Abstract:
Apparatus and process for the installation of collars and/or nuts on fasteners, particularly in the aerospace industry. The apparatus includes an industrial base robot supporting a mounting base carrying a gimbal and rotary drive for a lightweight sensing robot with a fastening/torque tool. The sensing robot operates to align and position a spin preventing projection such as a hex key in a fastener end and a rotatable socket to torque a nut or collar onto the fastener held against rotation. The related process is accomplished by sensors in conjunction with the sensing robot aligning the hex key with a recess in the fastener end, inserting the key into the fastener to hold it against rotation, and spinning a nut or collar onto the fastener. A wrenching component is sheared from the nut and removed after the nut or torque is applied.

Description:
PRIORITY CLAIM 
       [0001]    Benefit is claimed of the filing date of Sep. 22, 2014 of U.S. Provisional Patent Application Ser. No. 62/053,426, which application is herewith incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    This invention relates to the automatic alignment and torquing of backside nuts or collars onto fasteners such as bolt pins used in automated industrial assembly processes such as in the aerospace industry, and more particularly in one-up assembly processes. 
       BACKGROUND OF THE INVENTION 
       [0003]    The aerospace industry has been addressing the need to introduce automated techniques for drilling of work pieces and fastener insertion and torquing therein for the past decade. The latest trend is to attempt to implement flexible automation, via industrial robots, to limit the required floor space required for the process. However, the next evolution of drilling and fastener insertion automation requires alignment and installation of a backside collar or nut on a threaded fastener such as a bolt or pin at a specified torque. 
         [0004]    The installation of collars or nuts to such fasteners has predominately been a manual task within the aerospace industry, due to the complexity and obstacles inherently presented by current automation capacities. The primary obstacle has been the difficulty in aligning and applying the parts in emulation of human motion of alignment and torquing. Key variables of spinning a collar or nut onto a threaded fastener include the proper alignment of the collar or nut to the fastener, mitigating cross threading, and the holding of the fastener against turning or spinning as the nut or collar is spun thereon and torqued to a specific parameter. 
         [0005]    Another variable that is challenging is that of the smaller size fasteners to which a nut or collar must be aligned, and the holding of the fastener against spinning, when extended into and through a part drill hole of non-interference in relation to the fastener (in other words a hole whose diameter is greater than the outside diameter of the fastener to such extent the fastener can rotate in the hole). The variety of aerospace fasteners and the mechanical difficulty of aligning and engaging the fasteners make the indexing of the nut or collar on the fastener and the rotation of the nut or collar to full engagement to complete the threaded torque down operation, without rotating the fastener, very difficult. Thus it is desired to fully automate the alignment and torque of a nut onto a fastener in a manner duplicating the haptic or sensory capacities of a human. 
       SUMMARY OF THE INVENTION 
       [0006]    To these ends, these variables and obstacles are addressed by the combination of an industrialized sensing or second robot as an end effector in conjunction with a more traditional base or first robot supporting and operating the sensing robot, applied to align and torque nuts onto fasteners in an industrial operation as if conducted by human capacity. 
         [0007]    A unique robot-on-robot collaboration according to the invention assists in the starting point angle of the collar alignment process and the part fastening operation. This collaboration also makes possible the use of a base robot to place a pressure-foot firmly square to the part stack-up for the pin insertion. 
         [0008]    The use of an industrialized sensing robot with compliant axes (e.g., such as shown in Design Patent No. D692,041 incorporated herein by reference) and available commercially from KUKA Robotics Corporation of Shelby Township, Michigan as robot model KUKA LBR iiwa, and in U.S. Pat. No. 8,594,847 incorporated herein by reference, renders viable human-to-robot emulation through its sensory technology. However, this sensory technology is here utilized and particularly adapted, according to the invention, to mimic human functionality in a way previous industrial robots or systems do not. The torque sensors in each axis of the sensing robot allow the robot to align a spin-preventing component and socket drive with the fastener thus allowing it to ensure, for example, proper thread engagement (without cross-threading) of the collar or nut to a bolt pin and without a cooperating or ancillary vision system. This ability through the compliant axes of the sensing robot is also useful for the engagement of a fastening/torque tool carrying a fastener socket driver and spin preventing mechanism, described below, and for torquing a nut or collar onto the fastener. According to the invention, fasteners such as threaded bolt pins are modified to include a shape specific internal bore or recess for engagement by a projecting component of the fastening torque tool carried by the sensing robot. This inserted, projecting component keeps the fastener from spinning during nut or collar rotation and torquing. Torque sensors associated with the sensing robot and with the fastening/torque tool sense torque from the nut collar threading onto the fastener and provide data aberrations from cross threading or product structure. Sensed torque can provide data for control, start-over, rejection or other parameters as programmed in any suitable control in the particular application. Thus the invention provides process and application for , without a vision system, automatically aligning and securing a nut or collar to a bolt pin which in turn secures work pieces together. In addition, it will be appreciated that the fastening/torque tool also electronically provides reliable torque data useful with torque data from the sensing robot in the nut torquing. 
