Abstract:
An improved robot arrangement for performing predetermined tasks, such as paint finishing, features equipping a robot with a plurality of manipulatable arms, with at least two of the arms performing like operations. Alternatively, a plurality of commonly controlled manipulator arms may be provided by clustering a plurality of conventional single arm robots on a common mounting stand.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
   This application is a continuation of U.S. Ser. No. 09/947,142, filed Sep. 5, 2001 now U.S. Pat. No. 6,757,586. 

   BACKGROUND OF THE INVENTION 
   The invention relates generally to improvements in robotic systems performing automated manipulated functions on workpieces such as automotive vehicle bodies. More specifically, the invention pertains to robotic paint finishing of such objects in automatic paint finishing lines of high capacity. 
   Conventional robotic automotive paint finishing booths, such as that depicted in  FIGS. 1   a  and  1   b  utilize multiple paint atomizers as well as robots or reciprocator machines in order to distribute paint across all required surfaces of the object passing through the paint application booth. 
   The paint application process can be performed either on a moving or stationary object, such as a car body. In either case, the object is indexed down the finishing line after the paint application process is complete.  FIGS. 1   a  and  1   b  set forth a top and cross-sectional view, respectively, of a paint application zone  104  in a paint spray booth  100 . Six robots  102   a–f , three on each side of the paint application zone  104 , each carry a paint application or distribution device  107   a–f , such as a rotary bell, carried on a single manipulator arm or arm assembly  103   a–f . Conventionally, an automotive chassis  106  is conveyed by a conveyor system  108  down the center of the spray booth through application zone  104  and is painted by the sets of three individual robots with single manipulator arms stationed on either side of the conveyor system  108 . 
   Conventional paint robots  102   a–f  as shown in  FIGS. 1   a ,  1   b  typically respectively consist of a base segment  105   a–f  which can be stationary or movable in the direction of conveyor system  108  and an arm assembly  103   a–f  comprising a vertical arm segment, a horizontal arm segment and a wrist segment holding the paint application device  107   a–f.    
   The term “arm”, as used herein, is intended to encompass either a manipulator arm composed of a single arm element or an assembly comprising a multi-segment arm, where pairs of the segments may be interconnected by joints as shown in  FIGS. 1   a ,  1   b.    
   Such a prior art arrangement has the favorable features of repeatability of design, spare parts and maintenance; lower programming effort for identical robot units; and favorable downgrade arrangements should one of the robots fail. However, the prior art arrangement also presents important disadvantages. All robots are of the largest size required to paint the highest and the furthest portions of the object from the paint distribution devices, for example, the roof of the car body  106  shown in  FIGS. 1   a ,  1   b . Additionally, the maximum reach envelope of each robot  102  must be capable of covering both the lowest and the highest point of object  106 . This, in turn, requires that all robots  102   a - f  be equipped with the largest required reach envelope. 
   An additional disadvantage of the prior art arrangement is that the combined effect of large envelope and high paint applicator relocation speed requires a sturdier robot to cope with the static and dynamic loads that it must handle which, in turn, results in higher total system cost. Also disadvantageous is the fact that the robots  102  require a relatively wide booth in order to paint vertical surfaces on object  106 , due to the length of the manipulator arms of the robots. The robots  102  require space, either in front or at the back, in order to position the paint application device, such as an atomizer  107 , at a suitable spraying distance in front of the surface to be painted. 
   Additionally, robots  102  often must be moved forward or backward along the line in order to paint the lower portions of part  106 , such as a rocker panel, which requires a relatively longer spray booth paint application zone  104 , along with an additional traveling axis (also known as the X-rail) being provided for robot movement longitudinally along application zone  104 . 
   Finally, another disadvantage of the prior art arrangement is that at least two of the robots  102  perform very simple operations of reciprocating in the vertical surface of part  106 . A much simpler machine than a full 7-axis robot can perform this operation. 
