Patent Publication Number: US-2010115749-A1

Title: Flexible assembly for performing work on large surfaces

Description:
FIELD OF THE ART 
     The object of the present invention relates to systems that are used to perform work on large surfaces, such as machining, riveting, welding, inspection and painting for example, proposing an assembly that is easy to carry out, whereby it can act safely and precisely with the capacity for positioning in five shafts on any work surface. 
     STATE OF THE ART 
     Large structures such as airplanes, ships and the like are formed by large laminar surfaces adapted to the shape and configuration of their support structures. These configurations allow the surfaces to be complex curves on which it is necessary to perform the application work. Said tasks to be carried out include for example fixing the surfaces by means of rivets, welding or the like. 
     For all these tasks machines are currently used which are formed by large structures, regardless of the application surfaces, provided with the tools necessary for the operations to be carried out, said structures moving on external systems. These types of machines are very conditional in relation to the shape of the application surfaces, therefore their use is normally limited to the surfaces analyzed during their design. 
     There are also flexible machining systems which can move in order to place a machining head with respect to any point of a surface, such as the already expired solution of patent SE U.S. Pat. No. 8,305,818 for example, comprising a machining device formed by rails which are assembled on circular channels in which the ends of the sheets to be machined are inserted. In this solution a machining carriage moves on the curved rails in order to be placed at the machining points, but it does not assure the perpendicularity of the tool on the work surface, which can cause defective precision of the operations. 
     Patent document US 2002/0007548 also describes a machining device for forming airplane structures, comprising a machining carriage moving on rails arranged on a structure separated from the fuselage to be formed, which also takes away precision from the machining operations. 
     Other solutions such as those in patent documents U.S. Pat. No. 6,098,260 and US 2003/0116331, comprise a machining device formed by rails which are fixed by suction cups on the plates of the structure to be machined, a carriage which can move longitudinally being incorporated on said rails, on which another carriage carrying a machining head with the possibility of transverse movement is arranged. These solutions allow working with precision on flat surfaces, but do not assure the perpendicularity of the working tool with respect to the work surface when it is curved, therefore in this case the precision is also deficient. 
     OBJECT OF THE INVENTION 
     According to the present invention, a flexible machining assembly is proposed which is provided with constructive and functional features making it adaptable to operate with precision on any type of flat or curved surface, therefore being applicable for airplane fuselage structures or the like. 
     The assembly object of the invention consists of a frame in which the machining head is incorporated, the frame being provided with means for moving and lifting, provided with lifting and fixing systems, to thus be able to be placed in the necessary work positions, whereas the machining head is incorporated on a carriage provided with transverse movement on the frame. 
     According to an assembly embodiment, the means for moving the frame consist of two side groups provided with movement in height, longitudinal movement and a fixing system by means of suction cups. 
     The frame of the mobile assembly further incorporates at the lower part suction cups arranged in vertical spindles which are associated to a common actuation system by means of a servomotor and belt drive, such that said suction cups allow fixing the mobile assembly on the application surface in order to carry out the machining once the working head is placed in relation to the selected point, the path of the head for the machining being determined by means of the vertical movement, by means of the mentioned spindles of the fixing suction cups. 
     An arrangement is therefore achieved allowing movement on the work surface by means of the combined, action of the support-lifting and sliding assemblies, achieving the precise movement of the working head on the work surface in an alternate (step by step) manner. 
     The combination of said transfer on the application surface with the transverse movement of the carriage carrying the head, with respect to the frame, defines a Cartesian movement which allows placing the machining head exactly on the operation points, thus being able to be establish a perfect holding with the support assemblies themselves in each case, in order to carry out the operations to be performed at the indicated points by means of the vertical movement of the machining head (if the work requires it), placing the working head or assembly at the required angle with respect to the application surface. 
     The frame carrying the machining head can be incorporated according to another assembly embodiment, on flexible guide rails (CFRP) which are fixed by means of suction cups on the application surface. The carrier frame slides longitudinally and step by step on those guides, such that by combining this movement with the already existing movement in the frame itself, the vertical movement thereof and the transverse movement of the working head, the work point can be placed in the required location and angles. It must be pointed out that the positioning precision of the working head is independent of the positioning precision of the flexible guiding systems. 
     The longitudinal movement rails are formed by flexible profiles (CFRP) arranged in parallel and joined by means of transverse plates, said profiles having vacuum suction cups that allow the fixing on the structure to be machined, the profiles themselves being used as vacuum storage and distribution channels, sectoring the holding points in order to minimize the effects of possible local vacuum loses. 
     The actuation of said longitudinal movement in this case comprises a traction system and a locking system, being integrated in respective similar side assemblies, operating in a synchronised manner on the respective rails, said traction and locking systems acting in a coordinated sequence for a step by step forward movement. The coordinated movements allow controlling the position and alignment of the shafts according to the requirements demanded by the work to be performed. 
     The locking system forms, according to the point of the work process, a locking allowing the movement of the mobile assembly on the longitudinal profiles in a step of longitudinal movement, by means of the rolling sliding of the traction system on the profiles; the rolling means being in an elastic suspension arrangement with respect to the frame of the mobile assembly, which allows a vertical floatability of said mobile assembly. 
     The entire system is controlled by computer management equipment having various systems for adapting the equipment to the application surfaces, such as an on-line positioning reference and correction system based on two artificial vision cameras, for example. This control system, integrated into the computer control system, allows establishing the position of the work unit with respect to areas of the surface to be worked with special features, placing and correcting, if necessary, the parameters defining the location of the work unit on the application surface. It also has additional sensors increasing the capacity of the working head according to the tasks to be performed, such as for example, a hold-down plate with controller with the task of assuring that the parts to be worked are perfectly held down. This device has a system for regulating the hold-down force, also having an analog or digital system (optional) controlling the forward movement of the shaft. Z for very delicate or high precision work, such as cone countersinks, etc. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of the machining assembly object of the invention according to the embodiment of support by means of two lifting support assemblies. 
         FIG. 2  is a perspective view of the same machining assembly from another angle of observation. 
         FIGS. 3 and 4  are respective front and profile views of the previous machining assembly. 
         FIG. 5  is a perspective view of the block carrying the machining head. 
         FIG. 6  is a perspective view of the mobile frame of the machining assembly with one of the support groups. 
         FIG. 7  is a perspective view of the mobile frame of the machining assembly with its other support group. 
         FIG. 8  is a perspective view of the assembly embodiment of the machining assembly on movement rails. 
         FIGS. 9 and 10  are respective front and profile views of said arrangement of the machining assembly on movement rails. 
         FIG. 11  is a perspective view of the support rails of the machining assembly for the previous embodiment. 
         FIG. 12  is an enlarged perspective view of the arrangement of the assembly of the frame of the machining assembly on the movement rails. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The object of the invention relates to a flexible machining assembly, which is provided with constructive and functional features making it able to perform any type of operation with precision by simply changing the tool, on any type of flat or curved surface, therefore being applicable for structures such as airplane fuselage structures or the like. 
     The machining assembly object of the invention forms a work unit consisting of:
     A.—Two longitudinal drive units, of the work unit, which will be called hereinafter shafts X, which units are provided with a forward movement assembly, by means of a servomotor and a spindle with controlled clearance nuts, which can work together, creating a longitudinal forward movement on the application surface, or independently, achieving specific angular movements for special work.   

