Patent Publication Number: US-2023158600-A1

Title: Device for setting a connecting element

Description:
This patent application is the national phase entry of PCT/EP2021/060275, international application filing date Apr. 20, 2021, which claims the benefit and priority of and to German patent application no. 10 2020 110 855.9, filed Apr. 21, 2020. 
     PCT/EP2021/060275, international application filing date Apr. 20, 2021 and German patent application no. 10 2020 110 855.9, filed Apr. 21, 2021 are incorporated herein by reference hereto in their entireties. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention relates to a device for setting a connecting element. 
     In a manner known per se, a device for setting a connecting element with a top-side drive structure comprises a feed device for applying an axial force. Via the feed device, a contact force is applied to a rotary spindle and a drive bit connected to the latter for moving them in the setting direction. In particular, in the device according to the invention, the force applied to the screw, and thus to the connecting element, is more than 1.5 kN. The drive bit has drive structures arranged circumferentially and at the end in a setting direction in order to interlockingly cause the connecting element to rotate. Furthermore, the drive bit has an axial through-opening which is used for suctioning in the connecting element into place. 
     EP 2 632 629 B1 for example discloses the use of negative pressure for holding connecting elements temporarily on the rotary spindle. 
     In connecting elements that have small drive structures and that are coated, material may be abraded from the coating and deposit on the drive structures, causing unevenness, as a result of which the drive of the connecting element and the drive structures on the drive bit will no longer engage reliably. In cases where the connecting element is held in place by negative pressure, this thus means that sufficient negative pressure will not be reliably achieved. For this reason, parts that lack the required high manufacturing quality cannot be processed and must be rejected or will cause a defect during processing. 
     DE 10 2018 103 991 A1 proposes detecting the position of the drive element in the setting device. 
     SUMMARY OF THE INVENTION 
     It is the object of the invention to provide a device for setting a connecting element, which enables its reliable retention on the drive bit of the device, which permits higher tolerances or surface non-uniformities in the processing of coated connecting elements and thus provides a higher degree of error free operation in industrial manufacturing equipment. 
     According to the invention, the device comprises an insert element that has a suction surface on its end side which comes to rest against the head of the connecting element and delimits a suction cross-section circumferentially, which insert element is designed in such a way that the suction surface can move relative to the drive bit in the axial direction. 
     Furthermore, the insert element is designed in such a way that a negative pressure can be transmitted from the side of the insert element facing away in the setting direction to the suction surface of the insert element, wherein, before the suctioning of a connecting element, the suction surface adopts a first end position which is spaced apart in the setting direction from the through-opening end-side edge region that is adjacent to the suction surface. 
     In this way, the connecting element can be reliably suctioned onto the insert element and thus onto the drive bit, even if there is unevenness in the coating of the connecting element, particularly in the drive structures. 
     This ensures reliable retention of the connecting element because the suction surface will only come into contact with an unstructured area of the connecting element adjacent to the connecting element drive structures. Generally, the unstructured areas of the connecting element only exhibit minor to no unevenness caused by the coating. 
     Subsequently, the suction surface can then be moved axially relative to the drive bit so as to cause the drive structures to fully engage the connecting element. This is done in particular when the connecting element is placed on the component, preferably by applying a contact pressure to the suction surface in an axial direction opposite to the setting direction. 
     This reliably holds the connecting element is in place on the insert element until after the connecting element is placed on a top component layer, after which the connecting element can be inserted into the component by rotating it and exerting an axial force on it. 
     The suction pressure with which the connecting element is suctioned onto the insert element, and thus onto the drive bit, is in particular at least 0.3 bar. This preferably results in a negative pressure of between −0.3 bar and −0.85 bar. 
     Preferably, the drive bit can have a surface, in particular a flat surface, for transmitting the axial force required for performing the friction element welding process to the connecting element. As an alternative, the axial force can also be applied via the insert element. 
     In another embodiment of the invention, the drive structure may be a drive for an external drive, in which case the suction surface is located radially inside the drive structures. 
     As an alternative, the end-side drive structure of the drive bit may be a drive structure for an internal drive, in which case the suction surface is adjacent to or outside the drive structure. 
