Abstract:
The apparatus for fixing rivets ( 4 ) in structural parts ( 11 ) includes a positioning adapter ( 3 ) for fixing one end of a rivet in a structural component with the rivet ( 4 ) in a riveting position; a riveting adapter ( 5 ) for deforming another end of the rivet, which has a movable deforming device ( 34 ) for deforming the rivet by impact energy stored in it; and a device for changing or adjusting the impact energy ( 33 ) stored in the movable deforming device. A greater flexibility for adjustment of the required impact energy ( 33 ) to different boundary conditions is thus possible, which guarantees that a minimal number of working strokes or only a single working stroke is required to fasten a rivet ( 4 ) in a structural component ( 11 ). This reduces the mechanical stress on the riveting adapter ( 5 ) and the working robot ( 6 ) guiding it besides reducing the noise level.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for fixing rivets in structural components, which has a positioning adapter for fixing one end of a rivet in a riveting position in a structural component, a riveting adapter for deforming the other end of the rivet, which has a movable deforming device for deforming the rivet by means of impact energy stored in it. 
     According to the state of the art there are very many different mechanisms for insertion and fixing fastening elements, such as rivets, in a structural part. Thus, for example, DE 43 05 406 A1 discloses a so-called screw insertion and flattening system whose driving device inserting the respective fastening element in the structural part can be moved back and forth in horizontal guidance. The driving device thus should be designed so that the fastening elements can be reliably inserted in the hole in the structural part while maintaining a predefined press fit and can then be deformed. For this purpose a system is used, in which a very great eddy current is produced in a short time, which accelerates the driving device carrying the fastening element to be inserted into the structural part so that the fastening element is reliably inserted in the structural part. However this sort of apparatus has the disadvantage that very great stresses are put on the mounting system, which are frequently beyond the forces required for reliable insertion of the fastening element in the structural part. This has the result that either the service life is considerably limited or these stresses must be handled by over-dimensioning of parts. 
     Also so-called rivet hammer and rivet tongs are widely used for inserting and fixing fastening elements, such as rivets, in component parts. This sort of system is generally driven by pressurized air. The moving deforming or connecting device introducing the fastening element into the component part and fixing it in it is engaged with the fasting element until it has achieved the desired fixed or fastened position. Besides the inaccuracy of the assembly due to repeated contacts on one and the same fastening element, especially this sort of system has the disadvantage that it generates loud noise. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an apparatus for attaching structural components to each other, which permits precise and quiet connection of the structural components to each other. 
     This object and others, which will be made more apparent hereinafter, are attained in an apparatus for fixing rivets in structural components, which comprises a positioning adapter for fixing one end of a rivet in a structural component with the rivet in a riveting position and a riveting adapter for deforming another end of the rivet, which has a movable deforming device for deforming the rivet by means of impact energy stored in it. 
     According to the invention the apparatus includes means for changing or adjusting impact energy of the movable deforming device on the rivet. 
     Since the impact energy of the movable deforming device is changeable, great flexibility in adjustment of the obtainable impact energy to different boundary conditions is possible, which guarantees that a reduction in the working strokes is obtained; in the best case only a single working stroke is required for deformation of the rivet in the structural components to be connected. Above all, this reduces the mechanical stresses on the riveting adapter and the working robot guiding it, besides reducing operating noise. 
     In the simplest case the impact energy can be influenced by the following parameters: acceleration of the movable deforming device and the length of the acceleration path of this deforming device or its mass. Only one or all of these parameters should be considered, depending on the desired adjustment flexibility. Because these parameters are changeable in a simple manner, the adjustment of the impact energy of the movable deforming device is not complicated. 
     An especially advantageous embodiment of the invention results when the impact energies are determined according to the specific properties of the rivet element and/or the position of the riveting adapter in space, since these parameters immediately influence the required values of the deforming energy and thus the impact energy to be generated. 
