Abstract:
A receiving element which can be introduced into a borehole of at least one component includes a bolt presenting an outer surface that is approximately parallel and advantageously coaxial to a longitudinal axis of the bolt. The receiving element requires few materials and can therefore be produced at a low constructional cost while being provided with high dimensional stability and positioning accuracy. The bold includes an abrasion-resistant sintered material, and a metal tip provided on the front end of the shaft. The end part of the tip is engageable in a recess of the bolt, and there is a direct connection between the end part and the recess in the connection region on the front end of the bolt.

Description:
REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application of Ser. No. 10/593,988, filed Jan. 24, 2007 which is currently pending. The subject matter of the aforementioned prior application is hereby incorporated herein by reference. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The invention relates to a receiving element useful, for example, as a centering pin or receiving pin for centering and receiving components, in particular a plurality of metal sheet parts or at least one metal sheet part having a threaded female element, and more particularly employable in association with welding tools, in particular pressure welding tools, apparatus or machines. 
         [0003]    A receiving element is disclosed in WO 2004/069 468 A1, having a bolt that, in the area of its external surface, which is largely parallel to a longitudinal axis, includes at least two recesses with apertures. Arranged in these recesses are pins that comprise or contain wear-resistant material and that extend somewhat radially through said apertures and project over the external surface with a predefined overhang. Such receiving elements can be introduced into bores of at least one component for fixing and/or aligning for subsequent machining. For instance, if two metal sheets are to be joined to one another by welding, these contain receiving bores that match one another and into which a receiving element of the type cited is subsequently introduced for centering and receiving the metal sheets. Particularly in the case of large components, a plurality of such receiving elements are usefully provided as production or assembly aids. The receiving elements can also be employed as holding pins and/or guide pins in machines, systems, or machining systems for components, these being for instance automatic welding machines, punches, or presses. Production of these previously known receiving elements requires a certain complexity because first the at least two lateral apertures must be added to the bolt, which normally comprises metal, and then the at least two pins, which comprise or contain sintered material, must be introduced into the apertures, whereby in a useful manner in a further machining step, the pins projecting outward from the bolt are machined such that the surface areas of the pins that overhang farthest radially are located on a common surface. Even without performing this latter method step, adding at least two apertures to the bolt and preparing and inserting the two aforesaid pins entails production complexity that is not insubstantial. 
         [0004]    Moreover, a receiving element is disclosed in JP 02 290 696 A that has a sleeve comprising a sintered material, through which a bolt, provided with a tip, passes. The end of the bolt facing away from the tip is provided with a thread that engages in a threaded bore of an element provided with a male thread, the aforementioned sleeve being clamped axially between the bolt tip and the element. The production of the cylindrical sleeve made of sintered material is quite complex in order to avoid radial play in terms of the bolt that passes through and conversely to avoid undesired radial compression and associated waste during production. In addition, this receiving element also comprises at least three parts, specifically sleeve and bolt and the threaded element that has a male thread, and thus the various machining steps being disadvantageous especially during serial production of large numbers of units. 
         [0005]    Based upon the foregoing, the underlying object of the invention is to further develop a receiving element with less structural complexity while avoiding the aforesaid disadvantages such that high dimensional stability and positioning accuracy are assured for a long service life. The production of the receiving element should not require great complexity and/or material consumption, and should be economical to implement. Moreover, it should be possible without significant problem to assure the electrical insulation that is used when the receiving element is used or employed for producing a weld joint, in particular for metal sheet parts and/or one metal sheet part with threaded female elements. Furthermore, the receiving elements should especially be used in welding systems or devices, for example, for producing pressure welded joints. 
       SUMMARY OF THE INVENTION 
       [0006]    The receiving element in accordance with the invention is characterized by a simple and functionally appropriate structure. The bolt comprises wear-resistant sintered materials, preferably oxide ceramics or non-oxide ceramics, for example, Al 2 O 3 , ZrO 2 , or Si 3 N 4 , or mixtures thereof, and contains at a forward end thereof a recess in which a tip, comprising metal, advantageously, for example, steel or high-grade steel, engages and is attached at one end section. In the interior of the bolt, a direct or immediate connection is provided between the tip, via an end section thereof, and the recess, advantageously embodied, for example, as a blind hole, provided in the bolt. The recess, which is preferably coaxial with the longitudinal axis and/or penetrated thereby, permits a lasting and loadable connection in the comparatively short axially forward area of the bolt without a reduction in the cross-section of the bolt, whish is made of the high-performance ceramics or sintered material used, being necessary over the entire axial length. The interiorly situated forward connecting area extends only over a fraction (portion) of the entire length of the bolt, advantageously less than 50%, and more preferably less than 30% thereof. The end section of the tip and/or the forward connecting area possesses an axial length that is substantially smaller than the total length of the bolt. Furthermore, it is particularly important that the interiorly situated connecting area is reliably protected from attack by an environmental medium, for example, steam or aggressive gases. The fastening of the tip or its end section in the axial recess of the bolt is advantageously embodied as an adhesive joint, shrink fit, press fit or clamp connection. Mechanical processing, for example, circular grinding, is used to grind the exterior surface of the bolt embodied from sintered material and/or high-performance ceramics to the required aperture diameter for the component to be processed, in particular metal sheet or threaded female element. 