     Preferably, the insert element may comprise a sleeve which is held so as to be movable in an axial direction relative to the drive bit. The sleeve has a first contact surface, while the drive bit has a second contact surface. The second contact surface is designed to correspond to the first contact surface in such a way that, when the suction surface is in a predefined end position with respect to the drive bit, in particular projecting slightly in the setting direction, the contact surfaces interact in a sealing manner in such a way that a negative pressure can be transmitted through the sleeve. 
     This can preferably be implemented in that the contact surface on the sleeve is designed as a collar and the contact surface on the drive bit is designed as a shoulder, with the collar and shoulder extending transversely to the setting direction. This, on the one hand, allows a sealing arrangement to be created in that the contact surfaces of collar and shoulder rest against one another, and on the other hand, a stop can be provided between collar and shoulder which limits axial movement between sleeve and drive bit in the selling direction and thus provides a defined end position. 
     Preferably, the insert element can be designed in such a way that a spring preload in the setting direction presses the sleeve against the shoulder in the drive bit. In this way, the contact surfaces of collar and shoulder are actively pressed against each other, resulting in an improved sealing effect. In addition, such an arrangement ensures that, due to the spring preload of the sleeve for the suction process, the suction surface is reliably held in the defined end position relative to the drive bit, even if, for example, the setting direction is opposite to the direction of the gravitational force. 
     This allows the radial clearance of the sleeve relative to the drive bit to be made larger, which in turn improves the reliability of axial movement, as sufficient sealing is reliably achieved at the contact surface between collar and shoulder in an axial direction. 
     The spring preload is preferably generated by a spring arrangement, which spring arrangement comprises at least one spring that is supported on a spring seat which is arranged in a stationary manner with respect to the drive bit. 
     In particular, the spring arrangement may comprise a disk spring assembly or a spiral spring. 
     The spring seat may be provided by the rotary spindle, with the drive bit being screwed to the rotary spindle. 
     The spring seat can also be provided by an insert sleeve which is inserted in a fixed position in the drive bit by means of an interference fit, for example. The insert sleeve can also be connected to the drive bit by a transition fit, in particular an H7/m6 fit. 
     Preferably, the drive bit and the insert sleeve are matched to one another in such a way that the friction spindle connected to the drive bit supports the insert sleeve during the joining process, with the insert sleeve being supported against a shoulder in the drive bit in the setting direction. This permits a plug connection from the drive bit to the friction spindle, which allows replacement of the spring-loaded sleeve in the drive bit as an assembly, while the process forces are still transmitted from the spindle to the drive bit. 
     The preload is preferably selected such that the contact pressure from shoulder to collar will be sufficient to achieve the contact pressure for the required negative pressure, but that it will always be smaller than the smallest axial force occurring during the joining process. This is regularly achieved using a force of less than 1 kN, in particular a force of between 5 N and 100 N, to ensure that the drive bit will transmit the axial process forces. 
     The insert element with its sleeve are matched to the drive bit in such a way that the drive bit, which has a contact surface for transmitting the process force, will transmit more than 90% of the process force via the contact surface of the drive bit during the setting process. 
     In another preferred embodiment of the invention, the sleeve may have a stop located opposite to the setting direction, which stop comes into contact with the rotary spindle and/or the insert sleeve. 
     This allows the process force to be transferred in full or in part to the suction surface of the sleeve. The suction surface thus also serves as a pressure surface for transferring the process forces in full or in part required for the joining process. 
     The drive bit and the length of the sleeve, and the extent of the axial displacement of the sleeve, are matched to one another in such a way that, when the sleeve is in the stop position opposite to the setting direction, the drive structures of a connecting element and the drive structures of the drive bit will interlock and engage each other, but the axial process forces will be transmitted via the sleeve. 
     The stop lying opposite to the setting direction can be designed as a sleeve section, which is designed to have a larger diameter than the end-face diameter on the suction surface, with the transition from the larger to the smaller diameter being stepped, thus forming a shoulder. In particular, a spring is inserted inside the sleeve section with the larger diameter, which sleeve is supported against the shoulder in the setting direction and against the spring seat element in the direction opposite to the setting direction. 
     In yet another embodiment of the invention, the stop lying opposite the setting direction may be designed as a sleeve section having the same diameter as the end-face diameter. On the sleeve, a collar is provided which extends around the sleeve and on which the spring is supported, with the sleeve preferably passing through the spring. 