     When the movable deforming device is arranged horizontally movable within the riveting adapter, precise acceleration of a definite deforming mass is possible in a structurally simple manner, so that the impact energy is precisely adjusted. Based in part on the very high acceleration it is of special interest to guarantee as compact as possible a shape for the deforming device or mass element to be accelerated. This is achieved in a simple manner when the deforming device comprises an additional weight, a ram deforming the rivet associated with it and at least one carriage movable horizontally on which the latter elements are mounted. 
     So that recoil and thus repeated impacts of the ram on the rivet are avoided after a first contact of the ram with the rivet, the riveting adapter has a clamping unit, which causes a definite delay of the linear motion of the deforming device after it traverses the acceleration path and also brakes the motion of the movable deforming device after contact with the rivet. The braking of the linear guidance device and the movable deforming device can occur as simply as possible by pneumatic clamping means. 
     So that a precise position of the movable deforming device for setting a definite path over which the deforming device is accelerated is possible, the deforming device is driven by electrically driven linear motors in the horizontal direction within the riveting adapter in a preferred embodiment of the invention. 
     A simple adjustment of the length of the acceleration path is then possible when a linear guide system is associated with the movable deforming device, whose displacement measuring system is formed by a ruler or scale detectable by means of a sensor. The ruler or scale in the simplest case is directly integrated in the guide rails for the movable deforming device. 
     Because the horizontal component of the force of gravity acting on the deforming device acts either in or against the direction of the rivet according to the orientation of the riveting adapter, a precise adjustment of the impact energy requires information regarding the momentary orientation of the riveting adapter. In the simplest case this sort of information can be obtained when a position sensor constructed as an inclination sensor is mounted on the riveting adapter or on a segment of the working robot on which the riveting adapter is mounted. 
     Because of the complex relationship between the parameters influencing the impact energy it is appropriate to provided a control and processing unit for the riveting adapter, in which an editable executable computational algorithm or algorithms are stored, which determine the required value of the impact energy and the variables of the individual parameters, such as the mass of the movable deforming device, its acceleration and the length of the path over which the acceleration takes place. 
     In an advantageous further embodiment of the invention the control and processing unit is thus constructed so that the output signals generated in it cause the adjustment of the various parameters in the riveting adapter under consideration of different input data. 
     For improved monitoring of the running process the control and processing unit can have an associated display monitor so that the operator of the riveting station can visually display the various input data for the system as well as the calculated output data. 
     It is also advantageous when the riveting adapter is formed as end effecter of a working robot, so that it can be integrated in an existing production line without problems. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
       The objects, features and advantages of the invention will now be illustrated in more detail with the aid of the following description of the preferred embodiments, with reference to the accompanying figures in which: 
         FIG. 1  is a perspective view of the riveting station according to the invention; 
         FIG. 2  is a detailed side view of the riveting adapter according to the invention; 
         FIG. 3  is a perspective view showing the action of gravitational forces on the riveting adapter in different working positions; and 
         FIG. 4  is a diagrammatic view showing the determination of parameters in the riveting adapter according to the invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a riveting station  1 , which comprises a first working robot  2  with a pivoting positioning adapter  3  for preferably rivets  4  and an additional working robot  6  for guiding the riveting adapter  5  according to the invention. In a known manner the segments  7 ,  8  of the working robots  2 ,  6  pivot arbitrarily on pivot axes  9 ,  10  through space, so that the positioning adapter  3  and the riveting adapter  5  guided by the respective working robots  2 ,  6  can take arbitrary positions within the working areas of the working robots  2 ,  6 . The working areas of both working robots  2 ,  6  are adjusted relative to each other, so that they can cooperate at least in part of the regions covered by their action radii. The structural components  11  to be connected together are arranged in these regions in the riveting station  1 , so that the positioning adapter  3  and the riveting adapter can work together to insert and fasten the rivet  4  in the structural components  11  to be attached to each other. 