         [0007]    In contrast to receiving elements with tips made of ceramics, which can break off relatively easily, particularly when they have small diameters, using the metal tip prevents the extremely disadvantageous breakage with a high degree of functional assuredness. Thus components encountered in connection with the invention, in particular metal sheets, can be readily joined to one another using the suggested receiving elements, in particular in welding tools and/or pressure welding tools, even with threaded female elements that are quite small, in particular with M4, M5, M6, or M8 female threads, avoiding failure times and idle times for the welding tools or automatic welding systems and attaining long useful life periods. The bolt is advantageously produced, for example, by dry pressing, extrusion, or in an injection molding process and/or by mechanical processing. The bolt is advantageously embodied as a part, either as tube or bar, and is provided and/or fitted with the metal tip at the forward free end. 
         [0008]    Moreover, in particular for optimizing the insulation, a fastening body made of an insulating material, advantageously, for example, plastic, can be provided at the other end of the bolt from the tip, an adhesive joint, shrink fit, press fit, or clamp connection preferably being provided. By using high-performance ceramics for the bolt in conjunction with the tip made of metal, advantageously steel, and optionally arranging the fastening body made of insulating material at the other end, the inventive receiving element is characterized primarily by the following improved properties: specifically, high wear-resistance and/or extremely long service life and/or good dimensional stability and/or precise positioning accuracy and/or high surface quality and/or optimized electrical insulation. 
         [0009]    The invention is explained in greater detail in the following using the exemplary embodiments depicted in the drawings, without this resulting in any limitation. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]      FIG. 1  is a schematic depiction of an axial section of a first exemplary embodiment according to the invention; and 
           [0011]      FIG. 2  is an axial section of another exemplary embodiment according to the invention having a fastening body made of an insulating material for additional insulation. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]    In accordance with  FIG. 1 , a receiving element comprises a bolt  2 , and a tip  4  that is produced as a separate component having an end section  6  which engages in a recess  8  of the bolt  2  at a forward end of the latter. The bolt  2  comprises or contains wear-resistant sintered material, preferably oxide ceramics, such as, for example, Al 2 O 3  or ZrO 2 , or non-oxide ceramics such as Si 3 N 4 , or mixtures thereof. The forward section  10  of the tip  4  projects axially out of the bolt  2  and presents an exterior surface  12  that is at least approximately and/or largely conical. In the exit area from the bolt  2 , the tip  4  or the forward section  10  thereof includes a maximum external diameter  14  that is smaller by a prescribed amount than the external diameter  16  of the bolt  2  or the exterior surface  18  thereof. The recess  8  in the forward end of the bolt  2  is preferably embodied as a blind hole, and the end section  6  extends axially over only a fraction of the entire length of the bolt  2 . 
         [0013]    The exterior surface  18  runs largely parallel to the longitudinal axis  20  of the bolt or the entire receiving element and is advantageously embodied as a cylindrical exterior surface that is coaxial with the longitudinal axis  20 . Alternatively, the exterior surface  18  can have a polygonal exterior contour. As can be seen, a transition area  22  that tapers toward the end section  6  is present between the forward, advantageously conical, end section  6  and the exterior surface  18  of the bolt  2 . While the transition area  22  is optionally a component of the bolt  2 , the transition area  22  can alternatively also be a component of the tip  4 . The receiving element includes a stepped exterior contour with the forward section  10  of the tip  4  projecting out of the bolt  2 , the maximum external diameter  14  being substantially smaller than the external diameter  16  of the bolt. The transition area  22  presents a substantially smaller axial extension than the end section  6 . Moreover, the takeout angle or cone angle of the transition area  22  is preferably substantially larger than the takeout angle or cone angle of the end section  6 . 
         [0014]    Due to the substantially smaller external diameter  14  of the forward section  10  relative to the external diameter  16  of the bolt  2  and/or due to the transition area  22  according to the invention, certain introduction of the receiving element into an associated bore of the components to be centered by virtue of the receiving element, especially metal sheet and threaded female element, is assured. 
         [0015]    The tip  4  comprises metal, advantageously steel or high-quality steel, so that, even when the external diameters of the receiving element and the bolt  2  are quite small, the tip  4  will not be damaged or broken off and/or a long service life or useful life is attained for the receiving element. 
