Abstract:
Method for the production of a spindle nut ( 3 ) of a spherical thread drive mechanism, whereby the spindle nut ( 3 ) has at least one screw-shaped track ( 4 ) formed as a single piece on its inner circumference, whose threads ( 38 ) are limited by shoulders ( 6 ). The shoulder ( 6 ) is interrupted by a deflecting recess ( 23 ) at at least one deflecting position, in order to deflect balls ( 13 ) out of one thread into an adjacent thread ( 38 ). The method includes locating a tool arbor ( 56 ) in a hollow blank ( 57 ), whereby the tool arbor ( 56 ) has on its outer circumference a counter profile of the screw-shaped track ( 4 ) and a projecting part ( 59 ) for each deflecting recess. A tool operates on and reshapes the blank ( 57 ) from the exterior by exercising radial forces (F), whereby during the reshaping process the inner circumferential surface of the blank ( 57 ) is shaped according to the counter profile and to the projecting part ( 59 ) of the tool arbor ( 56 ) such that the screw-shaped track ( 4 ) and the deflecting recess ( 23 ) are formed.

Description:
This is application is a continuation of PCT/EP03/08338 filed Jul. 29, 2003. 

   BACKGROUND 
   The present invention relates to a method for the production of a spindle nut of a spherical thread drive mechanism. 
   From DE 31 00 349 C2, for example, a spherical thread drive mechanism of a spherical roll spindle and one of these encompassing bearing nuts under formation of an annular gap have been known, which have screw-shaped circular recessed tracks of the same slope facing one another. The threads of the tracks are separated from one another by means of corresponding screw-shaped circular raised shoulders. The tracks form spherical tracks that extend over an angle of circumference of approximately 360°, whereby bearing balls run in these spherical tracks. Each spherical track has an approximately S-shaped deflecting position, at which the balls are deflected out of one thread of the track into the adjacent thread. The spindle nut has an interruption in the shoulder at the deflecting position and a deflecting recess. The deflecting recess is necessary so that the balls can be raised over the corresponding shoulder of the spindle. The deflecting recesses are directly formed in the nut in an advantageous manner, such that these can be formed completely closed all around. The incorporation of the deflecting recesses can take place after the hardening of the spindle nut, for example, electrolytically or by means of electrical discharge machining. 
   This production of the deflecting recesses is very expensive for large runs of a series. 
   SUMMARY 
   The object of the present invention is to provide a method for the production of a spindle nut according to the invention, with which large lots can be produced in a cost-effective manner. 
   The method according to the invention provides for the following steps: arrangement of a tool arbor in a hollow blank, whereby the tool arbor has on its outer circumference a counter profile of the screw-shaped spherical track and a projecting part for each deflecting recess; providing a tool that operates on and reshapes the blank from the exterior by exercising radial forces, whereby during this reshaping process the inner circumferential surface of the blank is shaped according to the counter profile and to the projecting part of the tool arbor such that the screw-shaped spherical track and the deflecting recess are formed. During this process, material of the blank is displaced in order to produce the tracks and the deflecting recesses on the inner circumferential surface. 
   The method according to the invention can be carried out in a cost-effective manner. Well known reshaping methods suitable for the invention are, for example, kneading, cold forming by spinning, as well as fluid forming. The material of the blank is forced inwardly during this reshaping process and shaped to the contour of the tool arbor with the projecting parts. The well known kneading is suitable in a particular manner for the production of a spindle nut according to the invention, because rotationally unsymmetrical contours are easily produced by means of this method, whereby kneading jaws under radial impact action operate on the blank that is rotating relative to the kneading jaws and reshape them. 
   After the reshaping process, the tool arbor together with the projecting part is removed, after which the spindle nut can undergo a heat treatment. The spindle nut hardened in such a manner can be completed with additional component parts for the spherical thread drive mechanism. The method for the production of the spindle nut can take place with the subsequent heat treatment in production steps that follow one another, such that the spindle nuts according to the invention can be produced in a commercially efficient manner. 
   A device according to the invention for the implementation of the described method provides that the tool arbor has a recess in which the projecting part is formed as a stamp, which can be affixed in its extended position radially transverse outwards and inwards in comparison with the tool arbor, whereby the stamp is arranged in its extended position within the counter profile of the tool arbor. A problem-free removal is ensured with this device according to the invention. If the tool arbor is to be rotated forth out of the spindle nut in a screwing motion, the stamp is moved inward radially beforehand, such that a screwing motion is as problem-free as possible. 
