Abstract:
A head of a riveting device—for Hi-Lite type rivets—of at least two components of a structure for installing automatically collars on pins previously inserted in the structure. The head comprises: a collar installation tool; a collar supply to supply collars to the collar installation tool; a tool actuating device; a linear displacement device to linearly move the tool during the threading operation; a withdrawal device arranged to withdraw the second part of the collars; a control arrangement configured to automatically perform the installation of collars on pins and after this the withdrawal of the second part of the collars, using tools and collars appropriate for the pins. Also a robot having as end-effector the head and to a method of riveting two components of an aircraft fuselage are provided.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
     This application claims the benefit of the European patent application No. 12382056.5 filed on Feb. 20, 2012, the entire disclosures of which are incorporated herein by way of reference. 
     FIELD OF THE INVENTION 
     The present invention refers to riveting devices and methods for joining components of structures such as aircraft fuselages and, more particularly, to riveting devices and methods for the automatic installation of the collars on the pins in aircraft fuselages made of composite materials. 
     BACKGROUND OF THE INVENTION 
     Among the joining methods used to assemble aircraft structures made of composite materials, preferably Carbon Fiber Reinforced Plastic (CFRP), metallic materials or hybrid combinations of them, are well known riveting methods using short threaded rivets with a sliding adjustment such as the HI-LITE rivets manufactured by Hi Shear Corporation. 
     These rivets, developed exclusively for the aerospace industry, consist of a threaded pin whose head may be protruding or countersunk and a nut or collar which limits the torque applied by breaking a part of it. In the case of closed structures such as fuselages, which must use a large number of rivets to join the fuselage skin with the various internal stiffening elements (frames, stringers, beams), the installation of collars on pins previously inserted from the outside of the fuselage is usually carried out manually with the aid of a pneumatic tool. 
     The riveting process includes the following basic steps: 
     Operators are distributed in random areas for working in parallel. The order of collar installation is not important. 
     Each operator is provided with the collars that he will need (pre-deposited in separate boxes for each reference). 
     For each specific pin, the corresponding collar is selected, a manual threading operation of the collar on the pin with a ½-¾ turn is done and, using a pneumatic or electric tool, the complete fastening of the collar is done until a part of it breaks. 
     Finally, the broken part of the collar is manually extracted from the pneumatic or electric tool, with a jolt. 
     The head of the pneumatic or electric tool is relatively simple and therefore small in size. It consists of a central hexagonal pin which remains in a fixed position and blocks the rotation of the pin, and a socket through which it applies torque to the hexagonal head collar. Once it reaches the torque corresponding to the breaking point of the collar employed, the detached body part or surplus remains lodged in the socket. A slight jolt is enough to detach it. This process is laborious and has the disadvantage of being highly labor intensive, increasing the cost of the aircraft manufacture. Additionally the operators sometimes have to adopt non-ergonomic positions for the collar installation operations. 
     The present invention is directed to solving these problems. 
     SUMMARY OF THE INVENTION 
     An object of this invention is to automate the installation of collars on pins in riveting systems of at least two components of a structure, the collars having a first part which is designed to be attached to the pins and a second part to control the torque applied to the collars, separated from the first part by a frangible zone, which is designed to break when the torque reaches a predetermined value, in, particularly, big structures such as aircraft fuselages having low accessibility areas. 
     In one aspect, these and other objects are achieved by a head of a riveting device comprising: at least a collar installation tool; collar supply means to said collar installation tool; tool actuating means; linear displacement means during the threading operation; withdrawal means of the second part of the collars; control means arranged to automatically perform the installation of collars on pins and after this, the withdrawal of the second part of the collars, using tools and collars appropriate for each of the pins. 
     In embodiments of the invention the head also comprises artificial vision means adapted to perform recognition of the position and orientation of the pins so that the head can be properly positioned with respect to the pins. Hereby it is achieved a head having a useful pin recognition capability when their position is not available. 
     In embodiments of the invention the head also comprises cleaning means for removing any sealing material remaining on the pins. Hereby it is achieved a head capable of performing the cleaning of the pins before the installation of the collars on the pins. 
     In embodiments of the invention said tool actuating means comprise an electric or pneumatic motor. Hereby it is achieved a head with tool actuating means with a similar performance to the tools used in manual procedures for installing collars on pins. 
     In embodiments of the invention the head also comprises a vacuum duct connected to the collar installation tool. Hereby it is achieved a head capable of holding a collar which allows an effective installation of the collar on the pin. 
     In embodiments of the invention the collar supply means and the withdrawal means comprise collar supply ducts connected to collar deposits, a suction duct connected to a reservoir, a movable arm between the collar installation tool and the collar supply ducts or the suction duct and a vacuum duct for the movable arm. Hereby it is achieved a head able to efficiently feed the collar installation tool with the collars needed for their installation on the pins and to efficiently withdraw the detached parts of the collars. 
