Patent Abstract:
A screw nut from a metal material, which comprises a tapped hole and an inner groove which radially extends in relation to the longitudinal axis thereof. An annular collar is formed onto one of the faces of the screw nut and its cross-section is bent in the direction of the axis to such a degree as to delimit, together with a section of the face surrounding the tapped hole as a contact surface, a receiving slot that is directly associated therewith.

Full Description:
BACKGROUND OF THE INVENTION 
       [0001]    The invention relates to a screw nut comprising a metallic material with a threaded bore and an inner groove which is associated with the longitudinal axis of said threaded bore in radially circumferential fashion in accordance with the preamble of claim  1 . In addition, the invention deals with a method for producing the screw nut in accordance with the preamble of claim  14  and a tool in accordance with the preamble of claim  18  developed therefor. 
         [0002]    A nut and a method of the type mentioned at the outset are described in FR 2 557 652. 
         [0003]    U.S. Pat. No. 2,363,680 describes a nut of another type, in which an annular collar is upset and a thread is provided on the inwardly pointing side face thereof. The upset part of the annular collar has a wall thickness which is larger than a wall thickness of the bent connecting part and of the adjacent part which has not been upset. 
         [0004]    U.S. Pat. No. 2,952,289 discloses a nut, in which an annular collar is bent back and then axially compressed until it is positioned as close as possible to the free end of the nut. 
         [0005]    U.S. Pat. No. 2,385,390 discloses a nut with an annular collar, which has cutouts. 
         [0006]    A nut of another type is disclosed in the German patent 3 05 761, wherein the nut is provided with an annular hollow so as to form a safety nut, this process taking place by means of a drilling device on a machine tool with a revolving spindle, the spindle being aligned with a chuck for holding singular nuts or a plurality of nuts during the hollowing-out process. The hollow is formed before the thread is cut in. The hollow is located at the same distance from the two end faces of the nut. The thread is cut on both sides of the hollow with the same pitch. Then the nut is subjected to compression in order to achieve an offset of the thread parts on both sides of the hollow with respect to one another. 
         [0007]    The Swiss patent 2 49 469 also demonstrates a safety nut which is provided at its unloaded end with a channel by means of part of the thread being removed, with the result that an annular tab is produced which is subjected to upset forging after the main part of the thread. This is another way of providing a securing screw nut. 
         [0008]    The German patent 4 90 889 describes a securing action of a nut which is achieved by virtue of the fact that an annular groove with a wedge-shaped cross section is provided in the threaded bore, or in the core of the nut. In this case, too, the continuous thread is interrupted in the upper part of the nut by a cutout, which is designed in such a way that, as a result, a thin wall is produced, so that an upper subsection has a spring effect. Then, the upper subsection is constricted in terms of its diameter by being compressed and at the same time is compressed in terms of its height in order to achieve a cling effect of the nut. The thin wall piece which remains as a result of the cutout in this case produces a spring effect on the constricted and pitch-offset flank diameter of the upper thread part. 
         [0009]    These and other known nuts have considerable disadvantages in terms of their operation, but in particular with a view to the complex manufacture which needs to take place in metal-cutting fashion by means of part of the thread or the walls of the nut being removed in order to achieve a sprung securing effect of a thread part. 
         [0010]    In the knowledge of these particular facts, the inventor is confronted with the problem of providing a screw nut which can be used efficiently and primarily can be produced simply and quickly. 
       SUMMARY OF THE INVENTION 
       [0011]    According to the invention, an annular collar is integrally formed on one of the end faces of the screw nut and is bent cross-sectionally towards the axis in such a way that, with a section of this end face which surrounds the threaded bore as a bearing face, it delimits an accommodating slot which is directly associated therewith. 
         [0012]    In accordance with a further feature of the invention, the cross-sectionally deformed annular collar of the screw nut, which has a polygonal basic outline determined by wall face sections, forms a shaped collar, whose outer face runs at a radial distance from the axially parallel edges of the wall face sections of the screw nut; the accommodating slot is in this case arranged close to the outer face of the shaped collar and said shaped collar is preferably provided with an outer face, which is curved cross-sectionally towards the axis. 
         [0013]    Preferably, the accommodating slot, which provides two parallel peripheral edges, is inclined cross-sectionally at an angle with respect to these peripheral edges; however, it is also within the scope of the invention to allow the accommodating slot to run in a diametrical plane of the screw nut. 