         [0009]    Thus the invention provides haptic or compliance feedback operation in the application of applying and torquing nuts onto fasteners in industrial applications. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0010]    These and other objectives, advantages, apparatus and processes will become readily apparent from the following detail and written description and from the drawings appended hereto as follows: 
           [0011]      FIG. 1  is an isometric illustration of the invention including a base industrial robot, a lightweight sensing robot, a mounting base carried by the base industrial robot, a clamp foot carried by the mounting base and a fastening/torque tool carried and operated by the lightweight sensing robot. 
           [0012]      FIG. 2  is an isometric view of the invention of  FIG. 1  from the other side further showing rotary and gimbal drives and mounts for the lightweight sensing robot; 
           [0013]      FIG. 3  is an illustrative cross-sectional sketch of the fastener and approaching nut or collar and fastener holding/nut driver of the invention; 
           [0014]      FIG. 4  is similar to  FIG. 3  but illustrates a fastener with a nut or collar in aligned position for rotating onto the threaded fastener; 
           [0015]      FIG. 5  is an elevational, illustrative view in partial cross-section of a fastener; and 
           [0016]      FIG. 6  is an elevational, illustrative view as in  FIG. 5  but showing in addition a nut or collar threaded onto the fastener with a collar wrenching apparatus sheared off from the nut or collar during assembly. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0017]    As used herein, the term , “fastener”, refers to and includes any suitable fastener, preferably threaded at or proximate one end, and including bolts, bolt pins, screws or the like, which may be used interchangeably for such fasteners. 
         [0018]    The term, “sensing robot”, as used herein generally refers to handling robots, such as industrial robots according to the existing art, having a manipulator normally having two to six motion axes, which are normally rotational motion axes. The motion axes of the manipulator can each have force or torque sensors and/or position sensors assigned to them, with which the position and the forces or torques of the particular motion axes are registered directly. The motion axes are normally joints of a multisectional manipulator arm, or a pivot joint between the manipulator arm and the robot base. An end effector, for example a gripper, is normally situated at the free end of the manipulator or manipulator arm. Besides the pure control or regulation of position with the aid of the position sensors assigned to the motion axes, force and/or moment sensors of the motion axes may be utilized to monitor or control the forces and torques occurring at the manipulator arm. 
         [0019]    The monitoring, controlling and regulating of torques and forces that act on the manipulator is a necessary, or at least a desired type of regulation in many applications. For example, the manipulator can be controlled or regulated by means of force and moment axis sensors of the manipulator to generate a particular force or torque on a component. With moving attachments and/or basic components, it is possible to use force and/or moment axis sensors on the manipulator to prevent canting. The force and moment sensors of the manipulator can also be used to detect collisions. 
         [0020]    In industrial applications, the industrial robot is normally operated in an automatic mode. The industrial robot uses its manipulator to repeatedly carry out preprogrammed movement patterns independently. Since there is no direct human control in automatic mode, reliable functioning of all control and regulatory circuits is imperative to avoid misinterpreting the position and motion of the manipulator, as described in U.S. Pat. No. 8,594,847 which is fully incorporated herein by reference and is filed herewith as a part hereof. 