   The tool arbor can be formed in a hollow manner for the operation of the stamp, whereby a connecting rod arranged in the hollow tool arbor works with the stamp, such connecting rod being held in its extended position in a primary connecting position of the connecting rod of the stamp. The connecting rod is then brought into a second connecting position for removal from the mold, which makes an inward shift of the stamp possible. However, the tool arbor can also be filled with hydraulic fluid in place of a connecting rod, which can be pressurized, whereby this hydraulic fluid works together with the stamp of this type, which is held in its extended position by means of the adjacent pressure. After taking away the pressure, the stamp can be removed radially inward, in order to rotate the tool arbor out of the spindle nut using a screwing motion. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     An exemplary embodiment of the invention is described in connection with the drawings. In the drawings: 
       FIG. 1  is longitudinal section in schematic representation of a spherical thread drive mechanism; 
       FIG. 2  is a view of the processing of the nut of a spherical thread drive mechanism according to the invention with deflecting positions distributed over the circumference; 
       FIG. 3  is a longitudinal section view in partial representation of the nut of the thread drive mechanism according to the invention with inserted insertion bodies, but without the spindle; 
       FIG. 4  is a sectional view according to lines IV—IV in  FIG. 3  showing the arrangement according to  FIG. 3  with inserted spindles; 
       FIG. 5  is a cross section parallel to the corresponding view according to the lines V—V in  FIG. 4  of one of the insertion bodies of the deflecting system according to  FIGS. 3 and 4 ; 
       FIG. 6  shows a method according to the invention and a device according to the invention for the production of spindle nuts and 
       FIG. 7  is a view of an additional device according to the invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows the schematic assembly of a spherical roll spindle. The spindle  1  is encompassed by a bearing nut  3  by using an annular gap  2 . Depending on the type of a thread, a screw-shaped circular recessed track  4  is incorporated at the inner circumference of the nut  3 , which likewise faces a screw-shaped recessed track  5  on the outer side of the spindle  1 . Both of the tracks  4 ,  5  have the same slope and the individual threads of the track  4  of the nut  3  or the track  5  of the spindle  1  are separated from one another by means of a corresponding screw-shaped circular raised shoulder  6  or  7 . The nut  3  can be sealed at the end sides against the spindle  1  with the help of strippers (wiper rings)  8 ,  9 , and they can have a radially distant circumferential surface  10  at an end, with whose help the nut  3  can be fastened to an arbitrary component part  11 . In addition, cylindrical embodiments without a flange or with various other outer forms are possible. The flange  10  has, for example, a lubrication connection  12  for pouring a lubricant into the annular gap  2 . 
   The tracks  4 ,  5  of the nut and the spindle that are facing one another form spherical tracks or spherical runs, in which balls  13  revolve to bear the spindle  1 , which is itself rotating. As a result of the annular gap  2 , the spindle  1  does not lie adjacent to the nut  3 , and it supports itself on it only by means of the balls  13 . 
   In each case, the spherical tracks extend over an angle of circumference of 360°. In order to obtain spherical tracks enclosed in themselves (these are plotted with dotted lines in  FIG. 2 ), each spherical track contains an approximately S-shaped deflecting position  16 . At the same time, the deflecting positions  16  of the various spherical tracks are distributed equally over the circumference. A ball  13  entering from above in  FIG. 3 , from above the drawing plane (as is indicated with dotted lines in  FIG. 4 ), for example in the thread of the track  4  of the nut  3  and in the facing thread  39  of the track  5  of the spindle  1 , rolls along these threads  40  of the track  4  of the nut  3  and is led back into the thread of the track of the spindle  1  facing it. This track leads through to the lower end in  FIG. 3  out of the drawing plane, and the ball rolls off above the drawing plane into the related thread areas of the nut  3  and the spindle  1  that are not visible, until it enters again above in the thread  38  of the nut and the thread  39  of the spindle. Viewed as a whole, in this manner one obtains a screw-shaped spherical track that runs over almost 360°, whereby the ends of the screw-shaped areas at the deflecting positions  16  are associated with one another. The course of spherical tracks of this type, in which the balls are led back internally, are well-known, such that nothing further about them should be suggested. 