         [0014]    In a preferred, first variant of the invention, which is explained in particular with reference to  FIG. 7  to  FIG. 10  in detail within the scope of a first preferred embodiment of the invention, the annular collar is bent cross-sectionally towards the axis in such a way that the accommodating slot is open towards the threaded bore. That is to say that the peripheral edges of the accommodating slot are spaced apart from one another towards the threaded bore. 
         [0015]    In a second variant, which is explained in detail in particular with reference to  FIG. 11  to  FIG. 14  within the context of a further particularly preferred embodiment of the invention, the annular collar is bent cross-sectionally towards the axis in such a way that the accommodating slot is closed towards the threaded bore. That is to say that the peripheral edges of the accommodating slot in practice bear against one another towards the threaded bore. 
         [0016]    In both variants, a thread, which is formed in the end region of the bent shaped collar, is offset with respect to the remaining thread of the screw nut, with the result that the securing effect in accordance with the invention is produced when it is screwed onto a bolt or a screw by means of a resilient force acting against the thread flanks of the bolt or the screw. The offset of the thread provided in the end region of the bent shaped collar relative to the remaining thread of the screw nut is comparatively small and is possibly only a few tenths of a millimeter, for example 1 or 2 tenths of a millimeter, which is sufficient for producing the effect in accordance with the invention. Moreover, such an offset, as identified by the invention, can in practice only be achieved by the annular collar bent towards the axis in accordance with the invention. 
         [0017]    In order to vary a spring effect of the shaped collar, in particular to design it to be more flexible, it may be advantageous for sections of the annular collar, and correspondingly of the shaped collar, to run along the circumference of the screw nut. In this regard it is advantageous that adjacent sections of the annular collar/shaped collar are completely or partially separated from one another by an interruption, for example a notch or other gap. An individual section may have a more advantageous spring effect intended for a specific use in comparison with a shaped collar running along a full circumference of the screw nut. 
         [0018]    The feature that a retaining and/or sealing member is fixed in the accommodating slot, which retaining and/or sealing member protrudes towards the axis beyond the peripheral edges of said accommodating slot and, for example, bears on the inside against a screw pin, which is fixed in the thread of the screw nut, is of particular significance. 
         [0019]    The method according to the invention for producing a screw nut proposes that an annular collar with a circular free upper edge is integrally formed on an end face of a blank nut, which corresponds to the basic outline of the screw nut, and is curved cross-sectionally towards the longitudinal axis of the blank nut by a compression tool which is led up to said upper edge axially. In addition, the free upper edge of the annular collar is led up to the adjacent end face of the blank nut in circumferentially parallel fashion and is arranged at a distance therefrom. 
         [0020]    According to the invention, in addition, the annular collar is subjected to upset forging in an end region at its upper edge during the deformation, so that this end region has a larger cross section than the adjacent region of the shaped collar. 
         [0021]    In accordance with a further feature of the method according to the invention, an internal thread is cut into an axial hole channel of the blank nut or formed into it in another way, in particular also into the end region of the bent shaped collar. In order to complete the screw nut, said shaped collar should moreover be offset towards the internal thread once the internal thread has been formed. 
         [0022]    As long as this has not already happened during the bending of the annular collar, this can take place in such a way that the peripheral edges of the accommodating slot are spaced apart from one another or lie one on top of the other towards the threaded bore. The offset brings about a resiliently clamping force on the thread flanks of a bolt or screw when the latter is screwed to the screw nut. 
         [0023]    A tool which is suitable for carrying out the method contains, in a housing, a guide channel for a pressure plunger, which ends at an accommodating region, which is formed by an annular rim of a tool end face, for a workpiece; the pressure plunger is mounted in the guide channel in such a way that it is axially displaceable. In addition, this annular rim should have an inner face, which is curved cross-sectionally inwards towards the end face and which influences the way in which the annular collar curves during the pressing operation. 
         [0024]    It has proven to be favorable to position a free pressure front end of the pressure plunger onto the workpiece within the annular collar thereof, with the housing being arranged on it in such a way that it can be supplied to the annular collar of the workpiece. 