         [0021]    Turning now to the Figures, and particularly to  FIGS. 5 and 6  initially, there is disclosed therein a fastener or pin bolt  10  on an axis “a” having a head  11 , an extended shank  12  and a threaded portion  13  at or proximate a distal end portion of shank  12  from head  11 . The pin bolt  10  may also be referred to as a pin, bolt, screw or fastener as shown. Threaded portion  13  of shank  12  is shown in partially cut-away fashion in  FIG. 5  and thus facilitates illustration of a square sided, hexagonally-shaped or multi-sided recess or bore  14  provided co-axially in the end of bolt  10  opposite head  11 . 
         [0022]    For illustration, pin bolt  10  is shown extending through two work piece parts  18 ,  19  (see  FIGS. 3 ,  4 ). Parts  18 ,  19  are shown for environment purposes only in dashed lines in  FIGS. 5 ,  6 , and it is these parts that pin bolt  10  serves to hold together. 
         [0023]    With continued reference to  FIG. 6 , a nut or collar  20  is shown comprising preferably two components  21 ,  22 . Component  21  comprises a permanent nut or collar member for operative threading onto threaded portion  13  of bolt  10 . Component  22  comprises a wrenching element initially but frangibly secured to component  21 . Upon application of a predetermined torque to nut or collar  20 , as described herein, and after proper torquing of nut or collar  20 , the nut or collar  20  stops and component  22  shears off from the permanent element  21 , leaving element  21  in place on bolt  10 , securing pieces  18 ,  19  between head  11  and component  21 . Element  22  is then removed. 
         [0024]    Nut or collar  20  is made of any suitable material or materials for suitable engagement with bolt  10 . 
         [0025]      FIG. 5  illustrates bolt  10  with the nut  20  in dashed lines for clarity on illustration of bolt  10 , while  FIG. 6  illustrates final placement of nut or collar component  21  on bolt  10 , with a portion of the components of nut  20  shown in partial cross section. 
         [0026]    With reference now to  FIGS. 3 and 4 , these FIGS. illustrate the process of collar alignment with bolt  10  ( FIG. 3 ) and final positioning of collar  20  on bolt  10 ,  FIG. 4 . 
         [0027]      FIGS. 3 and 4  further illustrate both the collar spinning socket wrench  30  and the bolt locating and anti-rotating projecting hex pin  40 . 
         [0028]    As noted previously, bolt  10  has or defines a multi-sided, preferably square-sided or box-shaped bore  14  therein. More preferably bore  14  is in the shape of hexagonal configuration, generally about axis a. 
         [0029]    A hex-shaped pin  40  extends forwardly toward bolt  10  from the fastening/torque tool  50  (the fastening torque tool of  FIGS. 1 ,  2 ). The torque tool  50  drives a square, socket rotating driver  51 , or other shaped driver for socket wrench  30  as only graphically illustrated in  FIGS. 3 ,  4 . At the same time, hex pin  40  is fastened to apparatus  50  in a non-rotational function so hex pin  40  ( FIG. 4 ) does not spin or turn with respect to socket  30 . When hex pin  40  is in bore  14 , bolt pin  10  is prevented from rotation, regardless of the parameters of bolt-receiving apertures in parts  18 ,  19  in any suitable manner. 
         [0030]    Fastening torque tools such torque tool  50  are of any suitable construction, available as off-the-shelf items. Fastener torque tool  50  also includes torque sensors, as will be appreciated, which provide reliable torque data used with that provided by robot  70  to monitor different portions of the process. 
         [0031]      FIG. 3  illustrates the approach of pin  40 , nut  20  and socket  30  toward bolt  10 , but at an arbitrary angle thereto, ( FIG. 3 ) such as likely to be encountered in an assembly process. End of pin  40  seeks and is introduced into the bore  14  of bolt  10  thereafter holding it against rotation as socket  30  and collar  20  approach the bolt  10 , and align collar or nut  20  with the threads  13  of bolt  10 . Positioning and introduction of hex key  40  onto recess  14  is facilitated by the sensors associated in the axes of the sensing robot. Socket  30  is then spun to thread nut  20  onto pin  10 , but pin  10  is held against rotation by non-rotating hex pin  40  in bore  14 , even if bolt  10  is in non-binding or non-interfering relation with pieces  18 ,  19  (see  FIG. 4 ). Any cross-threading of element  20  on bolt  10  is sensed by the torque sensors of the sensing robot  70 , also indicating a degree of torque indicative of a product structure out of tolerance or aberration. Data from such torque sensing is used for reporting, control, start over or any other responsive protocol dictated by any suitable the application programming as will be appreciated. 