     In embodiments of the invention the actuation means of said movable arm are a rotatory actuator and a linear actuator. Hereby it is achieved a head with a suitable arm for providing collars to the collar installation tool and to withdraw from the collar installation tool the detached parts of the collars. 
     In embodiments of the invention the collar installation tool is selected among a straight tool, having its actuating terminal in the same axis of the tool actuating means, and an angled tool, having its actuating terminal in a displaced axis with respect to the axis of the tool actuating means, and the head is arranged so that said movable arm can reach the terminals of both collar installation tools. Hereby it is achieved a head with two interchangeable tools, where the straight tool will be used to install collars on easily accessible pins and where the angled tool will be used to install collars on pins inaccessible to the straight tool. 
     In embodiments of the invention the head is configured with at least two interchangeable assemblies of one collar installation tool and one tool actuating means adapted to different sizes of collars. Hereby it is achieved a modular head for effectively managing a wide range of collar references. 
     In another aspect, the above mentioned objects are achieved with a robot with an articulated arm having as end-effector the above-mentioned head and control means arranged for placing the end-effector in a suitable position for reaching the pins with the collar installation tool. 
     In embodiments of the invention, said robot is used in a section of an aircraft fuselage. Hereby it is achieved a suitable device for installing automatically collars on pins in a structure where the access to the pins is not easy. 
     In embodiments of the invention, the components of the structure to be riveted are made of composite materials and the pins are inserted in the structure without interference. Hereby it is achieved a suitable device for automatically installing collars on pins where the axis of the pins may have certain deviation with respect to a perpendicular axis to the fuselage skin. 
     In another aspect, the above mentioned objects are achieved with a method comprising the following steps: a) inserting said pins in said aircraft fuselage from the outside; b) installing said collars on the pins from the inside using the above mentioned robot. 
     In embodiments of the method the step a) is performed using an automated device for inserting the pins that can provide the coordinates of their locations and in step b) said coordinates are used by the control means of said robot for placing the head in a suitable position for reaching the pins with the collar installation tool. 
     Other desirable features and characteristics of the invention will become apparent from the subsequent detailed description of the invention and the appended claims, in relation with the enclosed drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 a -1 e    schematically show the sequence of operations for manually installing a collar on a pin using HI-LITE type rivets. 
         FIGS. 2 a  and 2 b    show, respectively, a threaded collar on a pin and a collar installed on a pin after the removal of the detached part. 
         FIG. 3  is a perspective view of a robot for an automated installation of collars according to the present invention. 
         FIG. 4  is a detailed view of the end-effector of said robot. 
         FIGS. 5 a  and 5 b    illustrate the sequence of operations to feed a straight tool of the end-effector with a collar. 
         FIGS. 6 a  and 6 b    illustrate the sequence of operations to feed an angled tool of the end-effector with a collar. 
         FIG. 7  shows an end-effector that can be configured with a straight tool or with an angled tool. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  schematically shows the typical steps of the manual process of installing a collar  13  on a pin  11  of a HI-LITE type rivet in a structure  10 . 
     In the first step ( FIG. 1 a   ) the pin  11  is inserted in the structure  10  in a sliding manner, i.e. without interference. 
     In the second step ( FIG. 1 b   ) a first thread (of small size) of the collar  13  on the pin  11  is done manually. 
     In the third step ( FIG. 1 c   ) a tool  7  (similar to an Allen wrench) is prepared for carrying out the final step of the installation of the collar  13  on the pin  11 . The tool comprises an actuating terminal comprising a central hexagonal bar  8  which remains fixed and locks the rotation of the pin  11  cooperating with a hole  12  at the end of the pin  11  and a socket  9  for applying a torque on the head of the collar  13  for threading it on the pin  11 . 
     In the fourth step ( FIG. 1 d   ) the process of applying torque to the collar  13  using the above-mentioned tool  7  is illustrated. 
     In the fifth step ( FIG. 1 e   ) the final result is shown. After reaching a predetermined torque, the second part  17  of the collar  13  is broken and remains lodged in the tool  7 . A slight jolt is enough to detach it. 
       FIGS. 2 a  and 2 b    illustrate in detail the final state of, respectively, the fourth and fifth steps. 
     The aim of the present invention focuses on automating the installation operations of the collars on the pins in a structure such as a section of the fuselage of an aircraft to be carried out during its assembly process which is usually done using mounting platforms. 
     The pins can be inserted into the fuselage manually or by an automated system that can be coordinated with the automated installation of the collars. In both cases the pin should be inserted in holes perpendicular to the surface of the fuselage to ensure proper pin orientation. 
     In an embodiment of the invention, the above-mentioned automation is achieved by a robot  21  (see  FIG. 3 ) with an articulated arm  23  at whose end stands as end-effector a head  25  with means for installing collars on pins previously inserted in the fuselage that is adapted to move along the fuselage mounting platforms to properly position the end-effector  25  in relation to each pin to proceed with the collar installation. A control device  27  is provided to operate the robot  21 . 
     We will now describe in more detail the main components of the device. 