         [0025]    In accordance with a further feature of the invention, that end of the pressure plunger which is remote from the free pressure front end is provided with at least one radially protruding stop member; an inner step of the housing is arranged as the opposing stop in the movement path of said stop member. 
         [0026]    Overall, an impressive solution is provided for achieving the object envisaged by the inventor. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0027]    Further advantages, features and details of the invention are given in the description below of preferred exemplary embodiments and in the drawings, in which: 
           [0028]      FIG. 1  shows a side view of a partially sectioned pressure-generating tool with a likewise partially sectioned workpiece which is associated with it in its longitudinal axis (at a distance); 
           [0029]      FIG. 2  shows the plan view of the workpiece in  FIG. 1 ; 
           [0030]      FIG. 3  shows an angled view of the workpiece reproduced in enlarged form in comparison with  FIG. 1  and  FIG. 2 ; 
           [0031]      FIG. 4  shows the partially sectioned side view of the tool with the workpiece partially accommodated; 
           [0032]      FIG. 5  shows an enlarged detail of the longitudinally sectioned tool with the workpiece deformed; 
           [0033]      FIG. 6  shows an enlarged detail from figure  FIG. 5  as denoted by the arrow VI therein; 
           [0034]      FIG. 7  shows an illustration of the deformed workpiece of the screw nut, which illustration corresponds to that in  FIG. 3 ; 
           [0035]      FIG. 8  shows the workpiece once it has been machined and the screw nut in a partially sectioned illustration; 
           [0036]      FIG. 9  shows the plan view of the machined workpiece and the screw nut from  FIG. 8 ; 
           [0037]      FIG. 10  shows a partial reproduction, which is enlarged in comparison with  FIG. 8 , of the machined workpiece and the screw nut; 
           [0038]      FIG. 11  shows an illustration of the deformed workpiece of the screw nut, which illustration corresponds to that in  FIG. 3 , in accordance with a developed embodiment; 
           [0039]      FIG. 12  shows the workpiece once it has been machined and the screw nut, in accordance with the developed embodiment shown in  FIG. 11 , in a partially sectioned illustration; 
           [0040]      FIG. 13  shows the plan view of the machined workpiece and the screw nut, in accordance with the developed embodiment shown in  FIG. 11 ; 
           [0041]      FIG. 14  shows a partial reproduction, which is enlarged in comparison with  FIG. 12 , of the workpiece and the screw nut, in accordance with the developed embodiment shown in  FIG. 11 ; 
           [0042]      FIG. 15  shows an angled view of a developed embodiment of a workpiece which has been reproduced on an enlarged scale in comparison with  FIG. 1  and  FIG. 2 . 
       
    
    
     DETAILED DESCRIPTION 
       [0043]    A metallic tool  10  for machining an annular workpiece  50  has a pressure plunger  12  with a length a of in this case 76 mm and a diameter d of approximately 10 mm, with a central stop plate  14  with a diameter d 1  of in this case 12 mm and an axial thickness b of 3 mm being shaped out of the upper (in  FIG. 1 ) end of said pressure plunger. The length of this diameter d of the pressure plunger  12 , and therefore of its pressure front end  15 , is dependent on the diameter of a hole channel (described further below) of a blank nut  52 . The pressure plunger  12  is mounted displaceably in a guide channel  16  of a sleeve-like housing  20 , whose axial length h is in this case given as 78 mm, given an outer diameter c of approximately 22 mm. The diameter e of the guide channel  16 , which runs in the housing longitudinal axis A, is slightly larger than the diameter d of this pressure plunger  12 . 
         [0044]    An annular collar  24  is integrally formed on the outer face  22  of the cylindrical housing  20  at the axial distance n of 23 mm from the upper opening rim  32  of said cylindrical housing. Firstly, a socket-like section  28  of the housing  20  ends at a diametrical plane D determined by the upper (in  FIG. 1 ) annular edge  26  of said annular collar, which socket-like section contains the guide channel  16  and merges at this plane D with a top section  30  of the housing  20 , which top section provides the mentioned opening rim  32 . Secondly, the guide channel  16  opens out into an axial channel  18  so as to form an annular inner step  17  as the opposing stop member for the stop plate  14 , which axial channel  18  acts as an extension of said guide channel, with the length of said axial channel being determined by this axial distance n of the annular collar  24  from the opening rim  32  and with the axial channel  18  running in the top section  30  of the housing  20 . The wall thickness z of 3 mm of the top section  30  is smaller than the wall thickness z 1  of approximately 5 mm of the socket-like section  28 . Moreover, the annular collar  24  has an inclined annular face  25  with respect to the socket-like section  28  in the region of said annular collar which is close to said socket-like section. 