   So that the balls  13  can be led back to the respective deflecting positions  16 , the shoulder  6  of the nut  3  has an interruption  19  at the deflecting position  16 . The dividing edges of these interruptions are designated with the reference numbers  20  and  21 . In addition, a deflecting recess  23  crossing the interruption  19  at the deflecting position  16  is incorporated into the wall of the nut  3  by means of a method described further below. The deflecting recess  23  is so deep that a ball that dips into it no longer touches the shoulder  7  of the spindle  1 . In this manner, the balls  13  can roll around in a radial direction outside the uninterrupted shoulder  7  of the spindle by means of the deflecting recess  23  and the interruption  19  of the shoulder  6  of the nut  3 . As a result, the balls  13  are located at the deflecting position  16  outside of interference with the track of the spindle  1 . After rolling through the deflecting recess  16 , the balls engage the track of the spindle  1  again and control it. 
   The measures described up until now are not yet sufficient to allow the balls to follow the path of the track to the deflecting position  16 . Namely, the balls  12  must still be prevented from rolling on straight ahead to the deflecting position  16  instead of the deflecting recess  23 . For this purpose, it is provided that deflecting surfaces reaching to both ends of the deflecting recess  16  in the track of the spindle and lifting these balls from this track into the deflecting recess are available, and that the spherical track is covered between the two deflecting surfaces on the spindle  1  by means of a covering that reaches into the annular gap  2  between nut  3  and spindle  1 . Therefore, the balls  13  are first diverted from one of the two deflecting surfaces from the spindle  1  to the deflecting recess  23 , after which they roll off from the covering, and after that come back again over the other deflecting surface in the track of the spindle. In a manner of speaking, both of the deflecting surfaces obstruct the balls from the path running on straight ahead, whereby one therefore requires a deflecting surface on both sides of the deflecting recess, because of course the spindle or the nut can rotate in both rotational directions, such that the balls must also be able to run through the spherical tracks in both directions. 
   The deflection of the balls  13  at the deflection positions  16  take place with the help of inserts. This involves insertion bodies  35 ,  36 ,  37 , which are represented in the  FIGS. 3 and 4  with thickly drawn lines, whereby only the insertion bodies  35  are complete, but the insertion bodies  36 ,  37  are shown as cut. Two insertion bodies are associated with each deflection position  16 . An insertion body is arranged between two spherical tracks adjacent to one another or spherical runs. These two insertion bodies, for example the insertion bodies  35 ,  36 , which are arranged for the deflection position containing the deflection recess  23 , are independent from one another and have a toric shape, in particular as appears graphically in  FIG. 4 . These toric bodies (which appear as essentially circular in the cross section) are curved corresponding to the tracks of the nut and of the spindle, which means they extend along an arc of a circle in the side view. One of the two insertion bodies, for example, the insertion body  35 , lies in the thread  38  of the track  4  of the nut  3 , as well as in the facing thread  39  of the track  5  of the spindle  1 . The other insertion body  36  is inserted into the adjacent thread  40  of the track  4  of the nut  3 , as well as into the track of the spindle facing this one, which is not visible in  FIG. 4 . Both of the insertion bodies  35 ,  36  associated with the respective deflecting positions are therefore arranged in adjacent threads of the tracks of the nut and of the spindle, whereby they come to an end at the respective deflecting positions  16  coming from opposite sides. At the same time, both of the insertion bodies  35 ,  36  face one another with their front sides at an angle, between which the respective deflecting recess  23  are located. In each case, these front sides, with their sections inserted into the track of the spindle  1 , are preferred for the formation of deflecting surfaces lifting the balls  13  out of the track  5  of the spindle  1 , and are cambered at an angle for the lateral control of the balls. In  FIG. 3 , in which the insertion bodies seen from the spindle are represented, the preferred sections  41 ,  42  are visible, which, according to  FIG. 4 , seat nearly aground for the track  5  of the spindle  1 , whereby a clearance is present here. The front sides return out of these sections  41 ,  42  in the longitudinal direction of the respective insertion bodies as seen towards the nut, whereby the dividing lines  43 ,  44  of the front sides  45 ,  46  running towards the nut are indicated with dotted lines in the  FIGS. 3 and 4 . At the same time, these front sides are positioned at an angle and cambered in such a manner that one obtains a flowing deflection of the balls in the deflecting recess  23 . In addition, each of the insertion bodies now contains a lateral projecting part  47  or  48  on the side of the interruption  19  relating to the deflecting recess  23  of the shoulder  6  of the nut  3 , whereby this projecting part runs up to the front side of the insertion body facing the respective deflecting position  16 . In addition, these projecting parts  47 ,  48  stand in extension for the shoulder  6  of the nut  3  over the interruption  19  of this shoulder, on which the deflecting recess  23  is located, whereby the projecting parts  47 ,  48  are arranged in the annular gap  2  between nut  3  and spindle  1 . As seen in the top view of the spindle, the projecting parts  47 ,  48  (see  FIG. 3 ) have a lightly rounded outer contour, which passes over into the dividing lines of the related front sides of the insertion bodies in a flowing manner. The two projecting parts  47 ,  48 , in each case belonging to an adjacent insertion body, face themselves with slight distance and in each case form a half of the covering of the spherical track for the spindle. Therefore, the balls are led inside the deflecting position on one hand at the bottom of the deflecting recess  23  and on the other hand not only at the cambered front side of the two insertion bodies, but also at the two projecting parts  47 ,  48 . 
