Abstract:
The device for setting rivets is characterized by a robot having a robot arm on which a setting device is held that comprises a supply unit connected to a reservoir of rivets, a feed unit for a respectively selected rivet, and a setting unit for the respective rivet. The device carries out an automatic mounting process with high efficiency and precision and sets the rivets fully automatically.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a device for automatically setting rivets. This regards particularly, but not exclusively, rivets that have an outer sleeve with a broadened sleeve head which is provided with a plurality of recesses that are uniformly distributed over the circumference for engagement of a holding tool, as well as an inner element similar to a screw bolt, which projects with a flattened attachment out of the sleeve head and is in threaded engagement with the sleeve on the opposite end portion. An annular intermediate section of the sleeve is pressed outwards by rotating the inner element in the sleeve and is pressed onto the component to which the rivet is to be fastened whereas the outer sleeve is rotation-locked, with the attachment being torn off in the end. 
       BACKGROUND 
       [0002]    With such rivets, sections of an aircraft body are e.g. interconnected and stiffening elements for the inner skin are fastened. The rivets of the type under consideration have so far been set and tightened with hand-held tools, which is a lengthy and cost-intensive work process in view of the huge number of rivets especially in aircraft construction. 
         [0003]    It is the object of the present invention to provide a device for setting rivets, which device carries out an automatic mounting process with high efficiency and precision and sets the rivets fully automatically. 
       SUMMARY OF THE INVENTION 
       [0004]    This object is achieved according to the invention by a device for setting rivets, comprising a robot having a robot arm on which a setting device is held that comprises a supply unit connected to a reservoir of rivets, a feed unit for a respectively selected rivet, and a setting unit for the respective rivet. Advantageous designs of the invention are described below. 
         [0005]    The device according to the invention preferably contains a robot having a robot arm, or a similar positioning unit, on which a setting device is held that comprises a supply unit with a reservoir of rivets of different types, preferably different length, a feed unit for a respectively selected rivet and a setting unit for the respective rivet. The supply unit is permanently fixed to the robot, i.e. it is not exchanged during use of the device according to the invention. 
         [0006]    The feed unit and the setting unit are preferably interconnected to form a conjoint subassembly that is held on the robot for rapid exchange. This means that during operation of the device according to the invention the robot selects the respectively desired subassembly among a number of subassemblies provided for, and establishes the operative connection with said subassembly by means of a standard quick-change unit. 
         [0007]    The supply unit communicates with a plurality of, e.g. six, rivet magazines, or rivet reservoirs, including associated feed hoses, which lead to a common connection for a single feed hose of the feed unit, and a source of compressed air that blows the respectively selected rivet out of the reservoir with compressed air into the feed hose of the feed unit. The feed hoses are each provided with a sensor which senses the passage of a rivet. 
         [0008]    Furthermore, it is suggested that the feed unit should comprise a sensor that checks whether the supplied rivet is accommodated in the gripper jaws after the braking operation, which is described below, has been carried out. For this purpose, preferably at a certain distance from the end of the feed hose, a ring sensor is provided that is expediently fastened to the feed hose. Whenever it is detected that a false rivet is supplied, an error signal is output for operating a mechanism that will transport the false rivet to a waste box of the setting device, as will be described in more detail further below. 
         [0009]    Advantageously, the end of the feed hose has positioned thereon a brake means which blocks the exit of the rivet-conveying compressed air upon a signal, which is expediently also output by the ring sensor. The brake means can consist of a brake plate that is advanced by a brake slide so as to block the exit opening of the compressed air on the feed hose. This has the consequence that the air located in front of the rivet is compressed to form an air cushion that decelerates the rivet to such a strong extent that it does not get damaged. With large rivets, compressed air can additionally be blown into the end section of the feed hose. This braking means constitutes a very advantageous feature of the present invention. 