         [0045]    The free end of the socket-like section  28  of the housing  20  is determined by an annular rim  34  with a height i of approximately 4 mm, an inner face  38 , which is inclined at an angle w of approximately 25° towards the longitudinal axis A, emerging from the annular edge  36  of said annular rim  34 . This inner face  38  ends at an end face  40 , which is inclined cross-sectionally with respect to the longitudinal axis A, of the housing socket-like section  28 . 
         [0046]    In  FIG. 1 , a workpiece  50  comprising a metal material is associated axially with the housing  20  or the annular rim  34  thereof. The workpiece in question here is the blank of a blank nut  52  with a hexagonal basic outline with an axial height q (determined by two end faces  54 ,  54   t  of the blank nut  52 ) of approximately 10 mm. A hole channel  58  extends in the workpiece longitudinal axis E between six wall face sections  56  of the blank nut  52  which intrinsically have straight faces. An annular collar  64  with a height q 1  of, for example, 5 mm and a small wall thickness t is integrally formed, axially parallel, on the upper end face  54  (shown in  FIG. 3 ) so as to delimit an inner annular bearing face  55 , the free upper edge  66  of said annular collar  64  having a circular basic outline. 
         [0047]    The pressure plunger  12  of the tool  10  is supplied coaxially to the workpiece  50  which rests on a basic area indicated by Q in such a way that the pressure front end  15  of said pressure plunger  12  matches this bearing face  55 , i.e. its inner diameter t 1  is slightly longer than the diameter d of the pressure front end  15 . When the housing  20  is lowered in the pressure direction P, the inclined inner faces  38  of the annular edge  36  thereof and the adjacent end face  40  deform the annular collar  64  of the workpiece  50  as shown in  FIGS. 5 ,  6  in the course of the cold extrusion process to form a shaped collar  74 , which is curved cross-sectionally towards the axis, with an internal thread  60  being shaped, for example cut, once this shaped collar has been produced in the hole channel  58 ; a fastening screw nut  70  sketched in figures  FIGS. 7 to 10  with a screw socket  72  with the height y, which screw socket provides these axially parallel wall face sections  56 , is thus produced; this hole channel  58  is formed into a screw hole or a threaded bore  62  by means of the internal thread being formed in it. Said screw hole or threaded bore is axially opposite the shaped collar  74  with the upper or outer face  76 , which is curved cross-sectionally towards the axis. This shaped collar is produced when this annular collar  64  is compressed as a result of the cross-sectional deformation thereof and contains a circumferential inner groove as the accommodating slot  78  for an insert ring (not illustrated). Once the internal thread  60  has been formed, the housing  20  or a corresponding tool is pressed onto the annular collar  64  and the latter is deformed slightly towards the internal thread  60 . 
         [0048]    The cross section of the accommodating slot  78 , which runs close to the outer face  76  of the shaped collar  74 , is inclined in figure  FIG. 10  towards its peripheral edges  80  at a flat angle k, but in a different configuration can also run in a diametrical plane of the shaped collar  74 , i.e. without any cross-sectional incline.  FIG. 6  illustrates the end region  81  of the inclined shaped collar  74 , which is subjected to upset forging during the shaping process, as a result of which an upset-forging bead  84  is formed at the free end, which upset-forging bead is cross-sectionally wider than the shaped collar  74  per se; these cross-sectional differences are not reproduced in figure  FIG. 10  for reasons of clarity. 
         [0049]      FIG. 10  shows an outer protrusion  82  of the radial width r between the axially parallel wall face section  56  and the outer face  76  of the shaped collar  74 , which outer protrusion  82  is the section of the mentioned upper end face  54 ; the radial width r shown of the outer protrusion  82  only exists at the axially parallel edges  57  of the wall face sections  56 . 
         [0050]    The above-mentioned insert ring, which is held in clamping fashion in the form of a ring element in the accommodating slot  78  and protrudes towards the axis beyond the peripheral edges  80  and bears, as a retaining and/or sealing member, against a screw pin or the like arranged in a screw hole  62 , is not illustrated. This insert ring is produced from a rigid material or a material which is flexible to a limited extent, depending on the function. 