     On each of the movements X, and in order to fix the work unit during the longitudinal movement, vacuum suction cups are placed assuring the rigidity and precision necessary for the movement.
     B.—A main frame, which is the joining link of all the subsystems of the work unit, the subsystems being:
       Mechanisms for forward movement towards the work surface, which hereinafter will be called shaft Z, which is provided with three or more forward movement assemblies, by means of servomotors, pulleys and spindles with controlled clearance screws, which can work together, creating a forward movement perpendicular to the work surface, or independently, achieving specific movements for special work.   
       

     At the end of each one of the movements Z, and in order to fix the work unit to the application surface, two vacuum suction cups are placed assuring the rigidity and precision necessary for the work applications. A great advantage is that this arrangement allows creating a highly rigid and precise working device, allowing the work of positioning in five shafts.
         Mechanism for forward movement parallel and perpendicular to the movement X, which hereinafter will be called internal movement X and Y, which, supported by the main frame, achieves the sliding of the working tool towards the suitable work location on a preloaded guiding system, by means of using a servomotor and spindle with a controlled clearance screw.   A hold-down plate with a depth controller responsible for assuring that the parts to be worked are held down correctly; this device having a system for regulating the hold-down force, and further having an analog or digital system (optional) controlling the forward movement of the shaft Z for very delicate high precision work, such as cone countersinks, etc.   A positioning reference and correction system, for example with artificial vision cameras, which system, integrated into the computer control system, allows establishing the position of the work unit with respect to areas of the application surface with special features, placing and correcting, if necessary, the parameters defining the location of the work unit on the application surface.       