   SUMMARY OF THE INVENTION 
   Accordingly, in a first aspect of the invention, in a robot for performing predetermined operations under direction of a controller, the invention provides an improvement whereunder the robot is equipped with a plurality of manipulatable arms with at least two of the plurality of arms performing like operations. 
   In another aspect of the invention, a robotic system for performing predetermined operations under direction of a controller utilizes a cluster comprising a plurality of single manipulator arm robots such that each of the plurality is coupled to a common mounting stand, with at least two of the plurality of arms performing like operations. 
   In yet another aspect of the invention, a paint finishing booth having a paint application zone utilizes an arrangement of paint application robots wherein a robot cluster has a plurality of commonly controlled manipulator arms, each equipped with at least a paint application device and positioned within the paint application zone of the booth for applying paint at a first side of a workpiece being transported through the application zone. 
   In still a further aspect of the invention, a robotic system for performing predetermined operations under direction of a controller utilizes a cluster of single manipulation arm robots such that at least two bases of the robots extend in different directions toward a mounting end of their respective manipulator arms. 

   
     BRIEF DESCRIPTION OF THE DRAWING 
     The objects and features of the invention will become apparent from a reading of a detailed description, taken in conjunction with the drawing, in which: 
       FIG. 1   a  presents a top plan view of a paint application booth arranged in accordance with prior utilization of single arm robots; 
       FIG. 1   b  is a cross-sectional view of the booth of  FIG. 1   a;    
       FIG. 2   a  is a top plan view of a paint application booth arranged in accordance with a first embodiment of the invention; 
       FIG. 2   b  is a cross-sectional view of the booth of  FIG. 2   a;    
       FIG. 3   a  is a top plan view of a booth arranged in accordance with a second embodiment of the invention; 
       FIG. 3   b  is a cross-sectional view of the booth of  FIG. 3   a;    
       FIG. 3   c  presents details of the mounting arrangement of the first robot cluster of  FIGS. 3   a  and  3   b;    
       FIG. 3   d  details of the mounting arrangement for the robot cluster on the opposite side of the booth of  FIG. 3   a;    
       FIG. 4   a  sets forth a top plan view of a paint application booth arranged in accordance with a third embodiment of the invention; 
       FIG. 4   b  is a cross-sectional view of the booth of  FIG. 4   a;    
       FIG. 4   c  sets forth details of the mounting arrangement of the first robot cluster of  FIGS. 4   a  and  4   b ; and 
       FIG. 4   d  sets forth the mounting details of the second robot cluster of the booth of  FIGS. 4   a  and  4   d.    
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   With reference to  FIGS. 2   a  and  2   b , a first embodiment of a robotic multi-arm arrangement in conformance with the invention is set forth. Paint spray booth  200  encloses a paint application zone  204  along which workpieces such as automotive bodies  206  are transported by a conveyor system  208 . 
   Positioned within paint application zone  204  on opposite sides of the conveyor system  208  are first and second clusters of robot arms or arm assemblies  202   a  and  202   b . In the embodiment of  FIGS. 2   a  and  2   b  each robot  202   a  and  202   b  is equipped with a plurality, in this specific example  3 , manipulator arms. Robot  202   a  has arms or arm assemblies  210   a ,  210   b  and  210   c  associated therewith, while on the opposite side of the booth  200  robot  202   b  is equipped with manipulator arms  212   a ,  212   b  and  212   c . Each of the arms  210  and  212  carry at their extremities or wrists a paint application device, such as a rotary bell or other conventional paint application element. Arm  210   a  carries paint application device  214   a , arm  210   b  carries device  214   b  and arm  210   c  carries device  214   c . Similarly, robot  202   b  has paint application device  216   a  mounted to arm  212   a , device  216   b  mounted to arm  212   b  and device  216   c  mounted to arm  212   c.  While arms  210   a–c  and  212   a–c  are shown as having two hinged segments, it is to be understood that in all embodiments described herein such arms could comprise single segments, or more than two segments. 
