowledge of the disclosed inventive concept, the person skilled in the art is able to undertake various changes, for example, with regard to the functioning or arrangement of individual elements stated in an exemplary embodiment without leaving the scope of the invention, which is defined by the claims and their legal equivalents, such as further explanations in the description. 
     LIST OF REFERENCE NUMERALS 
     
         
           1  Presetter 
           2  Hub 
           3  Round blank 
           4  Pressure roller 
           5  Pressure plate 
           6  Support ring 
           7  Pressure die 
           8  Guide column 
           9  Cone ring 
           10  Contour segment 
           10 ′ Contour segment 
           11  Contour segment 
           12  Base plate 
           13  Preform 
           14  Apron 
           15  Guide surface 
           16  Die 
           17  Die part 
           18  Sliding block 
           19  Longitudinal groove 
           20  Contour segment 
           21  Contour segment 
           22  Feather keys 
           22 A Spline connection 
           23  Cage raceway 
           24  Ball raceway 
           27  Support and centering plate 
           30  Molded body 
           31  Lower part 
           32  Inner contour