     The positioning adapter  3  arranged to pivot on the front end of the segment  7  of the first working robot  2  can be constructed in a way that is known and not described in further detail, so that a front end of the adapter unit  12  can hold or mount both the tool  13  for working or making holes  14  in the components  11  to be connected and also the rivets  4  for fastening the components  11  to each other. Usually the adapter unit  12  is provided with suitable tool and connecting element storage (not shown), from which different tools  13  are taken and returned to it and various quite different rivets  4  can be supplied to the adapter unit  12 . In the illustrated embodiment a rivet  4  would be conveyed to the adapter unit  12  of the positioning adapter  3 , which would insert it into one of the holes  14  through the structural components  11  to be connected by pivoting the segment  7  of the working robot  2 , so that the head  15  of the rivet  4  is flush with structural component  11  facing the positioning adapter  3 . In other embodiments the adapter unit  12  can have or mount several rivets  4  simultaneously, so that several rivets  4  can be inserted in appropriate holes  14  at the same time and can be fixed in position. Furthermore it is also conceivable that the segment  7  of the working robot  2  on which the positioning adapter  3  is mounted in its working position are fixed in position and only the adapter unit  12  is movable, for example, horizontally, so that first the tool  13  can make or work on the hole  14  and then the rivet  4  can be inserted in it. 
     If one or more rivets  4  are inserted in the components  11  to be connected by means of the adapter unit  12  of the positioning adapter  3 , in the next step according to the invention and in a manner still to be described in more detail the rivet  4  is deformed and thus the components  11  are fastened together. The riveting adapter  5  is guided by pivoting the segment  8  of the working robot  6  carrying the riveting adapter  5  about the respective pivot axes  10  toward the respective rivet  4 . 
     According to  FIG. 2  the riveting adapter  5  includes a supporting framework  16 , which in the simplest case is connected in a non-rotatable manner with the adapter flange  17  of the front segment  8  of the appropriate working robot  6 , so that the riveting adapter  5  can be guided by pivoting the individual segments  8  of the working robot  6  about the respective pivot axes  10  precisely in a working region of that working robot  6 . Positioning means  19  constructed as pneumatic cylinders  18  are mounted non-rotatably on the supporting framework  16  of the riveting adapter  5  in its outer peripheral region. The ends of the piston rods extending from the pneumatic cylinders  18  are attached to an adjusting flange  20  attached to a movable framework  21 . The movable framework  21  is mounted in the riveting adapter  5  so that it is movable relative to the supporting framework  16  in the horizontal directions  22  when the pneumatic cylinders  18  integrated in the supporting framework  16  are pressurized or depressurized. The front side of the movable framework  21  is penetrated by a so-called ram sleeve  23 , which protrudes through the front side of the movable framework  21 . The movable framework  21  can be guided on the rivet  4  protruding through the components  11  to be fastened together, when the pneumatic cylinders  18  on the supporting framework  16  are pressurized. Thus the front end of the ram sleeve  23  rests on the component  11  closest to it and the free end of the rivet  4  protrudes at least partially into the ram sleeve  23 . At the same time the position of the rivet  4  is fixed within the components  11  to be fastened together. In various embodiments of the invention the described pneumatic cylinders  18  can be replaced by electrically driven linear motors, which are not described further here, for exact positioning of the movable framework  21 . 
     A carriage  25  is horizontally movable on guide rails  24 , which are arranged inside the movable framework  21 . Moving means  27  is arranged to move the carriage  25  in the horizontal directions  22 . Moving means  27  comprises electrically driven linear motors  26 , which are mounted in the movable framework. Their stators  28  supporting and guiding the linear motors  26  extend under the carriage  25  along the movable framework  21  and are rigidly attached to it. The electrical adjusting motors  26  move along the stators  28  when they are activated. They move the carriage  25  of the riveting adapter  5  in the forward direction  30  to the ram sleeve  23  by means of a finger member  29  associated with them. The carriage  25  movable relative to the movable framework  21  carries at least one additional weight  31  and a ram  32  on its front end. The ram  32  is arranged on the carriage  25  so that it passes through the ram sleeve  23  when the carriage  25  executes a motion  22  in the forward direction  30  toward the ram sleeve  23  and strikes the end of the rivet  4  facing it. Energy stored in the ram  32  at the instant the ram  32  strikes the rivet  4 , which is called the impact energy  33  in the following description, deforms the rivet  4  in such a manner that the end facing the ram  32  is spread out or bulges out and thus a firm attachment of the components  11  is attained by means of the rivet  4 . In the illustrated embodiment according to the invention the carriage  25  movable relative to the movable framework  21 , the additional weight  31  and the ram  32  together form a movable deforming device  34 . 