   Placing each cluster of commonly controlled manipulator arms in a common substantially vertical plane substantially reduces the length L 1  of paint application zone  204  in comparison to the length L 2  which would be required for the prior art arrangement set forth in  FIGS. 1   a  and  1   b . This is due to the fact that the arrangement in accordance with the invention reduces the length of the required spray zone by assigning the portions of the part  206  to be coated by individual applicators in a vertical plane rather than in a horizontal direction along the spray booth as shown in the conventional arrangement of  FIGS. 1   a  and  1   b.    
   Such multiple manipulator arm clusters are referred to herein as “spider” or “octupus” robots. As with the conventional robots  102  of  FIG. 1   a , each arm associated with robots  202  of  FIG. 2   a  may comprise a vertical, a horizontal and a wrist segment. However, the arms and segments are in different lengths, with the option of adding arms in still different sizes to each cluster depending on the portion of the object  206  surface to be painted by a specific arm. Compared to the conventional arrangement of  FIGS. 1   a ,  1   b , the arrangement of  FIGS. 2   a ,  2   b  incorporates a different split of work areas of the individual robot arms  210  and  212 . The robots  102  in  FIGS. 1   a ,  1   b  are positioned along the longitudinal extent of the spray booth  100 , and these robots split their work areas according to the front, middle and rear portion of the object  106  to be coated. In this prior art arrangement, each robot is able to paint top (horizontal) surfaces, as well as middle and low vertical surfaces of the vehicle body  106 . Each robot  102  requires space for its working envelope, and this results in a spray booth length requirement (L 2  of  FIG. 2   a ), typically 30 feet and longer for an arrangement with six robots, three on each side of the booth. This relatively long spray booth requires a high cost of equipment investment, including ventilation air supply and exhaust, as well as environmental pollution control equipment. 
   The arrangement in accordance with the embodiment of  FIGS. 2   a ,  2   b  requires a much shorter spray booth length L 1 , typically one-half of the length L 2  required for the prior art arrangement. If even shorter arms of the robot arrangement in  FIGS. 2   a ,  2   b  are used for lower vertical surfaces of vehicle body  206  (which surfaces are the closest ones to the base of the robots  202 ) the width of the booth is also smaller, since the robots  202  do not require space for their elbows rearwardly of the robot base. The individual arms  210  and  212  have reach envelopes which do not have to be as large as those envelopes required for the prior art arrangement of  FIGS. 1   a ,  1   b . Each arm has a limited work area, and it should not interfere with the other arms, due to their different sizes, as illustrated in the cross-sectional view of spray booth  200  in  FIG. 2   b . Adding additional multiple arm robot sets along the spray booth, if the capacity of the line so requires, should not pose additional problems. 
   Hence, the embodiment of  FIGS. 2   a ,  2   b  offers the advantages of reduced booth length, reduced booth width and less longitudinal activity requirements for the robots  202 , since they operate mostly directly in front of their own bases. However, if required by a certain application to optimize the paint finishing process, robots  202  could be mounted on a longitudinal rail. 
   Additionally, the embodiment of  FIGS. 2   a ,  2   b  makes possible economical retrofits of the multi-arm clusters in existing shorter paint booths in older automotive assembly plants having stationary or slightly oscillating paint applicators. This enables the addition of the highly flexible robotic system without requiring adding length to the finish line. The approach will considerably increase the flexibility of the paint finishing line for new style vehicles coming in a variety of sizes. The embodiment of  FIGS. 2   a ,  2   b  further contributes to flexibility of the system through use of robot programming. 
   The embodiment of  FIGS. 2   a ,  2   b  illustrates a principal concept of the invention of providing multiple manipulator arms under common control of the robot, where the arms are all coupled to the same robot base. This approach may be limited in some applications, both in the working envelopes of the robot arms and in the availability of specifically required arm lengths in practical process arrangements. Hence, it is important to consider alternative embodiments which may, in some cases, allow more flexibility in motion of the individual manipulator arms, allow application of different arm lengths without interfering with each other, and use conventional robot modules in order to combine them into a multiple arm robot solution. 