     A particularly preferred embodiment of the invention may provide for the contact surface lying opposite the setting direction to be of a perforated design, since the sleeve has radial recesses at the sleeve end facing the spring seat element. This ensures that dirt entering into the insert element will not settle on the stop surface This also ensures that the coordination of sleeve length and extent of axial travel will not be impaired. 
     Additional advantages, features and possible applications of the present invention may be gathered from the following description in which reference is made to the embodiments illustrated in the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In the drawings, 
         FIG.  1    is a sectional view of a first embodiment according to the invention; 
         FIG.  2   a    is a sectional view taken at the drive bit; 
         FIG.  2   b    is a sectional view similar to that of  FIG.  2   a   , in which the connecting element is pressed against a component layer; 
         FIG.  3   a    is a sectional view of the drive bit through the drive structure in the suctioning position; 
         FIG.  3   b    is a detail according to  FIG.  3   a    in a working position according to  FIG.  2     b;    
         FIG.  4    is a view of another embodiment according to the invention; 
         FIG.  5    is a sectional view of another embodiment according to the invention; 
         FIG.  6    is a sectional view of yet another embodiment, a sleeve; 
         FIG.  7    is a sectional view of yet another embodiment, a sleeve; 
         FIG.  8    is a sectional view of another embodiment of the drive hit according to the invention; 
         FIG.  9   a    is a sectional view of another [. . . ] for processing a connecting element with an internal drive; 
         FIG.  9   b    is a view of a corresponding projection in the setting direction of the sleeve with respect to the drive bit, and 
         FIG.  9   c    is a sectional view taken along line C-C of  FIG.  9     a.    
     
    
    
     DESCRIPTION OF THE INVENTION 
       FIG.  1    is a schematic view of a device  10  according to the invention for setting a connecting element  100  with a top-side drive structure  22 , comprising a feed device  12  for applying an axial force, a rotary spindle  14  and a drive bit  20  connected thereto, which has drive structures  22  arranged circumferentially and at the end in a setting direction S in order to interlockingly cause the connecting element  100  to rotate. Furthermore, the device  10  comprises a suction unit  18  with which air can be suctioned out at the end side of the drive bit  20 . This makes it possible to suction a connecting element  100  onto the end side of the drive bit  20 . Once the connecting element  100  has been suctioned into contact, it is moved downwards in the setting direction S and is introduced into the component assembly  110 ,  112  by rotation of the rotary spindle  14  and under contact pressure generated by the feed device  12 , with the result that in particular the top component layer is penetrated by the connecting element  100 , and further the connecting element  100  is friction-welded to the bottom component layer  112  by means of the frictional energy introduced. In the case illustrated here, the feed device  12  is moved with respect to a counter-hold  120 , with component layers  110  and  112  resting on said counterhold  120  during the joining process. Usually, a hold-down device may also be provided for clamping the component layers  110 ,  112  in place, which hold-down device is not explicitly shown in this case. 
     According to the invention, an insert element  24  is provided which has a suction surface  26  on its end face, which circumferentially delimits a suction cross-section  30 , with said insert element  24  being configured such that the suction surface  26  can be moved in the axial direction relative to the drive bit  20 . 
     Negative pressure is transmitted from the side of the insert element  24  facing away in the setting direction S to the suction surface  26  of the insert element  24 , which suction surface  26  adopts a first end position which is spaced apart from the end-side edge region of the through-opening in the setting direction S before a connecting element  100  is being suctioned into contact. During the setting process, the insert element  24  is displaced by an extent E into a second position that is spaced apart from the first position in a direction opposite to the setting direction S. 
     Different variants of the drive bit  20  in different embodiments of the insert element  24  will now be described with reference to  FIGS.  2  to  9     c.    
       FIG.  2   a    is a sectional view taken at the drive bit  42  of a first embodiment of a setting device according to the invention. 
     The setting device includes the rotary spindle  40 , which rotates a connecting element  100  and which is used to impart the contact pressure required for making the connection. 
     In the present embodiment, a drive bit  42  is screwed onto the rotary spindle  40 . The drive bit  42  and the rotary spindle  40  are provided with a central duct  46 , via which a suction effect can be generated at the front end of the drive bit  42  by means of a suction unit  18 , for example a suction pump or a Venturi nozzle. 