     According to an assembly embodiment ( FIGS. 1 to 7 ), the mobile assembly incorporates two longitudinal forward movement systems ( 1 ), by means of a fixing system ( 2 ) and a traction system ( 3 ) which are integrated in similar respective assemblies acting in an independent or synchronised manner on both sides, the mobility of the assembly being determined by means of actuating both systems, causing a very precise step by step forward movement, due to the side actuations by means of independent servomotors ( 4 ). An independent actuation of these systems in turn corrects the angular positioning of the mobile assembly. 
     The mobile assembly consists of a frame ( 5 ), to which the traction-fixing systems are associated, the fixing system ( 2 ) of each side assembly comprising several vacuum suction cups assembled in pairs, whereas the traction system ( 3 ) of each of the mentioned side assemblies comprises an actuation by means of a servomotor ( 4 ), through a spindle ( 6 ) with a controlled clearance screw. 
     The frame ( 5 ) is supported, in the longitudinal movement X on the fixing suction cups, by means of pneumatic electroactuators ( 7 ) defining a floating suspension of said frame ( 5 ) during the movement, a carriage ( 8 ) being located on this frame ( 5 ) which can move transversely by means of actuation by a servomotor ( 9 ), the working head ( 10 ) being vertically incorporated in such carriage ( 8 ), which head can incorporate any type of machining tool for drilling, riveting, welding, etc. 
     The frame ( 5 ) further incorporates at the lower part vacuum suction cups ( 11 ), which are arranged by means of corresponding vertical spindles ( 12 ), an independent actuation system by means of a servomotor ( 13 ) and a belt drive ( 14 ) being connected to the mentioned spindles ( 12 ), thus determining a mobility allowing the vertical movement of the mobile assembly in order to position the working head ( 10 ) in relation to the application surface for the machining. 
     In another assembly embodiment ( FIGS. 8 to 12 ), the mobile assembly is assembled with respect to the rails ( 16 ), by means of a locking system and a traction system, which are also integrated in respective identical assemblies which act in a synchronised manner on the respective rails ( 16 ) of both sides, the mobility of the movement being determined by means of actuating both systems, causing a step by step forward movement which, together with the action of the actuation on both sides, gives rise to a great precision of the movement for placing the mobile assembly in the corresponding place. 
     In this case, the mobile assembly also consists of a frame, to which the traction and locking systems are associated, the locking system of each side assembly comprising a pneumatic clamp ( 17 ) which can perform a locking catch on the corresponding rail ( 16 ), whereas the traction system of each one of the mentioned side assemblies comprises sets of wheels ( 18 ) forming a rolling sliding on the inner edge of the respective rail ( 16 ), said sets of wheels ( 18 ) acting in a driving actuation by means of a servomotor ( 19 ), through a spindle ( 20 ) with a controlled clearance screw. 
     In this case, the frame ( 5 ) of the mobile assembly is supported on the sets of wheels ( 18 ) by means of pneumatic actuators ( 21 ) defining the floating suspension; the working head ( 10 ) being located on said frame ( 5 ) by means of a carriage ( 8 ) which can move transversally, in the same way as in the embodiment of  FIGS. 1 to 7  explained above. 
     The frame ( 5 ) also incorporates at the lower part vacuum suction cups ( 11 ), which are arranged by means of corresponding vertical spindles ( 12 ) with a hollow shaft, whereby vacuum is provided for actuating said suction cups ( 11 ), in this case a common actuation system by means of a servomotor ( 13 ) and a belt transmission ( 14 ) being connected to the mentioned spindles ( 12 ), also determining a mobility allowing the vertical movement of the mobile assembly in order to position the working head ( 10 ) in relation to the application surface for the machining. 
     The rails ( 16 ) are formed by flexible profiles made of CFRP, which rails are arranged in parallel, joined by means of transverse plates ( 22 ), in which extendable bolts ( 23 ) are incorporated, by means of which the exact positioning of the installation with respect to the application surface is provided. 
     Said profiles of the rails ( 16 ) incorporate at the lower part vacuum suction cups ( 24 ) having points of innocuous material for contacting the application surface, which allow establishing a reference for fixing the mentioned profiles on the application surface. 
     These profiles of the rails ( 16 ) are further used as distribution as vacuum storage and distribution channels necessary for the suction cups ( 24 ), sectoring the distribution in order to minimize the effects of possible local vacuum loses; although the bolts ( 23 ) of the transverse plates ( 22 ) prevent the work unit from falling in the event of vacuum loss in all the suction cups ( 24 ). 
     In both embodiments the suction cups ( 11 ) allow fixing the mobile assembly on the application surface in order to perform the machining, whereby achieving that the working head ( 10 ) is perfectly held in the position of the machining, said holding being directly applied from the block of the mobile assembly to the work surface. 
     According to said application the suction cups ( 11 ) are structured with two elastic support edges, by means of which the contact for the fixing on the application surface is formed, without it experiencing deterioration. At the inner part, said suction cups ( 11 ) further define a hard reference point, by means of which the fixing position on the application surface is exactly defined. 
     Detectors are further arranged in the different parts of the mobile assembly by means of which a control of the positioning is established, starting from an initial position which is established by means of one or more sensors ( 15 ) with respect to a predetermined reference point, correcting the deviations which can occur with respect to the programmed positions for performing the machining, the functional assembly being controlled by a computer system according to specific programs for the machining operations to be performed in each case.