   With reference to  FIGS. 3   a ,  3   b ,  3   c  and  3   d , a first alternate embodiment will now be described. The embodiment of  FIGS. 3   a – 3   d  is based on a combination of a plurality (in this specific example  3 ) of single arm or arm assembly robots mounted to a common mounting stand. 
   As used herein, “common mounting stand” is intended to encompass not only the single mounting stands set forth in the drawing, but also slightly separated stands grouped in a cluster with a separation distance between attachment points of the root arms of each robot being less than the length of the longest arm segment of all the arm assemblies in the cluster. 
   Likewise, the term “common controller” or “controller” is intended to encompass not only a single robot controller, but also a plurality of coordinated controllers, each controlling the motion of the individual robots within a cluster. 
   The invention additionally contemplates separate mounting stands within a cluster, wherein each robot base is mounted such that at least two of the bases extend in different directions toward a connection with their respective arms. 
   Booth  300  has a first manipulator arm cluster  302   a  and a second manipulator arm cluster  302   b  positioned at opposite sides of a conveyor system  308  which transports workpieces such as automotive bodies,  306  along a central portion of booth  300  through a paint application zone  304 . 
   As seen from  FIGS. 3   c ,  3   d  each robot cluster  302   a ,  302   b  has its individual single arm robot bases mounted to a rectanguloid mounting stand  303   a  for cluster  302   a  and  303   b  for cluster  302   b . The individual robots in each cluster are each mounted to mutually perpendicular or noncoplanar surfaces  305   a  for robot base  307 - 1 ,  305 B for robot base  307 - 2 , and  305   c  for robot base  307 - 3  of cluster  302   a . Similarly, as seen from  FIG. 3   d , common stand  303   b  presents three surfaces— 305   d  for mounting the base of robot  308 - 1 ,  305   e  for mounting the base of robot  308 - 2  and  305   f  for mounting the base of robot  308 - 3 . 
   Each robot of the cluster has coupled thereto a manipulator arm— 310 - 1  for robot  307 - 1 ,  310 - 2  for robot  307 - 2 ,  310 - 3  for robot  307 - 3 ,  311 - 1  for robot  308 - 1 ,  311 - 2  for robot  308 - 2  and  311 - 3  for robot  308 - 3 . 
   Also associated with each robot cluster is a plurality of paint application devices, with one or more application devices being associated with each robot manipulator arm. For cluster  302   a , the paint distribution or application devices are designated  312 - 1 ,  312 - 2  and  312 - 3  associated respectively with manipulator arms  310 - 1 ,  310 - 2  and  310 - 3 . Similarly, paint distribution or application devices  313 - 1 ,  313 - 2  and  313 - 3  are respectively associated with manipulator arms  311 - 1 ,  311 - 2  and  311 - 3  of cluster  302   b . As used herein, the term “paint distribution or application” refers to a process wherein a liquid or powder substance is applied to surfaces of an object, such as a car body. 
   With the arrangement of  FIGS. 3   a–d , as with the first embodiment, the required length L 3  of the paint application zone  304  is substantially smaller than that required, L 4 , for the prior art type of robot arrangement. 
   At least one middle robot of each cluster,  307 - 1  for cluster  302   a  and  308 - 1  for cluster  302   b , is equipped with arms of the longest reach of the plurality of arms in each cluster. This longest arm  310 - 1  and  311 - 1  is responsible for coating the highest vertical surface of body  306  and most of its horizontal surfaces, such as the roof of the body. The two side robots of each cluster  307 - 2 ,  307 - 3  for cluster  302   a  and  308 - 2 ,  308 - 3  for cluster  302   b  are rotated 90° from their normal orientation such that their vertical arms have become horizontal and almost parallel with the length of the booth. This orientation makes both side robots in each cluster completely free in their reciprocative motion over the vertical and lower horizontal surfaces of the object  306 . The two side robots of each cluster can be equipped with different or with the same arm lengths depending upon a specific coating process and the shape of the workpiece being coated. Additionally, the side robots can be mounted at any angle between 0° and 180° with respect to the middle robot. 