     An insert element  50  is inserted into the drive bit  42 , which comprises a sleeve  52  that has an annular suction surface  54  on its end face and which conveys the suction pressure to a connecting element  100  resting against the suction surface  54 . The insert element  50  further comprises a spring  56 , in particular a spiral spring, which is arranged between rotary spindle  40  and sleeve  52  in such a manner that sleeve  52  is preloaded in the setting direction S. 
     The sleeve  52  and the recess in the drive bit  42  are matched to one another in such a way that the sleeve  52  is mounted so as to be movable in the axial direction, but a first stop is formed which sets the maximum length A by which the sleeve  52  projects beyond the pressure surface  48 . 
     The fact that there is a projection length A in a suction position makes for good contact of the suction surface  54  with the head surface of the connecting element  100 , as any skewing of the connecting element  100  due to coating buildup in the drive structures  22  of the connecting element  100  is avoided. 
     Furthermore, the end of sleeve  52  lying opposite the setting direction S is aligned with drive bit  42  and rotary spindle  40  in such a way that sleeve  52  will abut against rotary spindle  40  when the suction surface  54  is at the level of the pressing surface  48  of drive bit  42 . 
     The stop is designed in such a way that the distance B in the suctioning position is at least as large as the projection length A. This ensures that substantial parts of the contact pressure are transmitted to the connecting element  100  via the drive bit  42 . 
     If distance B is equal to projection length A, contact pressure transmission can also be partially effected from the rotary spindle  40  to the connecting element  100  via the sleeve  52 . 
       FIG.  2   b    illustrates the arrangement according to the invention of  FIG.  2   a    when the connecting element  100  is being pressed against a component layer  110 ,  112 . In this situation, sleeve  52  is displaced against the spring force of spring  56  until the suction surface of sleeve  52  is flush with the pressure surface  48  of drive bit  42 . If the pressing force is not to be transmitted via sleeve  52 , sleeve  52  and the recess in drive bit  42  are matched in such a way that sleeve  52  will not abut against the rotary spindle in the pressed-on state. 
     Otherwise, in a coordinated arrangement in which sleeve  52  abuts against rotary spindle  40  when the suction surface  54  of sleeve  52  is flush with the pressure surface  48  of drive bit  42 , the pressure force can also be transmitted partially via the suction surface so that overall, a larger force transmission surface is available. This reduces the creation of impressions on the head of the connecting element  100 , which in particular preserves the coating of the element provided for corrosion prevention. In this case, the advance amount C corresponds to the projection length A. 
       FIG.  3   a    is a sectional view of the drive bit through the drive structure in the position where it is suctioned into contact. From this illustration, it can be clearly seen that there is a distinct distance D between the drive structures of drive bit  42  and the drive structures of connecting element  100 , so that any excess coating deposited on the drive structures will not affect the position of the connecting element  100  in relation to the drive bit  42 . 
       FIG.  3   b    is a detail of  FIG.  3   a    in a working position according to  FIG.  2   b   . It can be clearly seen in this view that, in the working position, the drive structures of drive bit  42  and the drive structures of connecting element  100  interlock and engage each other. The distance D is significantly smaller here than in  FIG.  3     a.    
       FIG.  4    is a view of a yet another embodiment of the invention, in which the insert element is configured as a circumferentially closed element that is elastic in an axial direction, in particular is designed as an O-ring  62 , which elastic element is inserted into the drive bit  60  on the end face. 
     The elasticity and the element cross-section of the elastic element are matched to one another in such a way that, in the case of an extended cross-section, the suction surface will be spaced a defined distance in the setting direction from the pressure surface of drive bit  60 , and that, when the connecting element  100  is pressed into contact by the process force, the insert element will be compressed in such a way that the pressure surface of drive bit  60  will bear against the head of connecting element  100 , and the insert element will be at the same level as the pressure surface of drive bit  60 . 
     The defined distance is selected in such a way that the drive structures of drive bit  60  and of connecting element  100  just barely will not interlock, as is also shown in  FIGS.  3   a   ,  3   b.    
     The elastic element preferably has a Shore hardness of between  50  and  120  Shore A. 
     This embodiment has the advantage that the insert element does not have to comprise any moving parts, but axial displacement of the suction surface is achieved exclusively via the elastic deformation of the insert element. 