   Each insertion body, for example the insertion body  35 , extends itself inside the related threads  38  or  39  of the nut  3  or of the spindle  1  up to the deflecting position of the adjacent spherical track, as appears graphically in  FIG. 3 . At the same time, the insertion body on the other front side  50 , which is associated with this adjacent deflecting position, is correspondingly formed like the already described front side and, in addition, a corresponding lateral projecting part  52  is present there. In other words, one rotates the insertion bodies  35 ,  36 ,  37  around its transverse medial axis  55  running in a radial direction around 180°, thus exactly the same shape results in turn. In this manner, the halves from two insertion bodies are assigned to each deflecting position, while the respective other half of each insertion body is assigned to one of the two adjacent deflecting positions. Thus the insertion body  35 , for example, limits the deflecting position related to the deflecting recess  23  with its one front side  45  and the laterally facing projecting part  47 , and the deflecting position or related spherical track adjacent to the left in  FIG. 3  with its other front side  50  and the laterally facing projecting part  51 . 
   It can be seen that the areas of the spherical tracks of the spindle that are not covered, and the nut that is located in each case between two deflecting positions, are filled by the insertion bodies, such that no empty space is present, into which one can otherwise inadvertently pour in balls during the assembly, which were split during operation. 
   For fastening the insertion bodies it is provided that a radially projecting fastening pin  52  is affixed to them on the outer circumference, which is inserted into a corresponding tapped blind hole  53  of the nut. Alternatively, the insertion bodies can also be attached with adhesive or weld. 
   Ideally, the insertion bodies  35 ,  36 ,  37  can be produced as single pieces out of plastic or metal. 
   It can be yet further seen from  FIGS. 3 through 5  that a continuous stepped surface  54  is present in the longitudinal direction on the outer circumference of the insertion bodies  35 ,  36 ,  37 , which passes over into the lower side of the respective lateral projecting part  47 ,  51  facing the spindle  1 , in order to obtain an appropriate radial and axial clearance in the spherical track of the spindle. 
     FIG. 6  shows in a schematic representation the production of the spindle nut  3  according to the invention, as well as a device according to the invention for carrying out the method. A tool arbor  56  is first introduced into a hollow blank  57 . The tool arbor  56  is provided with a counter profile (not represented here) on its outer shell surface for the track  4  of the spindle nut  3 . In addition, the tool arbor  56  is provided with a recess  58 , in which a radially arranged transverse stamp  59  is placed. As projecting part  60 , the stamp  59  forms the counter profile at the deflecting recess  23  at the inner circumferential surface of the spindle nut  3 . The tool arbor  56  is of a hollow design, whereby a connecting rod  61  is placed in the tool arbor  56  in an axial transverse manner. The connecting rod  61  is provided with a wedged surface  62 , which works together with a counter surface  63  of the stamp  59 .  FIG. 6  shows the stamp  59  in its extended position. External forces F now operate on the blank  57 , under which the material of the blank  57  is formed onto the contour of the tool arbor  56  with its stamp  59 . The force F is exerted over kneading jaws  64 , which are represented with dotted lines in the  FIG. 4 . The kneading jaws  64  carry out a compact stroke during a rotation relative to the blank  57 . This process is ended when the tracks  4  on the inner circumference of the blank  57  and the deflecting recess  23  are shaped. The connecting rod  61  is now axially shifted to the extent that the stamp  59  comes free. Now the stamp  59  can be shifted radially inwards. In this connection, the tool arbor  56  can then be un-screwed from the spindle nut  3 . 
     FIG. 7  shows the same method as does  FIG. 6 , but with a modified device for carrying out the method in comparison with  FIG. 6 . Here, instead of a connecting rod, hydraulic fluid  65  is poured into the hollow tool arbor  56 . The hydraulic fluid  65  can be pressurized. The stamp  59  is held in its position driven radially outward under the adjacent pressure. After the pressure is taken away, the stamp  59  can be shifted radially inward.