     The Robot 
     The robot  21  is arranged as a mobile device on the mounting platform of the fuselage so that it can approach the target area for installing a collar  13  on a pin  11 . After reaching the desired position, the robot  21  drives the arm  23  to align its end-effector  25  with the pin  11  where a collar  13  shall be installed. 
     The End-Effector 
     In the embodiment of the invention illustrated in  FIG. 4  the components of the end-effector  25  are the following: 
     A tool for installing a collar attached to a coupling interface  33 . Shown in 
       FIG. 4  is an angled tool  31 ′, but a straight tool  31  can be also used as we shall see later on, joined to said coupling interface  33 . The actuating terminal of said tools  31 ,  31 ′ has a similar configuration to the actuation terminal of the above-mentioned tool  7  (a central hexagonal bar  8  for blocking the rotation of the pin  11  and a socket  9  for applying a torque to the collar  13 ). 
     An electric or pneumatic motor  35  as actuating means of the tool  31 ,  31 ′ to rotate the socket  9 . 
     A vacuum duct  39  connected to the tool  31 ,  31 ′ that holds the collar on the tool  31 ,  31 ′. 
     Means for supplying collars  13  to the tool  31 ,  31 ′ comprising one or more supply ducts  41  (depending on the number of collar references being used), a distribution flange  43  of the collar supply ducts  41 , an L-shaped arm  45  for feeding the tools  31 ,  31 ′ with collars, a linear actuator  47  for the L-shaped arm  45 , a rotatory actuator for the L-shaped arm  45  comprising a spindle motor  49 , a transmission belt  51  and a guiding bar  53 , and a vacuum duct  55  for the L-shaped arm  45 . 
     Linear displacement means during the threading operation (not shown separately in  FIG. 4 ). These means can move either the tool  31 ,  31 ′ or the assembly motor  35 —tool  31 ,  31  or, even, the whole end-effector  25 . In the latter case the robot  21  will be used as actuator. In the other cases electric actuators, pneumatic actuators or springs could be used as actuators. 
     Withdrawal means for the removal of the second part  17  of the collar  13  comprising a suction duct  57 . 
     Artificial vision means  59 . 
     The operation of this end-effector  25  is schematically described as follows. Once the pin  11  where a collar  13  shall be installed is located using, if needed, the artificial vision means  59  and once the end-effector  25  is properly positioned with respect to the pin  11 , the collar supply means  41 ,  43  places a suitable collar  13  for the pin  11  in the arm  45  which carries the collar  13  by combining a linear movement (arrow F 1  down) and a rotational movement (arrow F 2 ) to the tool  31 ′ to which is transferred by the effect of a vacuum. Hereafter the tool  31 ′ installs the collar  13  on the pin  11  and the removal means  57  carry the second part  17  of the collar  13  which breaks away during the final stage of the installation to a reservoir of leftover material. 
     The electric or pneumatic motor  35  for actuating the tool  31 ,  31 ′ is common for the different types of tool  31 ,  31 ′ (straight or angled) and for the different sizes of collars  13 . It can have a control device  37  arranged to adapt its performance to the size of each collar  13 . The coupling interface  33  allows pneumatic and mechanical coupling between the electric motor  35  and the tool  31 ,  31 ′. 
     The choice of a straight tool  31  or an angled tool  31 ′ depends of course on the location of the pin  11 . 
     The end-effector  25  is coaxial to the axis of rotation of the last degree of freedom of the robot  21 . 
     The robot  21  also comprises a shelf (usually named automatic tooling changer) attached to it with an appropriate tooling for storing the different types of tools used, the different collars to be used by said collar supply device and the excess material. 
       FIGS. 5 a  and 5 b    show the sequence of feeding a collar  13  to a straight tool  31 . In  FIG. 5 a    it can be seen how the arm  45  is taking a collar  13  from the collar supply duct  41  and in  FIG. 5 b    it can be seen how the collar  13  is transferred from the arm  45  to the tool  31 . 
       FIGS. 6 a  and 6 b    show the sequence of feeding a collar to an angled tool  31 ′. 
     The interchangeability between straight and angled tools  31 ,  31 ′ requires that the axis of the straight tool  31  and the axis of the angled tool  31 ′ be within the turning radius of the arm  45 . 
     The Control of the Displacement of the Robot 
     Ideally the fuselage must be prepared in a mounting platform so that the robot  21  can use both the information available in the CAD system used for the design of the fuselage regarding its interior geometry and the location of the pins previously inserted either by a manual or an automated system (with a greater or lesser margin of error with respect to the location specified in the design). 
     From that information and the information provided by its sensor system, the movements of the robot  21  can be programmed in the control  27  to optimize the execution of the installation operation of the collars  13  on the pins  11 . 
     Although the present invention has been described in connection with various embodiments, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made, and are within the scope of the invention. 
     As is apparent from the foregoing specification, the invention is susceptible of being embodied with various alterations and modifications which may differ particularly from those that have been described in the preceding specification and description. It should be understood that I wish to embody within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.