       FIG.  5    is a sectional view of another embodiment of the invention, in which drive bit  70  has been screwed in place on rotary spindle  68 . An insert element  72 , which comprises a sleeve  74  and a spiral spring  76 , is inserted into the drive bit  70  so that it can move axially. The design with regard to the axial stops essentially corresponds to the design illustrated in  FIG.  2   . In contrast to  FIG.  2   , the width of suction surface  26 , which is designed as an annular surface, is selected to be significantly larger, so that the process forces are essentially transmitted to connecting element  100  via insert element  72 , i.e. in particular via sleeve  74 . The length of the sleeve and the distance of the head contact area on drive bit  70  are of equal length in this case. As already described with regard to  FIG.  2   , spiral spring  76  ensures axial positioning of sleeve  74  in the suctioning position, when sleeve  74  is not loaded from the outside. 
       FIG.  6    is a view of another embodiment of a sleeve  84 , which has its stop on rotary spindle  82  in the form of a continuous sleeve  84  that has a collar  88  which extends radially outward. A spring  86  lies over the upper end of sleeve  84  and is supported on rotary spindle  82  and on collar  88 . On its side facing away from the spring, collar  88  forms the stop surface on drive bit  80 , which determines the projection length C in the suctioning state. 
       FIG.  7    is a view of a particularly preferred design of a sleeve  90  that can be used in one of the Figures described above with slight modifications, namely in that the sleeve end  92  facing the rotary spindle has recesses  96 , in particular, circumferential recesses  96 . As a result, dirt suctioned in by the sleeve due to the suction effect, will not be deposited between sleeve  90  and the friction spindle, but will be able to enter the intermediate spaces formed by recesses  96 . This largely prevents an accumulation of dirt between sleeve  90  and rotary spindle from causing a displacement of the position of the stop in an axial direction. 
       FIG.  8    is a view of another embodiment of the invention which differs from the examples described above in two aspects, namely that, firstly, sleeve  152  exerts a stop exclusively against spring  156 , and, secondly, that drive bit  142  has a stop surface  144  for insert element  150 , so that drive bit  142  and insert element  150  can be mounted and dismounted together as an assembly on the rotary spindle  140 . 
     Preferably, the stop surface is the front-end surface of a thrust piece  144  which is pressed into drive bit  142 , in particular in a transition fit. Drive bit  142  additionally has latching means which can be connected to latching means of rotary spindle  140  in such a way that a rotary movement can be transmitted and the front end of rotary spindle  140  will bear against thrust piece  144 . Preferably, thrust piece  144  rests against a shoulder of drive bit  142  in the setting direction. This makes it possible to transmit the process force to drive bit  142  in a form-fitting manner. 
     In this manner, a quick-release means is created that allows easy replacement of the insert elements  150  in the event of wear or damage. 
     Spring  156  may be dimensioned such that when the suction surface is level with drive bit  142 , sleeve  152  will be fully compressed against either spring  156 , thereby partially transmitting process forces to connecting element  100  via sleeve  152 , or the spring will not yet be fully compressed, so that only the spring force will act on connecting element  100  via sleeve  152 . 
     The design of insert element  156  can be combined as desired with the other designs of insert element  150  described herein. 
       FIG.  9   a    is a view of another alternative embodiment in which a connecting element  300  is processed with an internal drive. In this connecting element, the pressure area and the suction area are provided externally of the internal drive, with the process force being imparted via sleeve  252 . Accordingly, sleeve  252  abuts on a rotary spindle receiving member  246  when drive bit  242  is fully engaged with the drive of connecting element  300 . As has also been described previously, the projection in the suction position is provided by a spring  256 , which is in particular a spiral spring. 
     A plurality of suction channels  248  are formed in drive bit  242 , each of which merges with suction ducts  258  formed in sleeve  252 . This makes it possible to suction connecting element  300  into place. 
     The sectional view is illustrated in more detail in  FIG.  9     c.    
       FIG.  9   b    shows the corresponding projection A in the setting direction of sleeve  252  relative to drive bit  242 . In this way, the internal drive of connecting element  300  is not yet fully engaged when the connecting element has been suctioned into place. 
       FIG.  9   c    is a sectional view taken along line C-C of  FIG.  9   a   . Here, suction ducts  258  of sleeve  252  are distributed along a circular ring on the pressing surface of sleeve  252 . Drive bit  242  is disposed centrally within sleeve  252  which is adapted to be movable axially relative to drive bit  242 .