         [0010]    According to a further proposal of the invention gripper jaws and return gripper jaws for a rivet that are connected to a movable slide are located underneath the brake means, i.e. when viewed in the feed direction of the rivet behind the brake means. The gripper jaws are positioned underneath the end of the feed hose and accommodate the arriving rivet and transport said rivet to the setting unit, which grips the rivet. The gripper jaws are displaced and the rivet is wetted with a sealing means. When an error signal is output, the return gripper jaws are moved to the rivet and position the rivet such that it is blown back by means of compressed air through an associated hose into the waste box. The gripper is returned into the basic position so that a new rivet can be supplied. Hence, the gripper has not got into contact with sealing means. 
         [0011]    The setting unit, the design of which is claimed as an independent invention, contains a reversing motor with a torque sensor, a rivet fastening element that is in drive communication with the motor via a free run that is unblocked in a first direction and blocked in a second direction, a rivet holding element for non-rotationally holding the rivet, the element being in communication with the motor via a free run that is blocked in the first direction and unblocked in the second direction, the two elements being pushed back against spring force into the setting unit, and an air channel which extends through the rivet fastening element and is connected to a source of vacuum and which terminates in a front accommodating gap of the rivet fastening element. Said accommodating gap serves to accommodate the attachment of the inner screw bolt-like element of the rivet, which element is rotated and tightened for fastening the rivet to the associated component until the attachment tears off. The rivet holding element is provided on its front face with noses that must engage into the recesses of the sleeve head of the rivet to hold the sleeve in a non-rotational manner. 
         [0012]    The automatic setting unit operates in the following way: The setting unit is moved by means of a movable slide to the rivet held between the gripper jaws and is pressed against said rivet, the rivet fastening element being pushed back by the attachment of the rivet and the rivet holding element by the sleeve head against the force of their springs into the setting unit. Subsequently, the motor of the setting unit is rotating in the right (or second) direction and entrains the rivet fastening element via the free runs “blocked in right direction”. As soon as the front accommodating gap of the rivet fastening element has been aligned with the position of the attachment of the rivet, the rivet fastening element is resiliently advanced (with accommodation of the attachment). This increases the torque of the motor, with the torque being measured. When the torque has reached a predetermined value, the drive will switch over, so that the motor will now rotate in the left direction. When the noses of the front face of the rivet holding element are in alignment with the position of the recesses on the sleeve head, the rivet holding element is resiliently advanced, whereupon the torque will rise. This ensures that the rivet is correctly gripped and that both engagement features have become operative. The motor will now stop. To hold the rivet, the vacuum is switched on. 
         [0013]    Subsequently, the setting unit is moved by the robot to the place of setting, whereupon the rivet is pushed by a linear advance unit into the bore in a monitored manner. The motor now performs a rotation in the right direction until the tear-off part of the rivet has been twisted off. The rivet holding element blocked in the right direction serves as an anti-rotation means with its noses. 
         [0014]    The torque curve is recorded; its evaluation makes it possible to draw conclusions about the quality of the connection. Thus the setting operation is completed, and the torn-off part is transported via a bent part for the return movement and a return slide for the bent part to a hose that blows the torn-off part into the waste box. 
         [0015]    The device according to the invention permits the setting of the rivets in a continuous process, which reliably avoids standstill times caused by an erroneously supplied false rivet, as well as damage to rivets during supply. The automatic device is flexible and operates with high precision and efficiency. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    Further features and details of the invention become apparent from the following description and from the drawings, in which: 
           [0017]      FIGS. 1   a  to  1   f  show a rivet in side views, in longitudinal sections, in a front view and in a perspective illustration; 
           [0018]      FIG. 2  is a perspective illustration of a robot with the device according to the invention; 
           [0019]      FIG. 3  is a perspective view of a feed unit; 
           [0020]      FIG. 4  is a perspective view of a supply unit; 
           [0021]      FIGS. 5 and 6  show a longitudinal section through a lower part of the feed unit and a top view on said part; 
           [0022]      FIG. 7  is a longitudinal section through a setting unit for the rivet shown in  FIG. 1 ; and 
           [0023]      FIG. 8  is a purely schematic illustration of the setting device. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0024]      FIGS. 1   a  to  1   e  show a rivet, which is called “Hand OSI-Bolt” and has so far been set by hand. The rivet includes an outer sleeve  1  with a broadened sleeve head  2  which in its front face comprises recesses  3   a  uniformly distributed over the circumference. An element  3  similar to a screw bolt is seated in the sleeve  1  with a flat attachment or tear-off part  4  projecting out of the sleeve  1 . The screw bolt-like element  3  is in threaded engagement  5  with the sleeve  1  on its end portion. 