         [0016]    In a particularly advantageous embodiment, the direct connection of the tip  4  or the end section  6  thereof in the correspondingly embodied recess  8  is provided as an adhesive joint, shrink fit, press fit, or clamp connection. The recess  8  is advantageously coaxial with the longitudinal axis  20 . For precise axial positioning of the tip  4  in the bolt  2 , a step  24  is present between the axially projecting forward section  4  and the end section  6  arranged in the recess  8 , such that the maximum external diameter  14  of the forward section  10  is larger by a prescribed amount than the external diameter  26  of the end section  6 . The step  24  thus forms a defined stop, in particular during insertion and/or when producing the connection between the bolt  2  and the tip  4 , which provides exact axial positioning and ultimately a defined axial length of the entire receiving element. Moreover, impermissibly high loading or even destruction of the connection between the tip  4  and the bolt  2  is avoided by virtue of the step  24 . 
         [0017]    The bolt  2  contains a fastening body  30  at an end facing away from the tip  4  for placing the receiving element in a tool, for example, a pressure welding tool. The fastening body  30  contains a flange, advantageously embodied as a radial extension for placement in the tool. As noted above, the receiving element is preferably embodied as a centering pin or receiving pin, and is used for centering and receiving components, in particular a plurality of metal sheet parts or at least one metal sheet part having a threaded female element. Furthermore, the receiving element is provided primarily for employment and/or use in welding tools, in particular pressure welding tools or apparatus or machines. Moreover, the inventive receiving element is characterized by relatively small external dimensions. Thus, the external diameter  16  of the bolt  2  is largely in the range of 3 to 12 mm, preferably 3.5 to 10 mm, and in particular from 4 to 8.5 mm. Thus, when using the inventive receiving element, even very small threaded female elements having internal diameters of M4 or M5 or M6 or M8 threads can be centered by means of the receiving element or received thereby and in associated machines or tools, such as, for example, pressure welding machines, can be joined to metal sheet parts, whereby even with such small radial dimensions, the tip is prevented with certainty from breaking off due to the suggested embodiment of the metal tip  4  and its integration into the bolt  2  made of high-performance ceramics and/or wear-resistant sintered material and ultimately high functional security and/or service life is attained. 
         [0018]      FIG. 2  illustrates another exemplary embodiment, according to which the fastening body  30  is not an integral component of the bolt  2  but rather is joined to the bolt  2  as a separate component. The fastening body  30  comprises a special electrically insulating material, for example, plastic, in order to assure additional and/or improved electrical insulation of the receiving element with respect to the tool, in particular a pressure welding tool. As can be seen, at a back end, the bolt  2  contains a second recess  32  in which a connecting section  34  of the fastening section  30  engages. The connecting section  34  is joined in the second recess  32  by an adhesive joint, shrink fit, press fit or clamp connection. Furthermore, the fastening body contains a radial expansion and/or a flange  36 , the external diameter of which is greater than the external diameter of the bolt  2 . A step is present between the connecting section  34  and the flange  36 , which serves to provide defined placement and/or axial alignment of the fastening body  30  with respect to the bolt  2 . As in the exemplary embodiment in accordance with  FIG. 1 , between the two recesses  8  and  32  the bolt  2  contains a massive intermediate area  38  that assures high stability and/or strength of the bolt  2  and thus of the entire receiving element. 
         [0019]    Alternatively, in the framework of the invention, the bolt  2  can have a single central recess that extends across the entire axial length. If, corresponding to  FIG. 2 , a separate fastening body  30  is provided at the back end, however, there is no immediate axial connection between the tip  4  arranged at the forward end and the fastening body  30  and consequently axial connecting forces between the tip  4  and the fastening body  30  are avoided in an advantageous manner. It is hereby also further stated that an interiorly situated recess can extend axially through the entire length of the bolt, including the integrally formed connecting body thereof, as well, alternatively to the embodiment in accordance with  FIG. 1 . However, the connecting area in such an embodiment is provided solely on the forward end of the bolt  2 . 
       LEGEND 
       [0020]      2  Bolt 
         [0021]      4  Tip 
         [0022]      6  End section of  4   
         [0023]      8  Recess in  2   
         [0024]      10  Forward section of  4   
         [0025]      12  Exterior surface of  6   
         [0026]      14  Maximum external diameter of  6   
         [0027]      16  External diameter of  2   
         [0028]      18  Exterior surface of  2   
         [0029]      20  Longitudinal axis 
         [0030]      22  Transition area 
         [0031]      24  Step between  4  and  6   
         [0032]      26  External diameter of  6   
         [0033]      30  Fastening body 
         [0034]      32  Second recess in  2   
         [0035]      34  Connecting section of  30   
         [0036]      36  Flange of  30   
         [0037]      38  Massive intermediate area of  2