         [0032]    Socket  30  engages shear element  22  to drive nut  21  element onto bolt  10 . Once element  21  is set on threads  13  to proper torque against piece  19 , driven or driver element  22  thereafter shears off from element  21 , leaving nut or collar  22  ( 20 ) securely in place on bolt  10  against piece  19 . 
         [0033]    Socket  30 , with element  22  and pin  40  is withdrawn axially, leaving bolt  20  and torqued element  21  holding pieces  18 ,  19  together. 
         [0034]    Turning now to  FIGS. 1 and 2 , there is shown therein the robotic combination supporting and orienting the nut aligning and torquing elements as described above. 
         [0035]    In  FIG. 1 , the invention is illustrated and includes an industrial robot  60 , a lightweight sensing robot  70  carried by a mounting base or plate  61  and the industrial base robot  60 . Base robot  60  is any suitable robot such as robot model KR210 available from KUKA Robotics Corporation of Shelby Township, Mich. One form of sensing robot  70  is described above. 
         [0036]    A clamp foot  62  is secured to base plate  61 , and in operation engages a work piece  19  (see for example  FIG. 3 ) to support workpieces  18 ,  19  when pin bolt  10  is seated therein. 
         [0037]    A fastening torque tool  50  (including socket  30  and hex pin  40 ) is carried by the lightweight sensing robot  70  for aligning and spinning the nut  20  onto pin bolt  10  as illustrated in  FIGS. 3 and 4 . 
         [0038]    Turning to  FIG. 2  the sensing robot  70  is carried by a gimbal mount  80  and is supported on a rotary drive  90  for movement in multiple axes to facilitate alignment of nut  20  with bolt  10  ( FIGS. 3 and 4 ). 
         [0039]    Clamp foot  62  is biased by robot  60  against workpieces  18 ,  19  and any suitable sensors associated with robot  70  serve to align fastening torque tool  50  and nut  20  with bolt  10  to spin and secure nut part  21  on bolt  10  without cross-threading. 
         [0040]    It will be appreciated that any suitable sensing robot such as robot  70 , described above, together with associated sensors, and operating in conjunction with base robot  60  such as described above, for initial gross-point positioning can be used as described herein to accurately position nut  20  with respect to bolt  10  and to align spin preventing pin  40  with bolt  10 , thereafter allowing tool  50  to complete nut-to-bolt threading and then retreat. 
         [0041]    Thus even where a nut  20  is not initially aligned with a fastener  10 , the combination of robots  60 , and  70 , with tool  50 , is useful to automate the alignment and assembly of nut-to-fastener, without human intervention, but with the same or similar result. 
         [0042]    With more particularity, the sensing or robot  70  according to this invention is available as described above and is further described in detail in the following patents and patent applications incorporated herein by reference and including U.S. Design Patent No. D692,041, U.S. Pat. No. 8,649,906 published under No. U.S. 2010/0324733; German patent documents DE 10 2007 063 099 A1; DE 10 2007 014 023 A1; and DE 10 2007 028 758 B4; as well as EP 1972414 (B1) and EP 2006 055 (B1), all incorporated herein by reference and copies of which are filed herewith as part hereof. 
         [0043]    Positional sensing and location of hex pin  40  in recess  14  is provided by such robot  70  as well as threading and turning of nut or collar  20  onto fastener  10 , rendered operational by robot  70  according to the capabilities of such robot as described here and in the US and foreign patent documents incorporated herein by reference. It will be appreciated that any suitable controls and software consistent with this disclosure can be used with these components. 
         [0044]    Thus according to the invention, the sensing or second robot  70  is located proximate the work parts and fastener  10  by the base or first robot  60 , then positions the hex key or pin  40  in alignment with the recess  14  in the fastener  10  to hold it against spinning as the nut  20  is torqued down by socket  30 , controlled or monitored by torque sensors of the sensing robot. 
         [0045]    Any suitable control system for the robots can be used to produce the operations as described herein. 
         [0046]    These and other modifications and advantages will be appreciated from the foregoing description and drawings without departing from the scope of the invention and applicant intends to be limited only by the claimed appended hereto.