         [0025]    The sleeve  1  is bipartite, so that upon rotation of the inner element  3  an annular radial flange  6  is formed that is firmly pressed onto a component to which the rivet will be fastened. Upon continued rotation of the inner element  3  the attachment  4  will tear off. 
         [0026]      FIG. 2  shows a robot  7  on the arm  8  of which the setting device  9  according to the invention is mounted, the device being adapted to be positioned such that the rivets can be inserted into the prepared bores. The device  9  includes a feed unit  10  which is combined with a setting unit  11  to form a subassembly, and a supply unit  12  including a reservoir of different rivets, as shown in  FIG. 4 . 
         [0027]    In the illustrated embodiment the supply unit  12  contains six feed hoses  13  for different rivets that terminate in a single feed hose  14  of the feed unit  10 . The supply unit  12  is fixed at the robot side whereas the feed unit  10  with the setting unit  11  is rapidly exchangeable at the tool side. The feed unit  10  includes a waste container  15  into which false or defective rivets and the tear-off parts  4  of the set rivets are blown. 
         [0028]      FIG. 8  is a purely schematic illustration showing the feed hoses  13  of the supply unit  12 , as well as the single feed hose  14  of the feed unit  10 . The end of the feed hose  14  has located thereon a brake means  17  which comprises a brake plate  18  that is movable by a brake cylinder  19  so as to either close the exit opening of the feed hose  14  in order to form an air cushion decelerating the arriving rivet, or in order to release the exit opening. The brake plate  18  has positioned in close vicinity thereto gripper jaws  19  and return gripper jaws  20  that are movable by means of a gripper cylinder  21  such that in the event of a supplied false rivet either the return gripper jaws  20  or the gripper jaws  19  are positioned such that they can receive the rivet after retraction of the brake plate  18 . The gripper jaws  19  position the rivet such that it can be accommodated by the setting unit  11  when the setting unit  11  is advanced by an associated movable slide  22  in a corresponding manner. A bent part  23  and a return slide  24  for the bent part are provided for blowing the tear-off parts  4  of the rivet into the waste box  15 . 
         [0029]    The setting unit  11  illustrated in  FIG. 7  is suited for setting rivets of the type shown in  FIGS. 1   a  to  1   e.  It should be noted that the arrangement of robot  7 , supply unit  12  and feed unit  10  is also suited for rivets of a different type. 
         [0030]    The setting unit  11  includes a reversing motor  25  connected to a torque sensor. The motor  25  rotates a motor shaft  26  that via a free run  27  blocked in left direction and unblocked in right direction is in drive communication with a rivet holding element  28  that on its front face comprises projections that, with a corresponding positioning, can enter into the recesses  3   a  of the sleeve head  2  of the associated rivet. The rivet holding element  28  can be pushed back against the force of a compression spring  29  into the housing of the setting unit  11 . 
         [0031]    In the other rotational direction of the motor  25  the drive shaft  26  rotatingly entrains, via a sleeve  30 , a rivet fastening element  31  that is provided at its free end with an accommodating gap  32  into which, with a corresponding positioning, the tear-off element  4  of a rivet can enter. An air channel  33  passing through the rivet fastening element  31  terminates in the accommodating gap  32 , the air channel being connectable to a source of vacuum via a connection  34  leading laterally out of the device  11 , so as to hold the rivet gripped by the elements  28  and  31 , so that said rivet can be transported to the intended bore. Furthermore,  FIG. 7  shows some bearings  35  of the setting unit  11 . 
         [0032]    The setting unit  11  can be used not only together with the supply unit  12  and the feed unit  11  with a robot, but can also be employed as a hand-operated device. It should be noted that the invention is not limited to the described and illustrated embodiment. Rather, all of the features disclosed in the description and drawings can be combined in any possible way individually. Likewise, the features illustrated in the drawings, which are not described separately, are also claimed as pertaining to the invention—insofar as they are novel.