   The embodiment of  FIGS. 3   a–d  presents a compromise in the required line length. The common base  303   a  and  303   b  of the three robot clusters becomes wider and the motion envelopes require more length of spray booth application zone L 3 , as compared to the length L 1  of  FIG. 2   a , but the robot manipulator arms as arranged in  FIGS. 3   a–d  are given more freedom and flexibility in programming of their required paths of travel. In any case, the required application zone length L 3  remains considerably shorter than the conventional required length of the prior art L 4 . As an additional advantage, this embodiment can be comprised of commercially available single arm robots, thus avoiding the need for a new special design of a single robot base having a plurality of manipulator arms. 
   A second alternative arrangement set forth in  FIGS. 4   a ,  4   b ,  4   c  and  4   d  represents an attempt to further reduce the number of robot manipulator arms per cluster from three to two where each two robot cluster set has two robots placed on opposing surfaces of a common carrier, preferably on top and underneath in a vertical arrangement as shown. 
   With reference to  FIGS. 4   a–d , booth  400  includes two robot clusters  402   a  and  402   b  mounted on opposite sides of conveyor system  408  in a paint application zone  404 , along which a workpiece, such as an automotive body  406  is transported. 
   In the embodiment of  FIGS. 4A–D , each paint application robot cluster  402   a, b  comprises a set of two single armed robots— 407 - 1  and  407 - 2  for cluster  402   a  and  408 - 1  and  408 - 2  for cluster  402   b . As seen from  FIGS. 4   c  and  4   d , the individual robots of each cluster are mounted on top of one another and facing in opposite directions utilizing a common mounting stand,  403   a  for cluster  402   a  having mounting surfaces  405   a  and  405   b  facing in opposite directions and respectively mounting the bases of robots  407 - 1  and  407 - 2 . Similarly, common mounting stand  403   b  for cluster  402   b  presents oppositely facing mounting surfaces  405   c  and  405   d  for respectively mounting bases for robots  408 - 1  and  408 - 2 . 
   Cluster  402   a  is equipped with two manipulator arms,  410 - 1  and  410 - 2 , while cluster  402   b  has manipulator arms  411 - 1  and  411 - 2  likewise extending in opposite directions at their bases. Each arm of each cluster is equipped with a paint application or distribution device  412 - 1  for arm  410 - 1 ,  412 - 2  for arm  410 - 2 ,  413 - 1  for arm  411 - 1  and  413 - 2  for arm  411 - 2 . 
   Again, the required application zone  404  length L 5  is seen to be substantially shorter, on the order of one-half of the required length L 6  which must be provided for prior art arrangements using horizontally-spaced individual arm robots in accordance with the prior art. 
   The longer arm of each cluster— 410 - 1  and  411 - 1  is mounted above the common stand and is responsible for the horizontal surfaces and upper vertical surfaces of body  406 . The shorter arms  410 - 2  and  411 - 2  are responsible for the lower portions of the vertical surfaces of the body  406 . 
   Whether or not one can reduce the number of manipulator arms in each cluster depends upon the available application throughput of the paint application devices  412 . 
   The invention has been described with reference to preferred embodiments which are presented for the sake of example only. Those skilled in the relevant art will readily recognize that one could combine the various embodiments set forth herein. For example, the embodiments of  FIGS. 3   a–d  and  FIGS. 4   a–d  could be combined by adding the side robot arms  310 - 2 ,  310 - 3  and  311 - 2  and  311 - 3  to the common mounting stands  403   a  and  403   b  of the embodiment of  FIGS. 4   a–d . This arrangement would comprise four manipulator arms per cluster and would be suitable for very high production capacities. 
   The scope and spirit of the invention is to be determined by appropriate interpretation of the appended claims.