     The movable framework  21  has a clamping device  35  on a front potion facing the components  11  to be fastened together, which has at least one stop  36 , which limits the horizontal motions  22  of the movable deforming device  34  caused by the linear motors  26  and in the simplest case brakes the deforming device  34  after successful impact of the ram  32  on the rivet  4 , so that recoil of the deforming device  34  and repeated contact with the rivet  4  is prevented. The deforming device  34  can be held pneumatically in the simplest case so that the additional weight  31  is drawn from it by producing a vacuum in the vicinity of the at least one stop. In other embodiments of the invention the clamping device  35  can be attached at another position, for example near the supporting framework  16 . The braking action on the movable deforming device  34  can be increased still further by associating damping elements in a manner, which is not shown in the drawing, with the finger member  29 , which absorb at least a part of the energy residing in the recoiling deforming device  34 . 
     The movable deforming device  34  is guided back to its initial position for performing additional riveting processes by running the linear motors  26  to their initial positions. The linear motors  26  return the deforming device  34  in the return direction  40  to the region of the movable framework  21  that is remote from the ram sleeve  23  and engage the movable deforming device  34  by means of a return element  38  associated with a linear displacement element  37 . The deforming device  34  is fixed in its initial position in the simplest case by a so-called spring-loaded clamping element  39 . So that the impact energy  33  of the movable deforming device  34  is adjustable in a manner according to the invention, a so-called linear guide device  41  with integrated distance measuring means is associated with at least one guide rail  24  attached to the movable framework  21 . These types of linear guide devices  41  are usually constructed so that the guide rails  24  carry them and they are associated with a displacement-measuring device  42 , for example, in the form of an engraved ruler or scale. The linear guide device  41  monitors this ruler or scale  43  by means of a suitable sensor  44 , so that the movable deforming device  34  can be exactly positioned by means of this arrangement including the ruler or scale  43 . 
     According to fundamental physical principles the impact energy  33  of the ram  32  on the rivet  4  is determined by the mass of the deforming device  34 , its acceleration and the available path over which it is accelerated. A first possibility for changing the impact energy  33  would be to use additional weights  31  of different mass. The higher the mass of the additional weight  31 , the higher the impact energy  33 . The exchange of the additional weights  31  however leads to considerable assembly effort. Also the impact energy range achievable in this manner is very limited, since usually the available space does not permit great flexibility for using different additional weights  31 . It is considerably more effective to change the impact energy  33  by changing the acceleration of the movable deforming device  34  and the length of the path over which the movable deforming device  34  is accelerated. The impact energy  33  may be changed by changing the acceleration of the movable deforming device  34 , which is achieved in a simple manner by changing the current supplied to the linear motors  26 . A higher acceleration of the movable deforming device  34  produces greater or higher impact energy  33 . Analogously the available path  45  for the acceleration can be varied. An increase in the path  45  over which the acceleration occurs leads similarly to greater impact energy  33 . To avoid higher delaying forces acting on the linear motors  26  the linear motors  26  are braked along a delay path  46  within the riveting adapter  5  at the end of the path over which the movable deforming device  34  is accelerated, during which the movable structural element moves further toward the rivet  4 . Next, after the deforming device contacts the rivet  4 , the deforming device  34  is braked by the clamping device  35  in the above-described way. 
     So that the movable structural element  34  generates an impact energy  33  which continuously guarantees that a sufficiently energetic deformation of the rivet  4  takes place for fastening the structural components  11  with each other by a single impact of the ram  32  on the rivet  4 , the change of the impact energy  33  must especially consider the properties of the components  11  to be connected, the properties of the rivet  4  and the position of the rivet adapter  5  in space. Material thickness and material-specific deformation properties, such as the elastic modulus, play a role regarding the deformability of the components  11  to be connected. Analogously the required deformation energy depends entirely essentially on the properties of the rivet  4 . The geometric dimensions and material properties of the rivet  4  play a role here. Also