         [0051]    In the embodiment shown in  FIG. 3  of a blank nut  52 , the annular collar  64  does not have a thread on its inner side facing towards the hole channel  58 . In those embodiments of a ready-machined screw nut  FIG. 7  to  FIG. 10 , on the one hand, and  FIG. 11  to  FIG. 14 , on the other hand, which differ from this latter embodiment, the annular collar has a thread on its inner side facing towards the threaded bore  62 , i.e. in the end region  81 . 
         [0052]    The thread in the end region  81  is offset with respect to the remaining internal thread  60  with a slight offset, in this case 1 to 2 tenths of a millimeter. When the screw nut is screwed on, for example the screw nut from  FIG. 10  or the screw nut from  FIG. 14 , the shaped collar  74  is therefore “bent up” in the opposite direction to the arrow direction denoted by S and, once the correct degree of thread pitch has been reached, snaps into the thread flanks of a bolt or screw thread, but while maintaining a certain stress which is achieved by the offset of the thread which is fitted in the end region  81  of the annular collar  64  which is bent towards the axis and brings about a corresponding spring force acting in the arrow direction denoted by S. A screw connection formed between the screw nut and a bolt or a screw is thereby secured against opening. 
         [0000]    In an embodiment which is developed in comparison with  FIG. 7  to  FIG. 10 ,  FIG. 11  to  FIG. 14  show a screw nut, in the case of which screw nut, which is otherwise as illustrated in the preceding  FIG. 1  to  FIG. 10 , in developed form the annular collar  64  is bent cross-sectionally towards the axis in such a way that the accommodating slot  78  is closed towards the threaded bore  62 . In this case, the peripheral edges  80  of the accommodating slot  78  bear against one another towards the threaded bore  62 . In other words, the accommodating slot  78  has a cross-sectional drop-shaped edging shown in  FIG. 14 , with the result that the peripheral edges  80  running on the accommodating slot  78  are now inclined with respect to one another in accordance with the angle k′, in the development of the angle k in  FIG. 10 . The peripheral edges  80  of the accommodating slot  78  can bear against one another completely towards the threaded bore  62  as a result of the shaped collar  74  towards the inner thread  60  once, as explained, the internal thread  60  has been formed both in the end region  81  and in the remaining screw nut. The subsequent offsetting of the shaped collar  74  is in this case achieved by final bending-in or upset-forging (to a slight extent corresponding to the offset) of the shaped collar  74 . In principle, in the embodiment illustrated in  FIG. 10 , an offset can be designed to be more pronounced, while in the embodiment illustrated in  FIG. 14 , a securing, resilient force can be achieved as a result of the increased bending of the shaped collar  74 . The offset can be in the region of 1 to 2 thread pitches. In the example in  FIG. 10 , the offset is 1.5 thread pitches. In the example in  FIG. 14 , the offset is 1 thread pitch. In the two embodiments, it has proven to be particularly advantageous that the end region  81 , which is adjacent to the accommodating slot, of the shaped collar  74  is thicker than the adjacent cross section thereof, which, as shown in  FIG. 6 , is comparatively thin and can therefore be bent back easily and simplifies the processing and production of the screw. 
         [0053]      FIG. 15  shows an embodiment of a workpiece  50 ′ which has been developed in comparison with that in  FIG. 3 , and this workpiece  50 ′, in the same way as the workpiece  50  shown in  FIG. 3 , can be used as the basis for a screw nut as shown in  FIG. 5  to  FIG. 14 . In the case of the workpiece  50 ′, only sections of the annular collar run along the circumference of the workpiece  50 ′. In this case, three sections  64 ′ are provided which are completely separated from one another by three interruptions in the form of gaps  65  and are integrally formed on the end face  54  of the workpiece  50 ′. 
         [0054]    The sections  64 ′ can be bent towards the axis, as described above ( FIG. 5 ,  FIG. 6 ) in order to obtain a screw nut in accordance with the concept of the invention. 
         [0055]    The spring action of a shaped collar formed from the sections  64 ′ is comparatively smoother and more flexible than that of a shaped collar running along the full circumference as shown in  FIG. 7  to  FIG. 14 .

Technology Classification (CPC): 5