the position of the riveting adapter  5  in space influences the impact energy  33 , since the components of the gravity forces (G −Gx, +Gx) due to the movable deforming device  34  acting in the direction of the ram  32  are directed in or opposite to the motion direction of the deforming device  34  according to the position of the riveting adapter  5  according to  FIG. 3 . So that the instantaneous position of the riveting adapter  5  can be determined at least one position sensor  48  constructed in a known manner as an inclination sensor  47  is associated with the riveting adapter  5 , which determines the deviation of the position of the riveting adapter  5  from a vertical orientation. In other embodiments of the invention, which have not been illustrated, the inclination sensor  47  can also be directly integrated on the front end of the segment  8 , since the riveting adapter  5  is non-rotatably attached to the front end of the segment  8 . 
     An electronic control and processing unit  49 , which is described in more detail hereinbelow, is in working connection with the riveting adapter  5  according to  FIG. 3  in operation, so that an optimization of the impact energy  33  is possible, wherein the impact energy  33  is immediately predetermined to be high enough so that connection of the components  11  by means of the rivet  4  to be deformed is possible by a single impact of the ram  32  of the riveting adapter  5  with the rivet  4 , so that the mechanical load or stress on the riveting adapter and the working robot  6  carrying it and the noise emission is kept small. In various embodiments the control and processing unit  49  can be mounted, as shown, directly on the riveting adapter  5  or in any arbitrary position on the working robot  6 . According to the embodiment shown in  FIG. 4  the inclination sensor  47  determining the inclination of the riveting adapter  5  transmits the inclination signals X generated by it to the control and processing unit  49 . Also an input device  50  is provided in the control and processing unit  49 , by which the mass of the movable deforming device  34  and specific data regarding the rivet  4  and/or the components  11  to be connected can be input by the operator. The control and processing unit  49  also has a memory module  51 , which can store various editable data input to the control and processing unit  49 . So that the operator can monitor the running process, the control and processing unit  49  has a display monitor  52  for alphanumeric or graphical display of the various process data. Also a calculation algorithm  54  is input to the control and processing unit  49 , which calculates output data  55  from input data  53  supplied to the control and processing unit  49 . The input data  53  includes the mass of the movable structural element  34  and the specific data for the connecting element  4  and the components  11  to be connected. The output data  55  includes first optimized values for the required impact energy  33  and adjustment parameters  56  for different operating devices of the riveting adapter  5 , which influence the impact energy  33 . The adjustment parameters  56  include the length of the path  45  over which acceleration takes place, the acceleration of the movable deforming device  34  obtained by means of the linear motors  26  and if needed the required mass of the movable deforming device  34 , which can be limited in the simplest case to the required mass of the additional weight  31 . Finally the control and processing unit  49  transmits the output signals Y 1  . . . Yn to appropriate operating organs of the riveting adapter  5  either by a wired data network  57  or a wireless network. In the simplest case the required length of the path  45  over which acceleration takes place can be adjusted so that the appropriate output signal Y 1  is transmitted to the linear guide device  41  and it takes the exact position for the movable deforming device  34  path by means of the displacement measuring device  42 , so that the determined path  45  of the acceleration of the structural element  34  can be traversed. Furthermore the acceleration signal coded in output signals Y can be transmitted to the linear motor  26 . The acceleration of the linear motor  26  is determined from this acceleration signal Y 2  in a control device, which is not illustrated in the drawing, associated with the linear motors  26 . The control device transmits the appropriate acceleration to the movable structural element  34  by means of the finger member  29 . In other embodiments of the invention a separate displacement measuring system  42 , which has not been illustrated, can be associated with the linear motors  26  for precise positioning, which increases the flexibility and accuracy of the adjustment of the impact energy  33 . Also advisory information can be displayed to the operator by means of the display monitor  52  so that the additional weight  31  integrated in the riveting adapter  5  can be replaced by an improved suitable additional weight  31  for reaching the required impact energy  33 . 
     It is within the abilities of those skilled in the art to vary the structure of the described embodiments in undisclosed ways or to use other mechanical systems in order to attain the described effects within the scope of the present invention. 
     
       
         
               
             
               
               
             
           
               
                   
               
               
                 PARTS LIST 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                  1 
                 Riveting station 
               
               
                  2 
                 Working robot 
               
               
                  3 
                 Positioning adapter 
               
               
                  4 
                 Rivet 
               
               
                  5 
                 Riveting adapter 
               
               
                  6 
                 Working robot 
               
               
                  7 
                 Segment 
               
               
                  8 
                 Segment 
               
               
                  9 
                 Pivot axis 
               
               
                 10 
                 Pivot axis 
               
               
                 11 
                 Structural component 
               
               
                 12 
                 Adapter unit 
               
               
                 13 
                 Tool 
               
               
                 14 
                 Hole 
               
               
                 15 
                 Rivet head 
               
               
                 16 
                 Supporting framework 
               
               
                 17 
                 Adapter flange 
               
               
                 18 
                 Pneumatic cylinder 
               
               
                 19 
                 Positioning means 
               
               
                 20 
                 Adjusting flange 
               
               
                 21 
                 Movable framework 
               
               
                 22 
                 Horizontal directions 
               
               
                 23 
                 Ram sleeve 
               
               
                 24 
                 Guide rails 
               
               
                 25 
                 Carriage 
               
               
                 26 
                 Linear motor 
               
               
                 27 
                 Moving means 
               
               
                 28 
                 Stator 
               
               
                 29 
                 Finger member 
               
               
                 30 
                 Forward direction 
               
               
                 31 
                 Additional weight 
               
               
                 32 
                 Ram 
               
               
                 33 
                 Impact energy 
               
               
                 34 
                 Deforming device 
               
               
                 35 
                 Clamping device 
               
               
                 36 
                 Stop 
               
               
                 37 
                 Linear displacement 
               
               
                   
                 system 
               
               
                 38 
                 Return element 
               
               
                 39 
                 Spring-loaded clamping 
               
               
                   
                 element 
               
               
                 40 
                 Return direction 
               
               
                 41 
                 Linear guide device 
               
               
                 42 
                 Displacement measuring 
               
               
                   
                 system 
               
               
                 43 
                 Ruler or scale 
               
               
                 44 
                 Sensor 
               
               
                 45 
                 Acceleration path 
               
               
                 46 
                 Delay path 
               
               
                 47 
                 Inclination sensor 
               
               
                 48 
                 Position sensor 
               
               
                 49 
                 Control and processing unit 
               
               
                 50 
                 Data field 
               
               
                 51 
                 Memory module 
               
               
                 52 
                 Display monitor 
               
               
                 53 
                 Input data 
               
               
                 54 
                 Computational algorithm 
               
               
                 55 
                 Output data 
               
               
                 56 
                 Adjustment 
               
               
                   
                 Parameter 
               
               
                 57 
                 Data line 
               
               
                 X 
                 Inclination signal 
               
               
                 Y1 . . . Yn 
                 Output signals 
               
               
                   
               
             
          
         
       
     
     The disclosure in German Patent Application DE 10 2004 005 859.8 on Feb. 5, 2004 is incorporated here by reference. This German Patent Application describes the invention described hereinabove and claimed in the claims appended hereinbelow and provides the basis for a claim of priority for the instant invention under 35 U.S.C. 119. 
     While the invention has been illustrated and described as embodied in an apparatus for fastening rivets in structural components, it is not intended to be limited to the details shown, since various modifications and changes may be made without departing in any way from the spirit of the present invention. 
     Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention. 
     What is claimed is new and is set forth in the following appended claims.